Polar with spoilers extended?

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

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

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

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.

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

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.

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

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.]

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.

Tony Verhulst wrote:

Assuming the U.S., not likely.

You're assuming wrong.