Polar with spoilers extended? [Archive]

Mike the Strike

October 22nd 07, 05:08 PM

On Oct 22, 2:57 pm, wrote:
> On Oct 21, 11:13 am, Tim Taylor > wrote:
>
>
>
> > On Oct 21, 10:50 am, " > wrote:
>
> > > Tim,
> > > I have flown with you, why do you want to know this information? You
> > > take off, fly far and fast and land when your glider touches the
> > > ground. I don't ever remember you "using" spoilers...
>
> > Tom,
>
> > LOL, thanks. It is purely an academic exercise from a safety
> > discussion we had about what are the best steps to follow if you are
> > high on final. I am trying to look at the difference between several
> > suggested techniques if full spoilers are not enough.
>
> > My list of preferences is:
> > 1. Full spoilers
> > 2. add forward slip
> > 3. add "S" turns
>
> > I have used the technique of slowing down to minimize forward speed,
> > increase sink and decrease glide angle. Others have suggested
> > increasing speed to increase drag. I am not a big fan of this
> > technique because I feel it minimizes options for the pilot and is
> > susceptible to pilot error that can end up in over shooting the LZ.
> > Last years article in soaring I believe confirms my feeling that this
> > is a technique that should not be held up as one of the primary
> > techniques that should be used. I am working on developing models to
> > asses each in terms of effectiveness, time required, safety and
> > options left to the pilot.
>
> > Tim
>
> If you are THAT much too high, wouldn't it also be prudent to consider
> a large 360? It may not be pretty, but let's face it, if you have
> turned final and just THEN realized you're way too high, you've
> already lost all your style points.

I only did a 360 once (my first solo landing in a high-performance
glass ship). I lost sight of the runway turning and ended up in a
worse position than if I had just continued.

These days, if I find myself a bit high, I apply full spoilers and
increase speed. If that's not enough, I add slip. Drag goes up at
least as the square of speed. I've never had a problem slowing down.

Mike

Nyal Williams

October 22nd 07, 05:12 PM

Frightening! That you would slow down to decrease
forward motion. What happens with downdrafts or wind
shear after you have given up the option for altitude
that speed gives you.

Forward slip in glass gliders won't get you much descent;
S-turns might eat up a good bit, but the high-parasitic
drag approach is a much more valuable tool.

Get about 4000ft agl near the pattern, open full spoilers,
and push over to about 70-80kts. When you've burnt
off 1000ft, lift the nose to the horizon until speed
drops to best l/d and then close the spoilers. You
will see that this is not a ballistic maneuver and
that it is completely controllable. I'm not sure a
speed curve for full divebrakes is needed; you can
eyeball this and make it come out right. Either find
an instructor who can demonstrate for you, or else
do it several times at altitude and when comfortable
practice it at lower altitude and on final. In the
latter situation you might do just a few seconds to
see how entry and recovery look and behave. There
is more probability of undershooting than overshooting,
in my experience, but you'll be aware that these are
about to happen before they become a serious problem.

I do these on BFRs routinely into a 2400ft strip.
Remember, you can break this off at any time, so you
don't have to give up options.

At 18:18 21 October 2007, Tim Taylor wrote:

>LOL, thanks. It is purely an academic exercise from
>a safety
>discussion we had about what are the best steps to
>follow if you are
>high on final. I am trying to look at the difference
>between several
>suggested techniques if full spoilers are not enough.
>
>My list of preferences is:
>1. Full spoilers
>2. add forward slip
>3. add 'S' turns
>
>I have used the technique of slowing down to minimize
>forward speed,
>increase sink and decrease glide angle. Others have
>suggested
>increasing speed to increase drag. I am not a big
>fan of this
>technique because I feel it minimizes options for the
>pilot and is
>susceptible to pilot error that can end up in over
>shooting the LZ.
>Last years article in soaring I believe confirms my
>feeling that this
>is a technique that should not be held up as one of
>the primary
>techniques that should be used. I am working on developing
>models to
>asses each in terms of effectiveness, time required,
>safety and
>options left to the pilot.
>
>Tim
>
>
>
>

Vaughn Simon

October 22nd 07, 05:27 PM

"jeplane" > wrote in message
ups.com...
> 360 on final?
>
> Mmhhhh.... Two things come to mind:
>
> - What if there are traffic in the pattern?
> - What if at the end of your 360, you end up too low?
>
> I like Tim's list better, and in fact, this is what I teach with
> students.

And mine too, but things don't always go according to plan. I got into a
situation as a student pilot where I did a 360 on final. It was a case where I
had a brisk tailwind on my downwind leg combined with strong lift. In spite of
full deployment of the wimpy spoilers on my 2-33, I was climbing rather than
descending in the pattern.

As a more experienced pilot, I might have ventured downwind for a few seconds
making the pattern a non-event, but as a student pilot I rejected that option
due to fear of overdoing things in the brisk wind and landing short. I could
have added slip starting early on the downwind, but didn't even think of it at
the time and that opportunity was quickly behind me. We had recently been
practicing low rope breaks, so I did the math and figured out what a 360 (2
"rope break" 180-degree turns) would cost me and went ahead and did it whilst on
final. It worked out great, but my instructor was not pleased.

Vaughn

Marc Ramsey[_2_]

October 22nd 07, 05:46 PM

Mike the Strike wrote:
> These days, if I find myself a bit high, I apply full spoilers and
> increase speed. If that's not enough, I add slip. Drag goes up at
> least as the square of speed. I've never had a problem slowing down.

For whatever reason (I don't really want to start that flame war again,
although I think the mods to the DDX quietly prove the point), I've
found that the Duo Discus does not take kindly to excessive speed on
approach. There is no elegant way to bleed off the excess energy, you
end up either floating down the runway, or forcing it down hot and
jamming on the brakes. It is best to maintain a proper approach speed
with full dive brakes and slip or S-turn as needed. I've heard that the
Libelle behaves in a similar fashion...

Marc

Eric Greenwell

October 22nd 07, 05:58 PM

BB wrote:
>> Others have suggested
>> increasing speed to increase drag. I am not a big fan of this
>> technique because I feel it minimizes options for the pilot and is
>> susceptible to pilot error that can end up in over shooting the LZ.
>
> I didn't think so either until Marty Eiler at Cal City demonstrated it
> for me as part of a BFR. Practiced, and properly done, it can produce
> an unbelievably steep angle from decision point to stopping point. Yes
> you have to point the nose at the ground and look temporarily like
> you'll undershoot. Definitely not for beginners, but not a maneuver to
> be dismissed either.

I find it a very useful technique if I am high enough on final to use
it. Generally, I use it shortly after turning final as I realize I am
too high, even with full spoiler. That's when I have 500' agl or so,
which is plenty. Going from 50 knots to 70 knots (watch the flap setting
speed) doubles the rate of energy loss. When I slow down to 50 knots
again (still at full spoiler), my new "aim point" is much closer, and I
can reduce the spoilers to (ideally) about half.

If I'm "low", say less than 200', when I decide I'm too high, slipping
is my choice. I've never used S turns: if I'm high enough to make turns
on final, it's easier and safer to dive off the speed.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Andreas Maurer

October 22nd 07, 06:11 PM

On 22 Oct 2007 16:12:47 GMT, Nyal Williams
> wrote:

>Forward slip in glass gliders won't get you much descent;

I'm not sure about that - the glass gliders that I have tried forward
slips with usually got really huge descent rates.

A few examples:
ASK-21, G-103, ASW-24: Sideslip very effective
DG-300, DG-505: Sideslip extremely effective
AS22-2: Sideslip pretty effective

Bye
Andreas

Chris Reed[_1_]

October 22nd 07, 06:27 PM

BB wrote:
>> Others have suggested
>> increasing speed to increase drag. I am not a big fan of this
>> technique because I feel it minimizes options for the pilot and is
>> susceptible to pilot error that can end up in over shooting the LZ.
>
> I didn't think so either until Marty Eiler at Cal City demonstrated it
> for me as part of a BFR. Practiced, and properly done, it can produce
> an unbelievably steep angle from decision point to stopping point. Yes
> you have to point the nose at the ground and look temporarily like
> you'll undershoot. Definitely not for beginners, but not a maneuver to
> be dismissed either.
>

I had this taught to me as part of my UK Basic Instructor renewal
course/checks. It works well in a glider with good airbrakes, but not in
something like my Open Cirrus (unless, perhaps, it's a long, long
approach so that there's time to drop below glide path with full brake
and normal approach speed, then bleed off the speed and come back into
the approach funnel at the proper speed).

It's one for the experienced (and properly taught) because you need to
know what's going to happen after you round out. In, say, a Puchacz, the
brakes are so good that you get only a comparatively small increase in
float. In my Cirrus, 10kt extra with full airbarke will far more than
double the float at a height where there is nothing you can do about it
except hang on. Libelles are known to be similar, and from a previous
poster the Duo Discus as well. Fortunately, those who fly gliders with
"weak" airbrakes soon learn about approach speed control ....

Mike the Strike

October 22nd 07, 07:34 PM

On Oct 22, 4:46 pm, Marc Ramsey > wrote:
> Mike the Strike wrote:
> > These days, if I find myself a bit high, I apply full spoilers and
> > increase speed. If that's not enough, I add slip. Drag goes up at
> > least as the square of speed. I've never had a problem slowing down.
>
> For whatever reason (I don't really want to start that flame war again,
> although I think the mods to the DDX quietly prove the point), I've
> found that the Duo Discus does not take kindly to excessive speed on
> approach. There is no elegant way to bleed off the excess energy, you
> end up either floating down the runway, or forcing it down hot and
> jamming on the brakes. It is best to maintain a proper approach speed
> with full dive brakes and slip or S-turn as needed. I've heard that the
> Libelle behaves in a similar fashion...
>
> Marc

I should add I am a lot more careful about setting up my approach in
my Discus 2 than I was in my ASW-20, which was equipped with the
"Jesus" flap. I set up my altitude on the downwind leg, and that's
where I'll use the dive brakes with higher speed. I like to be at the
proper altitude when I turn base so that I can get the speed right on
final.

I think we may both agree that you don't want to dive at the runway at
the last moment.

Mike

Dan G

October 22nd 07, 08:17 PM

On Oct 22, 5:58 pm, Eric Greenwell > wrote:
> I find it a very useful technique if I am high enough on final to use
> it. Generally, I use it shortly after turning final as I realize I am
> too high, even with full spoiler. That's when I have 500' agl or so,
> which is plenty. Going from 50 knots to 70 knots (watch the flap setting
> speed) doubles the rate of energy loss. When I slow down to 50 knots
> again (still at full spoiler), my new "aim point" is much closer, and I
> can reduce the spoilers to (ideally) about half.

All this is way outside my experience, and I'm not going to attempt it
myself (though I might nobble an instructor experienced at it).
However I still have a question: do you dive and then return to normal
approach speed before rounding out, or round out at the much faster
speed? If the latter, does not the extra float in ground effect negate
the losses from extra drag in the dive, especially with a slippery
glass ship versus a draggy wood and fabric glider (such as one a pilot
might train in)?

Dan

Martin Gregorie[_1_]

October 22nd 07, 08:52 PM

Marc Ramsey wrote:
> I've
> found that the Duo Discus does not take kindly to excessive speed on
> approach. There is no elegant way to bleed off the excess energy, you
> end up either floating down the runway, or forcing it down hot and
> jamming on the brakes. It is best to maintain a proper approach speed
> with full dive brakes and slip or S-turn as needed. I've heard that the
> Libelle behaves in a similar fashion...
>
I've not tried that in my Libelle on finals (a full brake slip has
always fixed that situation very nicely to date - like hitting DOWN in a
lift) but I have tried it higher, when I wanted to get down quickly to
circuit height. Popping the brakes at 70+ kts with the wheel down gave
me a noticeable boost forward against the straps and I found I had to
push the nose down quite a bit further than I expected to maintain 70.
This is in an H201 with upper and lower surface brakes, not a B series:
at this speed a Libelle's brakes aren't as wimpy as many folks say they are.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Andreas Maurer

October 22nd 07, 09:06 PM

On Mon, 22 Oct 2007 19:17:18 -0000, Dan G > wrote:

>However I still have a question: do you dive and then return to normal
>approach speed before rounding out, or round out at the much faster
>speed? If the latter, does not the extra float in ground effect negate
>the losses from extra drag in the dive, especially with a slippery
>glass ship versus a draggy wood and fabric glider (such as one a pilot
>might train in)?

You found the problem! :)
The key is to be back at normal approach speed while still outside the
ground effect.
This means you need to decide about using this maneuvre while still
fairly high.

Bye
Andreas

Alastair Harrison

October 22nd 07, 09:23 PM

Dan G wrote:
<SNIP>
> However I still have a question: do you dive and then return to normal
> approach speed before rounding out, or round out at the much faster
> speed? If the latter, does not the extra float in ground effect negate
> the losses from extra drag in the dive, especially with a slippery
> glass ship versus a draggy wood and fabric glider (such as one a pilot
> might train in)?
<SNIP>

I had this demonstrated to me by a very experienced instructor in a K13.
He had me fly a deliberately high and close in circuit until it was
clear that we'd be a long way up the field, even with full airbrake.
Then he took over and performed the 'energy dumping' manoeuvre, which
involved opening full brake and pointing the nose at the ground.

It all happened rather fast and was not unalarming, so my recollections
are not exact. However, I'm fairly sure the speed never exceeded 80kts.
Certainly the ground approached very rapidly. One moment we were in a
gross overshoot situation and the next moment I was concerned that we
might impact the ground before reaching the boundary wall. We came out
of the dive, popped over wall and settled on to the ground for one of
the shortest landings I've seen. I remember being surprised at how
quickly we lost the excess speed. Pulling out of a near-vertical dive
(at least that's what it felt like) with full airbrakes seems to scrub a
lot of energy very quickly.

I asked the instructor whether this would work in something more
slippery. He answered that it would, but of course it wouldn't be so
effective as in the K13. He even told that he had successfully
demonstrated it in a Duo, though I don't have any quantitative or
qualitative information to say how effective it was.

I was also taught this technique on a basic instructors course (in a
G103). But I'm always left thinking that it requires a high level of
skill to judge the roundout correctly. Leaving it just a second too
late would result in a rather rapid meeting with the ground. I think
I'd rather take my chances with a side slip.

Alastair

Brian[_1_]

October 22nd 07, 09:39 PM

On Oct 22, 10:12 am, Nyal Williams
> wrote:
> Frightening! That you would slow down to decrease
> forward motion. What happens with downdrafts or wind
> shear after you have given up the option for altitude
> that speed gives you.
>
<snip>

Frightening? Really? It actually works very well with a bit of head
wind. Backcountry power pilots occasionally use this technique as
well.

It could be "Frightening" on a normal approach but remember the
context. A Downdraft or Windshear would be welcomed as the whole point
is to lose altitude. It does requires some expertise in slow flight
and stall awareness. But then glider pilots or at least soaring pilots
are supposed to be the experts at slow flight. Once you get down
close to a normal approach angle simply accelerate (which will bleed
off some more altitude) to your normal approach speed and fly the
remaining part of the approach normally. In fact it is necessary that
at about 200 feet AGL or higher that you do accelerate to a normal
approach speed so that you will have enough energy to flare with.

I would strongly recommend practicing it with an instructor and in the
specific airplane before having to use it. Usually with gliders there
are other, as good, or better options to this technique.

Brian

J a c k[_2_]

October 22nd 07, 09:39 PM

Tim Taylor wrote:

[....]

> I have used the technique of slowing down to minimize forward speed,
> increase sink and decrease glide angle. Others have suggested
> increasing speed to increase drag. I am not a big fan of this
> technique because I feel it minimizes options for the pilot and is
> susceptible to pilot error that can end up in over shooting the LZ.
> Last years article in soaring I believe confirms my feeling that this
> is a technique that should not be held up as one of the primary
> techniques that should be used. I am working on developing models to
> asses each in terms of effectiveness, time required, safety and
> options left to the pilot.

Increasing speed has its uses, and it has the distinct advantage of
being able to get out of rather more easily and safely than slowing
down, when you find you have over-done it. Of course there is the
concern that those who find themselves needing a lot of it may not be
the persons who'll know promptly when they've had enough, nor how best
to handle having too much--but there are ways to avoid being one of them.

The S-turns can be helpful when one has both the horizontal and
vertical space for them, if we arrange to be finished with them before
we are low, and ALWAYS watch our drift, as it changes with altitude and
airspeed changes--both IAS and GS--throughout the final approach. I
often see people failing to correct for drift as soon as they should,
which only leads to further complications.

I've found it useful to practice with increasing amounts of variation
from the basic final approach airspeed, both plus and minus, in order to
get to know what works with my glider in the relatively controlled
environment of my home field. This is at least a start in preparing for
the inevitable off-field or strange-field approach and landing, not to
mention the unheralded/unheeded arrival of geese, Cessnas, Boeings, or
skydivers in the pattern.

I can only advise any rated pilot to try each of those techniques
under benign conditions, working in small increments away from the
nominal speeds and configurations, changing one variable on each
approach. Pretty much what you learned to do in high-school science
labs. It may not be rocket science, but please do have a plan on every
approach--just as you do on every departure--to include touchdown and
stop points. And when you are on the ground make sure you know why the
plan worked, or why it did not--before you take the next step.

Thanks for the opportunity to harangue the assemblage. I'll try to
remember to impose some limits on this sort of thing next time, possibly.

Jack

October 22nd 07, 10:02 PM

On Oct 22, 2:23 pm, Alastair Harrison >
wrote:
> I was also taught this technique on a basic instructors course (in a
> G103). But I'm always left thinking that it requires a high level of
> skill to judge the roundout correctly. Leaving it just a second too
> late would result in a rather rapid meeting with the ground. I think
> I'd rather take my chances with a side slip.

Perform the dive recovery in two steps:

Diving with full spoilers and 80-90 KIAS, do a fairly sharp roundout
at 50-60' (a wingspan, at least) above the ground. Then, while still
holding full spoilers, set up a glide angle similar to what you would
get if flying final at normal speed. Airspeed will continue to
diminish, and when you have reached the target airspeed, still
slightly above where the normal roundout would be, reduce spoilers, if
necessary, roundout and land.

Do not attempt to do the high speed roundout near the ground! Do it
in two distinct steps and all will be well. With practice, it may
appear you are doing it in a single step to a casual observer.

I don't demo this often enough to have a perfect picture in my mind
for explaining here, but I have not had any trouble talking someone
through the procedure in an ASK-21. And we do indeed end up stopping
at or before the 'normal' stopping point even though we turned final
at 800-1,000'.

-Tom

Eric Greenwell

October 22nd 07, 10:05 PM

Alastair Harrison wrote:
> Dan G wrote:
> <SNIP>
>> However I still have a question: do you dive and then return to normal
>> approach speed before rounding out, or round out at the much faster
>> speed? If the latter, does not the extra float in ground effect negate
>> the losses from extra drag in the dive, especially with a slippery
>> glass ship versus a draggy wood and fabric glider (such as one a pilot
>> might train in)?

snip

>
> I was also taught this technique on a basic instructors course (in a
> G103). But I'm always left thinking that it requires a high level of
> skill to judge the roundout correctly. Leaving it just a second too
> late would result in a rather rapid meeting with the ground. I think
> I'd rather take my chances with a side slip.

As Andreas points out, the maneuver we're talking about is performed
"high" at the early part of the final approach. When the glide to the
desired aim point "looks right", the glider is returned to the desired
approach speed (spoilers still fully out). The spoilers are then
retracted to about half way, and the approach is continued as you
normally would.

If you have to maintain the high speed all the way to the flare, you
were too high to use it. A slip might be better if you are "low" when
you decide full spoilers alone aren't enough.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

John Smith

October 22nd 07, 10:33 PM

Brian wrote:

> Frightening? Really? It actually works very well with a bit of head
> wind. Backcountry power pilots occasionally use this technique as
> well.

It's a completely different thing in a power plane. (Although I wouldn't
recommend it with power planes, either.)

A short look at a typical glider polar is all that is needed to
understand why your "technique" is a no-no. If you continue using it,
then it's only a question of time that we'll hear about you in the news.

Tom Gardner

October 22nd 07, 10:56 PM

On Oct 22, 9:23 pm, Alastair Harrison >
wrote:
> I had this demonstrated to me by a very experienced instructor in a K13.
> He had me fly a deliberately high and close in circuit until it was
> clear that we'd be a long way up the field, even with full airbrake.
> Then he took over and performed the 'energy dumping' manoeuvre, which
> involved opening full brake and pointing the nose at the ground.
>
> It all happened rather fast and was not unalarming, so my recollections
> are not exact. However, I'm fairly sure the speed never exceeded 80kts.
> Certainly the ground approached very rapidly. One moment we were in a
> gross overshoot situation and the next moment I was concerned that we
> might impact the ground before reaching the boundary wall. We came out
> of the dive, popped over wall and settled on to the ground for one of
> the shortest landings I've seen. I remember being surprised at how
> quickly we lost the excess speed. Pulling out of a near-vertical dive
> (at least that's what it felt like) with full airbrakes seems to scrub a
> lot of energy very quickly.

Once, when I was still pre-solo, with a 15kt headwind, I felt unsure
of the K13's penetration, so I deliberately turned onto finals at
about 600'
only just outside the airfield boundary. Given that its a 6000ft
landing strip,
there wasn't exactly a problem with overshoot, but there would have
been a walk.

However the instructor told me to get to 75knots and apply full
airbrake.
It felt like a 45degree dive into the ground - somewhat exhilarating.
I got serious groundrush at (I guess) about 100ft and consciously
started to pull out the dive. Very quickly I was satisfied that I
wasn't
going to hit the deck, and so returned to the roundout and pleasantly
short landing.

Overall the speed was always more than adequate for the windshear
conditions, and the plane lost height and stopped remarkably (to me)
quickly. During the debrief neither the instructor nor I was
concerned about my reactions during that manoeuver. There was
more discussion about how much deeper it would have been
sensible for me to go in K13/15kt.

Would I recommend it? Of course not!
Would I do it again? Yes, if it seemed that was the only course
of action, or if I was more skilled.

Alastair Harrison

October 22nd 07, 11:38 PM

Tom Gardner wrote:

>
> Once, when I was still pre-solo, with a 15kt headwind, I felt unsure
> of the K13's penetration, so I deliberately turned onto finals at
> about 600'
> only just outside the airfield boundary. Given that its a 6000ft
> landing strip,
> there wasn't exactly a problem with overshoot, but there would have
> been a walk.
>
> However the instructor told me to get to 75knots and apply full
> airbrake.
> It felt like a 45degree dive into the ground - somewhat exhilarating.
> I got serious groundrush at (I guess) about 100ft and consciously
> started to pull out the dive. Very quickly I was satisfied that I
> wasn't
> going to hit the deck, and so returned to the roundout and pleasantly
> short landing.
>
> Overall the speed was always more than adequate for the windshear
> conditions, and the plane lost height and stopped remarkably (to me)
> quickly. During the debrief neither the instructor nor I was
> concerned about my reactions during that manoeuver. There was
> more discussion about how much deeper it would have been
> sensible for me to go in K13/15kt.
>
> Would I recommend it? Of course not!
> Would I do it again? Yes, if it seemed that was the only course
> of action, or if I was more skilled.
>

Hello Tom. To be sure, if you ever need to be doing this at Aston Down
then you've got something very wrong :-)

The first demo given to me was at the more extreme end of what's
possible, and I think there may have been an element of willy waving on
the part of the chap demonstrating (what with the hop over the wall).
And I take the point that it's not usually necessary to finish the
manoeuvre at ground level. I was reintroduced to the technique in the
context of winch launch failures at awkward heights and positions in
short fields. Not enough height to do a 360, and marginally high for
landing ahead. So everything had to be done pretty accurately.

Alastair

Tom Gardner

October 22nd 07, 11:52 PM

On Oct 22, 11:38 pm, Alastair Harrison >
wrote:
> Hello Tom. To be sure, if you ever need to be doing this at Aston Down
> then you've got something very wrong :-)

Just so. It is a nice big target for <cough> inexperienced
</cough> pilots.

> And I take the point that it's not usually necessary to finish the
> manoeuvre at ground level.

I can only claim instinctive reactions, not pre-planned
choreography, unfortunately.

> I was reintroduced to the technique in the
> context of winch launch failures at awkward heights and positions in
> short fields. Not enough height to do a 360, and marginally high for
> landing ahead. So everything had to be done pretty accurately.

I decided not to learn at other local fields for just
that kind of reason.

P. Corbett

October 23rd 07, 12:55 AM

Regarding being high on final, there is a place for both the full
spoiler/increased approach airspeed and the slipping technique. Just as
important as being proficient doing them is knowing how to choose the
most appropriate for the conditions. For example if the wind is strong,
the full spoiler/increased speed is generally safe because losing the
energy at the bottom of the maneuver should be no problem. If the wind
is zero or very light and/or there is a long line of gliders waiting to
launch (we land and depart at 4220 MSL on the same runway at Tehachapi)
and therefore the landing runway is shorter than normal, a slip might be
most appropriate since you get a high sink rate without adding excessive
energy to get rid of at the bottom.

As for doing a 360 in the pattern, you may need a plan B when the guys
behind you take the runway away from you.

Paul
ZZ

Dan G wrote:
> On Oct 22, 5:58 pm, Eric Greenwell > wrote:
>> I find it a very useful technique if I am high enough on final to use
>> it. Generally, I use it shortly after turning final as I realize I am
>> too high, even with full spoiler. That's when I have 500' agl or so,
>> which is plenty. Going from 50 knots to 70 knots (watch the flap setting
>> speed) doubles the rate of energy loss. When I slow down to 50 knots
>> again (still at full spoiler), my new "aim point" is much closer, and I
>> can reduce the spoilers to (ideally) about half.
>
> All this is way outside my experience, and I'm not going to attempt it
> myself (though I might nobble an instructor experienced at it).
> However I still have a question: do you dive and then return to normal
> approach speed before rounding out, or round out at the much faster
> speed? If the latter, does not the extra float in ground effect negate
> the losses from extra drag in the dive, especially with a slippery
> glass ship versus a draggy wood and fabric glider (such as one a pilot
> might train in)?
>
>
> Dan
>

October 23rd 07, 01:07 AM

On Oct 22, 4:52 pm, Tom Gardner > wrote:
> > And I take the point that it's not usually necessary to finish the
> > manoeuvre at ground level.

IMHO, it's useful to demonstrate this on final approach, but a better
place to apply it in real life would be earlier in the landing
pattern. For example huge amounts of lift on downwind, so dive off
the altitude on base.

In the US southwest, where downbursts and the associated huge sink and
sometimes lift can happen, I've found myself turning a high final
expecting 40-50 knots headwind and it's vanished. I've also
experienced huge lift on base / final as the outflow curl decided to
position itself right at the end of the runway. So these are the
cases where I might be tempted to use the dive while on final
approach.

-Tom

Brian[_1_]

October 23rd 07, 01:17 AM

On Oct 22, 3:33 pm, John Smith > wrote:
> Brian wrote:
> > Frightening? Really? It actually works very well with a bit of head
> > wind. Backcountry power pilots occasionally use this technique as
> > well.
>
> It's a completely different thing in a power plane. (Although I wouldn't
> recommend it with power planes, either.)
>
> A short look at a typical glider polar is all that is needed to
> understand why your "technique" is a no-no. If you continue using it,
> then it's only a question of time that we'll hear about you in the news.

Looking at a polar is exactly why it works. It is called Speed to fly.
It really only works well when you have some headwind. It does work
somewhat in calm conditions but is really not very effective. It
probably doesn't work at all in a tailwind condition.

As noted gliders usually have a better ways of dealing with being
high. And since most people aren't excessivly high with a headwind it
does have limited use in gliders. There are really only two things
that can go wrong with using the technique and both should be easily
controllable. These are a Stall/Spin or continuing the slow approach
to too low of altitude to recover back to a normal approach speed.

Personally I seldom use it, The High Parasitic Drag approach and/or
Slips described above is usually more effective in a wider range of
conditions.

Brian

Nyal Williams

October 23rd 07, 02:13 AM

I first learned it in Minden and then refined it in
Cal City.

What the objecters have not realized is just how fast
you can bleed off tons of excess speed by lifting the
nose to the horizon with full spoilers out.

And again, the maneuver need not necessarily be carried
out to the threshold, even, much less to the round
out. You can use it to bleed off 200ft or 500ft when
you are at 1000ft on final [No, this is not the everyday
pattern or practice] and then you can lift the nose
and lose the speed when it looks like you are at the
normal height for that distance from the touchdown
point. When the speed drops to proper approach speed
you just adjust the spoilers and continue as normal.
Once you have done it it no longer appears to be a
dare-devil ride; it is entirely predictable.

At 00:12 23 October 2007, 5z wrote:
>On Oct 22, 4:52 pm, Tom Gardner wrote:
>> > And I take the point that it's not usually necessary
>>>to finish the
>> > manoeuvre at ground level.
>
>IMHO, it's useful to demonstrate this on final approach,
>but a better
>place to apply it in real life would be earlier in
>the landing
>pattern. For example huge amounts of lift on downwind,
>so dive off
>the altitude on base.
>
>In the US southwest, where downbursts and the associated
>huge sink and
>sometimes lift can happen, I've found myself turning
>a high final
>expecting 40-50 knots headwind and it's vanished.
>I've also
>experienced huge lift on base / final as the outflow
>curl decided to
>position itself right at the end of the runway. So
>these are the
>cases where I might be tempted to use the dive while
>on final
>approach.
>
>-Tom
>
>

Marc Ramsey[_2_]

October 23rd 07, 03:08 AM

Nyal Williams wrote:
> I first learned it in Minden and then refined it in
> Cal City.
>
> What the objecters have not realized is just how fast
> you can bleed off tons of excess speed by lifting the
> nose to the horizon with full spoilers out.

The objectors are pointing that there are some gliders whose spoilers
don't produce quite enough drag to manage this maneuver effectively. In
a glider that has effective spoilers (like a Ventus B) it's a blast.
But, in my experience (which were usually at 8000+ foot density
altitude), a Duo will accelerate rather quickly in a dive with full
spoilers, then take you halfway down the runway while you bleed off 15
or 20 knots of excess speed, even out of ground effect. If you bleed it
off more quickly, you're going up. I found a slipping turn to final
that is held for as long as needed to be far more effective. Your
mileage may vary...

Marc

[email protected]

October 23rd 07, 03:49 AM

On Oct 22, 7:57 am, wrote:
> On Oct 21, 11:13 am, Tim Taylor > wrote:
[snip]
> If you are THAT much too high, wouldn't it also be prudent to consider
> a large 360? It may not be pretty, but let's face it, if you have
> turned final and just THEN realized you're way too high, you've
> already lost all your style points.

Was this a serious comment? How many more people have to die to prove
you should not be suggesting turning away from the runway? A pilot was
killed in the Sierras in the last few years doing exactly this and we
had at least another major accident this year in the Sierras this year
with the same thing. It is on of the precursors to stall-spin
accidents, nasty scenarios like if unexpected lift cause the glider to
be high, the turn takes the glider out of lift, now you are going down
fast and pointing the wrong way. And low and the ground is coming up
at you, maybe I'll pull back more, push that foot to make the nose go
round, ugh, oh f!@#... Use S-turns, parasitic drag approaches, slips
etc. but don't turn away from the runway.

---

As for the high speed/paracitic drag approach Cindy Brinkner talked
about this at an SSA convention a few years ago. Maybe she has slides
available etc. I was suprised by the whispering amongst some people
in the audience about "ohh this is bad". I see it as a very useful
tool to have in your toolkit. I think Cindy's points were don't try it
by yourself - go take a ride with an knowledgeable instructor and that
in the hands of less experienced piltos in the right gliders this may
be a safer techqunique than slipping - I've seen pilots who have *no*
clue how to really slip to loose height, far too timid, nose just a
little off center - I have no idea if they were taught better and have
just forgotten or what.

Like Marc says the Duo tends to hold energy and makes this somewhat
less useful (but it still works, you do come down faster), but slips
work great in a Duo as compensation for not overly effective spoilers.
I was all set to demonstrate a parasitic drag approach in a Duo today
but the instructor doing the check ride thought a rope break would be
better :-(

Things are not black and white, I'd hope good pilots want to try out
different techniques, see what works best in different gliders and
situations and have the benefit of different tools at their disposal.

Darryl

Bruce

October 23rd 07, 07:46 AM

I have used the high speed parasitic drag approach, and others.

First point is - no-one here has mentioned that the appropriate action depends
on the wind speed and direction.

In all cases drag increases at the square of velocity.
If you have a really low drag glider that is optimised for high speed you might
not get that high a return.
In a low performance ship the results are dramatic.

Consider being way too high on final approach in a low wing loading wood and
fabric trainer. If you are in still air, or have a tail wind then diving will
work best. Maximum drag, get close to the ground, bleed speed off.
If you have a strong headwind you can slow down and increase your angle of
decent, not rate. This is the inverse calculation of working our McCready speed
for best XC distance. Here you want to reduce the distance by flying too slowly.
One hint - you will be descending through wind gradient so leave a height +
speed reserve to compensate close to the ground.

Another technique is - if you see you are too high turning onto final, why
continue the turn. Extend the base leg a bit, make a steep > 90 degree turn back
and line up. It is a sort of S turn, but more effective in that you start from
90 degrees to the landing point.

I know at least one pilot who has serious injuries from making an S turn and
losing it. So any of the approaches carries risk. We generally teach side
slipping as the preferred method, and with 6000 feet of runway - land long
rather than spin in trying to nail the threshold. Landing in a field is a
different matter.

I must agree the 360 is a bad idea. Not saying you should never do it - I did it
once to avoid conflicting traffic - but it is not advisable/comfortable to lose
sight of the runway low down. Use the appropriate one for the circumstances.

wrote:
> On Oct 22, 7:57 am, wrote:
>> On Oct 21, 11:13 am, Tim Taylor > wrote:
> [snip]
>> If you are THAT much too high, wouldn't it also be prudent to consider
>> a large 360? It may not be pretty, but let's face it, if you have
>> turned final and just THEN realized you're way too high, you've
>> already lost all your style points.
>
> Was this a serious comment? How many more people have to die to prove
> you should not be suggesting turning away from the runway? A pilot was
> killed in the Sierras in the last few years doing exactly this and we
> had at least another major accident this year in the Sierras this year
> with the same thing. It is on of the precursors to stall-spin
> accidents, nasty scenarios like if unexpected lift cause the glider to
> be high, the turn takes the glider out of lift, now you are going down
> fast and pointing the wrong way. And low and the ground is coming up
> at you, maybe I'll pull back more, push that foot to make the nose go
> round, ugh, oh f!@#... Use S-turns, parasitic drag approaches, slips
> etc. but don't turn away from the runway.
>
> ---
>
> As for the high speed/paracitic drag approach Cindy Brinkner talked
> about this at an SSA convention a few years ago. Maybe she has slides
> available etc. I was suprised by the whispering amongst some people
> in the audience about "ohh this is bad". I see it as a very useful
> tool to have in your toolkit. I think Cindy's points were don't try it
> by yourself - go take a ride with an knowledgeable instructor and that
> in the hands of less experienced piltos in the right gliders this may
> be a safer techqunique than slipping - I've seen pilots who have *no*
> clue how to really slip to loose height, far too timid, nose just a
> little off center - I have no idea if they were taught better and have
> just forgotten or what.
>
> Like Marc says the Duo tends to hold energy and makes this somewhat
> less useful (but it still works, you do come down faster), but slips
> work great in a Duo as compensation for not overly effective spoilers.
> I was all set to demonstrate a parasitic drag approach in a Duo today
> but the instructor doing the check ride thought a rope break would be
> better :-(
>
> Things are not black and white, I'd hope good pilots want to try out
> different techniques, see what works best in different gliders and
> situations and have the benefit of different tools at their disposal.
>
> Darryl
>
>

nimbusgb

October 23rd 07, 11:30 AM

On 22 Oct, 22:33, John Smith > wrote:
> Brian wrote:
> > Frightening? Really? It actually works very well with a bit of head
> > wind. Backcountry power pilots occasionally use this technique as
> > well.
>
> It's a completely different thing in a power plane. (Although I wouldn't
> recommend it with power planes, either.)
>
> A short look at a typical glider polar is all that is needed to
> understand why your "technique" is a no-no. If you continue using it,
> then it's only a question of time that we'll hear about you in the news.

Anyone tried option 4?

Stuffing the nose right down for 3 or 4 seconds will easily lose you
50m or more with only a small increase in airspeed since Newton gets
involved in the exercise. A bit of increased spoiler will overcome
that increase quickly. What's more you are playing with the safe side
of the energy curve!

To the poster who said that condor may not be a good tool to test
this. I suggest you try a copy. It really is a great sim and the
flight dynamics are superb. I believe that Lasham gliding club took
one ab-initio student right to solo standard on a sim before one or
two real circuits to get him away. Sims have come a long way.

Ian M

[email protected]

October 23rd 07, 12:36 PM

On Oct 22, 12:46 pm, Marc Ramsey > wrote:
> I've found that the Duo Discus does not take kindly to excessive speed on
> approach. There is no elegant way to bleed off the excess energy, you
> end up either floating down the runway, or forcing it down hot and
> jamming on the brakes. It is best to maintain a proper approach speed
> with full dive brakes and slip or S-turn as needed. I've heard that the
> Libelle behaves in a similar fashion...
>
> Marc

Hey Marc - The Duo spoilers are much maligned,
but often the problem is the wheelbrake.

Huh ?

Well, the wheelbrake engages at the end of the spoiler
travel. The mechanism is, well, um, even though its a
Cleveland wheel, the mechanism and hydraulics are
shall we say a bit confused.

So, people try to "tighten" the wheelbrake, and end up
just restricting the spoiler travel. And half the time the
wheelbrake still doesn't work.

Anybody have the measurement from wing surface
to spoiler cap, spoiler fully extended, on a properly
adjusted Duo so folks can do a quick check ? I'll
try get one of my partners to measure ours next
weekend...

And yes, I've seen this on Duo's in a number of
different locations...

Hope this helps,
Best Regards, Dave "YO"

PS: Yes, our Duo has effective spoilers, and its
the original model. But we don't trust the brake !

toad

October 23rd 07, 01:18 PM

On Oct 23, 6:30 am, nimbusgb > wrote:
....snip...
> To the poster who said that condor may not be a good tool to test
> this. I suggest you try a copy. It really is a great sim and the
> flight dynamics are superb. I believe that Lasham gliding club took
> one ab-initio student right to solo standard on a sim before one or
> two real circuits to get him away. Sims have come a long way.
>
> Ian M

I am planning on buying a copy and for general flying and basic
training I see great value in simulators. But the original posting
was about doing a flight test to determine performance such as descent
rates with spoilers extended, turns back to the airport, etc. Any
such data requires that not only does the simulator have all the right
aerodynamics models, but that it has complete and accurate data for
your specific model of glider. I doubt that Condor has test flown
every glider model extensively enough to confirm the accuracy of their
results.

BTW, I program flight simulators for SIkorsky AIrcraft. One of my
bosses has a rule "all simulators are guilty until proven innocent"

Todd Smith

Marc Ramsey[_2_]

October 23rd 07, 03:02 PM

wrote:
> Hey Marc - The Duo spoilers are much maligned,
> but often the problem is the wheelbrake.
>
> Huh ?
>
> Well, the wheelbrake engages at the end of the spoiler
> travel. The mechanism is, well, um, even though its a
> Cleveland wheel, the mechanism and hydraulics are
> shall we say a bit confused.

You may be right, our Duo had a great wheelbrake (almost disconcertingly
so), but relatively poor spoilers. That's not the say they were a
problem, just that one developed slightly different techniques for
arriving in an elegant fashion. In particular, in calm conditions I
preferred long shallow finals. In hairier situations, a slipping turn
to final with full spoilers allowed excellent control over descent rate,
with the added benefit that I could actually see the runway from the
back seat ;^)

I think the Duo Discus X does a great job of addressing the glidepath
control issue (imagined or not). When I win the lottery, after I order
my Antares, the DDX comes next...

Marc

Bill Daniels

October 23rd 07, 03:50 PM

"Marc Ramsey" > wrote in message
. ..
> wrote:
>> Hey Marc - The Duo spoilers are much maligned,
>> but often the problem is the wheelbrake.
>>
>> Huh ?
>>
>> Well, the wheelbrake engages at the end of the spoiler
>> travel. The mechanism is, well, um, even though its a
>> Cleveland wheel, the mechanism and hydraulics are
>> shall we say a bit confused.
>
> You may be right, our Duo had a great wheelbrake (almost disconcertingly
> so), but relatively poor spoilers. That's not the say they were a
> problem, just that one developed slightly different techniques for
> arriving in an elegant fashion. In particular, in calm conditions I
> preferred long shallow finals. In hairier situations, a slipping turn to
> final with full spoilers allowed excellent control over descent rate, with
> the added benefit that I could actually see the runway from the back seat
> ;^)
>
> I think the Duo Discus X does a great job of addressing the glidepath
> control issue (imagined or not). When I win the lottery, after I order my
> Antares, the DDX comes next...
>
> Marc

I think the Duo's airbrakes are better than many people think. The Duo is a
big heavy glider with lots of inertia. It doesn't like to change direction
quickly. That includes its behavior on sudden airbrake deployment. You
don't get a lot of sink right away.

My first reaction was that the airbrakes were weak but a little more
experience showed me that with a little patience, the brakes took effect and
produced a respectable decent rate. The Duo just makes you plan ahead a
little more than with a light single seater.

Bill Daniels

Bert Willing[_2_]

October 23rd 07, 04:13 PM

There are other big heavier gliders with lots of inertia, and they react
very well and immediately to the deployment of airbreaks.
Those on the original DuoDiscus are just a very bad design. But, as Marc
pointed out, a sideslip works well AND gets you a visual on the airfield
from the back seat (the second very bad design glitch of the Duo).

Bert

"Bill Daniels" <bildan@comcast-dot-net> wrote in message > I think the Duo's
airbrakes are better than many people think. The Duo is a
> big heavy glider with lots of inertia. It doesn't like to change
> direction quickly. That includes its behavior on sudden airbrake
> deployment. You don't get a lot of sink right away.
>
> My first reaction was that the airbrakes were weak but a little more
> experience showed me that with a little patience, the brakes took effect
> and produced a respectable decent rate. The Duo just makes you plan ahead
> a little more than with a light single seater.
>
> Bill Daniels
>

Nyal Williams

October 23rd 07, 05:25 PM

Certainly there are some gliders with inadequate divebrakes.
A modification was applied to the Cirrus. I've not
flown a Duo; perhaps it needs a mod; thin airfoils
are not conducive to installing wide vertical plates.

At 02:12 23 October 2007, Marc Ramsey wrote:
>Nyal Williams wrote:
>> I first learned it in Minden and then refined it in
>> Cal City.
>>
>> What the objecters have not realized is just how fast
>> you can bleed off tons of excess speed by lifting
>>the
>> nose to the horizon with full spoilers out.
>
>The objectors are pointing that there are some gliders
>whose spoilers
>don't produce quite enough drag to manage this maneuver
>effectively. In
>a glider that has effective spoilers (like a Ventus
>B) it's a blast.
>But, in my experience (which were usually at 8000+
>foot density
>altitude), a Duo will accelerate rather quickly in
>a dive with full
>spoilers, then take you halfway down the runway while
>you bleed off 15
>or 20 knots of excess speed, even out of ground effect.
> If you bleed it
>off more quickly, you're going up. I found a slipping
>turn to final
>that is held for as long as needed to be far more effective.
> Your
>mileage may vary...
>
>Marc
>

John Galloway[_1_]

October 23rd 07, 07:24 PM

as an ex Duo owner I agree with Dave Nadler and Bill
Daniels; the Duo airbrakes are better than their reputation:

The manual says the give a glide angle of 6.7:1 (which
fits with my measurements of 800fpm descent rate) at
approach speed which isn't barn door but should be
adequate. My D2cT manual quotes the same approach
glide angle (I observe the same sink rate of 800fpm)
- and reviewers assess the D2c airbrakes as very good.
I made the same observation as Bill about the Duo
brakes taking a couple of seconds for the drag to build
up - I thought it had something to do with a more turbulent
airflow as the trim changes nose down with the brakes
deployed(??)

The Duo airbrakes need a very strong pull to fully
open them - but this is aided on later ones by a mod
to the control linkage (also available as a simple
retrofit)

Also, our Duo was delivered with the airbrake lever
actuated hydraulic wheel brake picking up well before
full airbrake and I initially found it almost impossible
to pull full airbrake - it is easy to adjust the wheelbrake
and this, along with the linkage mod, helped a lot.

However our wheel brake was so effective that if the
glider touched down on grass with the wheel brake fully
on then the wheel didn't turn and the glider bounced
as if it had hit a rock. As a result I always had to
close the airbrakes a little before touch down which
increased float.

John Galloway

At 15:18 23 October 2007, Bert Willing wrote:
>There are other big heavier gliders with lots of inertia,
>and they react
>very well and immediately to the deployment of airbreaks.
>Those on the original DuoDiscus are just a very bad
>design. But, as Marc
>pointed out, a sideslip works well AND gets you a visual
>on the airfield
>from the back seat (the second very bad design glitch
>of the Duo).
>
>Bert
>
>'Bill Daniels' wrote in message > I think the Duo's
>>
>airbrakes are better than many people think. The Duo
>is a
>> big heavy glider with lots of inertia. It doesn't
>>like to change
>> direction quickly. That includes its behavior on
>>sudden airbrake
>> deployment. You don't get a lot of sink right away.
>>
>> My first reaction was that the airbrakes were weak
>>but a little more
>> experience showed me that with a little patience,
>>the brakes took effect
>> and produced a respectable decent rate. The Duo just
>>makes you plan ahead
>> a little more than with a light single seater.
>>
>> Bill Daniels
>>
>
>
>

John Smith

October 23rd 07, 08:00 PM

John Galloway schrieb:

> The manual says the give a glide angle of 6.7:1 (which
> fits with my measurements of 800fpm descent rate) at
> approach speed

Very interesting, indeed:

JAR 22.75 Descent, approach
It must be shown that the sailplane has a glide
slope not flatter than one in seven at a speed of
1·3 VS0 with air brakes extended at maximum
weight.

Marc Ramsey

October 23rd 07, 08:00 PM

John Galloway wrote:
> as an ex Duo owner I agree with Dave Nadler and Bill
> Daniels; the Duo airbrakes are better than their reputation:

Well, clearly, not all current and former Duo owners agree. Perhaps I'm
used to gliders with very effective spoilers, including various DG
models, ASW20s, Ventus Bs, etc. But, after 200 or so hours in our Duo
(and a couple of others in the area), I'll simply say that the spoilers
were workable with proper approach planning and airspeed, and that it
remains the only glider I've ever felt the need to slip on a routine
basis...

Marc

Andy[_1_]

October 23rd 07, 09:00 PM

On Oct 22, 9:12 am, Nyal Williams
> Forward slip in glass gliders won't get you much descent;

The ASW-19 and ASW-28 have a huge increase in sink rate in a full
rudder slip compared with airbrakes alone. What glass gliders are
you flying that do not slip well? Can you maintain a full rudder
slip, and I mean rudder on the stop and never comes off it until you
choose to exit the slip?

Andy

Gary Emerson

October 23rd 07, 11:12 PM

Bill Daniels wrote:
> "Marc Ramsey" > wrote in message
> . ..
>> wrote:
>>> Hey Marc - The Duo spoilers are much maligned,
>>> but often the problem is the wheelbrake.
>>>
>>> Huh ?
>>>
>>> Well, the wheelbrake engages at the end of the spoiler
>>> travel. The mechanism is, well, um, even though its a
>>> Cleveland wheel, the mechanism and hydraulics are
>>> shall we say a bit confused.
>> You may be right, our Duo had a great wheelbrake (almost disconcertingly
>> so), but relatively poor spoilers. That's not the say they were a
>> problem, just that one developed slightly different techniques for
>> arriving in an elegant fashion. In particular, in calm conditions I
>> preferred long shallow finals. In hairier situations, a slipping turn to
>> final with full spoilers allowed excellent control over descent rate, with
>> the added benefit that I could actually see the runway from the back seat
>> ;^)
>>
>> I think the Duo Discus X does a great job of addressing the glidepath
>> control issue (imagined or not). When I win the lottery, after I order my
>> Antares, the DDX comes next...
>>
>> Marc
>
> I think the Duo's airbrakes are better than many people think. The Duo is a
> big heavy glider with lots of inertia. It doesn't like to change direction
> quickly. That includes its behavior on sudden airbrake deployment. You
> don't get a lot of sink right away.
>
> My first reaction was that the airbrakes were weak but a little more
> experience showed me that with a little patience, the brakes took effect and
> produced a respectable decent rate. The Duo just makes you plan ahead a
> little more than with a light single seater.
>
> Bill Daniels
>
>
I've flown plenty in the Duo and while the dive brakes are not the most
powerful around, they do just fine. One is hard pressed to find a
glider that handles as well, with great performance. I wish I still had
it, and look forward to the day when I can order another Duo.

Nyal Williams

October 23rd 07, 11:12 PM

That was probably an overstatement; I meant as compared
to the HPDA. I have not flown a 19 or 28. I fly a
Discus B and a G-103 regularly, along with Blanik L-23s
for instructing. The Blaniks are the worst, and not
glass, of course. A fully locked rudder slip won't
allow much opposite aileron before it starts to turn
off course. Of course, that is not glass, (and I almost
made an anadiplosis there.)

At 20:06 23 October 2007, Andy wrote:
>On Oct 22, 9:12 am, Nyal Williams
>> Forward slip in glass gliders won't get you much descent;
>
>The ASW-19 and ASW-28 have a huge increase in sink
>rate in a full
>rudder slip compared with airbrakes alone. What glass
>gliders are
>you flying that do not slip well? Can you maintain
>a full rudder
>slip, and I mean rudder on the stop and never comes
>off it until you
>choose to exit the slip?
>
>
>Andy
>
>

October 24th 07, 02:06 AM

On Oct 23, 2:00 pm, Marc Ramsey > wrote:
> John Galloway wrote:
> > as an ex Duo owner I agree with Dave Nadler and Bill
> > Daniels; the Duo airbrakes are better than their reputation:
>
> Well, clearly, not all current and former Duo owners agree.

My 2c: (Our club has a duo, so based on some experience.) The actual
glide angle of the duo, with full spoilers out and at a stable
approach speed, is decently steep. Looking at this angle at altitude
is instructive. The duo seems not to lose speed as quickly as other
gliders when you open the spoilers, especially in ground effect. "Too
high" really often means "too fast". I think a lot of the perception
that the duo has poor divebreakes is realy that it does not slow down
fast, rather than the actual steady state glide angle is shallow.

This all makes some aerodynamic sense. The duo is heavier than basic
trainers, and much heavier than the single seaters we are used to.
"Spoilers" work as much by "spoiling lift" as by "increasing drag",
and much of the latter is induced drag due to the gap in the lift
distribution anyway.

John Cochrane

Marc Ramsey[_2_]

October 24th 07, 02:29 AM

BB wrote:
> On Oct 23, 2:00 pm, Marc Ramsey > wrote:
>> John Galloway wrote:
>>> as an ex Duo owner I agree with Dave Nadler and Bill
>>> Daniels; the Duo airbrakes are better than their reputation:
>> Well, clearly, not all current and former Duo owners agree.
>
> My 2c: (Our club has a duo, so based on some experience.) The actual
> glide angle of the duo, with full spoilers out and at a stable
> approach speed, is decently steep. Looking at this angle at altitude
> is instructive. The duo seems not to lose speed as quickly as other
> gliders when you open the spoilers, especially in ground effect. "Too
> high" really often means "too fast". I think a lot of the perception
> that the duo has poor divebreakes is realy that it does not slow down
> fast, rather than the actual steady state glide angle is shallow.
>
> This all makes some aerodynamic sense. The duo is heavier than basic
> trainers, and much heavier than the single seaters we are used to.
> "Spoilers" work as much by "spoiling lift" as by "increasing drag",
> and much of the latter is induced drag due to the gap in the lift
> distribution anyway.

That's how this whole discussion got started. Someone suggested that
the best thing to do when high on final is to dive with full spoilers,
pull up above ground effect and wait for the speed to bleed off. I said
that won't work too well with a Duo, as with full spoilers it isn't all
that draggy, will accelerate relatively quickly, and bleed off speed
slowly. Others said nonsense, the Duo has wonderful spoilers. And so
on, and so on...

Marc

October 24th 07, 03:08 AM

> That's how this whole discussion got started.

What, RAS going around in circles (in sink!) ? Unheard of!

I haven't tried the high parasitic drag maneuver in a duo yet. When
demonstrated by Marty Eiler in an ASK 21, it consisted of a near VNE
dive to the ground well short of the intended landing area, and then
bleeding off the speed quite low. The key is that you lose so much
energy near VNE with spoilers out, you can afford now to bleed off
speed, even in ground effect. Most of our duo discussions have not
invovlved such high speeds -- I'm curious how it might work. I know
that being high, 80 knots and aiming at the spot in a duo is a bad
combination, but that's not what we're taling about!

As fun as the high parasitic drag maneuver is, I wonder if anyone has
ever actually used it in combat. Has anyone been so flustered and out
of synch to get monstrously high in an off field landing, then had the
presence of mind and skill left to dive to the ground at near VNE,
aiming several hundreds of yards short of the intended small paddock
with fence at the far end, and had it work? The mental attitude that
gets to the problem seems incompatible with the attitude needed to
pull this one off. If you don't aim short enough in the dive, you just
crash into the far fence at really high speed. But I'd be curious to
hear a "it worked for me" story.

John Cochrane

[email protected]

October 24th 07, 03:15 AM

On Oct 23, 6:29 pm, Marc Ramsey > wrote:
> BB wrote:
[snip]
> That's how this whole discussion got started. Someone suggested that
> the best thing to do when high on final is to dive with full spoilers,
> pull up above ground effect and wait for the speed to bleed off. I said
> that won't work too well with a Duo, as with full spoilers it isn't all
> that draggy, will accelerate relatively quickly, and bleed off speed
> slowly. Others said nonsense, the Duo has wonderful spoilers. And so
> on, and so on...
>
> Marc

Then why don't you slip it in? The Duo slips quite well.

Darryl

(Sorry Marc I could not resist :-) )

Bill Daniels

October 24th 07, 03:46 AM

"BB" > wrote in message
ups.com...
>> That's how this whole discussion got started.
>
> What, RAS going around in circles (in sink!) ? Unheard of!
>
> I haven't tried the high parasitic drag maneuver in a duo yet. When
> demonstrated by Marty Eiler in an ASK 21, it consisted of a near VNE
> dive to the ground well short of the intended landing area, and then
> bleeding off the speed quite low. The key is that you lose so much
> energy near VNE with spoilers out, you can afford now to bleed off
> speed, even in ground effect. Most of our duo discussions have not
> invovlved such high speeds -- I'm curious how it might work. I know
> that being high, 80 knots and aiming at the spot in a duo is a bad
> combination, but that's not what we're taling about!
>
> As fun as the high parasitic drag maneuver is, I wonder if anyone has
> ever actually used it in combat. Has anyone been so flustered and out
> of synch to get monstrously high in an off field landing, then had the
> presence of mind and skill left to dive to the ground at near VNE,
> aiming several hundreds of yards short of the intended small paddock
> with fence at the far end, and had it work? The mental attitude that
> gets to the problem seems incompatible with the attitude needed to
> pull this one off. If you don't aim short enough in the dive, you just
> crash into the far fence at really high speed. But I'd be curious to
> hear a "it worked for me" story.
>
> John Cochrane
>

I have tried it with my big wing glider and for me the 'high parasite drag'
approach doesn't work unless you shift to a airspeed stabilized approach no
lower than 100 feet AGL.

My reasoning is that the ground effect starts at about a wingspan above the
ground so the bigger the wing the higher it starts. Just above the runway,
ground effect roughly doubles the L/D, (i.e. ~7:1 with full spoilers becomes
14:1) so in ground effect is a bad place to try to scrub off energy.

The key to the Duo spoilers seems to be a stabilized approach. It's a
really slippery glider and it's easy to let the airspeed creep up once your
eyes are on the aim point. In low wind/low turbulence conditions, nailing
the airspeed right on the yellow triangle while holding the glideslope to
the aim point can result in a fairly short landing. You can fly much higher
airspeed in the patern and on long final as long as the airspeed is reduced
to the calculated reference airspeed on short final.

Bill Daniels

Marc Ramsey[_2_]

October 24th 07, 03:50 AM

BB wrote:
> As fun as the high parasitic drag maneuver is, I wonder if anyone has
> ever actually used it in combat. Has anyone been so flustered and out
> of synch to get monstrously high in an off field landing, then had the
> presence of mind and skill left to dive to the ground at near VNE,
> aiming several hundreds of yards short of the intended small paddock
> with fence at the far end, and had it work? The mental attitude that
> gets to the problem seems incompatible with the attitude needed to
> pull this one off. If you don't aim short enough in the dive, you just
> crash into the far fence at really high speed. But I'd be curious to
> hear a "it worked for me" story.

In reality, I almost always have too little altitude rather than too
much when I'm trying to sneek into a field. I did use this sort of
technique with my Ventus a couple of times to get over trees and into
short fields, but it had trailing edge dive brakes that would allow me
to hold 60 to 65 knots in a dive, then round out, slow down, and plop it
in. There is no way I could make that work in a Duo, or most other
gliders...

Marc

Louis McDonald

October 24th 07, 04:27 AM

Back to Tim's original question ---- it appears that the effectiveness of
the high parasite drag (HPD) approach varies depending on the glider. Even
if we don't have the absolute speed polar of a given glider with the
spoilers out, we should be able to figure out a relative measurement that
gives us some idea of a "good" HPD glider vs a "not so good" HPD glider.
It's been about 26 years since my last aero course, but I think I remember
that the term we care about here is wetted area; however you smarter people
please correct me as needed. The measure I propose would be:

Wetted area clean / wetted area with full spoilers, then multiply by the
wing loading. The bigger the number - the less effective the HPD maneuver
in that glider. Maybe we don't even need the wing loading - I'm not
certain, but it would seem reasonable to me that the HPD maneuver would be
progressively less effective with higher wing loadings.

Alright --- ready to be shot full of holes.

Lou McDonald
"LM"

"Tim Taylor" > wrote in message
ps.com...
>I am working though some calculations and need the sink rate as a
> function of speed with the spoilers fully extended. Does anyone know
> of such data for a glider? How do spoilers extended affect sink rate
> as a function of speed?
>
> Thanks,
>
> Tim
>

Tim Taylor

October 24th 07, 10:36 AM

High on Final, Summary

Thanks to all that have given input so far. My original intent was to
do some modeling before starting the discussion, but this is RAS and
it has a life of it's own.

So here is the issue. You are high on final and full spoilers are to
enough; what do you do?

List of options so far:

1. Slip
2. "S" turns
3. Dive until intercepting normal angle for spoilers
4. Dive until near the ground, then decelerate
5. Slow down until intercepting normal angle for spoilers
6. 360 degree turn

Unfortunately I still don't have good data for what happens to the
polar as speed increases with the spoilers open. Condor was a good
suggestion, and I am working to see if I can get meaningful data from
it.

John Cochrane brought the discussion back to the real point which is
what would you use in the real world? It is interesting but not that
useful to discuss how you do this at your home airport with 2500 to
9000 feet of runway and know precisely the field elevation. When your
aircraft and your own safety are on the line in a real off-field, what
are you going to do?

This is where I find teaching some of these other techniques
interesting, but possibly dangerous. The rule of primacy for learning
or as the Doobie Brothers album from the 70's title "What were once
vices are now habits" suggests we will do in an emergency what we have
practiced. Is someone really going to dive a glider to the ground and
pull out to land in a short off field landing? Is there really a need
to be on the ground 10 seconds faster than using some of the other
techniques? Maybe only if a severe thunderstorm is approaching and
you must be on the ground now. I think in general the high parasitic
drag technique being taught by some schools is a hyped method that may
give some less experienced pilots the idea this is a good technique to
use for off-field landings. I think it is time to get back to basics
and teach sound techniques that provide the best tools for pilots to
use day in and day out.

The dive until intercepting normal angle for spoilers has some merit,
but I still think should be used with caution. Why, because we train
to look at landings from a specific angle for a narrow range of
landing speeds. To dive at high speed leaves the aircraft with a much
greater kinetic energy that must still be lost someplace. Depending
on the ship type some may take much longer to dissipate this excess
and make it more difficult to precisely hit a touch down point. Often
the greater sink rate is held up as the reason for using this
technique. It is true that sink rate goes up with speed, but the
actual decent angle does not go up nearly as much. For my Ventus B at
45 knots descent rate is 122 ft/min while at 135 knots it is 894 ft/
min, but actual loss per nautical mile is 163 ft/ktm verses 397 ft/
ktm. The other thing we don't mention is the average pilot going to
handle the decision making process better at higher speeds and less
time? At stable speeds it takes about 11 seconds to lose 300 feet at
135 knots with the spoilers out verses 22 seconds at 45 knots. Do we
need that extra time to make proper judgment and fine adjustments to
hit a target for a tight off-field landing?

Ok, lets try a hypothetical (well maybe not, been there done that ;-)
off-field landing.

The situation: You are 70 miles from home over unfamiliar territory
(read not sure of exact elevation of the terrain below, your altimeter
is useless now). You have gone for a Cu over a dry lake bed and it
doesn't work. You have selected a landing site in the lake bed that
is about 350 feet long and 100 feet wide that looks safe to land.
There are tree stumps and other object in other parts of the lakebed.
There are no obstructions on the ends of the site so you can do a
normal approach. The winds are 15 to 20mph out of the south so you
are landing from the north to south. As you drop lower you make a
rectangular pattern over the site checking for any missed obstacles.
The downwind is fast with the tailwind, as you turn base you estimate
you are 400 feet. Your adrenaline is pumping as you prepare for a
fairly technical landing. You want to keep it close so that you don't
end up short back into the wind and you turn base a little too soon.
You are on short final about 350 feet, but about 100 feet over full
spoilers decent. What do you do?

Slip?
"S" turns?
Dive until intercepting normal angle for spoilers?
Dive until near the ground, and then decelerate?
Slow down until intercepting normal angle for spoilers?
360 degree turn?

In the real world nearly 15 years ago this was in a 1970 "A" model
Standard Cirrus. If you think the Duo will float try the Standard
Cirrus. What should we be teaching students? You are somewhere
between 11 and 30 seconds from being on the ground and that 100 extra
feet will take you past the whole safe landing area and into the tree
stumps.

Dive until intercepting normal angle for spoilers?

Maybe, but can you dive, lose the altitude, decelerate and get it on
the ground for a tail wheel first, full stall landing? I would give
this a 6 out of 10. This also shortens the time available to make
adjustments and requires rapid and precise decisions.

Dive until near the ground, and then decelerate?

My guess is your chances are slim that you can pull this off and get
the ship stopped. Especially, if you were flying my Std. Cirrus. My
rating is a 1 out of 10.

360 degree turn?

I never like to turn my back on a field. Low and with the winds a
good result is not likely. My rating is a 0 out of 10.

Slow down until intercepting normal angle for spoilers?

This technique is useful for very high approaches, but must be broken
off before 300 feet agl because you must have height to accelerate and
be able to recover from any inadvertent stalls. From about 1000 feet
to 500 feet this technique has the advantage of giving a higher decent
rate and giving the pilot more time to evaluate the situation, but the
pilot must be ready to respond to any sign of stall. My rating is a 0
out of 10 here.

"S" turns?

This might be useful. You are low, but may have time to extend the
your descent. Any turn at this point will require nearly at least 180
degrees of turning (45 away, 90 back and 45 back to final.) and up to
360 degrees with three changes in direction and roll. The advantage
is your speed stays constant and you can see the touchdown point the
whole time. A disadvantages is you are no longer lined up on the
target so your perception changes as you roll and move to the side.
My rating is a 7 out of 10 here.

Slip?

The forward slip can be very effective at bringing "most" ships down.
Check you flight manual of your aircraft and practice at altitude.
The old joke about you could always tell who the Std. Cirrus and
Libelle pilots were because they were slipping on final is true. But
we got very good at it. It would nearly double the sink rate and when
kicked out you were nearly at the correct speed. The Std. Cirrus if
flown even 5 knots too fast would float a long way before settling.
The nice thing about a slip is your speed and angles all stay the same
without speeding up the process. You can use your trained judgment to
say the angle looks about right here and kick out of the slip and
proceed with a normal landing. My rating is a 10 out of 10 here.

Summary
Each situation is different, but I think we should focus on teaching
techniques that are robust and give that average pilot the best
opportunity to have a good outcome in an off-field landing. I know of
very few off-field landings that start at 1000 feet at the end of down
wind. If I have found that much lift on downwind I have cycled the
gear and am climbing out, not landing. Any technique that requires
bleeding speed in ground effect should not be taught as anything other
than a curiosity and never considered for off-filed landings.

Andy[_1_]

October 24th 07, 01:42 PM

On Oct 23, 3:12 pm, Nyal Williams
>A fully locked rudder slip won't allow much opposite aileron before it >starts to turn off course.

Was that comment related to a specific type or was it a general
comment on characteristics of all gliders?

Specific to the ASW-19B (that I owned and with the CG I flew it at) -
I could sustain a stable slip with full airbrakes, gear down, with
the rudder on the stop and the stick hard in the opposite corner. I
practiced this at the start of every season and it saved a couple of
very tight off airport landings for me.

Andy

Andy[_1_]

October 24th 07, 01:57 PM

On Oct 21, 12:23 am, Tim Taylor > wrote:
> I am working though some calculations and need the sink rate as a
> function of speed with the spoilers fully extended. Does anyone know
> of such data for a glider? How do spoilers extended affect sink rate
> as a function of speed?

I have one data point for the ASW 19B. Gear down, full airbrake, IAS
90kts, sink 3,300fpm. Flight data 4/20/91 EW barograph.

Andy

[email protected]

October 24th 07, 02:09 PM

On Oct 24, 5:36 am, Tim Taylor > wrote:
> High on Final, Summary
>
> Thanks to all that have given input so far. My original intent was to
> do some modeling before starting the discussion, but this is RAS and
> it has a life of it's own.
>
> So here is the issue. You are high on final and full spoilers are to
> enough; what do you do?
>
> List of options so far:
>
> 1. Slip
> 2. "S" turns
> 3. Dive until intercepting normal angle for spoilers
> 4. Dive until near the ground, then decelerate
> 5. Slow down until intercepting normal angle for spoilers
> 6. 360 degree turn
>
> Unfortunately I still don't have good data for what happens to the
> polar as speed increases with the spoilers open. Condor was a good
> suggestion, and I am working to see if I can get meaningful data from
> it.
>
> John Cochrane brought the discussion back to the real point which is
> what would you use in the real world? It is interesting but not that
> useful to discuss how you do this at your home airport with 2500 to
> 9000 feet of runway and know precisely the field elevation. When your
> aircraft and your own safety are on the line in a real off-field, what
> are you going to do?
>
> This is where I find teaching some of these other techniques
> interesting, but possibly dangerous. The rule of primacy for learning
> or as the Doobie Brothers album from the 70's title "What were once
> vices are now habits" suggests we will do in an emergency what we have
> practiced. Is someone really going to dive a glider to the ground and
> pull out to land in a short off field landing? Is there really a need
> to be on the ground 10 seconds faster than using some of the other
> techniques? Maybe only if a severe thunderstorm is approaching and
> you must be on the ground now. I think in general the high parasitic
> drag technique being taught by some schools is a hyped method that may
> give some less experienced pilots the idea this is a good technique to
> use for off-field landings. I think it is time to get back to basics
> and teach sound techniques that provide the best tools for pilots to
> use day in and day out.
>
> The dive until intercepting normal angle for spoilers has some merit,
> but I still think should be used with caution. Why, because we train
> to look at landings from a specific angle for a narrow range of
> landing speeds. To dive at high speed leaves the aircraft with a much
> greater kinetic energy that must still be lost someplace. Depending
> on the ship type some may take much longer to dissipate this excess
> and make it more difficult to precisely hit a touch down point. Often
> the greater sink rate is held up as the reason for using this
> technique. It is true that sink rate goes up with speed, but the
> actual decent angle does not go up nearly as much. For my Ventus B at
> 45 knots descent rate is 122 ft/min while at 135 knots it is 894 ft/
> min, but actual loss per nautical mile is 163 ft/ktm verses 397 ft/
> ktm. The other thing we don't mention is the average pilot going to
> handle the decision making process better at higher speeds and less
> time? At stable speeds it takes about 11 seconds to lose 300 feet at
> 135 knots with the spoilers out verses 22 seconds at 45 knots. Do we
> need that extra time to make proper judgment and fine adjustments to
> hit a target for a tight off-field landing?
>
> Ok, lets try a hypothetical (well maybe not, been there done that ;-)
> off-field landing.
>
> The situation: You are 70 miles from home over unfamiliar territory
> (read not sure of exact elevation of the terrain below, your altimeter
> is useless now). You have gone for a Cu over a dry lake bed and it
> doesn't work. You have selected a landing site in the lake bed that
> is about 350 feet long and 100 feet wide that looks safe to land.
> There are tree stumps and other object in other parts of the lakebed.
> There are no obstructions on the ends of the site so you can do a
> normal approach. The winds are 15 to 20mph out of the south so you
> are landing from the north to south. As you drop lower you make a
> rectangular pattern over the site checking for any missed obstacles.
> The downwind is fast with the tailwind, as you turn base you estimate
> you are 400 feet. Your adrenaline is pumping as you prepare for a
> fairly technical landing. You want to keep it close so that you don't
> end up short back into the wind and you turn base a little too soon.
> You are on short final about 350 feet, but about 100 feet over full
> spoilers decent. What do you do?
>
> Slip?
> "S" turns?
> Dive until intercepting normal angle for spoilers?
> Dive until near the ground, and then decelerate?
> Slow down until intercepting normal angle for spoilers?
> 360 degree turn?
>
> In the real world nearly 15 years ago this was in a 1970 "A" model
> Standard Cirrus. If you think the Duo will float try the Standard
> Cirrus. What should we be teaching students? You are somewhere
> between 11 and 30 seconds from being on the ground and that 100 extra
> feet will take you past the whole safe landing area and into the tree
> stumps.
>
> Dive until intercepting normal angle for spoilers?
>
> Maybe, but can you dive, lose the altitude, decelerate and get it on
> the ground for a tail wheel first, full stall landing? I would give
> this a 6 out of 10. This also shortens the time available to make
> adjustments and requires rapid and precise decisions.
>
> Dive until near the ground, and then decelerate?
>
> My guess is your chances are slim that you can pull this off and get
> the ship stopped. Especially, if you were flying my Std. Cirrus. My
> rating is a 1 out of 10.
>
> 360 degree turn?
>
> I never like to turn my back on a field. Low and with the winds a
> good result is not likely. My rating is a 0 out of 10.
>
> Slow down until intercepting normal angle for spoilers?
>
> This technique is useful for very high approaches, but must be broken
> off before 300 feet agl because you must have height to accelerate and
> be able to recover from any inadvertent stalls. From about 1000 feet
> to 500 feet this technique has the advantage of giving a higher decent
> rate and giving the pilot more time to evaluate the situation, but the
> pilot must be ready to respond to any sign of stall. My rating is a 0
> out of 10 here.
>
> "S" turns?
>
> This might be useful. You are low, but may have time to extend the
> your descent. Any turn at this point will require nearly at least 180
> degrees of turning (45 away, 90 back and 45 back to final.) and up to
> 360 degrees with three changes in direction and roll. The advantage
> is your speed stays constant and you can see the touchdown point the
> whole time. A disadvantages is you are no longer lined up on the
> target so your perception changes as you roll and move to the side.
> My rating is a 7 out of 10 here.
>
> Slip?
>
> The forward slip can be very effective at bringing "most" ships down.
> Check you flight manual of your aircraft and practice at altitude.
> The old joke about you could always tell who the Std. Cirrus and
> Libelle pilots were because they were slipping on final is true. But
> we got very good at it. It would nearly double the sink rate and when
> kicked out you were nearly at the correct speed. The Std. Cirrus if
> flown even 5 knots too fast would float a long way before settling.
> The nice thing about a slip is your speed and angles all stay the same
> without speeding up the process. You can use your trained judgment to
> say the angle looks about right here and kick out of the slip and
> proceed with a normal landing. My rating is a 10 out of 10 here.
>
> Summary
> Each situation is different, but I think we should focus on teaching
> techniques that are robust and give that average pilot the best
> opportunity to have a good outcome in an off-field landing. I know of
> very few off-field landings that start at 1000 feet at the end of down
> wind. If I have found that much lift on downwind I have cycled the
> gear and am climbing out, not landing. Any technique that requires
> bleeding speed in ground effect should not be taught as anything other
> than a curiosity and never considered for off-filed landings.

Great summary Tim !

To further your point on training: One thing we need to do in
training is demonstrate the effect of flying the final too fast.
Back-to-back pattern flights with different final speeds and
the same aim point really help pilots internalize this.
Especially for transition pilots (Cirrus, 1-35 come to mind),
practicing this on an appropriately long runway brings
religion to pattern energy management like no amount
of briefing...

Be careful out there,
Best Regards, Dave "YO"

October 24th 07, 03:48 PM

On Oct 24, 7:09 am, wrote:
> Great summary Tim !

I agree.

A quick response to the above choices would be based on how much too
high I was. And Tim's list is pretty much in the correct order:

1. Slip
2. "S" turns
The first one likely being an overshoot of the turn to final, then a
120-180 back toward the runway, repeat if necessary, then line up on
the runway.

3. Dive until intercepting normal angle for spoilers
4. Dive until near the ground, then decelerate
Not sure if I like this one... I think #3 is the proper way to do
it. Though, if one is REALLY high, then the proper angle for 'normal'
final would be pretty close to the ground. I would be in this
situation if there are strong winds and chance of downbursts (been
there, done that). Turn final way high expecting the 40+ headwind to
be there (perhaps downburst since the storm is nearby), but instead
the wind quits! In my ASW-20B, I just did a full flap, full spoiler
slip with the nose way below the horizon, so it really was a diving
slip - remember I was WAAAY high. Ended up stopping at my intended
spot even though there was a slight 2-3 knot tailwind.

5. Slow down until intercepting normal angle for spoilers
Perhaps

6. 360 degree turn
Actually, I doubt one would be on final when this decision is made, so
perhaps a 270 degree turn from base to final. But only if the weather
is considered to be benign. I watched an ASW-22BL do this at a fairly
low altitude while going into a fairly short field on a relatively
calm day and it made sense. Due to the ship's low sink rate, the
pilot was able to drop perhaps 100' and also end up slightly farther
away from the touchdown spot.

-Tom

Marc Ramsey

October 24th 07, 06:05 PM

Tim Taylor wrote:
> High on Final, Summary
>
> Thanks to all that have given input so far. My original intent was to
> do some modeling before starting the discussion, but this is RAS and
> it has a life of it's own.
>
> So here is the issue. You are high on final and full spoilers are to
> enough; what do you do?
>
> List of options so far:
>
> 1. Slip
> 2. "S" turns
> 3. Dive until intercepting normal angle for spoilers
> 4. Dive until near the ground, then decelerate
> 5. Slow down until intercepting normal angle for spoilers
> 6. 360 degree turn
>
> Unfortunately I still don't have good data for what happens to the
> polar as speed increases with the spoilers open. Condor was a good
> suggestion, and I am working to see if I can get meaningful data from
> it.
>
> John Cochrane brought the discussion back to the real point which is
> what would you use in the real world? It is interesting but not that
> useful to discuss how you do this at your home airport with 2500 to
> 9000 feet of runway and know precisely the field elevation. When your
> aircraft and your own safety are on the line in a real off-field, what
> are you going to do?

What I do must be taken with a grain of salt, because I'm not an
instructor, pretty much learned how to deal with field landings by trial
and error, have 20 or 30 of them under my belt (5 to 10 in "small"
fields), and have yet to do any more damage than scuff up the underside
of the nose.

First, I *never* fly a normal pattern. I fly directly overhead high
enough to make one or more big lazy circles around the field at approach
speed, so I can look carefully for fences, wires, rocks, figure out
which way the field is sloped, get an idea of the actual wind direction,
potential for sink, get a picture of just how high I am above the field,
and pick the spot where I plan to touch down. When it becomes clear
that I won't be able to make another 360 (and I've found that pretty
easy to determine), I shift the circle as needed to approximate an
abbreviated downwind, base, and final, and will use spoilers, landing
flaps, slips, adjustments to the circle, etc., to get myself into the
field as best I can. I never let myself get out of reach or visibility
to the touch down point, and keep plenty of energy in case it becomes
clear that I need to make a last second shift to a different touch down
point (and that has happened more than once). Using this approach, I've
never found myself too high or low to land when I commit to final
approach...

Marc

[email protected]

October 24th 07, 06:05 PM

On Oct 21, 12:13 pm, Tim Taylor > wrote:
> [...] It is purely an academic exercise from a safety
> discussion we had about what are the best steps to follow if you are
> high on final. I am trying to look at the difference between several
> suggested techniques if full spoilers are not enough.
>

Since I was a participant in the original discussion, I
feel obliged to throw in my $0.02 even though the thread has
been hijacked. Truth in advertising: while I am a CFI-G,
the vast majority of my dual given has been in powered
airplanes.

First, Tim's method works for him and probably for many
other pilots. This does not mean that it works for all
pilots, or even most pilots. By analogy, some maneuvers might
be a piece-of-cake for a proficient aerobatic
pilot (that would not be me) but deadly for others. The
low airspeed drag-it-in kind of approach that some
have advocated for power planes falls into this category.
One of the skills an instructor must bring to the table
is the ability to figure out what approach is best for the student
and teach that.

The aerodynamics of Tim's maneuver - slow down and
get on the "back side" of the polar - mean that the plane
has lost both potential and kinetic energy. The two methods
lose comparable amounts of potential energy, so the loss of
kinetic energy is significant. Loss of kinetic energy
also means loss of maneuverability in all axes, due to
reduced airflow over the control surfaces. So, a glider
that has slowed and hits big sink will take longer to
recover than one with a higher airspeed, due to
reduced elevator effectiveness.

Also, the slower glider is just a few knots above stall, so
a rather small wind shear (headwind-to-tailwind) will
lead to a stall and more loss of altitude. For this reason alone I
would be uncomfortable teaching it to new pilots.

John Smith

October 24th 07, 06:46 PM

Brian wrote:

> Looking at a polar is exactly why it works. It is called Speed to fly.
> It really only works well when you have some headwind. It does work
> somewhat in calm conditions but is really not very effective. It
> probably doesn't work at all in a tailwind condition.

First I thought that you were pulling our legs, but it seems you're
actually serious.

Every year a couple of pilots die because they are too slow on approach.
Where I fly, a student will fail his checkride big time if he's only one
knot below the yellow triangle on final. *Especially* with a headwind.
If you don't understand this, I *strongly* recommend you talk to a
knowledgeble instructor.

Rory O'Conor[_2_]

October 24th 07, 09:40 PM

Author: John Smith >Date/Time: 17:40 24 October 2007=
First I thought that you were pulling our legs, but it seems you're actuall=
y serious.Every year a couple of pilots die because they are too slow on ap=
proach. Where I fly, a student will fail his checkride big time if he's onl=
y one knot below the yellow triangle on final.=20
=20
-
=20
Whilst I understand your sentiment, I think this is over the top. The yello=
w triangle is best approach speed at all up weight.
For a glider that takes water ballast, this may well be 2-3 knots higher th=
an the best approach speed at dry weight. ie one knot slower than yellow tr=
iangle may be higher than 1.3x stall speed for particular set-up.
=20
I have found out the hard way about too slow approaches. My SLMG best engin=
e speed is 49 knots which is lower than the approach speed of 55 knots. Whe=
n the engine does not start at low level, with wet wings and an uphill land=
ing, you find out that the extra speed is required to enable a flare, and o=
nly incidentally to prevent a stall/spin.
=20
Rory
__________________________________________________ _______________
Celeb spotting =96 Play CelebMashup and win cool prizes
https://www.celebmashup.com=

Vaughn Simon

October 24th 07, 10:29 PM

"5Z" > wrote in message
ups.com...

> perhaps a 270 degree turn from base to final. But only if the weather
> is considered to be benign. I watched an ASW-22BL do this at a fairly
> low altitude while going into a fairly short field on a relatively
> calm day and it made sense. Due to the ship's low sink rate, the
> pilot was able to drop perhaps 100' and also end up slightly farther
> away from the touchdown spot.

My gosh, an honestly new idea (at least to me). In my book, that qualifies
as #7. It would not be my first choice, but if you allow yourself get to the
point where your best choices are behind you, the 270 degree turn from base to
final could be the better of several bad options.

Vaughn

John Smith

October 24th 07, 10:45 PM

Rory O'Conor wrote:

> Whilst I understand your sentiment, I think this is over the top. The yello=
> w triangle is best approach speed at all up weight.
> For a glider that takes water ballast, this may well be 2-3 knots higher th=
> an the best approach speed at dry weight. ie one knot slower than yellow tr=
> iangle may be higher than 1.3x stall speed for particular set-up.

The point is not the triangle. The point is that the student has to call
out a target speed and then hold that speed. 5 knots more is tolerated,
but 1 knot below is not. Simply not. No way. Period.

Now if the student calls out a target speed lower than the yellow
triangle, the expert will ask him why. If the student can explain, then
it may be ok. On the other hand, if there is a headwind, the student
must compensate for this. Rule of thumb is add 1/2 wind speed. (And
certainly not slower than without wind, as some other hero suggested.)
Again, the expert will ask what wind speed the student estimates and why.

As for water ballast, well, I've yet to see a student who flyes with
ballast on his checkride.

Rory O'Conor[_2_]

October 24th 07, 10:49 PM

On Oct 22, 7:57 am, wrote:> On Oct 21, 11:13 am, T=
im Taylor wrote:[snip]> If you are THAT much too high, wouldn't it also be =
prudent to consider> a large 360? It may not be pretty, but let's face it, =
if you have
I would join the crowd voting a 360 turn on final, a score of 0/10.
=20
If you are cool about scratching at 400ft AGL then fine, but if you like to=
terminate your thermalling by 800ft AGL then dont consider it. The workloa=
d when turning low down is enormous and you need to be prepared to push the=
nose groundwards against your instincts if the speed shows any sign of ble=
eding off.
=20
Dont do full turns below the height you would be prepared to do them when s=
cratching.
=20
Rory
__________________________________________________ _______________
Celeb spotting =96 Play CelebMashup and win cool prizes
https://www.celebmashup.com=

bagmaker

October 24th 07, 11:53 PM

Tims summary is a good one, thanks!
I have to add my thinking, open to scrutiny.
1- whatever needs to be done to get the a/c to an acceptable landing position above and before the field needs to be done early, to minimise ground effects. (theoretically, if this is adhered to, the problems wouldnt eventuate, as the pilot would have noticed his/her extra altitude before arriving at final and modified the curcuit to suit.)
So, slips, s turns etc, must be initiated as soon as the over-energy issue is recognised.
2-if the pilot is high-energy when arriving in the flare it is way too late, a long or harsh landing is inevitable.

concluding the above, s turns are going to be a logical option, as you are just extending your base turn, then back again toward the field and repeat at a reasonable altitude, into the wind. Unfortunately, the turns will be at a higher speed, sloppily co-ordinated with the brakes out, so if you survive them, you will probably land correctly!

The issue is one of observation, the fact is there has been previos mis-observation, so, will the pilot suddenly realise? - possibly not. The more time that is taken to realise it, the more serios the problem results.

Quite the conundrum!

thanks for a great post

bagger

Tony Verhulst

October 25th 07, 12:00 AM

> My gosh, an honestly new idea (at least to me). In my book, that qualifies
> as #7. It would not be my first choice, but if you allow yourself get to the
> point where your best choices are behind you, the 270 degree turn from base to
> final could be the better of several bad options.

My choice, given this situation. would be one or more figure 8's with
all turns toward the runway. In a 270, the first third of the turn is
heading away from the runway - not good down low if you hit unexpected sink.

Tony V. "6N"

Tony Verhulst

October 25th 07, 12:21 AM

> Every year a couple of pilots die because they are too slow on approach.
> Where I fly, a student will fail his checkride big time if he's only one
> knot below the yellow triangle on final.

Assuming the U.S., not likely. I admit that being slow on final is bad
news, but the Practical Test Standard for the private pilot exam calls
for +10/-5 knots as being acceptable for a final approach speed (page
1-16 - see below). If one of my students was "pink slipped" for being
one knot slow on final, I would advise him to challenge the failure -
and he would win. An examiner simply does not have that kind of
latitude. If the applicant flies to the PTS, he gets his license. I
agree that if there is a headwind, "recommended approach airspeed" will
be higher than the "yellow trangle".

Tony V.

LANDINGS
Q. TASK: NORMAL AND CROSSWIND LANDING
NOTE: If a crosswind condition does not exist, the applicant’s
knowledge of crosswind elements shall be evaluated through oral
testing.
REFERENCES: Soaring Flight Manual, Glider Flight Manual.
Objective. To determine that the applicant:
1. Exhibits knowledge of the elements related to normal and
crosswind approach and landing procedures.
2. Adjusts flaps, spoilers, or dive brakes, as appropriate.
3. Maintains recommended approach airspeed, +10/-5 knots.

Martin Gregorie[_1_]

October 25th 07, 12:24 AM

Tony Verhulst wrote:
>
>> My gosh, an honestly new idea (at least to me). In my book, that
>> qualifies as #7. It would not be my first choice, but if you allow
>> yourself get to the point where your best choices are behind you, the
>> 270 degree turn from base to final could be the better of several bad
>> options.
>
>
> My choice, given this situation. would be one or more figure 8's with
> all turns toward the runway. In a 270, the first third of the turn is
> heading away from the runway - not good down low if you hit unexpected
> sink.
>
But would you prefer a figure 8 to a 270 in something with as low a roll
rate as an ASW22 or ASH25?

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Tony Verhulst

October 25th 07, 01:06 AM

>> My choice, given this situation. would be one or more figure 8's with
>> all turns toward the runway. In a 270, the first third of the turn is
>> heading away from the runway - not good down low if you hit unexpected
>> sink.
>>
> But would you prefer a figure 8 to a 270 in something with as low a roll
> rate as an ASW22 or ASH25?

Good point! I've not flown these gliders and maybe, in these, a 270 is
preferable - I don't know, you tell me :-). My glider is an LS6.

Tony V.

Brian[_1_]

October 25th 07, 04:44 AM

> First I thought that you were pulling our legs, but it seems you're
> actually serious.
>
> Every year a couple of pilots die because they are too slow on approach.
> Where I fly, a student will fail his checkride big time if he's only one
> knot below the yellow triangle on final. *Especially* with a headwind.
> If you don't understand this, I *strongly* recommend you talk to a
> knowledgeble instructor.

I will be the first to agree that pilots die every year because they
are too slow on the approach. However I have not been able to find any
evidence that any of these were caused by the pilot intentinally
flying the approach slower than normal. In fact in nearly every case
I have examined it appears more likely that pilot was flying by sight
and feel and not paying any attention at all to the airspeed. Often
they are landing or flying downwind which gives the illusion of
airspeed, as does flying close to the ground. If fact the few pilots I
have been able to interview or read their description of the accident
described it as feeling like the controls went limp and had no effect.
The didn't make any mention of airspeed. It is not hard to find this
description in NTSB reports for power aircraft. I believe nearly all
Stall Spin Accidents are caused by the illusion of speed. The pilot
thinks he going fast so he doesn't look at the airspeed indicator and
he is not thinking about a stall or a spin.

Brian

[email protected]

October 25th 07, 05:57 AM

On Oct 24, 8:44 pm, Brian > wrote:
> > First I thought that you were pulling our legs, but it seems you're
> > actually serious.
>
> > Every year a couple of pilots die because they are too slow on approach.
> > Where I fly, a student will fail his checkride big time if he's only one
> > knot below the yellow triangle on final. *Especially* with a headwind.
> > If you don't understand this, I *strongly* recommend you talk to a
> > knowledgeble instructor.
>
> I will be the first to agree that pilots die every year because they
> are too slow on the approach. However I have not been able to find any
> evidence that any of these were caused by the pilot intentinally
> flying the approach slower than normal. In fact in nearly every case
> I have examined it appears more likely that pilot was flying by sight
> and feel and not paying any attention at all to the airspeed. Often
> they are landing or flying downwind which gives the illusion of
> airspeed, as does flying close to the ground. If fact the few pilots I
> have been able to interview or read their description of the accident
> described it as feeling like the controls went limp and had no effect.
> The didn't make any mention of airspeed. It is not hard to find this
> description in NTSB reports for power aircraft. I believe nearly all
> Stall Spin Accidents are caused by the illusion of speed. The pilot
> thinks he going fast so he doesn't look at the airspeed indicator and
> he is not thinking about a stall or a spin.
>
> Brian

I'm pretty sure that's not a true. I know of at least a couple of
accidents where the pilot was knowingly flying as slow as possible and/
or s-turning on final to get into a tight spot. Both were fatal.

I think the best way to think about this is in terms of energy
dissipation between wherever you start and some fixed touchdown point
(or stopping point if you are willing to plant the glider on the
ground and use the wheel brake too). Frankly if I am looking at a
finite distance to an unpleasent end of the field I will do whatever I
can to burn energy - before and after touchdown.

For starters I took a look at my ASW-27B factory polar. It turns out
that I will fly the same L/D spoilers closed at 37 knots (stall) as at
86 knots. This is basically the breakeven tradeoff between between
high induced and and high parasitic drag manuevers. If I add spoilers
I am adding a parasitic drag device which increases in effectiveness
with the square of velocity. That means that the breakeven speed for
the parasitic maneuver has to be lower than 86 knots. You don't need
to get to Vne to do better by going faster - even 70-75 knots is
probably better.

The ground effect argument has some merit I think, but keep in mind
that you can always stop the manuever before you get into ground
effect and bleeed off airspeed at 100' or so - you will still be
ahead. The altitude you consume slowing form the higher speed will be
roughly equal to the altitude you burned getting to the higher speed.

This is for still air. If I add headwind the breakeven airspeed for
speeding up versus slowing down goes up, but in most cases I'd be hard
pressed to believe that with spoilers out you will get a better energy
dissipation going slow than fast. At some point there will be a
crossover as headwind goes up. Just think of a headwind that is
greater than your stall speed to convince yourself.

Theory aside, I am convinced that as a practical matter making the
glider as draggy as possible and adding speed is almost always a more
practical and safe solution to slowing down and maneuvering at low
altitude. Stall/spin is a buzz-kill.

Lastl;y, I have done the parasitic drag maneuver down to touchdown in
a G-103 with spoilers closed and convinced myself that it is the
preferred method. I 'm guessing a Duo with the boards out is at least
as draggy as a G-103 clean.

My 2c.

9B

John Smith

October 25th 07, 09:52 AM

Tony Verhulst wrote:

> Assuming the U.S., not likely.

You're assuming wrong.

Stefan

October 25th 07, 09:56 AM

Brian wrote:

> I will be the first to agree that pilots die every year because they
> are too slow on the approach. However I have not been able to find any
> evidence that any of these were caused by the pilot intentinally
> flying the approach slower than normal.

It's hard to tell after a fatal accident whether he was intentionally or
accidentally too slow... :-/ But if you're actually correct, well, then
you'll be the first.

John Smith

October 25th 07, 10:03 AM

Brian wrote:

> However I have not been able to find any
> evidence that any of these were caused by the pilot intentinally
> flying the approach slower than normal.

After a fatal accident, it's usually hard to tell whether he was
intentionally or accidentally too slow... :-/

But if you're correct, well, then you'll be the first... :-/

Martin Gregorie[_1_]

October 25th 07, 01:19 PM

Tony Verhulst wrote:
>
>>> My choice, given this situation. would be one or more figure 8's with
>>> all turns toward the runway. In a 270, the first third of the turn is
>>> heading away from the runway - not good down low if you hit
>>> unexpected sink.
>>>
>> But would you prefer a figure 8 to a 270 in something with as low a
>> roll rate as an ASW22 or ASH25?
>
>
> Good point! I've not flown these gliders and maybe, in these, a 270 is
> preferable - I don't know, you tell me :-). My glider is an LS6.
>
I was asking, not telling!

Apart from club two seaters, all my flying has been in 15m types,
currently a Libelle. I've had one ride in an ASH-25 and flown a Nimbus 3
once. In both cases the low roll rate and high inertia round all axes
struck me as being very different from my usual mounts. I raised the
issue in the hopes of getting a response from pilots who regularly fly
big wings.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Eric Greenwell

October 25th 07, 06:48 PM

Tim Taylor wrote:

> So here is the issue. You are high on final and full spoilers aren't
> enough; what do you do?
>
> List of options so far:
>
> 1. Slip
> 2. "S" turns
> 3. Dive until intercepting normal angle for spoilers
> 4. Dive until near the ground, then decelerate
> 5. Slow down until intercepting normal angle for spoilers
> 6. 360 degree turn
>
> Unfortunately I still don't have good data for what happens to the
> polar as speed increases with the spoilers open. Condor was a good
> suggestion, and I am working to see if I can get meaningful data from
> it.
>
> John Cochrane brought the discussion back to the real point which is
> what would you use in the real world? It is interesting but not that
> useful to discuss how you do this at your home airport with 2500 to
> 9000 feet of runway and know precisely the field elevation. When your
> aircraft and your own safety are on the line in a real off-field, what
> are you going to do?
> Is there really a need
> to be on the ground 10 seconds faster than using some of the other
> techniques? Maybe only if a severe thunderstorm is approaching and
> you must be on the ground now.

Fast approaching weather is a good reason for an "expedited landing",
and besides thunderstorms, there gust fronts, snow, rain, and blowing
dust. And also other reasons: there are a dozen gliders approaching at
high speed to finish a contest task; you want to land before sunset and
are still high; you want to land before the tow plane so you don't
interfere with the next tow (or have the next tow interfere with your
landing); airplanes are holding their takeoff until you land; to fit in
between the four airplanes circulating in the pattern doing incessant
touch and go's; getting out of the way before the skydivers exit the
jump plane. I've done it for all those reasons.

Regardless of the need to get down quickly, Option 3, as I use it, is
something I do on final after a normal pattern entry. It's not a "get
down quicker" technique.

snip

> It is true that sink rate goes up with speed, but the
> actual decent angle does not go up nearly as much. For my Ventus B at
> 45 knots descent rate is 122 ft/min while at 135 knots it is 894 ft/
> min, but actual loss per nautical mile is 163 ft/ktm verses 397 ft/
> ktm.

This is not a good comparison, because these numbers are for a "clean"
glider, where the major drag at 45 knots is *induced* drag (which
reduces as speed increases), at 135 knots the major drag is *parasitic*,
and you've gone to negative flaps to reduce drag!

With the gear and spoilers out, landing flap selected, the drag will
increase more rapidly with speed than for your example, as the drag is
significantly parasitic to begin with.

> The other thing we don't mention is the average pilot going to
> handle the decision making process better at higher speeds and less
> time? At stable speeds it takes about 11 seconds to lose 300 feet at
> 135 knots with the spoilers out verses 22 seconds at 45 knots.

These numbers way off: the Ventus (spoilers out) has a 800 fpm sink rate
at 45 knots (seems too high), and it is only 1600 fpm at 135 knots
(seems too low)? Three times the speed and only double the descent rate?
Even clean, the descent rate increased a factor of 7.

>
> Ok, lets try a hypothetical (well maybe not, been there done that ;-)
> off-field landing.

snip

>
> Slip?

Yes, when I had the Std Cirrus (I practiced slips a lot, because it has
poor spoilers); no, with the ASW 20 C (slips work fine, however); maybe,
in my ASH 26 E (I don't practice them much).

> "S" turns?

Never, at that altitude.

> Dive until intercepting normal angle for spoilers?

Yes, in Ka-6E (got to love those divebrakes!); Yes, in the ASW 20 C (got
to love those 40 deg landing flaps!); yes, in the ASH 26 E.

> Dive until near the ground, and then decelerate?

No, Std Cirrus; no, Ka-6e (it will be on glide path well before it gets
near the ground); probably won't need to with the 20 C; might be what
happens with the ASH 26 E, with it's 8.3 psf wing loading.

> Slow down until intercepting normal angle for spoilers?

Never.

> 360 degree turn?

Never.

snip
> Dive until intercepting normal angle for spoilers?
>
> Maybe, but can you dive, lose the altitude, decelerate and get it on
> the ground for a tail wheel first, full stall landing?

As others have pointed out - bad idea. I might be able to manage it the
Ka-6e with it's huge spoilers and light wing loading (5 psf); the
Cirrus, 20, and 26 would be put on the ground as soon as possible with
full air and wheel brakes and some forward stick to give maximum
traction. I think the 20 would stop the soonest of these three.

snip

> Summary
> Each situation is different, but I think we should focus on teaching
> techniques that are robust and give that average pilot the best
> opportunity to have a good outcome in an off-field landing. I know of
> very few off-field landings that start at 1000 feet at the end of down
> wind.

The off-field landing "technique" of turning final at 800' instead of
400' is "robust", in my opinion, and should be one of the things we
teach. A lot (majority?) of bad outcomes during an off-airport landing
have "too low" when starting the landing pattern as a major factor.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Bruce

October 25th 07, 08:00 PM

This is the kind of rigid thinking that kills people.

While I entirely concur that being too slow on final approach is dangerous, one
has to understand the variables. If you teach that the needle has to be ON the
yellow triangle, what happens to the pilot when he suddenly notices the glider
he is in doesn't have one. While under pressure in a difficult situation.

For every weight and configuration there is a stall speed.
For every wind condition there is a different factor to add to stall to get to a
safe approach speed.

Personally I would far rather fly with someone who knows exactly why he/she is
trying to maintain a particular speed, than someone who is a master at nailing
some arbitrary speed. Which happens to be perfect for one set of conditions.

As a Std Cirrus driver (pre serial 75) I can vouch for the wisdom of being at
the right speed. Too fast by even a small margin and you will float forever, and
PIO if you try to fly it on. Too slow and the handling gets very interesting if
there is turbulence. That right speed varies widely depending on the wind and
other circumstances.

Maybe we make it too complicated - our rule is you have to be able to decide an
appropriate approach speed, explain why you chose it, and then keep within 5km/h
of it.

John Smith wrote:
> Brian wrote:
>
>> Looking at a polar is exactly why it works. It is called Speed to fly.
>> It really only works well when you have some headwind. It does work
>> somewhat in calm conditions but is really not very effective. It
>> probably doesn't work at all in a tailwind condition.
>
> First I thought that you were pulling our legs, but it seems you're
> actually serious.
>
> Every year a couple of pilots die because they are too slow on approach.
> Where I fly, a student will fail his checkride big time if he's only one
> knot below the yellow triangle on final. *Especially* with a headwind.
> If you don't understand this, I *strongly* recommend you talk to a
> knowledgeble instructor.

Chris Reed[_1_]

October 25th 07, 10:47 PM

bagmaker wrote:
> I have to add my thinking, open to scrutiny.
> 1- whatever needs to be done to get the a/c to an acceptable landing
> position above and before the field needs to be done early, to minimise
> ground effects. (theoretically, if this is adhered to, the problems
> wouldnt eventuate, as the pilot would have noticed his/her extra
> altitude before arriving at final and modified the curcuit to suit.)

Good point. No-one has mentioned using airbrakes on the base leg, or
even the downwind leg. I often do this if the sink is less than I
anticipated or I hit lift. Once a pilot has some experience it's really
easy to see at this stage if you will be too high, and losing the excess
height early makes the last part of base and the approach much easier
than if you leave all the excess height to be lost in the approach.

I recall that when being trained, I was told not to use airbrakes until
I'd turned finals (though also that in post-solo training it was pointed
out to me that I could now break this rule).

Is it possible that we are too heavily conditioned not to use airbrakes
before the final turn?

In my Open Cirrus I'd rather turn finals a *little* too low, as if I fly
the first part of the approach without brakes I'll soon intercept the
approach funnel. Turning too high is always more difficult. Note that in
a K8 the opposite is true - too low might not be fixable and losing
height is easy (and often not optional!). One of the points which comes
out clearly from this thread is that the answers are very glider-specific.

So I guess my preferred answer is:

0. Lose the excess height before making the final turn, in whatever way
works for you.

[PS For those blessed with a tailchute, I can highly recommend
practising opening the tailchute towards the end of the downwind leg. If
you need it for a real field landing, the approach is too late - what if
it fails to deploy? The feeling of despair as you are clearly too low is
balanced by the elation when you realise that you will make the field
after all. Anyone trying this will need to fly a curved path from end of
downwind to touchdown, as a formal circuit is *far* too scary and will
probably leave you short.]

John Smith

October 25th 07, 11:07 PM

Bruce wrote:

> This is the kind of rigid thinking that kills people.

You can't be rigid enough when it comes to final approach speed.

> If you teach that the
> needle has to be ON the yellow triangle, what happens to the pilot when
> he suddenly notices the glider he is in doesn't have one.

Yeah, yeah, yeah. I would expect from a glider pilot that he doesn't
"suddenly" discover on short final that there isn't such a triangle, but
that he familiarizes himself with the glider before the flight. If he
doesn't, then many other things have gone wrong during his training.

> For every weight and configuration there is a stall speed.

Of course. But the other poster proposed to slow down to the point where
you get a steeper approach. For me, this is a *very* rigid no-no. I
don't think that rigidness in this point kills people. I even tend to
think the contrary.

J a c k[_2_]

October 27th 07, 10:21 PM

Bill Daniels wrote:

> I think the Duo's airbrakes are better than many people think. The Duo is a
> big heavy glider with lots of inertia. It doesn't like to change direction
> quickly. That includes its behavior on sudden airbrake deployment. You
> don't get a lot of sink right away.
>
> My first reaction was that the airbrakes were weak but a little more
> experience showed me that with a little patience, the brakes took effect and
> produced a respectable decent rate. The Duo just makes you plan ahead a
> little more than with a light single seater.

In other words, the Duo "airbrakes" are not very effective. Lots of big,
heavy, fast aircraft do have effective spoilers/speedbrakes/"airbrakes",
or whatever you want to call them, that make the desired changes in
speed/rate of descent promptly.

Every car's acceleration from 35 to 65 for merging into Interstate
highway traffic is adequate--if you are willing to wait for it.

I learned to "plan ahead" when passing on two lane roads in my VW
Beetles and early un-blown Corvairs. I know what planning ahead means
and that is not "performance" as we like to think of it. The same goes
for sailplane spoilers whose effects are not prompt, and rudders which
are not effective enough to allow a good steep high descent-rate slip.

Jack

J a c k[_2_]

October 27th 07, 10:36 PM

BB wrote:

> As fun as the high parasitic drag maneuver is, I wonder if anyone has
> ever actually used it in combat. Has anyone been so flustered and out
> of synch to get monstrously high in an off field landing, then had the
> presence of mind and skill left to dive to the ground at near VNE,
> aiming several hundreds of yards short of the intended small paddock
> with fence at the far end, and had it work? The mental attitude that
> gets to the problem seems incompatible with the attitude needed to
> pull this one off.

In "combat"? In a Duo?

There are a number of real combat stories about people keeping the speed
high in damaged aircraft to get down out of the fight, through clouds,
etc. to find a safer area for a forced landing or bailout--so as not to
be hosed while under canopy, or to avoid setting up a big slow pattern
that would make them a sitting duck--but I think that diverges from what
you are asking.

I don't think fighter pilots get a chance to practice engine out
landings much, so yes, they adapt. The best adaptation is that for which
the mental groundwork is laid _on_ the ground.

Sailplane pilots have the incomparable advantage of doing their
preparation on the ground _and_ in the air by planning and practicing
both low- and high-energy approaches, as has been outlined here in
previous postings by several contributors.

Jack

J a c k[_2_]

October 28th 07, 04:23 AM

Tim Taylor wrote:

> The situation: You are 70 miles from home over unfamiliar territory
> (read not sure of exact elevation of the terrain below, your altimeter
> is useless now). You have gone for a Cu over a dry lake bed and it
> doesn't work. You have selected a landing site in the lake bed that
> is about 350 feet long and 100 feet wide that looks safe to land.
> There are tree stumps and other object in other parts of the lakebed.
> There are no obstructions on the ends of the site so you can do a
> normal approach. The winds are 15 to 20mph out of the south so you
> are landing from the north to south. As you drop lower you make a
> rectangular pattern over the site checking for any missed obstacles.
> The downwind is fast with the tailwind, as you turn base you estimate
> you are 400 feet. Your adrenaline is pumping as you prepare for a
> fairly technical landing. You want to keep it close so that you don't
> end up short back into the wind and you turn base a little too soon.
> You are on short final about 350 feet, but about 100 feet over full
> spoilers decent. What do you do?

Tim,

We've already screwed up a bunch of things to get ourselves here, but
then we may do that from time to time, so:

S-turns.

In this situation I want more time: to achieve the necessary descent
while flying the ship in the way I most frequently fly it--this is not
the time for something completely different--even though I can
_probably_ do a "360" from that height with a "clean" wing. _Know_ what
your configuration is. Gear? Spoilers? If there is any cross-wind, turn
into the wind initially, using anything from a 45 to 120 degree turn
depending on conditions, but I'll be more comfortable with 60 to 80
degrees; keep the touchdown area in sight; control speed carefully; do
not hurry the process; continually assess drift, obstructions, and
condition of roll-out space as your vantage point changes while crossing
the extended runway centerline.

Do not continue maneuvering below a safe altitude. The last 100 feet
should look as normal as any you've ever done. If not you've been in too
much of a hurry to get to the runway. Just relax and fly around until
you get to where everything looks about right again--really, thats what
we always do, isn't it? That's why we must be able fly the pattern very
comfortably without reference to the altimeter.

When airliners need more spacing on final approach, something similar to
this method is surprisingly effective without disturbing the customers
too much.

One more note: if every approach we fly at our home field looks just the
same as every other one, we may not be learning enough. Mix it up a
little. Where I fly that's rarely a problem, though, and I think that's
good for us in the long run.

Jack