helicopters

[mandid12]

can they fly upside down??

[kuhugaq]

they can flip over but cannot sustain inverted flight

[mlbt]

certain ones can pull vertical loops, but each time they do they drop a little. they couldnt do it in the same spot ad infinitum
As for a straight line, no chance......

[RATTER15]

They work on downdraft from the rotor blades if you turn it upside down it is then an updraft forcing the chopper to the ground, big no no!!

[kermit911]

I know on some helicopters the rotor blades pivot and can creat an updraft. So if the helicopter is upside down that would be a down draft. RC helicopters do it all the time.

[RATTER15]

I stand corrected, but you know what I mean!

[Ralph]

As kermit911 says, radio controlled helicopters can and do fly upside down. The lift of a helicopter is controlles by adjusting the pitch (angle to the horizontal) of the rotor blades. If you go to extremes, then you can produce lift in the opposite direction and keep the model flying upside down.

Real full size helicopters cannot fly upside down and in almost all circumstances cannot loop. There are two main reasons for this, both to do with the rotor blades.

The main reason is that real size rotor blades cannot be made stiff enough to do inverted flight. If you look at the blades of a helicopter as it hovers, you can see a very definite upward curve towards the tip. If you picture this happening the other way around on an upside down helicopter, you'll see that they would chop the tail off! There is no material that will prevent this. The best for the job is carbon fibre, but that's what they're already made of.

Models use rotors with a symmetrical cross section that will happily produce lift in either direction by just adjusting the pitch. Real helicopters need to be a bit more efficient about things and so are designed to be good at producing lift only in the up direction.

[gary baldy]

I believe the new generation Apache attack helicopter is capable of flying upside for long periods.
Why it should want to do this i dont know but i saw a programme on the Discovery Channel about it so it must be true!

[Skids]

The Sea Stallion can barrel roll while both the Apache and the Lynx AH.7 can both perform verticle loops. Neither maneouvre involves actually flying upside down, the aircraft is merely upside down for a brief moment during which time lift is lost. Lift is regained when they're right side up.

[dom_e]

Certain Helicopters can pull Inverse Pitch. Mainly Navy Helicopters can fly down so while the rotors are in flight speed they can stay glued to the deck of an aircraft carrier, if this didn't happen they wouldn't stay with the floor on choppy seas and damage the aircraft. Inverse pitch is normally appiled until the rotors stop then gravity kicks in. However as this forces then down, helicopters when flying upside down can ude inverse pitch to have a bit of lift. this in no way provides enough lift to keep the aircraft airborne, but it does prolong the lenth of time it can do it! And i Work With Lynx Mk7 And 9 And Apache :-D