Wingdrop while stalling

drake wrote:

Hi,
there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally). There is no inherent imbalance in the c.g. location due to
the fuel tanks ot fuel flow. What could be causing such a wing drop
while stalling? Is it soem inherent instability in the roll axis?

Sounds like a good rudder trainer.

Lars,
Fit wedges on the leading edges at the wing roots to force a root
stall. Some WW2 era military trainers tip stalled to enhance training
experience and the root wedge fix is used to remove the characteristic
(and surprise) for civilian warbird use.
Albert

(drake) wrote in message om...
Any help/advice/recollection of previous such problems and what you
did to fix it will be greatly appreciated.

Lars

On Sat, 10 Jan 2004 00:03:57 GMT, john smith
wrote:

drake wrote:

Hi,
there is a HAL HPT-32 (pistonengined 2 seater trainer light a/c)
which, when attempting a stall, does not pitch down correctly. Instead
one of the wings (either port or starboard (50/50)... no gyro problems
due to engine) almost always drops, and this genreally results in the
a/c entering a spin (which the rookie pilots are unable to handle,
generally). There is no inherent imbalance in the c.g. location due to
the fuel tanks ot fuel flow. What could be causing such a wing drop
while stalling? Is it soem inherent instability in the roll axis?

Sounds like a good rudder trainer.

Sounds like my Debonair. And...no it doesn't have wedges on the wing
roots although it does have the little 1/4 inch stall strips about 6
inches long. I don't think the first 60 or so had any washout either,
but I'd have to dig deeper on that.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Ditto Chuck's response. On one of my experimental gliders, I designed a
delta-wing using a reflex airfoil (M-178 I think.) However, I did not wash out
the tips, and I used wingtips that terminated in a sharp points. Big mistake.
When tested at high AOA's, massive tip stalls caused the wing to roll 45
degrees and yaw 180 degrees about every 3 seconds.

Curiously enough, the Wright boys (yep, them again) used washed out wingtips on
the 1902 glider.

Harry "flies under polyethylene too" Frey

PS: Funny what you can learn from watching the (stress) hawks fly. Isn't it?

Wright1902Glider wrote:

When tested at high AOA's, massive tip stalls caused the wing to roll 45
degrees and yaw 180 degrees about every 3 seconds.

Was this a model or was it piloted?

Dave 'bowling balls' Hyde

Dave Hyde wrote:
Wright1902Glider wrote:


When tested at high AOA's, massive tip stalls caused the wing to roll 45
degrees and yaw 180 degrees about every 3 seconds.


Was this a model or was it piloted?

Dave 'bowling balls' Hyde

Yea, that'd be heck in a dog fight. You could fly a tight landing
pattern, though.

Nafod "nafod" 40

Hi all,

Thanks for your replies.

The a/c in question is:
http://www.bharat-rakshak.com/IAF/Im...nt/Deepak.html

The wingdrop problem has been solved (some years back). Just learnt
that all the engineers did was to replace the counter-sunk flat top
rivets on the wing-top (holding the skin to the ribs) were replaced by
protruding pan-head rivets, which apparently energised the flow (made
it more turbulent?). There were rivets all over the wing, but more
towards the wing-root side. This solved the wing drop problem i.e. the
wing drop while stalling was then gentle enough to be handled by
novice pilots. I still am not completely satisfied with the turbulence
explaination... why should a more "energised" flow make the wing drop
less violent?

One character who worked on this kite several years ago said that the
stall actually started mid-wing, and progressed very quickly, so that
one wing (entire wing, not just the tip or root) stalled and dropped.
Dunno if he was farting or not.

Has anybody used the protruding rivet approach before to solve wing
aerodynamic problems before? Quite a minimalist solution!

Drake Lars

drake wrote:

Hi all,

Thanks for your replies.

The a/c in question is:
http://www.bharat-rakshak.com/IAF/Im...nt/Deepak.html

The wingdrop problem has been solved (some years back). Just learnt
that all the engineers did was to replace the counter-sunk flat top
rivets on the wing-top (holding the skin to the ribs) were replaced by
protruding pan-head rivets, which apparently energised the flow (made
it more turbulent?). There were rivets all over the wing, but more
towards the wing-root side. This solved the wing drop problem i.e. the
wing drop while stalling was then gentle enough to be handled by
novice pilots. I still am not completely satisfied with the turbulence
explaination... why should a more "energised" flow make the wing drop
less violent?

Sounds like the round head rivets are acting like turbulators.

If the boundry layer is not attached to the surface, none of the
"energy" in the flow is transfered to the surface.

Basically, tickling the boundry layer like that causes it to reattach
to the surface. That's what they mean by "energizing" the flow.

Make more sense?

Richard (the new improved)Lamb

Hi ya'll!

Separation bubbles?


OT: BTW, my experimental glider was a full-sized HG, and I tested it both
clipped-in and unclipped. The second method was preferable, as the first
allowed the glider to drag me all over the beach at Kitty Hawk. I should note
that when I designed this machine, I had very little understanding of the fine
points of non-rigid delta-wing aerodynamics. There's a photo of it on my
website. Its the "Stormy Petrel 3" photo. The "Stormy Petrel 2A" was a
modified "Batso" glider and flew fairly well.

Harry
http://hometown.aol.com/wright1902/page3.html

Todd

Further on your experience.

A number of model airplanes I have seen had very rapid roll off as the
airspeed was reduced approaching the stall. On landing this caused the
wing to drop and bird cartwheel.

One solution was to glue a piece of string along the crown of the air
foil.

Another was to put a wedge shaped piece of balsa on the wing leading
edge near the fuselage.

Both seemed to work ok and made the birds flyable by new bees.

Same techniques will work on full size aircraft.

Big John
Pilot ROCAF


On Thu, 15 Jan 2004 14:51:10 -0500, Todd Pattist
wrote:

Richard Lamb wrote:

Sounds like the round head rivets are acting like turbulators.

My glider uses a strip of tape that looks like Dymo labeling
tape with a string of periods punched into it to turbulate
the flow.
Todd Pattist
(Remove DONTSPAMME from address to email reply.)
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