stub wings

[baranfin]

I was just thinking about the stub wings on helicopters. Are the main disadvantages the wieght penalty or is it more because of the downwash hitting them? If it was because of the downwash striking the wing would it make sense to maybe put them on some sort of hinge? That way they could be rotated out of the way for hovering/low speed flight and deployed for cruise.
Your thoughts guys?

[Vfrpilotpb]

Is there room on the R22? if so it could be a good idea for those who lose their rotor rev's. <img src="wink.gif" border="0">

[Nick Lappos]

baranfin,

Don't think of stub wings, call them wings. The lift gained at high speed is significant, and unloads the rotor so that stall is averted. Winged helicopters can gain 20 knots top speed, or so.

The weight is a penalty, but the vertical drag is eye-watering. The typical helicpter vertical drag (which "feels" like weight, and subtracts from hover performance exactly so) is about 5% of gross weiht, so a 20000 pound helo loses 1000 pounds of payload due to vertical drag. The wing can easily add another 5 to 10% vertical drag (the V-22 wing probably costs about 8%), which is an awesome penlty. Since typical helicopters have payloads that are 40% of the maximum gross weight, a loss of 10% of gross weight costs 25% of payload.

Pivoting wings, big flaps that dump down in hover and many other schemes have been tried. Since the wing is an important structure, any scheme must be completely fool-proof or a catastrophe could result.

Stepniewski and Keys "Rotary-Wing Aerodynamics" has a whole chapter on winged helicopters.

[Robbo Jock]

You could have an arrangement like that on the Tornado or F-111 - so you'd have a Swing-Wing
Fling-Wing. :)

[nucleus33]

Maybe we need a wing that is centered under the fuselage, so that is it "hidden" from the rotor at hover, though I suppose that in forward flight regimens a wing underneath could have it's airflow blocked by the fuselage.

How do wings affect the forward tilt of the disc and fuselage in different regimens?

How do designer determine where to position the wings?

Thanks,

Hans Conser

[Dave Jackson]

from the Department of Demented Designs

http://www.unicopter.com/temporary/lightbulb_idea.gif
(dept. motto ~ The lights never go out ~ 'Cause the light never really came on.)
____________


Shape the helicopter's fuselage as a lifting body. Then give the mast the ability to be vertical in hover but pitch forward and down by 10 - 30 degrees in forward flight.

<img src="smile.gif" border="0"> <img src="smile.gif" border="0">

[Grey Area]

I was discussing this very topic with a Eurocopter designer a while back.

When they stuck wings on a Gazelle the chief pilot took the first flight (as you do) then couldnt stop the thing as the lift from the wing reduced the available flare in level flight. When they did more study they found, not surprisingly, that the bigger the wing the more the aircraft behaved like a fixed wing aircraft, hence a variable incidence or free wing would do better - I believe Westlands are or are about to fly a winged Lynx soon. I imagine there's a lot of reasearch to do before we see a commercial one.

GA

[widgeon]

On the comanche ( sp ? ) does the weapons pylon give any appreciable lift ? ( looks a bit like a stub wing) And talking of lifting bodies the fuse shape looks like it may develop some lift as well.

[baranfin]

As I understand it (and I may be totally wrong here) The wings of smaller planes are attached to the fuselage with one or two large spars. If you wanted to make a variable incidince wing, concievebly you could rotate it around one of the forward spars. When I first posted the question I was thinking more of just rotating the wing 90 deg to reduce the form drag.

[Lu Zuckerman]

It would seem to me that if you could rotate the wing in order to reduce the downward force of the rotor wash which would reduce lift the wing would still develop lift and cause the helicopter to move backwards necessitating the use of forward cyclic. When the helicopter moves through tranlational lift the wing would then have a large amount of drag necessitating the use of a power servo or jackscrew to return the wing to the normal position. This would increase the weight and the complexity of the aircraft systems. I may be wrong but the only operational helicopters that have wings are gun ships and most of the time they are using their offensive weapons while flying and when the use these weapons while at the hover they have no problem due to the amount of installed power.

Depending on the helicopter design the wings are installed to allow reduced collective in forward flight by offsetting the lift required from the main rotor. Most helicopters that have wings enjoy this same feature but the main reason for the wings is to hang things from such as weapons, fuel tanks and supporting electronic systems.

Maybe Nick can tell us if the weapons supporting system on the UH-60 generates any lift in flight and what the penalties are while in a hover.

[Dave Jackson]

For slow helicopters, the addition of wings does not appear to be advantageous. The money and weight etc. would be better spent by increasing the existing engine, power train and rotor. Initially, Schramm's new recreational Helicycle offered the option of adding a pair of wings and a pair of pusher props plus engines, at the wing tips.

For high-speed helicopters, the wings must be complimented by an additional device that produces forward thrust. This is moving into the domain of VTOL aircraft.

VTOL aircraft have a number of problems that may be eventually worked out, but to me, they have one problem that none of the current ideas have solved. This is the burden of carrying the 'deadweight' of forward flight components during vertical flight and then the burden of carrying the 'deadweight' of hover flight components during forward flight.

This brings up, from the depths of the Department of Demented Designs, a crazy idea for short and regular routes. Leave the vertical flight components on the ground and only take the horizontal flight components aloft. Perhaps something like the catapult and arrestor cables on an aircraft carrier.

So much for dumb ideas. I will now join Lu, by bending over. <img src="redface.gif" border="0">

[Robbo Jock]

Another one from Dept Dem Des Ltd:
How about a biplane arrangement, with the top wing hinged at the root, so the tip drops down to the bottom wing in the hover, thus gently guiding the downwash out and round the lower wing and as if by magic the drag disappears! All you'd need is a hinge at the root and a couple of lengths of wire at the tip to stop the wing flying up too far when it's generating lift in flight.

I need a darkened room to lie down in and a cold flannel for my forehead. <img src="smile.gif" border="0">

[jayteeto]

Got it!! Attach an engine to the stub wings, get them to flap up and down in the hover and they could add to the lift................... I'll get my coat! <img src="tongue.gif" border="0">

[B Sousa]

Stub Wings.....Hmmmmmmm I sort of like that. I had "Stub Wings" on the Cobra. They worked wonderfully well as I didnt have to have all that crap hanging from them, in the cockpit causing clutter....