Flaps and V-Tails of Death

[Wallace Berry]

Hi all,

I'm here to report that I cheated death and survived a flight in a
glider with the dreaded "Landing Flaps and V-Tails of Death". Jim Harper
graciously allowed me to fly his beautiful HP-16. What's an HP-16 you
say? Well, looks to be just like the HP-18 (or I should say the HP-18 is
just like the -16) except that the -16 has a large and comfortable all
metal cockpit instead of the narrow composite cockpit of the -18.

Jim's -16 is equipped with winglets and, as far as I know, the ailerons
are standard (not with the J.D. Colling mod, correct me if I'm wrong
Jim). Center stick. Tow was behind our 180hp Cessna 175 on a 275 foot
long rope. Started out in -2 flap position, went to + 5 at 40 knots. Had
no trouble keeping the wings level. The bird lifted off level and was
easy to fly on tow. Released and tried slow flight (no stalls), flight
up to 90 knots. Steep turns, etc. Well sealed and quiet. Good rudder
response and easy to coordinate compared to my 301 Libelle. More stable
in a thermal than my Libelle. Aileron response was a little slower than
my Libelle at thermaling speeds, but was positive and more than adequate
for centering thermals. Climbed a few hundred feet in a very week
thermal. Very nice thermalling glider.

Landing was the best part. I stayed high and close in the pattern. I
rolled on some flap on downwind, maybe 30 degrees or so. I was way high
on final so I started rolling in more flaps. I never quite got to the
full 90 degrees mark as I had the nose down at a truly obscene angle
just to maintain 50 knots. Steeper than my 301 with the tailchute and
full divebrakes. Steeper than a Mosquito with everything hanging out.
This was more like parachuting than flying. Nothing but dirt out the
front of the canopy. The horizon was visible more towards the top of the
canopy. I aimed at a target and just kept the nose pointed there. I
pulled back on the stick when I ran out of nerve. The bird settled on
with a slight bump of the tailwheel and a little bounce as the main
dropped on (I flared just a bit too much). I have no doubt that I could
easily put this bird in a tiny field much easier than I could my Libelle
(and that is not difficult at all).

So, I'd have to say that all the bad things I've been told about landing
flaps on gliders and V-tails are definitely untrue with respect to the
HP-16. It is a comfortable and easy to fly glider and compares very well
to my Libelle and also to other glass birds, including my favorites for
handling, the Mosquito and LS-4.

[Eric Greenwell]

Wallace Berry wrote:

> So, I'd have to say that all the bad things I've been told about landing
> flaps on gliders and V-tails are definitely untrue with respect to the
> HP-16.

If you believe that, perhaps you haven't been told "all the bad things".
For example, I've had HP pilots tell me getting sucked up into a cloud
can be "awkward" to deal with when all you've got is flaps.

My first and only flight in an HP went like Mr. Berry's; even so, I hope
anyone beginning to fly a flaps only glider gets thorough checkout,
because there are ways to go wrong.

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Eric Greenwell
Washington State
USA

[Bob Whelan]

"Eric Greenwell" wrote in message
> Wallace Berry wrote:
>
> > So, I'd have to say that all the bad things I've been told about landing
> > flaps on gliders and V-tails are definitely untrue with respect to the
> > HP-16.
>
> If you believe that, perhaps you haven't been told "all the bad things".
> For example, I've had HP pilots tell me getting sucked up into a cloud
> can be "awkward" to deal with when all you've got is flaps.
>
> My first and only flight in an HP went like Mr. Berry's; even so, I hope
> anyone beginning to fly a flaps only glider gets thorough checkout,
> because there are ways to go wrong.

No offense, Eric, but speaking from the vantage point of one with all his
>1-26 glide-ratio time in flaps-only ships (C-70, HP-14, Zuni), the more
powerful the flaps, the _less_ 'exciting' it need be if you allow yourself
to get sucked into a cloud. (For those unfamiliar with lift in the western
U.S., streets miles long and wide containing lift exceeding 10 knots are not
uncommon, and 'getting sucked into a cloud' _can_ happen, even if relatively
savvy and switched on...scale effects, new experience learning curves, etc.)

Can we take as a given that what's 'thrilling' about IFR flight with a VFR
panel is the very real possibility of pulling wings off in the ensuing
spiral dive? If that's true, then the more drag you have available...and
flapped HP's tend to have a LOT of disposable drag [a great thing as Wallace
B. better understands now, :-)]...the less thrilling blind flight. My HP-14
wouldn't exceed 55 knots (as I recall) with full flaps when left to its own
(hands-off) devices for minutes on-end. Sure, it took on some interesting
attitudes as it alternately nosed up, stalled, fell off on a wing, regained
speed, nosed up...etc., but there was no way it was ever going to come close
to maneuvering speed. To avoid the repeated stalling, all one needed to do
was hold 40 knots with full flaps (required forward stick). You'd
eventually end up in a steep spiral, but, so what?

My Zuni is less forgiving (considerably weaker flaps...i.e. less drag than
the HP-14) in this regard, and will pretty soon exceed 75 knots
hands-off-the-stick in the zoom, stall, fall off sequence, but like the HP
is utterly innocuous if trimmed aft w. full flaps and held at 40 (or 45 or
whatever one is comfortable with). Again, you're likely to eventually end
up in a tight spiral if using this technique, but you're not going to pull
the wings off.

IMHO, playing imaginary mind games (and backed up by considerable
experimentation over the years), my personal adrenaline level will be a lot
lower in a flaps-only ship having 'adequate drag' (and I know of no 15-meter
flap-only ships that do not) than in a spoilers-only ship if I envision
being in a big, turbulent cloud with a VFR panel. For the record, I'm aware
of the 'benign spiral mode.'

Actually, I suspect 'flapped cloud safety' comes not so much the flaps
as-such, but from their high level of drag. Imagine a tail-chute-only of
'ridiculously large diameter' to see what I mean...likewise, 'ridiculously
large spoilers'. For non-U.S. pilots, the most powerful spoiler-only
gliders I know of are the Schweizer 1-34 and 2-32, both of which have
terminal-velocity-limiting dive brakes. Personally, I'd much rather come
out the bottom of a cloud doing 40 knots in a spiral than at Vne more or
less vertically. Adrenaline may have its place in the human condition, but
I prefer to keep mine out of the cockpit!

Regards,
Bob - you can't have too much disposable drag - Whelan


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[Eric Greenwell]

Bob Whelan wrote:
> "Eric Greenwell" wrote in message
>
>>Wallace Berry wrote:
>>
>>
>>>So, I'd have to say that all the bad things I've been told about landing
>>>flaps on gliders and V-tails are definitely untrue with respect to the
>>>HP-16.
>>
>>If you believe that, perhaps you haven't been told "all the bad things".
>>For example, I've had HP pilots tell me getting sucked up into a cloud
>>can be "awkward" to deal with when all you've got is flaps.
>>
>>My first and only flight in an HP went like Mr. Berry's; even so, I hope
>>anyone beginning to fly a flaps only glider gets thorough checkout,
>>because there are ways to go wrong.
>
>
> No offense, Eric, but speaking from the vantage point of one with all his
>
> 1-26 glide-ratio time in flaps-only ships (C-70, HP-14, Zuni), the more
> powerful the flaps, the _less_ 'exciting' it need be if you allow yourself
> to get sucked into a cloud.

The situations described to me were the difficulty of avoiding the cloud
entry in the first place. A pilot can open his spoilers at 90 knots and
begin descending immediately, but deploying the flaps at 90 knots first
increases your altitude, making it much harder to stay out of the cloud.
If you do lose control in a cloud, lots of drag is an advantage.

The main point I hoped to make is landings aren't the only way spoilers
and glide path flap operation differs, and one good landing isn't enough
to know the pitfalls, even for landings. I think everyone agrees the HP
series is a great ship to make off-field landings in the hands of a good
pilot.
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Eric Greenwell
Washington State
USA

[Bob Whelan]

Eric Greenwell originally replied...
> >>If you believe that, perhaps you haven't been told "all the bad things".
> >>For example, I've had HP pilots tell me getting sucked up into a cloud
> >>can be "awkward" to deal with when all you've got is flaps.
> >>
> >>My first and only flight in an HP went like Mr. Berry's; even so, I hope
> >>anyone beginning to fly a flaps only glider gets thorough checkout,
> >>because there are ways to go wrong.

Bob Whelan followed with...
> >
> > No offense, Eric, but speaking from the vantage point of one with all
his
> > (greater-than)
> > 1-26 glide-ratio time in flaps-only ships (C-70, HP-14, Zuni), the more
> > powerful the flaps, the _less_ 'exciting' it need be if you allow
yourself
> > to get sucked into a cloud.
>

Eric G. further replied...
> The situations described to me were the difficulty of avoiding the cloud
> entry in the first place. A pilot can open his spoilers at 90 knots and
> begin descending immediately, but deploying the flaps at 90 knots first
> increases your altitude, making it much harder to stay out of the cloud.
>If you do lose control in a cloud, lots of drag is an advantage.
>
> The main point I hoped to make is landings aren't the only way spoilers
> and glide path flap operation differs, and one good landing isn't enough
> to know the pitfalls, even for landings. I think everyone agrees the HP
> series is a great ship to make off-field landings in the hands of a good
> pilot.

I figured there was some nuance I was missing. No harm no foul. I agree
with all your points. For my part I just wanted to throw out for general
consideration that though flaps ARE different than spoilers, 'different'
doesn't necessarily strongly equate with 'bad.' Nor does 'different'
necessarily strongly equate with 'large cojones.'

Free information is always worth every cent paid for it, but (in my
flap-biased view) there seems to be more misleading/'flaps are bad'
information floating around about flaps than there is of the sort to be
found in this particular thread...which thus far contains accurate - if
necessarily incomplete - information in every post.

Just to provide a counterpoint to your scenario of avoiding the cloud in the
first place (always a good idea, if not always achieved), it's worth
pondering how ANYone comes to the decision s/he may require imminent cloud
avoidance techniques. Consider the particular case of a powerful western
U.S. cloud street. Odds are J. Pilot will be cruising along at 80+ mph and
suddenly have a "HolyCOW!' moment upon realizing cloud avoidance is
necessary. Options likely to spring to the surprised mind?: 1) course
change; 2) nosing over/adding energy; 3) adding gear drag; 4) adding
flap/spoiler drag. All will be exciting in a suddenly more thrill-filled
cockpit.

I've spoken to 2 pilots (years apart) soon after each first intentionally
opened spoilers at above-pattern speeds, one in a St'd Cirrus near 120 knots
trying to get below a finish gate in a regionals, and the other in an
Astir-CS trying to avoid being sucked into a big, wide, western cloudstreet
who had options 1, 2, & 3 prove insufficient. We laughed about things
because we were on the ground, but they were both wide-eyed recollecting the
BIG negative G event occasioned by opening spoilers at
higher-than-pattern-speeds, even though both had time to realize prior to
pulling the spoiler handle they were treading in new (for them, at the
times) territory. Playing Joe Test Pilot is always best done (IMHO) under
more controlled conditions than 'needing' to play JTP.

FWIW, I thought the St'd Cirrus pilot did by far the more foolish
thing...because he took an avoidable risk, whereas the Astir CS pilot felt
he had no other choice. Both whanged their heads on the canopy. The Astir
pilot wound up in a high-speed, gear-down, spoilers-out slip trying
desperately to stay out of the cloud street. About the time he could see he
was going to be successful avoiding the cloud, he heard a radio call to the
effect, "Glider at XXX over YYY, this is Cessna ZZZ. Are you OK?" Being at
XXX over YYY, he declined to answer (would've required a 3rd hand w/o a boom
mic), though afterwards he could appreciate a certain irony in the
situation!

Regards,
Bob W.



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[Doug Hoffman]

> From: Eric Greenwell >
>
> If you believe that, perhaps you haven't been told "all the bad things".
> For example, I've had HP pilots tell me getting sucked up into a cloud
> can be "awkward" to deal with when all you've got is flaps.

"all the bad things"? Do go on, Eric.

I fly an RS-15 and I don't worry about spoiler(s) not being connected or
accidentally opening. There are some very positive things about the HPs.
Also, when landing flaps are deployed the ship becomes incredibly stable and
the stall speed decreases. That's a nice feeling when down low.

>
> My first and only flight in an HP went like Mr. Berry's; even so, I hope
> anyone beginning to fly a flaps only glider gets thorough checkout,
> because there are ways to go wrong.

As with any ship that is "new in type" to the pilot. But good advice.

Regards,

-Doug

[Wayne Paul]

Here are some pictures of Jim Harper's HP-16:
http://www.soaridaho.com/Schreder/HP-16/N8DC/N8DC_First_Flight.htm

Wayne
http://www.soaridaho.com/


"Wallace Berry" > wrote in message
...
> Hi all,
>
> I'm here to report that I cheated death and survived a flight in a
> glider with the dreaded "Landing Flaps and V-Tails of Death". Jim Harper
> graciously allowed me to fly his beautiful HP-16. What's an HP-16 you
> say? Well, looks to be just like the HP-18 (or I should say the HP-18 is
> just like the -16) except that the -16 has a large and comfortable all
> metal cockpit instead of the narrow composite cockpit of the -18.
>
> Jim's -16 is equipped with winglets and, as far as I know, the ailerons
> are standard (not with the J.D. Colling mod, correct me if I'm wrong
> Jim). Center stick. Tow was behind our 180hp Cessna 175 on a 275 foot
> long rope. Started out in -2 flap position, went to + 5 at 40 knots. Had
> no trouble keeping the wings level. The bird lifted off level and was
> easy to fly on tow. Released and tried slow flight (no stalls), flight
> up to 90 knots. Steep turns, etc. Well sealed and quiet. Good rudder
> response and easy to coordinate compared to my 301 Libelle. More stable
> in a thermal than my Libelle. Aileron response was a little slower than
> my Libelle at thermaling speeds, but was positive and more than adequate
> for centering thermals. Climbed a few hundred feet in a very week
> thermal. Very nice thermalling glider.
>
> Landing was the best part. I stayed high and close in the pattern. I
> rolled on some flap on downwind, maybe 30 degrees or so. I was way high
> on final so I started rolling in more flaps. I never quite got to the
> full 90 degrees mark as I had the nose down at a truly obscene angle
> just to maintain 50 knots. Steeper than my 301 with the tailchute and
> full divebrakes. Steeper than a Mosquito with everything hanging out.
> This was more like parachuting than flying. Nothing but dirt out the
> front of the canopy. The horizon was visible more towards the top of the
> canopy. I aimed at a target and just kept the nose pointed there. I
> pulled back on the stick when I ran out of nerve. The bird settled on
> with a slight bump of the tailwheel and a little bounce as the main
> dropped on (I flared just a bit too much). I have no doubt that I could
> easily put this bird in a tiny field much easier than I could my Libelle
> (and that is not difficult at all).
>
> So, I'd have to say that all the bad things I've been told about landing
> flaps on gliders and V-tails are definitely untrue with respect to the
> HP-16. It is a comfortable and easy to fly glider and compares very well
> to my Libelle and also to other glass birds, including my favorites for
> handling, the Mosquito and LS-4.

[Scott Correa]

> The situations described to me were the difficulty of avoiding the cloud
> entry in the first place. A pilot can open his spoilers at 90 knots and
> begin descending immediately, but deploying the flaps at 90 knots first
> increases your altitude, making it much harder to stay out of the cloud.
> If you do lose control in a cloud, lots of drag is an advantage.
>
> The main point I hoped to make is landings aren't the only way spoilers
> and glide path flap operation differs, and one good landing isn't enough
> to know the pitfalls, even for landings. I think everyone agrees the HP
> series is a great ship to make off-field landings in the hands of a good
> pilot.
> --
> -----
> Replace "SPAM" with "charter" to email me directly
>
> Eric Greenwell
> Washington State
> USA


Eric.
Good points.... But flap deployment at speed needn't cause an altitude
change.
Roll 40 or so your favorite direction, g up and put them out. Minimal
altitude gain if any.

Scott.

[Al]

Scott remember Eric speaks for the little old lady division of the SSA. ;)

Winter is here let the fun begin.

Al


"Scott Correa" > wrote in message
...
>
> > The situations described to me were the difficulty of avoiding the cloud
> > entry in the first place. A pilot can open his spoilers at 90 knots and
> > begin descending immediately, but deploying the flaps at 90 knots first
> > increases your altitude, making it much harder to stay out of the cloud.
> > If you do lose control in a cloud, lots of drag is an advantage.
> >
> > The main point I hoped to make is landings aren't the only way spoilers
> > and glide path flap operation differs, and one good landing isn't enough
> > to know the pitfalls, even for landings. I think everyone agrees the HP
> > series is a great ship to make off-field landings in the hands of a good
> > pilot.
> > --
> > -----
> > Replace "SPAM" with "charter" to email me directly
> >
> > Eric Greenwell
> > Washington State
> > USA
>
>
> Eric.
> Good points.... But flap deployment at speed needn't cause an altitude
> change.
> Roll 40 or so your favorite direction, g up and put them out. Minimal
> altitude gain if any.
>
> Scott.
>
>

[Wallace Berry]

In article >,
Eric Greenwell > wrote:

> Wallace Berry wrote:
>
> > So, I'd have to say that all the bad things I've been told about landing
> > flaps on gliders and V-tails are definitely untrue with respect to the
> > HP-16.
>
> If you believe that, perhaps you haven't been told "all the bad things".
> For example, I've had HP pilots tell me getting sucked up into a cloud
> can be "awkward" to deal with when all you've got is flaps.
>
> My first and only flight in an HP went like Mr. Berry's; even so, I hope
> anyone beginning to fly a flaps only glider gets thorough checkout,
> because there are ways to go wrong.

No doubt there are ways to go wrong, but every design has it's quirks. I
would sooner turn a low time pilot loose in that HP-16 than my 301
Libelle.

For sure my one experience in a landing flapped equipped bird is far too
little experience to generalize. That's why I limited my comments to the
HP-16. However, I have been told horror stories about V-tails and
landing flaps. You know the stories. I was told the V-tail HP's were
hard to fly and dangerous for any but the most experienced fliers. I'm
no ace but I thought the thing was very easy to fly. Maybe the other
HP's are different. The main myth is that you can't modulate the flaps
to control glide path. In the HP-16, I rolled the flaps on and off
within a fairly wide range and the glider behaved very much like a
glider with very effective divebrakes. I would be very comfortable
landing Jim's HP-16 in any reasonably landable field.

Deploying flaps at high speeds can be problematic in a number of ships.
I have heard that at least one 301 Libelle structural failure was due to
flap deployment at a speed significantly above Vne. However, a number of
ships which have flaps that deploy with the divebrakes have maximum
deployment speed limitations too. And, not to forget, deployment of just
divebrakes at high speeds can be dangerous. I think a couple of open
class ships have lost their wings when the divebrakes were deployed well
over Vne.

As for getting sucked into a cloud, I would have an easier time keeping
that HP-16 out of the cloud than my Libelle with it's relatively
ineffective divebrakes. I have been in the gear down, full divebrakes
and full slip configuration diving for the edge of the cloud at high
speed to keep from getting sucked in.


Fly safe,

Wallace

[JJ Sinclair]

OK, It's winter time and I'm bored, so let me throw my 2 cents in here. The
only flight I ever had in a ship with flaps only was in a PIK-20B. It was a
test flight after a broken fuselage. Things went well until it got time to
land. I rolled in 45 degrees of flaps and everything looked just about right.
Came over the fence at 50 knots and waited for her to settle down. I waited and
waited and waited. By now I had floated down most of the 4000 foot runway and
I'm still floating about 1 foot off the ground. What do I do? Musn't dump the
flaps or she will drop like a stone, right? Finally got the wheel on the ground
and jumped on the brake.
That night I read the flight manual and it said to slowely crank off the flaps
in this situation. I think the flaps only ships are OK, but require a different
set of skills that must be mastered. Probably not for the low time pilot or
those who don't read the flight manual before flight. My real problem was being
about 5 knots too fast. Proper speed control is critical.
JJ Sinclair

[Eric Greenwell]

Wallace Berry wrote:

> As for getting sucked into a cloud, I would have an easier time keeping
> that HP-16 out of the cloud than my Libelle with it's relatively
> ineffective divebrakes. I have been in the gear down, full divebrakes
> and full slip configuration diving for the edge of the cloud at high
> speed to keep from getting sucked in.

The 301 definitely has weak spoilers (good wheel brake, though!), which
is one reason I moved to an ASW 20C.

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Eric Greenwell
Washington State
USA

[Eric Greenwell]

JJ Sinclair wrote:

> OK, It's winter time and I'm bored, so let me throw my 2 cents in here. The
> only flight I ever had in a ship with flaps only was in a PIK-20B. It was a
> test flight after a broken fuselage. Things went well until it got time to
> land. I rolled in 45 degrees of flaps and everything looked just about right.
> Came over the fence at 50 knots and waited for her to settle down. I waited and
> waited and waited. By now I had floated down most of the 4000 foot runway and
> I'm still floating about 1 foot off the ground. What do I do? Musn't dump the
> flaps or she will drop like a stone, right? Finally got the wheel on the ground
> and jumped on the brake.
> That night I read the flight manual and it said to slowely crank off the flaps
> in this situation. I think the flaps only ships are OK, but require a different
> set of skills that must be mastered. Probably not for the low time pilot or
> those who don't read the flight manual before flight. My real problem was being
> about 5 knots too fast. Proper speed control is critical.

So I'm told. Our club had a member from Long Island, where the club
there had a 1-35. He said they got rid of it after a while because they
got tired of pulling it out of the weeds at the end. Without a landing
flap equipped two seater, they weren't able to train their low time
pilots well enough to land it properly. I think there would be a lot
more acceptance of HP style flaps if we had two seaters to train in.

--
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Eric Greenwell
Washington State
USA

[Eric Greenwell]

Wayne Paul wrote:

> Here are some pictures of Jim Harper's HP-16:
> http://www.soaridaho.com/Schreder/HP-16/N8DC/N8DC_First_Flight.htm
>
> Wayne
> http://www.soaridaho.com/
>
>
> "Wallace Berry" > wrote in message
> ...

Wayne, what's it like to land an HP in a strong, gusty wind? Do you use
a higher approach speed and only partial flap?
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Eric Greenwell
Washington State
USA

[Bob Kuykendall]

Earlier, JJ wrote:

> I rolled in 45 degrees of flaps and
> everything looked just about right.
> Came over the fence at 50 knots and
> waited for her to settle down...

If it's floating down the runway, you just don't have enough flaps
cranked in. Dick Schreder pointed this out when he wrote the
instructions on test flying the HP-11:

http://www.soaridaho.com/Schreder/HP-11/HP-11_Flight_Testing.html

which says:

: If the HP-11 is floating down the
: runway and doesn't want to slow down,
: you just don't have enough flap
: cranked down.

That was in 1963, and I'm pretty sure that it still applies. The same
advice is also repeated in the test flight instructions for the HP-14
and HP-18.

When flying my HP-11 at Air Sailing when the wind favored 21 I
generally stopped right in front of the windmill near the
intersection. Just as I cross the edge of the sage along runway 17 I
would crank on the full 90, flare across 17, and come to a halt within
less than 100 yards of touchdown. And that's landing downhill in a
ship equipped with a go-kart style band-on-tire wheel brake.

The secret to the HP landing technique is to be proactive about
increasing stick forward pressure as you crank on the flaps. If you
try to be reactive, and wait until you see the airspeed change, you've
already gotten too slow. So the technique that works well is to get
the stick moving in the right direction as you crank the flaps on or
off, and worry about refining the speed control later. Control system
engineers call this a "feed forward" system, since there's just not
time to wait for feedback before starting corrective action.

As far as getting sucked into a cloud, the only time it happened to me
it was scary, but other than that rather tame. I cranked on about 75
degrees of flaps, put out the wheel to silence the warning buzzer, and
trundled out the bottom in a 45-degree dive at about 50 knots. The
important thing is to get the flaps out before you exceed the Vfe
speeds.

On another branch of this thread, Eric observes that one reason that
flaps are an issue is that there are so few two-seaters with 90-degree
flaps. I agree; this is one of the primary reasons that the next HP
kit will not be developed with 90-degree flaps. If anybody really
wants one, I can set the wings up for it, but the primary
configuration will have airbrakes. Personally, I really do prefer the
flaps over airbrakes. However, I do not have the resources to
prosecute an ideological battle on their behalf. If anybody wants to
know the depth to which I've sold out in pursuit of a successful
career as a sailplane developer, feel free to let this be the measure
of it.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24

[Robert Ehrlich]

Eric Greenwell wrote:
>
> JJ Sinclair wrote:
>
> > OK, It's winter time and I'm bored, so let me throw my 2 cents in here. The
> > only flight I ever had in a ship with flaps only was in a PIK-20B. It was a
> > test flight after a broken fuselage. Things went well until it got time to
> > land. I rolled in 45 degrees of flaps and everything looked just about right.
> > Came over the fence at 50 knots and waited for her to settle down. I waited and
> > waited and waited. By now I had floated down most of the 4000 foot runway and
> > I'm still floating about 1 foot off the ground. What do I do? Musn't dump the
> > flaps or she will drop like a stone, right? Finally got the wheel on the ground
> > and jumped on the brake.
> > That night I read the flight manual and it said to slowely crank off the flaps
> > in this situation. I think the flaps only ships are OK, but require a different
> > set of skills that must be mastered. Probably not for the low time pilot or
> > those who don't read the flight manual before flight. My real problem was being
> > about 5 knots too fast. Proper speed control is critical.
>
> So I'm told. Our club had a member from Long Island, where the club
> there had a 1-35. He said they got rid of it after a while because they
> got tired of pulling it out of the weeds at the end. Without a landing
> flap equipped two seater, they weren't able to train their low time
> pilots well enough to land it properly. I think there would be a lot
> more acceptance of HP style flaps if we had two seaters to train in.
>

Flaps only ships are very rare in France and kowledge about their handling
is probably even more rare. I wonder how one can handle in such a ship what
is described in our flight Bible, the "blue book" (Manuel du pilote Vol a Voile,
i.e. glider pilot's manual) as the 3 most common mistakes when landing:
1) flare to high; 2) flare with excessive back stick action; 3) bounce.
In this 3 cases the glider comes a few feet above the ground at a speed
just marginally above stall speed and quickly decaying due to the drag of
open airbrakes. The immediate action to avoid that the glider falls on
the ground like a stone in the following seconds is to retract the air-brakes,
so that the drag stops killing your speed and you regain some lift, then
try to land better ahead. But what can you do with no air-brakes?

[Eric Greenwell]

Bob Kuykendall wrote:

> On another branch of this thread, Eric observes that one reason that
> flaps are an issue is that there are so few two-seaters with 90-degree
> flaps. I agree; this is one of the primary reasons that the next HP
> kit will not be developed with 90-degree flaps. If anybody really
> wants one, I can set the wings up for it, but the primary
> configuration will have airbrakes. Personally, I really do prefer the
> flaps over airbrakes. However, I do not have the resources to
> prosecute an ideological battle on their behalf. If anybody wants to
> know the depth to which I've sold out in pursuit of a successful
> career as a sailplane developer, feel free to let this be the measure
> of it.

Are there engineering or manufacturing issues that make spoilers a more
desirable choice these days? For example, a fiberglass wing might be
more flexible than a metal one, which would make a 90 degree flap harder
to implement. The early ASW 20 had problems this way with it's 60 degree
flap setting.

--
-----
Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

[Udo Rumpf]

"Robert Ehrlich" > wrote in message
...
> Eric Greenwell wrote:
> >
> > JJ Sinclair wrote:
> >
> > > OK, It's winter time and I'm bored, so let me throw my 2 cents in
here. The
> > > only flight I ever had in a ship with flaps only was in a PIK-20B. It
was a
> > > test flight after a broken fuselage. Things went well until it got
time to
> > > land. I rolled in 45 degrees of flaps and everything looked just about
right.
> > > Came over the fence at 50 knots and waited for her to settle down. I
waited and
> > > waited and waited. By now I had floated down most of the 4000 foot
runway and
> > > I'm still floating about 1 foot off the ground. What do I do? Musn't
dump the
> > > flaps or she will drop like a stone, right? Finally got the wheel on
the ground
> > > and jumped on the brake.
> > > That night I read the flight manual and it said to slowely crank off
the flaps
> > > in this situation. I think the flaps only ships are OK, but require a
different
> > > set of skills that must be mastered. Probably not for the low time
pilot or
> > > those who don't read the flight manual before flight. My real problem
was being
> > > about 5 knots too fast. Proper speed control is critical.
> >
> > So I'm told. Our club had a member from Long Island, where the club
> > there had a 1-35. He said they got rid of it after a while because they
> > got tired of pulling it out of the weeds at the end. Without a landing
> > flap equipped two seater, they weren't able to train their low time
> > pilots well enough to land it properly. I think there would be a lot
> > more acceptance of HP style flaps if we had two seaters to train in.
> >
>
> Flaps only ships are very rare in France and kowledge about their handling
> is probably even more rare. I wonder how one can handle in such a ship
what
> is described in our flight Bible, the "blue book" (Manuel du pilote Vol a
Voile,
> i.e. glider pilot's manual) as the 3 most common mistakes when landing:
> 1) flare to high; 2) flare with excessive back stick action; 3) bounce.
> In this 3 cases the glider comes a few feet above the ground at a speed
> just marginally above stall speed and quickly decaying due to the drag of
> open airbrakes. The immediate action to avoid that the glider falls on
> the ground like a stone in the following seconds is to retract the
air-brakes,
> so that the drag stops killing your speed and you regain some lift, then
> try to land better ahead. But what can you do with no air-brakes?

The landing is executed in a way as not to use full 90 degree flap in the
final stages of the final. Rather manage the final approach in a way that
allows the use of less flap. You will have some flap action in reserve to
arrest any excessive sink, similar to using only partial spoiler.

In Fact, when looking at my flying style with the flap only glider,
I use the flap, like you would use the spoiler. I constantly make use of
them
during the pattern to place my self at any point I would like to be.
When making misjudgements it is no different to correct them, as with
spoilered gliders.

It is best for a newcomer to place the glider relative high on final
crank in full flaps and aim for the beginning of the run way.
That way you will have enough speed for corrections if you make a
misjudgement and if you are on glide path you burn of all the energy very
quickly. It really does not matter if you use and extra 200 feet.
In the end it the touch down speed that counts.

As for out landings into small fields with high obstacle, it requires
different approaches and only practice at your home field will make you
proficient.

Udo

[Bill Daniels]

"Robert Ehrlich" > wrote in message
...
> Eric Greenwell wrote:
> >
> > JJ Sinclair wrote:
> >
> > > OK, It's winter time and I'm bored, so let me throw my 2 cents in
here. The
> > > only flight I ever had in a ship with flaps only was in a PIK-20B. It
was a
> > > test flight after a broken fuselage. Things went well until it got
time to
> > > land. I rolled in 45 degrees of flaps and everything looked just about
right.
> > > Came over the fence at 50 knots and waited for her to settle down. I
waited and
> > > waited and waited. By now I had floated down most of the 4000 foot
runway and
> > > I'm still floating about 1 foot off the ground. What do I do? Musn't
dump the
> > > flaps or she will drop like a stone, right? Finally got the wheel on
the ground
> > > and jumped on the brake.
> > > That night I read the flight manual and it said to slowely crank off
the flaps
> > > in this situation. I think the flaps only ships are OK, but require a
different
> > > set of skills that must be mastered. Probably not for the low time
pilot or
> > > those who don't read the flight manual before flight. My real problem
was being
> > > about 5 knots too fast. Proper speed control is critical.
> >
> > So I'm told. Our club had a member from Long Island, where the club
> > there had a 1-35. He said they got rid of it after a while because they
> > got tired of pulling it out of the weeds at the end. Without a landing
> > flap equipped two seater, they weren't able to train their low time
> > pilots well enough to land it properly. I think there would be a lot
> > more acceptance of HP style flaps if we had two seaters to train in.
> >
>
> Flaps only ships are very rare in France and kowledge about their handling
> is probably even more rare. I wonder how one can handle in such a ship
what
> is described in our flight Bible, the "blue book" (Manuel du pilote Vol a
Voile,
> i.e. glider pilot's manual) as the 3 most common mistakes when landing:
> 1) flare to high; 2) flare with excessive back stick action; 3) bounce.
> In this 3 cases the glider comes a few feet above the ground at a speed
> just marginally above stall speed and quickly decaying due to the drag of
> open airbrakes. The immediate action to avoid that the glider falls on
> the ground like a stone in the following seconds is to retract the
air-brakes,
> so that the drag stops killing your speed and you regain some lift, then
> try to land better ahead. But what can you do with no air-brakes?

Flaps, once deflected beyond about 10 degrees, produce mainly drag. In
steady-state glides, drag is drag whether produced by flaps or spoilers.
For a given amount of drag, a flapped glider will have the nose much further
down than a glider with spoilers, however. This gives a much better view of
the runway.

The main difference is in the transients as the drag devices are extended or
retracted. The trick with flaps is to manage the transients. Yanking on
flaps from the retracted position will produce a upward transient before the
drag steepens the glide path. Yanking on spoilers will produce a downward
transient before the glider settles into a steeper glide. This generally
means that the pilot should not make large, sudden changes in flap settings
near the ground - but this is good advice for spoilers as well.

Large flap deflections change the relationship between pitch and airspeed.
Large changes in pitch result in small changes in airspeed so that the nose
can be steeply down and the airspeed will not increase much. This invites
the technique popular with HP glider pilots of just aiming the glider
steeply down at the flair point with 90 degrees of flap deployed. If the
glide appears to be overshooting the aim point, pushing the nose further
down steepens the glide without much increase in airspeed. If it appears
that you are undershooting, just raise the nose a little and shallow the
glide. Extremely accurate landings are possible with no changes made in the
flap setting.

The height to start the flare is a bit tricky to judge at first and the
flare is greatly exaggerated compared to spoiler only gliders. If you flare
too high, the recovery is to just relax some of the back stick and let the
glider settle before completing the flare. "Leave 'em where they are" is
good advice when landing with flaps.

I really like flaps. They eliminate the discontinuity in the upper wing
surface created by the spoiler box. Once mastered, they permit much lower
energy landings than with spoilers.

A for as a trainer, the IS28b2 Lark can be landed with flaps only although
the glide is quite shallow. I looked at the flap drive geometry on my Lark
with the thought that it might be modified to allow 45 degrees or more of
positive flap just for training scenarios. It would be possible but the
paperwork would be a nightmare.

Bill Daniels

[Bob Whelan]

"Robert Ehrlich" wrote...
> Flaps only ships are very rare in France and kowledge about their handling
> is probably even more rare. I wonder how one can handle in such a ship
what
> is described in our flight Bible, the "blue book" (Manuel du pilote Vol a
Voile,
> i.e. glider pilot's manual) as the 3 most common mistakes when landing:
> 1) flare to high; 2) flare with excessive back stick action; 3) bounce.
> In this 3 cases the glider comes a few feet above the ground at a speed
> just marginally above stall speed and quickly decaying due to the drag of
> open airbrakes. The immediate action to avoid that the glider falls on
> the ground like a stone in the following seconds is to retract the
air-brakes,
> so that the drag stops killing your speed and you regain some lift, then
> try to land better ahead. But what can you do with no air-brakes?

Speed control is important in gracefully landing flaps-only gliders
(spoilers-only too, of course). What I've found - and often seen - is that
gliders' large-deflection flaps essentially 'quit working' as drag producing
devices if landed 'too fast.' True even for HP-16's. Come in too fast and
you _will_ float a long ways in flapped gliders...unless you slowly ease off
on the flaps, in which case the ship will gently settle...sort of the
flaps-only equivalent of easing on more spoilers if running out of field.
Certainly not a Big Deal if understood beforehand.

BTW, the most common mistake I've seen in flapped ships IS landing too
fast...probably fallout from: 1) (U.S. centric) training in Schweizer 2-33's
in which being too fast doesn't generally lead to landing alarm/excitement;
and 2) (worldwide?) training in reasonably benign (in the touchdown sense)
spoilers-only, nose-dragging trainers lacking a springy nosewheel. G-103's
in the U.S. often tell the tale of what bad can happen when trying to force
one of them on the ground at too fast a speed (PIO/fuselage damage/etc.).

Regarding your specific questions, in the event someone DOES manage to flare
too high (whether from doing a good flare but too high, or from
over-aggressive aft-stick motion/'ballooning', or simply bounces the
touchdown) in a flaps-only ship, the only proper recourse is to wait. If
you're savvy enough and have time, you can re-establish the proper pitch
angle for touchdown _then_ wait...but wait. Don't churn the stick and don't
adjust the flap position. The bad news is drag IS high and ground-effect
DOES hugely lessen as speed decays. The good news is there is usually a LOT
of downwash, even on a truly botched flare with full flaps, and it's not the
easiest thing to do to drop a flapped ship in from 3 feet. Certainly no
more difficult IMHO than doing so in a spoilers-only ship. Dropping in
either configuration is possible, of course.

IMHO, about the only situation I can envision where a flaps-only ship IS
worse than a spoilers-only one is that of getting low and slow on the
approach. Is there a spoilers-only driver alive who doesn't take some
comfort in the thought s/he can slam the spoilers shut in that situation and
not distinctly improve things in the near-term future? Get yourself in that
situation in a flaps-only ship and you're essentially out of options. The
GOOD news is that you're much more likely to get low and slow in a ship
having weak landing aids...generally not a problem in gliders having _only_
large deflection flaps as landing aids.

Regards,
Bob W.


---
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[Bob Kuykendall]

Earlier, Eric Greenwell wrote:

> Are there engineering or manufacturing
> issues that make spoilers a more
> desirable choice these days? For
> example, a fiberglass wing might be
> more flexible than a metal one, which
> would make a 90 degree flap harder
> to implement. The early ASW 20 had
> problems this way with it's 60 degree
>flap setting.

Boy, you picked up on that one quick!

I'm not qualified to address the actual engineering
aspects of this issue. But speaking from the perspective
of a sailplane development pundit:

I think that, absolutely, implementing 90-degree flaps
on a composite wing has complications that you wouldn't
find on a more rigid metal wing. However, the lessons
of the PIK-20B and the Zuni suggest that it is doable.

As you point out, the big problem is bending of the
wing with fully deployed flaps, which tries to bend
the flaps in the plane in which they are most rigid.
I suspect that overcoming this issue requires the right
layup type and fiber orientation. I'd have to do test
sections to be sure, but I think that either aramids
or possibly newer polyethelyne fibers on some sort
of bias orientation would be required. That might give
reasonable torsional stiffness without undue bending
stiffness. It seems to work for the LS-6, which uses
Kevlar (tm) laminates in the flaperons.

Of course, a stiffer wing than the old ASW-20 would
help, too. That, and more hinge points and more drive
points.

Before I tried it for sure, what I'd want to do would
be to test a candidate flap section, and see how close
I can get it to the predicted wing curvature at the
ultimate loading limit. It might turn out to be necessary
to either make the wing stiffer, or to limit loading
to a lower G value under landing flap deployment. Or
perhaps something else entirely. That's what testing
is for.

Thanks, and best regards to all

Bob K.

[Jim Harper]

Wallace Berry > wrote in message >...
lots of good stuff snipped...

Geeze, Wally. Thanks! Just a couple of responses through the entire
thread.

Floating down the runway? More flaps. With 90 degrees and the nose
level...she stops pretty close to right now. Might want to make sure
you aren't more than that foot or so above the ground, or you test
Schreder's wonderful shock absorbtion.

Clouds? Full flaps at whatever speed you are going aren't going to put
you up much...and you will come down quite quickly...and out of the
cloud. If you go 90 degrees in my 16, you can pretty much let go of
the stick (at altitude) and it descends quite docilly...well...it bobs
and weaves but it don't scare me much. There is a bunch of drag there.
I should note that I am at the forward limit of the CG.

My biggest concern about the -16 is that it is gonna ruin me for other
gliders. No way will I ever find similar glidepath control. I can
modulate out of pretty much any amount of trouble.

At any rate, Wally, thanks again. I love to share! And I had to fly
tow anyway!!

Jim

[Wayne Paul]

"Eric Greenwell" > wrote in message
...
>
> Wayne, what's it like to land an HP in a strong, gusty wind? Do you use
> a higher approach speed and only partial flap?
>

Eric,

I am a low time glider pilot and I think more experienced pilots could
provide more insight then I; however, from my limited experience you are
right on target.

Several years ago I purchase a HP-16T (now owned by Brian Case). I search
the web for information and found almost nothing, so I started a web site to
act as a repository of information relating to Dick's designs. The site was
well receive by HP/RS/RHJ owner and article, pictures, etc started arriving.
The result is http://www.soaridaho.com/Schreder The information on the site
reflects the cooperation of HP enthusiasts, not my expertise.

Bob Kuykendall started a complementary service by forming the hp-gliders
news group. (http://groups.yahoo.com/group/hp-gliders). The combination of
the two resources have served Schreder sailplane design owners over the past
five+ years.

After I sold my HP-16T to Brian I purchase a HP-14 which I have been
restoring for the past 3 years.

Here are some relevant landing related articles that I have collected:

Dick Schreder --
http://www.soaridaho.com/Schreder/Stories/Schreder_on_Flaps.htm
Steve du Pont -- http://www.soaridaho.com/Schreder/Large-span_flaps.html

Bob Kuykendall -
http://www.soaridaho.com/Schreder/Stories/Preparing_for_first_HP_flight.htm

Wayne
http://www.soaridaho.com

[JJ Sinclair]

Bob K wrote>>>>>>>>..>
>As you point out, the big problem is bending of the
>wing with fully deployed flaps, which tries to bend
>the flaps in the plane in which they are most rigid.

If one were to bounce, or land in a rough field, in one's ASW-20, with 45
degrees of flap on, the downward motion of the wings would force the deployed
flaps to move up, thus bending the internal flap push-rods. I would think some
sort of sliding push-rod arrangement might prevent this situation. The Ventus
has a gas strut that will allow the deployed flaps to come back up. Do I have
the Ventus gas strut figured out correctly, you Ventus drivers?
JJ Sinclair

[Bob Gibbons]

On Tue, 18 Nov 2003 07:47:58 -0800, Eric Greenwell
> wrote:

.... text deleted ...
>
>Wayne, what's it like to land an HP in a strong, gusty wind? Do you use
>a higher approach speed and only partial flap?
>--

Eric, I resisted jumping into this thread, but for what it's worth,
while I no longer fly a PIK, I did own a PIK20B for 18 years and have
something over 2000 hours in this 90deg flap only ship.

Most of the important points on 90deg flaps have already been said.

- they are different, so there is an initial learning curve that is
made more difficult by the lack of 90deg flaped trainers. I often
recommended new PIK pilots to get an hour in a Cessna 150 to get a
feel for high flap deflection behavior.

- once mastered, they can be modulated during any portion of the
pattern with no problem. As has been said before, if you are floating
and can not get the ship down, put on more flap. Once the main wheel
is on the ground, dump the flap (full negative (up)) to plant the ship
on the ground.

- Like any flapped ship, so not get below the flaps up stall speed
during the pattern, until your final flare. This allows you to
modulate the flaps with no concern about pulling out flap and
stalling.

- On the PIK, I recommended new pilots move the PIK flap handle (5
turns total) in full 360deg increments, always stopping at the top of
the circle. This made modulation like normal spoilers, pulling the
handle back from the top position lowered flap, increased drag, just
like pulling back a spoiler handle. And the opposite for pushing
forward from a top position, less drag.

- Relating to your question, the only drawback I found in the 90deg
flaps was landing in very gusty conditions. Here I would limit the
down flap to something like 45deg. Since this only occured with strong
headwind components, I did not need large flap deflections.

- The strong advantage to the 90deg flaps was in short field landing,
where you could point the ship at a spot on the ground and modulate
the flaps to control airspeed. BTW, the only time in all my flying
that I used 90deg flaps was in off-field landings over a tree line,
and for routine practice. Typical landing flap varied between 30deg
and 60deg.

Bob

[Robert Ehrlich]

Bob Whelan wrote:
> ...
> IMHO, about the only situation I can envision where a flaps-only ship IS
> worse than a spoilers-only one is that of getting low and slow on the
> approach. Is there a spoilers-only driver alive who doesn't take some
> comfort in the thought s/he can slam the spoilers shut in that situation and
> not distinctly improve things in the near-term future? Get yourself in that
> situation in a flaps-only ship and you're essentially out of options. The
> GOOD news is that you're much more likely to get low and slow in a ship
> having weak landing aids...generally not a problem in gliders having _only_
> large deflection flaps as landing aids.
> ...

Except for the presence of the runway instead of unlandable terrain below
the glider, this is exactly the situation of my question, and so the answer,
as I suspected, is that you are out of options.

[Silent Flyer]

When Slingbys tried to produce the HP14 for the British market they ran into
trouble with the use of flaps only for cloud flying. At that time to get an
airworthiness certification the glider had to have speed limiting devices
for cloud flying. It had been proved in test flying that the flaps
certainly limited the airspeed to "rough air max." but the test pilot ( John
Williamson) reported if the airspeed was already high and rising, the effort
required to lower the flaps down to 90 degrees was just too much.

If the sailplane was genuinely going out of control in cloud the flaps would
be useless. Various methods were tried to overcome this including a high
pressure air bottle to actuate pneumatic jacks- unfortunately at high speeds
forcing the flaps down in this manner caused problems with the supporting
secondary spar structure requiring yet further modifications.

DB

[Al]

The Ventus Strut is pushing up.
Part of the preflight on my Ventus B is to push down on the inboard flap
both sides to feel the gas strut pressure.

Al

"JJ Sinclair" > wrote in message
...
> Bob K wrote>>>>>>>>..>
> >As you point out, the big problem is bending of the
> >wing with fully deployed flaps, which tries to bend
> >the flaps in the plane in which they are most rigid.
>
> If one were to bounce, or land in a rough field, in one's ASW-20, with 45
> degrees of flap on, the downward motion of the wings would force the
deployed
> flaps to move up, thus bending the internal flap push-rods. I would think
some
> sort of sliding push-rod arrangement might prevent this situation. The
Ventus
> has a gas strut that will allow the deployed flaps to come back up. Do I
have
> the Ventus gas strut figured out correctly, you Ventus drivers?
> JJ Sinclair

[Jim Harper]

"Bob Whelan" > wrote in message >...
[snip]
> Speed control is important in gracefully landing flaps-only gliders
> (spoilers-only too, of course). What I've found - and often seen - is that
> gliders' large-deflection flaps essentially 'quit working' as drag producing
> devices if landed 'too fast.' True even for HP-16's. Come in too fast and
> you _will_ float a long ways in flapped gliders...unless you slowly ease off
> on the flaps, in which case the ship will gently settle...
[good stuff snipped]
> IMHO, about the only situation I can envision where a flaps-only ship IS
> worse than a spoilers-only one is that of getting low and slow on the
> approach.
[snip]
> Regards,
> Bob W.

Hi, Bob and all.

With all humility and with the following caveats, I would like to
mildly disagree and vehemently agree with a couple of your points.
First the caveats: I am not all that experienced, and have only flown
my HP-16 for one summer, I think I am qualified to comment, but by no
means am an expert. The following comments ONLY apply to my HP-16,
N8DC, with 90 degree flaps, standard sized flaps (no flap was
sacrificed to improve the ailerons), and flown fairly CG forward.

Mild disagreement on the too fast comment. I think that the only way
to make my -16 float would be to be going too fast and then roll off
the flaps. 90 degree flaps require an impressive deck angle just to
keep the speed in the 60mph range on approach. If, when I get close to
the ground, I flare, any excess speed, and I mean ANY excess speed is
gone very quickly, and I land. Period. An approach with, say, 60
degrees of flap would indeed float if I had too much speed on, and as
such, one possible corrective action would be to roll off the flaps,
if I had slowed considerably...otherwise, more flaps is usually the
right answer. This airplane will not float with maximum flaps. There
have got to be 6 square feet of aluminum hanging perpendicular to the
airflow...we stop pretty quickly.

A minor expansion on that. It is very difficult to get the airplane to
accelerate with 90 degree flaps...If I should let the airspeed decay
on approach with full flaps, I need to push the nose down to
frightening angles...as in hanging from the straps...to
accelerate...or just roll off some flaps, which is what I do. This
presupposes that we are talking 45-60+ speed range. I would very much
not like to get much below 45 with full flaps. The aircraft's stall
characteristics are quite benign, but recovery requires a fair amount
of altitude with flaps at that level.

Conversely, speed control on appoach is quite trivial. Should I, for
whatever reason, let the speed creep up...more flaps...less speed. It
is amazingly linear...and better than any speed/lift control device I
have used, including throttle.

To agree emphatically on another point: Low and slow with flaps on is
a VERY BAD THING (tm). Too fast is no problem...roll the flaps in to
slow, roll them out to stretch. Too slow, and your options
are...well...gone. So that is an area of the performance curve that I
avoid.

I too went into the -16 wondering about all of the forked-tailed flaps
of doom talk. Turns out that my airplane is an absolute pussycat. If
yer ever planning on being around LaGrange, GA some weekend, drop me a
note. We might can work something out!

Jim

[Michael]

Robert Ehrlich > wrote
> Except for the presence of the runway instead of unlandable terrain below
> the glider, this is exactly the situation of my question, and so the answer,
> as I suspected, is that you are out of options.

I think that's rather overstated. Unless you have botched the pattern
so throroughly that you are at 30 degrees of flap and coming up short,
you do exactly what you do in a spoiler-only ship - you retract the
flaps. The difference is this - you can't just retract completely, as
you would spoilers, because retracting that last 30 degrees is going
to cause a transient drop you won't like. However, going from 90
degrees to 45 causes no loss of lift at all, and a huge loss of drag -
thus causing airspeed to increase, which allows lifting the nose and
dramatically flattening the approach. This was certainly the case in
my HP-11, and I can't imagine it would be much different on other
flaps-only gliders.

Michael

[Robert Ehrlich]

Michael wrote:
>
> Robert Ehrlich > wrote
> > Except for the presence of the runway instead of unlandable terrain below
> > the glider, this is exactly the situation of my question, and so the answer,
> > as I suspected, is that you are out of options.
>
> I think that's rather overstated. Unless you have botched the pattern
> so throroughly that you are at 30 degrees of flap and coming up short,
> you do exactly what you do in a spoiler-only ship - you retract the
> flaps. The difference is this - you can't just retract completely, as
> you would spoilers, because retracting that last 30 degrees is going
> to cause a transient drop you won't like. However, going from 90
> degrees to 45 causes no loss of lift at all, and a huge loss of drag -
> thus causing airspeed to increase, which allows lifting the nose and
> dramatically flattening the approach. This was certainly the case in
> my HP-11, and I can't imagine it would be much different on other
> flaps-only gliders.

This will work on approach, when you have the nose down attitude
corresponding to the flaps setting but not in the situation of my
initial question, i.e. just after a botched flare, a few feet above
the runnway and no nose down attitude. In this case retracting the
flaps will cause a loss of drag, but no so huge, i.e. the drag will
much more than in zero flaps or zero spoilers configuration and there
is no gain in lift and no change in the stall speed, you don't have
the altitude that you can convert into speed, so I think that you are
going to fall on the ground, with a slighly increased delay compared
to what would happen if you didn't retract some flaps.

[JJ Sinclair]

Al wrote>>>>>>>>>>>>>..>
>The Ventus Strut is pushing up.
>Part of the preflight on my Ventus B is to push down on the inboard flap
>both sides to feel the gas strut pressure.

So, what is the purpose of the air strut?
JJ Sinclair

[Steve]

Robert Ehrlich > wrote
> Except for the presence of the runway instead of unlandable terrain below
> the glider, this is exactly the situation of my question, and so the answer,
> as I suspected, is that you are out of options.

Let me ask you this, Robert. Put yourself 5 feet above ground, 1 knot
above stall in any glider. Flaps, spoilers, trailing edge air brakes,
drag chute, or whatever. It is probably not going to be a pretty
landing, is it? About all you can do is try and get the nose down a
bit and then rotate one last time to reduce the smiting the ground
will give you. But you asked a good question.

I personally like my flapped ships. If you do put yourself in the
situation (botched flare, bounce, etc) you can also roll on a bit more
flap just before the smiting and soften the blow a bit. Assuming, of
course, you weren't already at full flap. I have had to do this twice
in my 1100 hours of Zuni flying. Once in an off-field landing on a
gusty day with a strong wind shear encounter at about 50 feet (I think
I lost 15 to 20 knots, but I was too busy looking outside to know for
sure). I stopped with the tail less than 10 feet into the field. I
have pictures to prove it. And nothing was even so much as scratched.
The other was over a runway, again involving a bit of wind shear.
Works nice. Pull and crank.

I also have flapped time in an HP-16, and an HP-14. Spoilered time
includes Ka-6 and 604, among others.

Interesting safety note for you all to think about: We have all seen
incidents involving spoilers openning on tow. I bet you have never
seen an inadvertant flap deployment on tow, have you?

Steve Leonard
Second Highest Time Zuni Pilot
(Bob Whelan still has more hours in them than me)

[Bob Whelan]

To expand on the earlier statement I made that flaps essentially 'quit
working' if a glider so-equipped is landed 'too fast,' even a short-span
(55') HP-14 with original (long) length flaps exhibits the behavior.
Understand we're talking a rather fine point here when considering HP
gliders (which generally have LOTS of flap compared to other flapped gliders
with which I'm reasonably familiar...Zuni's, Concept 70's, Nuggets and
PIK-20A/B's).

At the time I sold my '14 I felt I could easily put it into any field an
experienced 1-26 pilot would go for...and some unavailable to 1-26's
(because of the HP's steeper approach capability). May not have been
correct, but that's the confidence I felt in the bird. (Prior to the HP, I
flew a 1-26; it, too, is a ship that helps pilots build confidence in the
basics.)

I'd encourage any driver of a flapped ship to experiment at the home field
to convince himself to what degree his or her ship exhibits the 'quits
working' behavior. Once you're comfortable and consistent making
_full-flap_ approaches, roundouts and touchdowns under reasonable
conditions, start adding a speed increment coming downhill. Use the same
aiming point as for your normal landings. For example, if you're consistent
at 45 knots, pick up the next landing to 50 knots, then to 55, etc. Do the
flare carrying the extra speed, so's to end up nose-down a foot or so off
the deck, waiting for the speed to bleed off. Not 'too far' above your
normal approach speed, you'll find you're amazed at how much farther the
bird will float before 'drag overcomes downwash.'

The weaker the flaps, the more noticeable the effect.

The only reason I mentioned the effect is because discovering it on a
short-field outlanding made in dicey conditions that may encourage the pilot
to carry some extra speed (e.g. gusty winds, conditions conducive to wind
shear, etc.) is likely to set off some more ill-considered 'flaps are spawn
of the devil' stories!

For the record, I never experienced an indicated airspeed change due to
windshear in my HP-14 when making full flap approaches. I _have_
experienced them in my Zuni making full flap approaches. I'm reasonably
satisfied the difference lies in the flaps...the HP's were draggier,
necessitating a considerably nose-lower attitude. Get nose down enough, and
horizontal wind shear speed deltas in essence decouple from the glider's
airspeed. Imagine being able to do a vertical approach - your touchdown
spot will change due to horizontal windshear, but not your indicated
airspeed.

Since not all windspeed changes occur in the horizontal plane, a prudent
pilot may opt to carry extra speed despite powerful flaps, but the way to
shoehorn into a small field under those conditions is to begin bleeding the
extra speed off earlier/higher in the flare.

Regards,
Bob W.


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[Bob Kuykendall]

Earlier, Robert Ehrlich > wrote:

> This will work on approach, when you have the nose down attitude
> corresponding to the flaps setting but not in the situation of my
> initial question, i.e. just after a botched flare, a few feet above
> the runnway and no nose down attitude. In this case retracting the
> flaps will cause a loss of drag, but no so huge, i.e. the drag will
> much more than in zero flaps or zero spoilers configuration and there
> is no gain in lift and no change in the stall speed, you don't have
> the altitude that you can convert into speed, so I think that you are
> going to fall on the ground, with a slighly increased delay compared
> to what would happen if you didn't retract some flaps.

I have gone from plus 60 degrees to full negative, and then back to
plus 90, all within a few feet of the runway. It is rarely necessary
to do that (it sure wasn't when I tried it), but it can be done. All
it takes is speed, distance, careful modulation of pitch attitude and
a flare for the dramatic.

I think that what it boils down to is that everybody who has flown a
flapped aircraft knows that "sinking feeling" that you get when you
reduce the flap deflection, and most of them think that there's
nothing they can do about it. And that's wrong. If you apply the right
pressure to the stick in the right direction at the right time, you
can go from zero to full flaps and back again with no added or
subtracted vertical acceleration. This is, of course, slightly limited
by the longitudinal inertia of the aircraft; but is basically true for
all practical flap application rates. All it takes is practice.

Flaps are not magical lift-conjuring and lift-disappearing devices.
They are just a way of modulating the effective camber of the airfoil
section so as to change its L/D polar. All you need to do with the
stick is to adjust the angle of attack so as to maintain a constant L
value as you modulate the flaps to achieve the desired D value. And
that value can get very large indeed.

The only odd corner to flapped ships is that they, like most gliders
(all that I know of) stall at a higher speed with the flaps retracted
than with flaps deployed. So it is true that if you are just above
stall speed and you bring the flaps up, you could stall even without
changing the speed or loading. For example, the book values show the
HP-18 stalling at 35 mph at flaps 60, and 40 mph at flaps 0 (both at
770 lbs gross). However, it is expected that when you're operating
near the ground you have much more margin over stall than that 5 mph
difference. Gusts and/or wind gradient effects will often account for
more than twice that.

Bob K.
http://www.hpaircraft.com

[Duane Eisenbeiss]

"JJ Sinclair" > wrote in message
...
> Al wrote>>>>>>>>>>>>>..>
> >The Ventus Strut is pushing up.
> >Part of the preflight on my Ventus B is to push down on the inboard flap
> >both sides to feel the gas strut pressure.
>
> So, what is the purpose of the air strut?
> JJ Sinclair

Maybe it has no real purpose. The Ventus 2bx does not have a air strut on
the flap linkage (at least I have not seen one). Maybe S-H decided that one
was not needed.

Duane

[Mike Borgelt]

On 20 Nov 2003 00:32:06 GMT, (JJ Sinclair) wrote:

>Al wrote>>>>>>>>>>>>>..>
>>The Ventus Strut is pushing up.
>>Part of the preflight on my Ventus B is to push down on the inboard flap
>>both sides to feel the gas strut pressure.
>
>So, what is the purpose of the air strut?
>JJ Sinclair

So the flap pushrod can shorten when you open the brakes. It is much
the same in the Mini Nimbus and Mosquito and gas struts in gliders are
a disaster waiting to happen to you. When they fail it is usually with
no warning. Try getting one while at a contest in the boonies. I found
that the one from the hatch of a VW Golf (Rabbit in the US)fitted.

Mike Borgelt

[Mark James Boyd]

I think that some folks got it right on the money
when they say that flapped ships are just different.
At some flap deflection (maybe 20, 30, 45 deg) the
wing may be better than 0 flap for floating down the
runway. So 0 flap or 90 flap may be great
for landing while something in between may cause
lots of floating.

Seems to make sense intellectually, but may take a little
getting used to. I'm glad someone mentioned
the PIK-20, we have one at our club and we
have a newer pilot getting used to it, but things
were quite different from the Blanik (our only flapped
trainer).

I was always under the impression that Fowler flaps
reduced stall speed, but didn't think plain flaps
did much other than just add drag. On the
Katana, AA-1 Grumman, and Tomahawk (all power planes)
they seem to do nothing but add drag. Interesting
to hear these experiences, and I'll certainly
look at the next HP I come across more carefully.

As far as V-tails go, anything to reduce wetted area
is good, right? ;-P

[Scott Correa]

"Mark James Boyd" > wrote in message
news:3fbc8231$1@darkstar...
> As far as V-tails go, anything to reduce wetted area
> is good, right? ;-P

I was under the impression that V tails don't reduce wetted area......
There is a number called tail volume coefficient. Distribution
of this area in a V ot T planform results in the same wetted area.
You might make the case that the V tails are of a higher aspect ratio
and "better" but you also have to account for crosswind performance.
The max crosswind you can land in is determined by rudder effectiveness.
(I'll skip the wing low attitude/long wing problem) A V tail reduces up
elevator authority as the crosswind component grows. So it appears that
a V tail gliders minimum approach speed go's up as a function of the
crosswind. There may be insufficient "elevator" area or pitch authority
to flare as opposed to straight line flight where both elevons/elevators
will be moving "up".

Scott

[Udo Rumpf]

> I was under the impression that V tails don't reduce wetted area......
> There is a number called tail volume coefficient. Distribution
> of this area in a V ot T planform results in the same wetted area.
> You might make the case that the V tails are of a higher aspect ratio
> and "better" but you also have to account for crosswind performance.
> The max crosswind you can land in is determined by rudder effectiveness.
> (I'll skip the wing low attitude/long wing problem) A V tail reduces up
> elevator authority as the crosswind component grows. So it appears that
> a V tail gliders minimum approach speed go's up as a function of the
> crosswind. There may be insufficient "elevator" area or pitch authority
> to flare as opposed to straight line flight where both elevons/elevators
> will be moving "up".
>
> Scott
I would like to add,
If the V tail has a fixed stab the moving elements have to be large, because
of that, the airfoil can not achieve its aero dynamic potential. In the
case of
the HP 18, the hinge line at the root is at 45% and at the tip at 55%.
With
an all flying V tail this could be improved.
Over all the T-tail is the most effective, as each element can be optimized
for the function in term of size and aero dynamically generally and
specifically
having different airfoil for the Horizontal and vertical stab.

Udo

[Kirk Stant]

(Mark James Boyd) wrote in message news:<3fbc8231$1@darkstar>...

> I was always under the impression that Fowler flaps
> reduced stall speed, but didn't think plain flaps
> did much other than just add drag. On the
> Katana, AA-1 Grumman, and Tomahawk (all power planes)
> they seem to do nothing but add drag. Interesting
> to hear these experiences, and I'll certainly
> look at the next HP I come across more carefully.

All flaps will lower stall speed at small settings - even split flaps.
That's why you usually have a takeoff setting for soft and/or short
fields.

Boy, I havn't flown an AA-1 (the original, American Aviation Yankee,
with the "hot" wing) in a LONG time (32 years!) but I seem to remember
it's flaps didn't do much at all - at least compared to any Cessna.
Sure was a fun little thing to buzz around in, though!
>
> As far as V-tails go, anything to reduce wetted area
> is good, right? ;-P

This is a bit of a myth, I think. You still need the same tail volume
regardless of tail configuration, so you end up with basically the
same wetted area. If you cut down the size of the tails, you start
having stability problems (the Bonanza was originally a bit marginal,
I think), which is probably how V-tails on gliders got their bad
reputation in the first place. HPs apparently got it right from the
start. The theoretical saving is in reduced interference drag due to
fewer intersections (less of an advantage compared to T-tails) and
reduced weight (a big advantage compared to T-tails). Then there is
the rudder-elevator mixer issue...

They do look nicely retro, though. And the Fouga Magister proves that
the V tail can work beautifully in a relatively high performance fully
aerobatic jet trainer.

Finally, let's face it, V-tails were a fashion for a while in the late
40s and 50s (Bonanza, Magister, SHKs, Sisu, HPs, etc.) Now, T-tails
are the "cool" tail - which probably has a lot to do with why the poor
little PW-5 is dissed so much.

Kirk

[Eric Greenwell]

Kirk Stant wrote:

> They do look nicely retro, though. And the Fouga Magister proves that
> the V tail can work beautifully in a relatively high performance fully
> aerobatic jet trainer.

And I'm told the Salto does quite well as a Vee tailed aerobatic glider.


--
-----
Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

[J Larsson]

(JJ Sinclair) wrote in message >...
> Al wrote>>>>>>>>>>>>>..>
> >The Ventus Strut is pushing up.
> >Part of the preflight on my Ventus B is to push down on the inboard flap
> >both sides to feel the gas strut pressure.
>
> So, what is the purpose of the air strut?
> JJ Sinclair


I believe the flap / spoiler-drive mechanism on the Ventus a/b is more
or less identical to the Mini Nimbus / Mosquito solution. Last winter,
I and my co-owner, replaced the gas struts on our Mini Nimbus C. After
spending a few hours studying the finer details of this clever
arrangement I dare say that the struts do indeed have a purpose.

There are two struts involved, one of them is (as far as I can figure
out) used to balance out the forces in the spoiler handle and ensure
locking of the spoilers in their in and locked position. This strut
will work against the movement of the spoiler-handle for the first
part of the spoiler deployment, and then change into working to
further open the spoiler. As Mini Nimbus drivers knows, the forces in
the spoiler handle will immediately after unlocking them be very low,
you may even have to hold them back for the first 1 / 4 of spoiler
travel. After this the force will increase as also the flaps will be
deployed. The gas strut will, to some extent, limit the force
variations during spoiler operation. I would assume that this is also
true for the early Ventus models. The spoiler-flap operation on our
Mini was improved after replacing the strut.

The second gas strut is there to push the flaps up against a stop. The
position of the stop is altered with the flap handle. If you push the
flaps downwards, the gas strut is compressed, and when you release it
will spring back against the stop, which is -7 to +8 degrees depending
on flap setting. This is clever! When the spoilers are deployed, they
will after initially opening some 30 degrees, catch on to the flaps
and rotate these to (I believe) 60 degrees. The flaps will during this
operation be pushed away from the stop and the gas strut will be
compressed.

The result, for those not yet acquainted with gliders equipped with
this very efficient and easy to use arrangement, is that for the first
part of the spoiler deployment, only the spoilers will open. After
approximately 1 / 3 of travel the flaps will also start to drop
increasing the effect of the spoiler. When fully deployed, the flaps
will be at 60 degrees, and you will be hanging in your straps viewing
the runway from the same perspective as the HP pilots describes.

Well, this was probably impossible to understand, at least for those
who haven't looked inside a Mini Nimbus, Mosquito or early Ventus.

After flying the Mini for a couple of seasons I really like this
system. The steep approach angles it enables means safer landings over
masks. The only downside is that the glider will float some in the
ground effect if you are carrying to much speed. Not a lot, but more
than say a LS-3 or some other glider with big conventional
Shemmp-Hirth brakes. I would assume that the float effect is still a
lot less than for gliders with only flaps.

We bought our struts directly from Schemmp Hirth, they were not at all
expensive and the delivery was swift. At least one of the struts have
some custom made fittings that will save you some work of you get them
from SH.

Happy soaring
Jan Larsson
Sweden

Ps. The website of my club
http://www.flygklubben.bojn.net/

[Doug Hoffman]

> From: (Kirk Stant)
>>
>> As far as V-tails go, anything to reduce wetted area
>> is good, right? ;-P
>
> This is a bit of a myth, I think. You still need the same tail volume
> regardless of tail configuration, so you end up with basically the
> same wetted area. If you cut down the size of the tails, you start
> having stability problems (the Bonanza was originally a bit marginal,
> I think), which is probably how V-tails on gliders got their bad
> reputation in the first place. HPs apparently got it right from the
> start. The theoretical saving is in reduced interference drag due to
> fewer intersections (less of an advantage compared to T-tails) and
> reduced weight (a big advantage compared to T-tails).

Right. Also, according to Dick Schreder, the V-tail shares the T-tail's
advantage of being up out of harm's way if landing in tall crop. The
conventional tail suffers there. Dick also spoke of the advantage of the
V-tail for the metal home builder, which obviously applies to the HPs. Just
build 2 identical parts, mirror imaged.

-Doug

( "Flaps and V-Tails of Death", you gotta love that subject title)

[Dave Nadler \YO\]

Thanks Wallace ! I love my RHJ-8, though its flaps aren't quite as
effective as the HP-14 I once owned. Note that the HP's (later ones
anyway) are *much* easier to land than some other flapped ships, as
the flaps can produce much more drag. The 1-35 (especially the
models with less flap) requires much more precise speed control
to avoid floating across the aerodrome. Required speed precision
varies quite a lot between sailplanes (different models of 1-35,
PIK, HPs with different flap/aileron lengths, Monerai, C-70), so
be careful of generalizing too much ! Also, forked-tailed-devils
vary a lot (and many HPs have been modified - tail lengths and
angles), so again don't generalize too much...

Best Regards, Dave "YO"

"Wallace Berry" > wrote in message
...
> Hi all,
>
> I'm here to report that I cheated death and survived a flight in a
> glider with the dreaded "Landing Flaps and V-Tails of Death". Jim Harper
> graciously allowed me to fly his beautiful HP-16. What's an HP-16 you
> say? Well, looks to be just like the HP-18 (or I should say the HP-18 is
> just like the -16) except that the -16 has a large and comfortable all
> metal cockpit instead of the narrow composite cockpit of the -18.
>
> Jim's -16 is equipped with winglets and, as far as I know, the ailerons
> are standard (not with the J.D. Colling mod, correct me if I'm wrong
> Jim). Center stick. Tow was behind our 180hp Cessna 175 on a 275 foot
> long rope. Started out in -2 flap position, went to + 5 at 40 knots. Had
> no trouble keeping the wings level. The bird lifted off level and was
> easy to fly on tow. Released and tried slow flight (no stalls), flight
> up to 90 knots. Steep turns, etc. Well sealed and quiet. Good rudder
> response and easy to coordinate compared to my 301 Libelle. More stable
> in a thermal than my Libelle. Aileron response was a little slower than
> my Libelle at thermaling speeds, but was positive and more than adequate
> for centering thermals. Climbed a few hundred feet in a very week
> thermal. Very nice thermalling glider.
>
> Landing was the best part. I stayed high and close in the pattern. I
> rolled on some flap on downwind, maybe 30 degrees or so. I was way high
> on final so I started rolling in more flaps. I never quite got to the
> full 90 degrees mark as I had the nose down at a truly obscene angle
> just to maintain 50 knots. Steeper than my 301 with the tailchute and
> full divebrakes. Steeper than a Mosquito with everything hanging out.
> This was more like parachuting than flying. Nothing but dirt out the
> front of the canopy. The horizon was visible more towards the top of the
> canopy. I aimed at a target and just kept the nose pointed there. I
> pulled back on the stick when I ran out of nerve. The bird settled on
> with a slight bump of the tailwheel and a little bounce as the main
> dropped on (I flared just a bit too much). I have no doubt that I could
> easily put this bird in a tiny field much easier than I could my Libelle
> (and that is not difficult at all).
>
> So, I'd have to say that all the bad things I've been told about landing
> flaps on gliders and V-tails are definitely untrue with respect to the
> HP-16. It is a comfortable and easy to fly glider and compares very well
> to my Libelle and also to other glass birds, including my favorites for
> handling, the Mosquito and LS-4.

[Michael]

Robert Ehrlich > wrote
> This will work on approach, when you have the nose down attitude
> corresponding to the flaps setting but not in the situation of my
> initial question, i.e. just after a botched flare, a few feet above
> the runnway and no nose down attitude. In this case retracting the
> flaps will cause a loss of drag, but no so huge, i.e. the drag will
> much more than in zero flaps or zero spoilers configuration

I do not concur. Imagine, for example, a similar situation involving
a glider with approach flaps and spoilers, such as the Blanik L-13.
It is normally landed with full flaps, and spoilers are used for
glideslope control. It is also a common primary trainer, so the
situation you cite comes up with some regularity. The solution is to
retract the spoilers - but you still have flaps hanging out. How is
this any different from retracting Schreder-type flaps to 30 degrees?

> and there
> is no gain in lift and no change in the stall speed, you don't have
> the altitude that you can convert into speed, so I think that you are
> going to fall on the ground, with a slighly increased delay compared
> to what would happen if you didn't retract some flaps.

Actually, you will fly onto the ground, and if you're not careful you
will float. With the flaps retracted to 30 degrees, the HP-11
certainly had a tendency to float even when brought in at very low
airspeed. In fact, after some experimentation I came to the
conclusion that if my flap mechanicsm were to ever fail with the flaps
at less than 30 degrees, I would need about 2 miles of runway to stop.

Michael

[Robert Ehrlich]

Michael wrote:
>
> Robert Ehrlich > wrote
> > This will work on approach, when you have the nose down attitude
> > corresponding to the flaps setting but not in the situation of my
> > initial question, i.e. just after a botched flare, a few feet above
> > the runnway and no nose down attitude. In this case retracting the
> > flaps will cause a loss of drag, but no so huge, i.e. the drag will
> > much more than in zero flaps or zero spoilers configuration
>
> I do not concur. Imagine, for example, a similar situation involving
> a glider with approach flaps and spoilers, such as the Blanik L-13.
> It is normally landed with full flaps, and spoilers are used for
> glideslope control. It is also a common primary trainer, so the
> situation you cite comes up with some regularity. The solution is to
> retract the spoilers - but you still have flaps hanging out. How is
> this any different from retracting Schreder-type flaps to 30 degrees?
>
> > and there
> > is no gain in lift and no change in the stall speed, you don't have
> > the altitude that you can convert into speed, so I think that you are
> > going to fall on the ground, with a slighly increased delay compared
> > to what would happen if you didn't retract some flaps.
>
> Actually, you will fly onto the ground, and if you're not careful you
> will float. With the flaps retracted to 30 degrees, the HP-11
> certainly had a tendency to float even when brought in at very low
> airspeed. In fact, after some experimentation I came to the
> conclusion that if my flap mechanicsm were to ever fail with the flaps
> at less than 30 degrees, I would need about 2 miles of runway to stop.
>

OK, I have no experience on this kind of ship, I was just trying to
figure how to handle this situation. What you are saying is that
in the range 30-90 degrees on this ship, flaps work like spoilers
on usual (from my point of view) gliders, i.e. retracting them to
30 degrees brings the drag at a level similar to that of a non-flapped
ship with spoilers closed, without change in lift. So the important
thing in order to be able to recover from the 3 most common mistakes
is to have the flaps at more than 30 degrees when you begin the flare.

[Mark James Boyd]

Someone mentioned that landing with T or V tail is
better than conventional tail in tall crop.

I'd like to know of someone who has landed
in crop with a conventional tail. Any
stories out there?

It strikes me that the yaw of crop hitting a
wing is the real problem. A conventional tail,
if it grabs the crop BEFORE the wing does,
might actually keep the glider straighter,
kind of a keel effect?

Maybe in 2-3 foot crop this means the
conventional tail is damaged but T-tail isn't,
but in very tall crop, the conventional
tail is damaged and the glider
pancakes in straight in vs. yawing
and rolling T-tail (since a wing hits first).

Any opinions about this? Anyone
have anecdotes? I've wondered
the same thing about high-wing vs. low-wing
water landings in power aircraft...

[Bruce Hoult]

In article >,
(Michael) wrote:

> Imagine, for example, a similar situation involving
> a glider with approach flaps and spoilers, such as the Blanik L-13.
> It is normally landed with full flaps

It's a few years since I've flown a Blanik, but I've flown 5 different
L-13s a total of 110 flights. I'd estimate that at least 105 of those
landings would have been with zero flap.

-- Bruce

[Brian Case]

Don't know about conventional tails. But I have been helping rebuild a
DG202 (T-tail) that landing in a tall wheat feild. It caught a wing
tip and turned sideways breaking nearly every part in the fuselage.
(Major Damage) Don't know if a conventional tail would have helped.

Brian

[tango4]

The trick with landing in tall growth is not flaring at the top of the
'crop' but continuing to fly down to ground level. I flared early and
'landed' at 1.5 metre above the deck. The resulting 'loud bang' was the
ASW20's main wheel being pushed up into the fuselage. Thankfully the
structure absorbed the impact and I got away without any back injury.

Of course the problem with flying into the tops of uneven tall growth is the
potential to catch a wingtip and 'groundloop' at 1 metre with the resulting
potential for 'major' damage and resulting injury. In hindsight I'm not sure
that I didn't actually inadvertently do the right thing.

My incident happened when I changed my mind on finals just to be closer to
the field access road. Dumb, dumb, dumb, I was closer to the access road but
the damage took 6 weeks to repair!

Ian



"Brian Case" > wrote in message
om...
> Don't know about conventional tails. But I have been helping rebuild a
> DG202 (T-tail) that landing in a tall wheat feild. It caught a wing
> tip and turned sideways breaking nearly every part in the fuselage.
> (Major Damage) Don't know if a conventional tail would have helped.
>
> Brian

[JJ Sinclair]

Mark wrote>>>>>>>>>>>>>>>>
>It strikes me that the yaw of crop hitting a
>wing is the real problem.

You're completely right about this. I got my LS-6 after its previous owner
tried to land in 8 foot high corn. The fuselage broke in 3 places, before
anything hit the ground. The major problem is catching a wing tip and then
performing a flying ground loop. My wing took the sudden reversal in direction
very well and was just scraped up a bit. The fuselage (mainly the tail mass)
wasn't able to turn that fast and failed (in compression) on the inside, of the
very rapid left turn that was commanded when the left wing tip hit the corn.
That's a massive moment arm (25 feet). The spar is tremendously strong when
loaded in this way (for and aft) but the fuselage isn't. The ASH-25 has an arm
of 43 feet and one must never place ones wing tip in any crops. Plowed ground
is my choice, because DIRT DON'T HURT.


JJ Sinclair

[Jack Glendening]

Wallace Berry wrote:
> I never quite got to the
> full 90 degrees mark as I had the nose down at a truly obscene angle
> just to maintain 50 knots. Steeper than my 301 with the tailchute and
> full divebrakes. Steeper than a Mosquito with everything hanging out.
> This was more like parachuting than flying. Nothing but dirt out the
> front of the canopy.

Anyone know what the actual L/D value is with 90 degrees of flaps ??

[Wayne Paul]

Jack,

Here is an article written George Moffat:

http://www.soaridaho.com/Schreder/HP-14/FLIGHT_TESTING_THE_14.html

The HP-14 answer to your question is found in the third from last paragraph.

Paul Bikle's T-6 version the HP-14 limited flap deflection to 68 degrees.
In the following article he states that 68 degrees provides a glide ration
of 6 to 1.
http://www.soaridaho.com/Schreder/HP-14/T-6.html

Wayne
http://www.soaridaho.com/Schreder



"Jack Glendening" > wrote in message
ink.net...
> Wallace Berry wrote:
> > I never quite got to the
> > full 90 degrees mark as I had the nose down at a truly obscene angle
> > just to maintain 50 knots. Steeper than my 301 with the tailchute and
> > full divebrakes. Steeper than a Mosquito with everything hanging out.
> > This was more like parachuting than flying. Nothing but dirt out the
> > front of the canopy.
>
> Anyone know what the actual L/D value is with 90 degrees of flaps ??
>

[Dylan Smith]

In article et>,
Jack Glendening wrote:
> Anyone know what the actual L/D value is with 90 degrees of flaps ??

Probably no more than 4:1.

A friend let me fly his HP-11. His advice to me about how to flare when
using 90 degrees flap: wait until you're certain you're going to crash,
then count to three, then flare!

It works, too.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Jack Glendening]

Wayne Paul wrote:
> The HP-14 answer to your question is found in the third from last paragraph.

The 40 degree angle given there equates to a 1.2:1 glide ratio - about
the same as that of the space shuttle !

[Bob Whelan]

"Jack Glendening" wondered...
> Wallace Berry wrote:
> > I never quite got to the
> > full 90 degrees mark as I had the nose down at a truly obscene angle
> > just to maintain 50 knots. Steeper than my 301 with the tailchute and
> > full divebrakes. Steeper than a Mosquito with everything hanging out.
> > This was more like parachuting than flying. Nothing but dirt out the
> > front of the canopy.
>
> Anyone know what the actual L/D value is with 90 degrees of flaps ??

For my short-wing-span/long-flap-span HP-14, my guesstimate was somewhere
between 2:1 and 4:1, based on a number of approaches w. full flaps during
which I noted: a) altitude when crossing a plane (estimated to be)
perpendicular to the ground, and b) actual touchdown point. The horizontal
distance was later paced off. Crude, but it satisfied my curiosity. The
slightest headwind was easily apparent in the glidepath. Great Fun.

Two 'How steep IS it?" tales...

1) Before I fully appreciated how abbie-normal the '14's descent path
relative to other airplanes/gliders was, I once had a C-150 driver walk
across the field to where I was fiddling with my '14 not too long after a
routine landing. His first words after determining I was the pilot of the
ship were, "Boy! I thought a Cessna 150 had powerful flaps until I saw your
landing."

2) After another routine landing, a lady passing some time at the commercial
glider operator's location was reported to have screamed (in alarm/fear as
related to me) upon looking up and seeing the HP on a normal short final.

The HP's I've observed from the ground on approaches are distinctly
'different' when compared to 'normal spoilered gliders'. One difference is
it's kind of like a reverse winch launch in that you see the top of the ship
rather than its end-on profile. But unlike a winch launch during which the
ship goes uphill rapidly (compared to aerotow ascent rates), or, the descent
rate of a spoilered ship pointed so nose low, flapped ships comes downhill
ridiculously
slowly in the visual sense.

It wouldn't surprise me if this visual difference is *one* of the reasons so
much 'flaps are dangerously difficult glider landing devices' nonsense
arises. As others have previously noted, the view from the cockpit - while
different (in my supine HP-14 it initially felt like you were standing on
the rudder pedals) - is No Big Deal if you simply fly airspeed and altitude
(letting attitude fall out in the wash). You've a tremendously good view of
the landing zone, the ship is rock steady, and you have plenty of time to
make sound decisions on the way downhill. And as Moffat notes, should you
ever stall an HP-14 with full flaps (something I exploratively did many
times at altitude), the altitude loss is negligible since you're already
pointed/sliding downhill to begin with.

As a final note, the only reason I spouted off in this thread because a post
must've triggered my proselytization button. Yes, I'm a fan of landing
flaps. Yes, I wish my Zuni had my former HP-14's flaps. Yes, I learned on
spoilers. No, I don't lose sleep over the fact I'm apparently in a gliding
minority in my flap opinions...

However, I (sometimes, wry chuckle) DO speak up when misguided opinions that
undeservedly bash a wonderful (if little known and appreciated)
outlanding/safety aid just because it's 'different' are volunteered. It's
not the ignorance (we're all ignorant about some things) or the opinion
(we're entitled to our own) I object to - it's the sharing of both as
implicit fact. My experience in this silly/wonderful sport we're privileged
to be able to indulge in is that keeping an open mind about our areas of
ignorance often has soaring rewards not immediately apparent.

Regards,
Bob - skeptically opinionated - W.


---
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[Fred the Red Shirt]

On a related note it appears that the Marske Monarch useds flaps
(and spoilers both?):

http://www.continuo.com/marske/kits.htm

Basically, this is a flying wing with neither elevator nor
canards. I'm curious as to how pitch is controlled.

--

FF

[Bob Kuykendall]

Earlier, (Fred the Red Shirt) wrote:

> On a related note it appears that
> the Marske Monarch useds flaps
> (and spoilers both ... this is
> a flying wing with neither
> elevator nor canards. I'm curious
> as to how pitch is controlled.

I don't think that that's quite an accurate assessment of the Monarch
configuration.

The movable control surface on the wing inboard trailing edge performs
the same function as the elevator on a conventional tailed aircraft.
It responds to fore-and-aft motion of the stick and controls the pitch
attitude. It is sometimes (but not always) called an "elevon" on a
tailless aircraft. Its location aft of the CG gives it adequate moment
arm to perform its function.

Another interesting tailless aircraft is the Brightstar SWIFT, which
is a swept-wing tailless glider that uses flaps for pitch control. The
name is an acronym meaning Swept Wing with Inboard Flaps for Trim.

The sweep of the SWIFT wing places the flaps far enough forward so
that deflecting them down causes a pitch-up moment. The value of this
feature is that pitching up is done by effectively increasing the wing
camber, which better suits the wing to slower flight.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

[Fred the Red Shirt]

(Bob Kuykendall) wrote in message >...
> Earlier, (Fred the Red Shirt) wrote:
>
> > On a related note it appears that
> > the Marske Monarch useds flaps
> > (and spoilers both ... this is
> > a flying wing with neither
> > elevator nor canards. I'm curious
> > as to how pitch is controlled.
>
> I don't think that that's quite an accurate assessment of the Monarch
> configuration.
>
> The movable control surface on the wing inboard trailing edge performs
> the same function as the elevator on a conventional tailed aircraft.
> It responds to fore-and-aft motion of the stick and controls the pitch
> attitude. It is sometimes (but not always) called an "elevon" on a
> tailless aircraft. Its location aft of the CG gives it adequate moment
> arm to perform its function.

I see. There was some discussion on the site of cg shifting for pitch
control but it was't clear if that was used in the Monarch or not. It
seems to me that it would be wasteful to add weight for that purpose
though I suppose you could put the pilot's seat on wheels and
roll him back and forth for pitch control.

>
> Another interesting tailless aircraft is the Brightstar SWIFT, which
> is a swept-wing tailless glider that uses flaps for pitch control. The
> name is an acronym meaning Swept Wing with Inboard Flaps for Trim.
>
> The sweep of the SWIFT wing places the flaps far enough forward so
> that deflecting them down causes a pitch-up moment. The value of this
> feature is that pitching up is done by effectively increasing the wing
> camber, which better suits the wing to slower flight.
>

Oh, cool. The flaps are functionally similar to canards.

Thanks for the info.

--

FF