Helicopter doing back flips

[Guest JRMobile]

I was unawre that a helicopter could do aeros until I came across this clip.

 

Why doesnt:rotary: the gyroscopic principle apply here?

 

 

 

[Guest ozzie]

I saw this performance at Airventure. Damm scary to see a rotary wing doing this sort of thing. But it seems to stay together.

 

 

[Tomo]

Didn't this guy crash?

 

 

[dazza 38]

I have seen a couple choppers do aero's.Lynx and squirrel.Depends on the rotor head design.Has to be a rigid design, like the squirrel with its composite/fibreglass StarFlex design.

 

 

[Guest JRMobile]

As far as I can check, Chuck Aaron, Chief Helicopter Pilot at Red Bull, is still up and about.

 

Cheers John

 

 

[foxy]

hafta say, one way or another......thats unreal to see!!

 

 

[deadstick]

hafta say, one way or another......thats unreal to see!!

Yep, pretty cool and does rely on the type of head used in the helo, whilst on exchange with the Royal Navy I saw a german linx roll on its back from the hover and roll through and accelerate away, but have never been in a helo whilst doing aeros , some mates have. The RAN used to allow barrel roles in the squirrells but it was causing too much fatigue induced maintenance, the ARH (tiger) is fully Aerobatic, but I dont think there is any tactical advantage in aero's as it would bleed off to much energy and leave you a sitting duck.

 

 

[Guest DJH]

Why bother??? I think the hover is a much more clever trick.....John.

 

 

[Greg Spiers]

By now you all probably have researched it. I'm a bit of a late starter ya know! Don't try it with a semi rigid rotor head like a Jet Ranger, B47 KH4, R22 or R44 or 66, Rotorway, Scorpion or any other number of contenders. It must, for simplicity sake, be a fully articulated rotor head most of which are three blades or more. I think I am correct in suggesting a semi rigid head does not allow for the blades to 'flap' enough in order to roll it over in negative 'G'. The blades will come up against the stops wrap around you like a banana skin, if they don't snap off and the rest will be history. I am not sure what pilot inputs are required to successfully manage this trick but I don't really want to know!! Straight and level is good fun too!!

 

 

[facthunter]

I would be pretty sure the design load calculations were not envisaging what that is put through there. You can't wave a magic wand and just dismiss gyroscopic forces. Nev

 

 

[Guernsey]

If you click on the little I in the top right hand corner of the video picture it has an explanation there.

 

Alan.

 

 

[facthunter]

FIXED blades still apply the forces to the shaft. That doesn't happen when they move freely. Nev

 

 

[Head in the clouds]

It must, for simplicity sake, be a fully articulated rotor head ......

I've got some video somewhere (I'll see if I can find and post it here) of me flying loops in a Hughes 500C which has an articulated head and you can clearly see a large amount of movement/displacement of the whole rotor disc, at times the blade tips come alarmingly close to the tailboom. Loops are all positive G of course and you'd be history if you ever fell out of one and lost positive G, even zero G would have your tail off in an instant. Although it's cool to do and looks daring it's actually no different from flying loops in a plane.

 

If you want to do anything involving negative G, like the OP's post shows, you certainly cannot do it with an articulated head, or a semi-rigid teetering head like the other examples you mentioned, it has to be a fully rigid head, as Dazza said like the Starflex head on the Eurocopters. The Lynx mentioned above does have an articulated head and does do some very neat aeros but never below zero G. A long while ago I did hear that they were experimenting with a hinge locker to permit negative G manoeuvres but as mentioned above I doubt they really had a need except to impress at airshows.

 

Articulated heads do allow you a great deal of manoeuvrability though, because the blades can flap to symmetry of lift independently of each other, and they also have lead/lag hinges which allows them to arrange themselves around the circle so that the whole disc is always in dynamic balance, so they make for a very smooth rotor system.

 

Teetering heads are the most restricting, you can't do much with them except quite smoothly, any abrupt control inputs can result in mast-bumping where the head runs out of teeter travel and if it bumps the mast severely enough you can bend the top of the mast, the blades won't ever wrap around you though, or break off unless you got to a stage where the aircraft was tumbling, and even then it's extremely unlikely. The worst condition for mast bumping is when you have a high forward speed because the disc tilts left the faster you go (in a US left-from-above rotation rotor) as the blades rise and fall to equalise their lift around the disc, so if you want to roll right suddenly it's not too bad because you have a lot of disc tilt available before you bump the mast but if you're going fast and need to roll left you're better off doing it v-e-r-y smoothly ...

 

 

[Greg Spiers]

Thanks H, cleared a lot for me, not that I am intending to exercise the right but informative nonetheless.

 

Ta.

 

G

 

 

[M61A1]

These are my babies.......not my video. video quality is a bit poor, but shows what they can do.

 

 

 

[M61A1]

I would be pretty sure the design load calculations were not envisaging what that is put through there. You can't wave a magic wand and just dismiss gyroscopic forces. Nev

The gyroscopic forces are part of your control system. While all the pilot control inputs are in the correct sense, the actual flight control inputs are 90 deg prior. Meaning that on the Tiger for example, an input increasing AoA as the blade passes over the tail, will result in the gyroscopic precession rolling you to the right. Essentially, you are using gyroscopic precession to your advantage.There is a youtube video about the Red Bull aerobatic heli, he roughly outlines the mods to his aircraft that allow it to do aero's regularly without breaking it.