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Aerobatic Maneuvers - Definition of

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Aerobatic Maneuvers - Definition of

Old 18th May 2008, 06:57
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Aerobatic Maneuvers - Definition of

While reviewing the limitations section of the RFM of our beloved helicopter we find the limitation:

"Aerobatic maneuvers prohibited."

We all nodded sagely and agreed this is a good thing.

Then someone asked: "What combination of attitude, roll rate ect. would constitute aerobatics?"

We looked everywhere but could not find an exact definition except:

"According to the FAA (FAR §91.303), aerobatic flight is defined as “an intentional maneuver involving an abrupt change in an aircraft’s attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight.”

Pretty vague I think.

Anyone have a better definition?

NO I am not advocating the performance of any aerobatic flight - just trying to define the threshold of what we would call aerobatics in a helicopter regardless of type or capability.

I think aerobatics are like pornography - it might be hard to define but you'll know it when you see it!
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Old 18th May 2008, 08:31
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Apparently you're required to wear a parachute if you exceed 60 degrees of bank or +/- 30 degrees pitch, so that could be a guide. I'm sure most of us break that one daily...
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Old 18th May 2008, 08:32
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Thanks for that.

I have heard that definition more than once and it seems widely accepted.

A reference to some FAA, CAA, CARS or ICAO "rule" would be nice.

I assume that for Bell and Sikorsky products either the company has a definition or the FAA does.

Perhaps Nick Lappos will have an answer.

Kind of like someone saying "No Speeding" and not telling you the speed limit or saying that "Speeding is driving the vehicle at an abnormal velocity."
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Old 18th May 2008, 08:33
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for fixed-wing, yes, that is what we use, 30° in pitch and 60° in bank. A lot of the modern stuff has Bitching Betty saying "Bank angle, Bank angle..." if you go past 45° of bank, even, but that is for Part 25, Transport Category aircraft.

I seem to remember seeing something more than those limits when being given a hop in B-206s and B-212s but I could be mistaken in that. You could ask those topless Nigerian ladies in their dug-out canoes what they saw, I guess, if you take them for reliable witnesses.
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Old 18th May 2008, 11:27
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We had the same question during our 135 T/R course in Donauworth:

Q: What is an aerobatic maneuver, how do we know how to avoid it?
A: You can do 90° of pitch or bank, and you won't exceed the limits...

That was it. No other reply was given no matter what.
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Old 18th May 2008, 12:30
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Not the same thing...

You have certain G limits, positive and negative, that you can hold to while also putting your airframe into some pretty weird attitudes. The humble barrel roll is a perfect example of this, when you are inverted but with positive G if it's properly flown.

The thing is, though, it is the attitude that defines "aerobatics", not the G-loading. For instance, I can easily put my airplane up on a wing-tip without pulling much G, simply by not pulling much nose-up pitch, letting it descend at 1 G, but that would still be an aerobatic manoeuvre, legally speaking.

I think the regulators are worried about us getting something wrong, hence the limits to what attitudes we can put our aircraft into as the only easy thing to define. If we were only told not to exceed a G limit, well, I could barrel roll my Twin Otter and be alright with that so long as I made no mistakes. Get it just a little bit wrong though, when things can happen fast, and then I could easily bend or break it.

I was very interested to see a "buttonhook" flown in a B-212, something very like a wingover. I could see that it might easily turn into a tailslide in the hands of a clumsy pilot, when I suppose the helo would come apart.
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Old 18th May 2008, 13:14
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To inform the debate, the military definition is/was "manouevres exceeding 90 degrees in pitch or roll".

This was used for the (RAF) Gazelle displays in the 70s/80s, which got around the then accommpanying rule "aerobatic manouevres are prohibited in helicopters."

..... and then along came the Lynx .......
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Old 19th May 2008, 02:13
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Fly past a crowd. If they clap and cheer, it's aerobatics.
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Old 19th May 2008, 02:36
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Why do it? Rent a Pitts!

You answered your own question well when you quoted FARs as saying:
"According to the FAA (FAR §91.303), aerobatic flight is defined as “an intentional manoeuvre involving an abrupt change in an aircraft’s attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight.”

Most countries will have a similar phrase in their documentation...and yes the starting point was probably an ICAO Annex.

Albatross, you are a big bird, surely it doesn’t take one of the wisest birds to explain to you what abnormal or abrupt feels like?
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Old 19th May 2008, 06:34
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Thanks Shortshaft - Now I can log all my ILS approaches as Aerobatic time.

I was just trying to find a more definitive answer than the FAR gives.

OVERDRIVE - Great Answer - LOL.
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Old 19th May 2008, 08:18
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Change to 407 FMS

Famously Bell are said to have added an FMS after a 407 performed a pretty impressive display at a South African airshow (video available to watch at the regular outlets - the commentator is a tad surprised).

As the proud new owner watched gleefully, sat alongside was the local Bell rep. As the display ended the rep turned to the owner and advised him the aircraft was good only now for scrap...and soon thereafter the FM supplement appeared banning aerobatics (although as this threads notes, the definitions are vague). Shame, since the airframe is more than strong enough.
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Old 19th May 2008, 08:39
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I think, the statement ( aerobatics are prohibited ) in the FM has something to do with certification requirements?
Look into the FM of the famous BO 105, its also in there. But aerobatics are no problem with a skilled and well trained pilot ( p.e. Red Bull, German Army )

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Old 19th May 2008, 08:47
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Presumably the 300C can be described as 'aerobatic'?

I've just been watching Dennis Kenyon's DVD, which features 'aerobatic displays' in his Hughes/Schweizer.
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Old 19th May 2008, 12:26
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I thin DK describes his routine as display, not aerobatic flying. Maybe he'll drop by this thread and let us know.

For me the onset of redout or brownout is a good starting point. maybe not in the old R22 though.
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Old 20th May 2008, 06:42
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From (Court ruling) http://www.ntsb.gov/alj/o_n_o/docs/AVIATION/3655.PDF

The FAA Administrator in his reply brief concedes that the regulation (FAR section 91.71(d) defines acrobatic flight as "...an intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight.") does not define acrobatic flight in terms of specific degrees of pitch or banking, but asserts that such specificity is unnecessary and would be undesirable, given the wide variation in aircraft and their design capabilities.

Australia has much the same
Civil Aviation Regulation 2 acrobatic flight means manoeuvres intentionally performed by an aircraft involving an abrupt change in its attitude, an abnormal attitude, or an abnormal variation in speed.

but goes on to say
Civil Aviation Regulation 155 Acrobatic flight
(2) For the purposes of subregulation (1), straight and steady stalls or turns in which the angle of bank does not exceed 60 degrees shall be deemed not to be acrobatic flight.
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Old 20th May 2008, 12:40
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The question is certainly a paradigm of sorts.

I have personnally witnessed the insides of transmissions, one of which was removed from a helicopter of the, "so called Famed" blue Eagles, which had been removed at 28, - THAT IS TWENTY EIGHT TOTAL HOURS FROM NEW.

On the tag was the reason.

Now I have to say that some of us took the mickey out of this little predicament quite some,I mean we flew 'em - an flew 'em - an' held our mouth, jess right, (well we thought so) an' we used words like 'tally ho' and bandits (cattle) at your 4 oclock, an' we wore RAYBANS and dramk beer like it was goin' out of fashion, - an swaggered around and none of our transmissions still had the blue on the gears after all'o'that, an we thought we had been misled.

So for the aerobatis team, the Blue Angels, just what is "AEROBATIC FLIGHT"?
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Old 20th May 2008, 20:23
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Aerobatics in rotary

Hallo lads,

A thread quite dear to my heart.

Its a consideration ... I won't call it a problem ... that I have had to address for thirty-five years. I'm about to run through my One thousand, two hundred and thirteenth public display next month at London City Airport, so it is always important that the rules aren't bent. Insurance is also a major consideration.

As has been noted here, I refer to my air shows as 'display flying.' and being a DAE it is important that intending DAs understand the basics.

Having discussed the matter with the safety regulation guys at the display division of our CAA, the numbers that seem to be accepted are 'any manoeuver that doesn't exceed either 90 degrees in roll or 60 degrees in pitch.'

That seems reasonable to me. Of course the BK 105 and the Lynx manoeuvres leave that defintion for dead.

As to exessive changes in attitude, I'd like to think that my standard display routine stays well within the requirement there. I routinely place my pace notes on the seat alongside me and they do need to stay there throughout the sequence.

Out of interest, and before I finally quit the display scene, I plan to produce a display manual for DAEs. I just feel that the basics I have learnt over the years need to be formally set out somewhere.

As I have oft quoted here ... I dearly want to see some younger pilots come in to the display scene when my hat is finally put to bed.

Take care all and safe flying,

Dennis Kenyon.
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Old 20th May 2008, 20:39
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great idea, would like to see something in paper about your exploits! Met you briefly at Redhill during Veeany's safety evening. have you thought about running some sort of course for budding display pilots?
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Old 20th May 2008, 21:55
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Interesting stuff here...

Where did I get that 60° in bank and 30° in pitch from, anyway? I know what the U.S. FARs say, and it is not there in so many numbers, no. This is some extra information defining an "abnormal attitude" but where exactly do those numbers come from? Perhaps they are in Part One, "Definitions", in the Airman's Information Manual, which I do not have here ready to hand. Or it might be one of those things that "everyone knows" that is not strictly correct.

This 90° in bank and 60° in pitch; is that specific to one pilot's display routine or is that the general UK CAA definition of the starting limits for an "abnormal attitude" where aerobatic flight begins?
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Old 21st May 2008, 03:24
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Several years ago (in the early 1980's) I wrote the following to discuss my views and opinions regarding ICAS policy and the ACE program as they apply to helicopter aerobatic flight. It may answer a few questions concerning the US FAA Aerobatic restriction.


In the U.S., the definition of aerobatic flight is contained within FAR Part 91, Subpart D - Special Flight Operations and says:
"No person may operate an aircraft in aerobatic flight-
(a) Over any congested area of a city, town, or settlement;
(b) Over an open air assembly of persons;
(c) Within a control zone or Federal airway;
(d) Below an altitude of 1,500 feet above the surface; or
(e) When flight visibility is less than three statue miles.

For the purposes of this section, aerobatic flight means
an intentional maneuver involving an abrupt change in an
aircraft's attitude, or abnormal acceleration, not necessary
for normal flight."

This rule applies to aircraft in general and does not distinguish between airplanes and helicopters.

Aerobatic flight is somewhat further defined by FAR Part 91.307 Parachutes and parachuting which states in part the following:
"(c) Unless each occupant of the aircraft is wearing an approved parachute, no pilot of a civil aircraft carrying any person (other than a crewmember) may execute any intentional maneuver that exceeds-
(1) A bank of 60 degrees relative to the horizon; or
(2) A nose-up or nose-down attitude of 30 degrees relative to the horizon."

Although aerobatic or acrobatic flight is not mentioned within this regulation, the FAA has interpreted flight beyond these limits as aerobatic. This regulation does not differentiate between airplanes and helicopters. It should be noted that few people who have successfully parachuted from an out of control helicopter.

These broad definitions are quantified for airplanes in the certification requirements of FAR Part 23-Airworthiness Standards: Normal, Utility, Acrobatic, and Commuter Category Airplanes, which states the following:

"FAR Part 23.3 Airplane categories.
(a) The normal category is limited to airplanes that have
a seating configuration, excluding pilot seats, of nine or
less, a maximum certified takeoff weight of 12,500 pounds
or less, and intended for non-acrobatic operation. Non-
acrobatic operation includes:
(1) Any maneuver incident
to normal flying;
(2) Stalls (except whip stalls); and
(3) Lazy eights, chandelles, and steep turns, in which
the angle of bank is not more than 600.

(b) The utility category is limited to airplanes that have
a seating configuration, excluding pilot seats, of nine or
less, a maximum takeoff of 12,500 pounds or less, and
intended for limited acrobatic operation. Airplanes
certified in the utility category may be used in any of the
operations covered under paragraph (a) of this section and
in limited acrobatic operations. Limited acrobatic operation includes:
(1) Spins (if approved for the particular type of
airplane); and
(2) Lazy eights, chandelles, and steep turns, in which
the angle of bank is more than 60 degrees.

(c) The acrobatic category is limited to airplanes that
have a seating configuration, excluding pilot seats, of
nine or less, a maximum certificated takeoff weight of
12,500 pounds or less, and intended for use without
restrictions, other than those shown to be necessary as a
result of required flight tests.

(d) The commuter category is limited to propeller-driven,
multiengine airplanes that have a seating configuration,
excluding pilot seats, of 19 or less, and a maximum
certificated takeoff weight of 19,000 pounds or less,
intended for nonacrobatic operation as described in
paragraph (a) of this section.

(e) Airplanes may be type certificated in more than one
category of this part if the requirements of each requested
category are met."

There is only a Normal category for US rotorcraft. There is no Utility or Aerobatic category. The rules do not exist to certify a helicopter in these categories even if they did exist. The US does allow Restricted category operations and the issuance of a Special Airworthiness for purposes that include Show/Exhibition. All helicopters in the US approved for aerobatic operations must do so with a Special Airworthiness certificate. The FAA will individually approve any intended maneuver for display and require that certain limitations and restrictions apply when those maneuvers are performed.

US helicopter certification requirements are contained in CAM 6 Rotorcraft Airworthiness: Normal Category (the old rules) or FAR Part 27 Airworthiness Standards: Normal Category Rotorcraft (the new rules) which prescribes airworthiness standards for the issue of type certificates, and changes to those certificates, for normal category rotorcraft with maximum weights of 6,000 pounds or less. Acrobatic and utility categories are not directly addressed by either regulation. The subject is indirectly addressed in section 6.718, Types of operation, of CAM 6. This section states: "The type of operation to which a rotorcraft is limited shall be established on the basis of flight characteristics and the equipment installed". FAR Part 27 is even more indirect. The regulations pertaining to Flight Characteristics in FAR 27.141 General, and 27.143 Controllability and maneuverability limit operations to those within the limits of the helicopter and in 27.141 (b); "Be able to maintain any required flight condition and make a smooth transition from any flight condition to any other flight condition without exceptional piloting skill, alertness, or strength, and without danger of exceeding the limit load factor under any operating condition probable for the type..."

The only realistic definition of helicopter aerobatic maneuvers is contained within Chapter 49 Issue A Certificate of Waiver or Authorization: FAR Section 91.79 (Aviation Event) within Part 17 General Provisions B., (11) which states: "Helicopters may perform aerobatic maneuvers no closer than 1,000 feet horizontally from a spectator area. These maneuvers are described as a 90 degree pitch down, split "S", loop, and barrel roll. Performers proposing to use these maneuvers in an air show must produce evidence of approval by AFS-20."

The FAA took the position several years ago that unless specific aerobatic maneuvers were included in 'kinds of operation' and therefore tested as any other maneuver would be during certification testing leading to the issuance of a type certificate, then those 'kinds of operation' were not authorized. There is nothing to prevent any manufacturer from including any aerobatic maneuver in the application for certification, testing to prove that aerobatic maneuver can be performed safely, and then listing those maneuvers as 'approved kinds of operation'. This is not an unreasonable expectation today, but did not exist in the early days of rotorcraft certification. In those days, if you could do something within the limitations and restrictions of the aircraft, it was not prohibited.

Older US helicopters did not have an aerobatic maneuver restriction in the flight manual. The H300 and H500 are examples. Both have performed numerous fully aerobatic displays (by any definition) within the limitations specified in the type certificate. In the 1980's the FAA realized that many of these maneuver had not been tested as part of certification testing and instructed the manufacturer to 'insert' the prohibition against aerobatic maneuvers in the limitation section of the flight manual. I will not go into the details of the negotiations that took place but the end result is that Hughes/MDHI reluctantly complied with the FAA request.

As a side note, a few years later MDHI decided to certify the MD500 NOTAR as aerobatic for loops, rolls, split-s, hammerheads and a few other maneuvers. A flight strained aircraft performed all those maneuvers within expected performance limitations. The FAA regulatory process could not handle the request in a timely manner so MDHI withdrew the request so as to not delay certification.

The answer to your question is that some helicopters cannot perform aerobatic maneuvers safely and have a prohibition for that reason. Others are prohibited because manufacturers do not want to incur the additional cost of certification or because the FAA does not - until this day - have a aerobatic category for helicopters. Hope this answers some of your questions.
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