FAA Definition of "Aerobatics"

[PPRuNeUser0211]

Chaps, wonder if anyone can shed any clarifying light on an issue.

I'm trying to find out what would be considered an aerobatic manoeuvre (SP?) in a helicopter....

The FAA definition is ”Any manoeuvre involving an abrubt change in an aircraft’s attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight”.

FAA vs Bjork (Http://www.ntsb.gov/O_n_O/docs/AVIATION/4784.PDF) appears to be convicting a chap of conducting unauthorised aerobatics overhead an airfield in the '90s. From the description of one of the witnesses and my understanding of what's written, based on the fact he admits he went to 60 AOB, in what sounds like a wingover/chandelle he gets convicted for aeros. There are a couple of other references to cases which appear to involve AOBs less than this. Anyone know of links to documentation of these cases, or the particulars?

However.... the FAA display inspector's handbook (or something along those lines, have not seen the exact document myself) says that 90 aob vs 90 aop is the minimum defined limit for aerobatics. Controversial you might say....

Grateful if anyone could shed light on this, in light of the FAA's woefully inadequate definition!

Cheers,

Targ

[Mark 1]

There are different definitions for different purposes.

I believe the FAA require parachutes to be worn if exceeding 60 degrees angle of bank or pitch.

The UK ANO defines:
‘Aerobatic manoeuvres’ includes loops, spins, rolls, bunts, stall turns, inverted flying
and any other similar manoeuvre;

and refers to these in the ANO regarding wearing harnesses and in the Rules of the Air:

Aerobatic manoeuvres
18 An aircraft shall not carry out any aerobatic manoeuvre:
(a) over the congested area of any city, town or settlement; or
(b) within controlled airspace except with the consent of the appropriate air traffic
control unit.

We (UK) do not have a prohibition, as such, of aeros over an airfield.

Other than that its down to the flight manual, pilot's ability and airmanship as to what is reasonable.

[PPRuNeUser0211]

Mark, cheers, yeah, the problem is that the a/c is "not cleared for aerobatic manoeuvres" but fails to establish what that actually means.... The definition used is that of the FAA (tacky plastic american aircraft) and I'd quite like to pin down exactly what one can actually do with the aircraft!

[Mark 1]

I see what you mean. I guess its an aircraft certification definition that's required. A&C at the CAA may be able to help, as they will have approved the flight manual for UK approval.

Typically, for a non-aerobatic aeroplane, it excludes all the aforementioned maneuvers, except maybe spins. It sometimes specifically includes lazy-eights and chandelles to comply with US training requirements.

Where a lazy-8 becomes a wifferdill or wing-over is another matter!

[PPRuNeUser0211]

CAA quote their flight envelope for the a/c as being that defined in the a/c's flight manual, which only defines the a/c as "not being cleared for aeros"......

So what is the maximum angle of bank? or the maximum angle of pitch? You'd think they would clearly define this wouldn't you!?

[barit1]

In Googling around for a refresher, I found:
http://www.richstowell.com/howto.htm

...from which I quoteth:

>>>>>

4. Definitions.

Aerobatics/Acrobatics.
FAR 91.303 defines aerobatic flight thusly: an intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight. Note that aerobatic flight is not demarcated by a specific pitch attitude or bank angle. (Aerobatic flight is often mistakenly thought to occur only when an aircraft exceeds 30 degrees of pitch or 60 degrees of bank relative to the horizon. This 30/60 rule, which appears under FAR 91.307 (c), merely specifies the conditions under which parachutes must be worn by the occupants of an aircraft.) In the classical sense, the term aerobatics includes spinning, looping, and rolling an aircraft through 360 degrees of yaw, pitch, and roll.

>>>>>

Now I have a problem with this subjective demarcation of "abrupt change" and "not necessary for normal flight" - after all a touch-and-go is "not necessary for normal flight", nor is a V1 cut or a power-on stall. We do plenty of manuvers that are part of the training curriculum, that might be regarded by an inexpert witness as stunts or abnormal.

You've got my attention!

[PPRuNeUser0211]

Exactly! The definition is rubbish, especially when applied in my context... define normal flight.... It's completely ludicrous.

The 30/60 is interesting... didn't know about the parachute thing, but suppose it makes sense.

My point is, however: is there a legal precedent for an angle of bank which is considered to be the limit of acceptable "normal" flight? Or is it just left to argue ones case?

Also, would a 60 AOB "wingover" albeit not actually a wingover being at 60 AOB, be an aerobatic manoeuvre?

[Empty Cruise]

"...not necessary for normal flight..." - oh my!

That sentence does leave a bit of room for interpretation, to say the least. Normal flight for a 200-hr-PPL-around-the-contryside sort of trip - or normal flight for a cropdusting aeroplane, or a glider tug, or...

If the AFM is not specific in limiting either the range of manoeuvres allowable, or set specific body angle limits or bank limits - the authorities might have a hard time getting a conviction as long as the limit loadfactor is not exceeded.

Have several times exceeded 60 deg. AoB in non-aerobatic aircraft, without having performed aerobatics - after all, the aircraft can be flown perfectly safe at 90 deg. AoB & 0 G for the purpose of e.g. avoiding confligting traffic (often done in gliders). This is by no means an aerobatic manoeuvre - to have done aerobatics, you will need an intentionally executed precision manoeuvre (involving abrupt changing of etc. etc.) with the sole purpose of operating the aircraft being either training, competition or display.

I think the FAA might be a bit out on a limb here. They define aerobatics based on angle of bank & pitch, but these have very little bearing upon the actual execution of a given manoeuvre. Looking at roll, pitch & yaw rate, G load and rate-of-G-onset are probably better measures of how "abrupt" a change of attitude or flightpath is. Secondly, several non-aerobatic aircraft are allowed to spin - and if the aircraft does not exceed 60 deg. bank & 30 deg. pitch in that manoeuvre - we are talking real aerobatics (flat spin). Does this imply that the FAA imposes limitations above & beyond the manufacturers'? If so - it would be easier to state "Manoeuvres exceeding etc. etc. are forbidden, unless the aircraft is approved for aerobatics".

I have no experience with heli aeros - you might want to contact the IAF (International Aerobatic Federation), as I'm convinced they can help.

Brgds fm
Empty

[PPRuNeUser0211]

Cheers all, check this out
http://www.ntsb.gov/O_n_O/docs/AVIATION/4717.PDF

King air mate gets rumbled for 45 AOB and 5 1/2 thousand FPM and gets away with it, precisely because he brought expert witnesses to the stand to testify that for parachuting that was perfectly normal!

Methinks FAA need to get off their backsides and define something

[DennisK]

HELI AEROS

As a CAA approved heli DAE, the subject has to be dear to my heart, since I've been doing air shows and the associated manoeuvres for some thirty years.

So the legality of what we do had to be determined quite a few years ago, since as we all know, most FM's state in loud and clear terms, "no aerobatic manoeuvres"

Before the CAA had a dedicated DA system, I extracted their definition as being.... and I quote from CAA Test Pilot, Ken Reid in the mid 1970's. "any manoeuvre where the roll angle exceeds 90 degrees and the pitch angle 60 degrees." I have never requested a further definition since my insurers have been content to cover my display routines since 1974. (now just passed 1200 practice and actual public displays.) It is interesting to note that a CAA helicopter display authority simply clears the pilot for.... and I quote again.... "flypasts only"

It is further interesting that the FIA approved world helicopter championships are only ever referred to as 'Freestyle Flying' but as our recently published display DVD reveals, virtually all this year's entrants at Rouen flew 360 degree repeating pedal turns, spins and occasionally a full loop.

I only ever refer to the loops as a 270 or 360 degree 'wing-over' manoeuvre. ie a standard steep turn in a vertical plane!!

I'd have to say, heli aeros have been a grey area for as long as I can remember, but I certainly would not want to see such display flying stopped. I can only recall two public accidents in thirty years and while that is certainly two too many, it doesn't point to there being a significant problem.

I believe the CAA DAE system is working, and while the number of rotary DA's is not high, there is still a nil 'civil accident rate' in the UK.

Would like other views.


Dennis K

[NickLappos]

The FAA can and will grab you if you act foolishly, and then find the right paragraph. If you fly over a city and flip around to 59 degrees of bank and 29 degrees nose down, don't expect to find that you get an apology from the Feds when they realize that you had 1 degree of margin!

More fools have killed themselves in airplanes doing dumb things to impress their neighbors, even in B-52's.

That all being said, the definition is "not necessary for normal flight" and this does not mean a touch and go.

If you have trouble with the ambiguous definition of "Aerobatics", try "careless and reckless." There are no hard numbers to define foolish behavior, because fools are so very ingenious in developing new foolish things.

[barit1]

Don't tell the fuzz please -

I once went out for an hour or so in a PT-22 with Irwin Treager (of Aircraft Gas Turbine Engine Technology fame) in the back seat. We had seat chutes in the bucket seats, but they weren't legal (slightly out of date) so we weren't planning aerobatics - just normal PPL lazy eights, slow flight, stalls ...

After a few normal power-off stalls, he suggested I try one cross-controlled. I held about one-third rudder with opposite stick as we approached the stall -

Then ZOOM! The horizon turned 360° before I had a chance to even think about recovering! The PT-22 was notorious for approach-configuration stall-spin accidents, and I just had a demonstration (at 3000' fortunately).

The little Ryan had just a few degrees sweepback, and I quickly learned what sweepback means in yawed flight.