Nick,

This discussion brings up something I've wondered about for some time... I've read most of the available books about Cobra ops in Vietnam - and am under the impression that the pilots would regularly perform maneuvers in getting set up for a "run" that would appear to be just the sort of thing that a teetering rotor wouldn't like very much - i.e. an unloaded dive. Were these guys just real careful to always keep the rotor loaded?

Also, I have some OH-6 training tapes from '67/'68 that show "wingover" type maneuvers... I have the same question about those; it seems like that would unload the (non-teetering, of course) main rotor.

thanks,

Dave Blevins

blave,
The rocket run entry used to be done as a bunt or low g pushover, but in 1969 an emergency flight warning went out for Cobras to avoid the low g. We simply pushed over a bit more gently, with no difficutly. The dive is a 1 g maneuver, and no sweat.

We all did "wingovers" or target returns, and they made us feel quite aerobatic. As long as you pull 1 g or more in the whole maneuver, it could be done safely.

The OH-6, and the UH-60, AH-64 and the S-76 all have moderate offset main rotor heads (4 to 5 %) that permit quite a bit of control at zero g. These aircraft can all be coaxed into impressive shows. We express the percent hinge offset as the ratio of the flapping hinge to the rotor radius, so a 25 foot rotor radius with the flapping hinge 1 foot from the center of the mast has 4% offset. This is a measure of the snappiness of the cyclic, and also of the control power remaining at zero g. Later in the week I'll post a little discussion of hinge offset for those who wish to go deeper into it. For a BO-105/BK-117/RAH-66 the hinge offset is in the 10 to 15% range, ideal for such messing around.

Nick....now I have never been accused of being "bright" and afterall...heck...I read about it how to do it....any well gee....but you are right.....my internal self preservation gyro...has never let me down for those intentional misdeameanors I have been tempted to commit. It has however, deserted me on more than one time when unintentional felonies have occurred!

:(

-------------------Quote N Lappos------------------------------------
Aerobatics in helos in general should be left to the bar talk. Doing this stuff without a test pilot and a good insurance policy is not too bright, definately illegal, and not conducive to longevity (to paraphrase Bomber Harris).



:( Brings to mind the bloke in the ENG MD600 (LA?), last words were something like "watch this" as he attempted to roll the ac in front of friends alongside in a R44.

They got to watch as the ac chopped the tail off mid manouvre, plummeted to earth killing pilot + cameraman.

Kinda ruined everyone's day:(

Hone22, the NTSB report is #MIA00FA102. Occured in Florida. The pilot apparently was doing a wingover that turned into a hammerhead? It seems that he unloaded the blades a bit too much.

If you want to barrel roll things - then get a plank and do it in that. Helicopters are great fun for lots of things...but let's be reasonable about it!

Keep the blue above the brown. Just remember that ones' rotor blades have a nasty habit of coming down (or up) to meet you if you're doing something silly.

I say this as a young pilot who intends to get old!

Flysafe (and the right way up!!)

Buttline,
Having in my past had the pleasure (if that's the correct word) of practising and performing limited aerobatics in the lynx heli I would advise you not to even think about it!! The accident always starts with "I wonder if" unless you are with a test pilot in a competent machine!!!!

Nick,
Do you know of, or remember a certain F. Zimmerman (think thats the correct name) who used to throw a BO105 around a few years ago - always thought that he was a guy with a death wish!
FLIR

Aerobatics in helos is like gilding lillies
 

FLIR,
I do recall his name and fame, I saw a video he performed in while flying a PAH-1 BO-105. It was awsome.

Also Sigfried Hoffman, who died mysteriously while filming a movie in the States, even with his experience, something got him.

I have done quite a bit of helo aerobatics, many of the Discovery Channel shots of split S or roll maneuvers of Sikorsky's are mine, but I admit I still haven't figured out why.....

No other flying machine can pull to a stop, pedal turn and then sprint away. To toss a helo around until it performs like a Spad proves little, I think. Much better to do what we do best, and get better at that.
Nick

Low N aaahrr and Flir,

I respectfully refer you to the first sentence in my original post..."Don't worry, I have no intention of trying it but.." Actually, if the truth be known, I'm a bit of a coward now I've past 30!

I've seen it done in Lynx's, Gazelles and of course Nick's stuff on Discovery but they never show what's going on with the controls...

I've sat in Lynxes while the QHI beside me demonstrated back flips. Fun but very scary. That, more than anything else confirmed where my own limitations lie. The machine might be able to do it but not if I'm the pilot!

Okay can a civilian ask a question?

Thank you. Is it really possible to fly a heilocopter up side down or is a loop de loop sort of a controlled stall that you hope to come out of before the Laws of Physics start working against you? If I didn't ask it correctly try it this way is the photo with the horizon upside down and the binoculars floating in midair real or PhotoStudio?

Thanks

Loops and aerobatics
 

I just did a google search for a CH53. Somebody looped that beast up and around? It looks like a hippo with a whirly gig on its head. Thats the most ungainly 11 tons Ive ever seen. How cool

Now that you have seen it Richard ... imagine a slow roll ... I am searching for the video ... can not find it on my hard drive and yes ... damn - I had it ! :mad:

Take note : Slow roll NOT a loop - maybe it can do one from 20 000 vt AGL ? :p

T_richard
I wasn't 'correcting' your post, just hoping to tempt TC to tell us more about the pic. I should have added a ;) .

Excuse me guys

Would someone please clarify for a civilian what a helio can do. I recognize that helios come in different shapes and sizes. I suspect that chinooks handle very differently then a cobra, what about a Hind M24?, or a Bell. I don't expect a primer on every airframe made, just an short outline of what a frame of a certain size can do. I know from years of experiance what I can do in different power boats and sail boats. Happy to share info if you care

Basic can you loop a helio for real or do you just throw it up and hope it comes through the loop before you run out of air?

Thanks

Huh????
 

To: Gunship

Please explain what hydraulics are used to effect lead and lag.

:confused:

T_Richard

The answer to your question is YES. Some helicopter types CAN loop - BK117, BO105 & Eurocopter Tiger (they are the three that I have seen).

Not all helicopters can loop due to the characteristics of their rotor systems. The beauty of the BO105 and BK117 is that their rotor systems are hingeless (or rigid for want of a better word). What this means is that they have no hinges to allow leading, lagging or flapping of the blades as they fly through the air. The blades themselves do these three functions. The beauty of this system is that they retain control power even down to -1g. To be precise, the BK117 and BO105 retains approx. 90% control power at -1g. What this means is that the rotor system has 90% ability to move into a new attitude at -1g. This is pretty good for a helicopter.

Down side - the ride can be a little bumpy but after the pilot becomes familiar with the flying characteristics - not too bad.

Enough of the Nerdy stuff. :8

T Richard: you have been extremely patient with us all, trying to expand your knowledge of helos. Whether some can do loops or rolls. Or is it mirrors and string technology?
Well I can honestly tell you that the real answer is:
somewhere up there in the clouds......................:uhoh: