Backward Blade I didn't mean to imply that 'all' of the maneuvres I listed have been performed in every helicopter out there, only that I have witnessed, have seen on film, or have heard of people doing something that might be considered aero in just about every helicopter that has been built. Some have even managed to do so successfully. I have seen skewed loops in a B206 and an R-22. I happen to consider loops in those aircraft to be extremely dangerous because if the slightest mistake is made then the outcome is likely to be fatal.

[email protected] I could not agree with you more. Without a recording G meter one has very little ability to determine if the G limits of the helicopter are being maintained.

I am often asked why Boeing performs the same routine in the Apache at every airshow. The reason is that aerobatic envelope expansion was conducted at mission gross weights to 7K Hd in an aircraft that was fully flight strained. We also did abort maneuvres such as an inverted pull through at high G from a pitch coupled roll which, as you well know, can involve some unusually high G. We know that those maneuvres and the maneuvres necessary to recover the aircraft if they go wrong, can be safely performed within all aircraft limits. We also know that they cause only a very slight reduction in the calculated lives of certain components. We don't do other maneuvres because I have no way of knowing with certainty that there are no detrimental affects to component lives unless we do another flight strain and that is very expensive.

Helicopters that are specially certificated to perform maneuvres beyond their certificated envelope are required to have a G meter installed. Further the FAA is beginning to require at the very least a vigorous engineering analysis of the proposed maneuvers for the very reasons you espouse. Many designs can do these maneuvres without coming apart in flight, but the real problem then becomes how much reduction in time-life components should be applied since these maneuvres haven't been applied to normal SN curves.

Helicopter Acrobatics
 

Rich Lee's comments are right on target and hopefully will be read by all those flying acrobatic-like manuevers.

Particularly poignant are his observations about the Apache demonstration manuevers having been accomplished first in an instrumented aircraft so that the associated flight loads could be determined, in such a way that subsequent fatigue damage ( if any ) could be tracked.

At Sikorsky, we did exactly the same thing for the S-67 aircraft, which had an "approved" acrobatic envelope. ( Approval arising from an internal assessment from structural flight test management within the company ). The S-76 program that Nick Lappos referred to was similarly covered.

A couple of observations on this subject, arising from personal familiarity with the various related programs at Sikorsky:

1. A "G" meter is of some assistance for an acrobatic helicopter, but is not the limiting factor by any means in many cases. That is because the static strength of the fuselage and aerodynamic appurtenances such as stabilizer/stabilator is not so much the issue as much as rotor stall related loads. For example, the same 3.0 "G" snap turn at sea level will produce much lower rotating control loads than when attempted at Hd=10K ft*. Same comment applies to the same manuever performed at a very light weight versus at a maximum permitted weight. Simply stated, rotating control loads are not linearly related to "G" alone. We found, in addition, that other factors, such as the collective position at the manuever entry point, influenced control loads for a "same "G, same weight, same Hd" manuever; the higher the collective at the cyclic pull point, the higher the control loads.

* In fact, control load behavior at altitude can exhibit other unexpected anomalies. The CH-53A aircraft had a Cruise Guide system, which was an indicator tied to an LVDT ( Linear Variable Differential Transducer ) embedded a the main rotor servo, i.e., it measured main rotor servo loads. At sea level and up thru the lower altitude/weight combinations covered by the original CH-53 qualification testing, the cruise guide load data agreed excellently with the rest of the rotation component loads and was a terrific leading indication of stall and high control loads. But when the USAF HH-53C arrived on the scene, with bigger engines and a higher gross weight/altitude operating spectrum, the main rotor control load behavior changed dramatically at the stall point, the main rotor servo load frequency signature changed, the peak main rotor servo loads flattened out, while the push rod loads were going up exponentially. Cockpit vibration cues did not provide a clue as to what was occurring. The point is that helicopter control loads associated with flight seemingly within the flight envelope is a complex subject.

2. Other control loads beyond main rotor stall related loads need to be known. Just one example: tail rotor bending stresses related to the gyroscopically induced loads during rolling manuevers are, typically for at least the SA tail rotor configurations, higher in left high roll rate manuevers than in high right roll rate manuevers. These loads can be high enough to be a candidate for manuever cycle counting and component life adjustment, if one plans on doing the manuevers on a repetitive basis.

I believe that the point Rich Lee referred to, and that I would heartily agree with, is that, for any helicopter, if an operator is intending to perform manuevers outside the normal, a consultation with the manufacturer to determine and confirm that these manuevers are covered by the flight test qualification program, and what the ramification with regard to component replacement times might be, ought to be priority one.

Thanks,
John Dixson

Thankyou to you test driver gurus for shedding some light on the definition of helicopter aeros.

I think you may be some distance from my original question though, when one filters through your 'high tech' talk and then mentally trangresses back to Dennis K's pedal turn in fixed vertical plane in an 'old tech' H269 for example.

Where does this leave the aspiring enthusiast who is wishing to learn?

I guess the thread became a bit discordant at one stage, and I apologize for my part in that with my choice of language being, "sorry wrong", when in fact it should have been, 'sorry I disagree'.

We certainly don't need to go over the ground again of who needs to demonstrate to whom the unpredicability, for demonstrations, of any sort to succeed as judged by the public.

And I disagree that any demonstration, be it military salesman ship or country airshow, is for any thing other than the very common reason to impress, regardless of the type of organised audience. That must be plain, surely.

BTW those machines that have attempted lamchevacks , esp in close proximity to the ground, sometimes 'kick awhile' before they become still.

In a couple of dreadful situations, so have their occupants, of which I have been aware of at close quarters.

For the sake of newbies lets disendorse the encylcopedia of F/W aeros from any fanciful notions that they may have.

A simple rule could be - never get a situation where your fuel load may not be flying in close formation with you fuel tank exit point. That should insure that oneis never close to the dreaded mast bumping weightlessness etc.

machines that can fly inverted by design surely must have been acquanted with fuel systems that can handle that.

topendtorqueGo to Russia, get your hands on a Mil MI-34S Hermit and an instructor with helicopter aerobatics qualifications, and then enjoy the pleasure of flying a purpose built aerobatic helicopter. Or ...... just watch the video

http://www.madskies.com/tag/aerobatic/

Thanks, Rich, I had a look. A bit out of my league, I don't have one of those Elton John / Corey / Lleyton back to front cancer caps in my cupboard, and don't fancy wearing one either. That is if that is what it takes to swan one of those machines around like a drunk sailor.

I do say though the machine itself looks quite impressive.

Heli Display flying
 

A big thanks to the many guys who are contributing to the post.

I'd have to say that I have been far from aware of the goodly number of pilots who have knowledge of the display manoeuvres being employed ... and it is especially good to see input from guys like Nick Lappos.

In the case of the Enstrom Shark, the display sequence I worked up for the 1970s Farnborough shows was passed to me by the one time factory test pilots, being Mike Meger and Mott Stanchfield, both displayed the 280C at the 1973 & 1974 events. In fact it was in 1973, that I crewed for Mike Meger when he took first place in the second ever world heli championships 'freestyle' event at Middle Wallop, England.

My display routine was more than thoroughly investigated by the engineering division at the Enstrom plant in Menominee. The Chief designers, Herb Mosely and Paul Schultz went through each manoeuvre before giving me clearance. In those days there was no CAA involvement and the DA didn't exist. I flew a dozen displays with tell-tale equipment fitted to the M/R hub and max rotor disc defelection measurement ... all proved acceptable and the display I'm performing in 2008 are identical to the 1970s sequence.

I have 17 set manoeuvres where each have a 'gate' speed and height. The two are interchangeable for operating conditions. And yes, I have flown the sequence with a 'G' meter AND a rearward reading ASI. The manoeuvres to be flown for any given display are set out based on the display location, atmospheric conditions and the time slot requested.

I'm approaching my 1214th public display at the London City Airport event next month so I regard the display as well established. I take note of the variant views on such flying, but in the same way a violinists, a showjumper, a singer or all the other areas where the participant is pleasing the spectator, I feel rotary displays are a worthwhile part of our industry. Motivation? Just as written, but I have to add, the immense personal satisfaction of performing well for the air show crowd. (then there is the money!)

To answer 'Top End Torque' (something I never achieve in display work) the set manoeuvres you refer to were laid down by the FIA for the 1986 world champs event. Rather like ice dancing, competitors were offered a selection of manoeuvres are varying difficulty, but each carrying correspondingly more marks. In theory a display pilot could win the event using a constant hover! But it would have to be a good one!

I have taken part in the subsequent 1992, 2002 and 2005 world champ events and haven't seen the 1986 system used since. Now a 500 metre box with a 500 ft max height is provided in which the display pilot flies his preferred 'freestyle' manoeuvres in a strictly set time of 180 seconds, so every manoeuvre needs to score!

Display flying is obviously something very dear to my heart, especially as AD is catching up all too quickly and I'm fascinated to read ppruners posts. I'm also hoping to display either the Enstrom 480T or the Schweizer in Utah in a couple of weeks time.

This year, the champs are to be held in Germany, near Leipzig. I'll be there and would love to get a place as the oldest pilot to win something in a world championship event. Seventy-Six and counting!

Safe and good flying to you all.

Dennis Kenyon.

Dennis
check your pm's, I'll chuck you through a maneuvre for you to run your mind over.
tet.

I have very much enjoyed the posts from crab, John, Nick and others; but Dennis, it's about time you wrote a book, isn't it?:ok:

I agree Rich, it would be very popular with rotorheads all round the world.

Out of interest - is Dennis our oldest (still flying) contributor on this forum? The thought of still being able to fly in one's 70's seems quite incredible. Nice one Dennis:ok:

Anno Domini
 

Now ... now - out there. I'm only old in calendar years. The spirit is still very much alive and throbbing! I've a way to go to catch up with the immortal Bob Hoover.

I did a book a few years back. Just a helicopter yarn flyers might enjoy. "Appointment on Lake Michigan" .... available from Amazon or www.electrocution.com. Phil Croucher's business.

I am working on a 'Display Manual' where I am setting out my display manoeuves and the associated handling. Not sure where its market will be, but I'm hoping it will at least lay down some basics for future display pilots. The difficulty is that display flying is very type sensitive so I can only cover the types I have displayed. Just the Enstrom 280/280c and 480 Turbine, the Schweizer 269 series, MD 500 series and the Westland Scout.

Others out there have similar or more experience on the more sophisticated types, so perhaps my manual could be the starter page for those interested.

Best wishes to all out there and safe flying lads,

Dennis Kenyon.

Out of interest Dennis, how many successful display pilots have arrived via a direct/deliberate path? That is to say, set out with display and aerobatic flying as their goal, as opposed to a development from initially a certain length of more regular commercial flying maybe?

It guess many are from a military or manufacturer testing background (understandably), but are there many of the top guys that came effectively from a PPL and straight into aerobatic training? I understand the relatively small world that it is, and the considerable costs early on... but has it been done by many?

"Just"! Which is/was your favourite, and the most inherently natural for display work, as supplied, in an overall sense?

For what it's worth, I believe Starlight Aviation in Cape Town, South Africa has a Test Pilot training course where they teach aerobatic maneuvers in a 105.

I don't know if it would be a suitable training forum for budding display pilots, but worth checking out.