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Brett

Aerobatic aircraft certification

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I was just wondering what is involved with the certification of aircraft for aerobatics. What got me started thinking about it was reading an article about the Bonanza which even brought out a few aerobatic models (Wooahh Aero's in a Bonanza) and was thinking about something closer to home like the Sierra,,, A fair whack cheaper than a RV and longer range :re feul and roomier than a Sonex.

 

 

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Yes I am aware of the PPL and endorsement requirement ,nothing wrong with registering VH ,, was more curious about what is involved with getting the actual aircraft certified ,how manufacturers go about it . I think after almost completing my first aircraft build (about 3 weeks away) there is no way on this earth I would build another just for aero's,,specially if it was a single seater. If I was to build another it would be a four seater (but then that would be not aerobatic ) for the sole reason I could register it experimental and do the maintenance myself.

 

 

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"There are significant gyroscopic forces on an aircraft engine used for aerobatics and typically their TBO is reduced unless the engine is engineered for the typical aerobatic forces."

 

David

 

Really ?? 062_book.gif.f66253742d25e17391c5980536af74da.gif

 

Jake J

 

 

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So I am told Jake, e.g. there is an aerobatic version of the 0-320 it is has an 'A' designation somewhere in the number, it has beefed up main bearing at the prop end and I not sure but I believe it may have beefed up crankcase webbing as well.

DJPAcro can give us the good oil on this one his Decathalon has the 'A' engine.

 

David

That would be handy to know. Thanks in anticipation DJP :big_grin:

 

Oh, BTW Mahlon in the Lycoming Yahoo forum is also excellent value for all things 'engine' ie Lycosaurus & Continental.

 

Jake J

 

 

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Some of my friends have aerobatic aircraft with Lycoming O-320 engines in them. They get a TBO of 2000 hrs regardless, same as in a non-aerobatic aeroplane. One is running well after 2500 hrs.

 

Another thought that he'd add the inverted oil system to be kinder to the engine plus stop it throwing oil overboard but was dismayed to find that his TBO would reduce to 1600 hrs because it would be considered as if it had an "A" in front of the model designation.

 

My AEIO-320 has the stronger crankshaft flange which was introduced because snap rolls and tumbles were found to result in failure of the standard crankshaft - as far as I know that was only in aggressive manoeuvres such as done by a Pitts, especially those with heavy propellers. My Decathlon does neither snaps nor tumbles.

 

I'm glad that David only offered a discussion on the 320 as it gets harder above that with the other mods that he indicated. Plus people put high compression pistons in, run regularly beyond the red-line rpm, do flat inverted spins at max power etc.

 

 

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The other thing is demonstration of satisfactory recovery from any spin mode possible for approval to do intentional spins. The same scope of testing that Cessna undertook recently for its Skycatcher.

 

 

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"...........and typically their TBO is reduced unless the engine is engineered for the typical aerobatic forces."

 

David

 

Don't take offence please, I was just questioning the veracity of your statement - wouldn't want anyone to have 'bad' info 003_cheezy_grin.gif.c5a94fc2937f61b556d8146a1bc97ef8.gif

 

Jake J

 

 

 

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Well Brett....

 

A fascinating question. The Citabria (Champion Model 7) along with the Bonanza, were only ever certified to the relatively basic requirements of FAA CAR 3 back in the 1940s. In the case of the Champion... How do you sell a seemingly outdated machine in the mid 1960s? Answer... Paint some stripes on it and declare it to be aerobatic ! Strengthen the wing spars....not likely !

 

Oh yeah. Beech did this with both the Debonair and Musketeer using "Utility Category", where only a +4.4G limit is needed. How do you get 4.4Gs? Simple, just reduce the allowable AUW when using the machine aerobatically.

 

So what we see is a very blurred line between aerobatic and non-aerobatic, in terms of the hardware.

 

The simple truth is that SOME (and only some!!!) non-aerobatic types are just as strong or stronger than some types that are approved for aerobatic flight.

 

We know that some machines that may be flown under RAAus registration are stated to be suitable for aerobatics (in varying degree) by their manufacturers and at least two types are out and out stunt planes.

 

Of course, the degree to which any given aerobatic type can be aerobated is a whole other discussion.

 

The original reason for the prohibition on aerobatic flight (3 axis machines) is no longer valid. It is time to amend the relevent CAO.........RAAus where are you?

 

Cheers

 

Nong

 

 

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All the standard Musketeers and Bonanzas were certified in Utility at max weight (no wonder the airframes have an excellent repuation for toughness). The aerobatic versions are 6g limit at the appropriate weight (refer the Type Certificate Data Sheet). An aerobatic Bonanza is about to arrive at Lilydale so friends of the owner will be able to sample it.

 

The April 2011 issue of Sport Aerobatics magazine has articles on two aerobatic LSA's. The Clipped Wing Cub is a mod to the original Cub which made it aerobatic - obviously pre-dated the LSA rules but in the USA older aeroplanes can be categorised as LSA if they satisfy the rules - plus, they can still do aerobatics.

 

The other article was on the RANS S-9 being built by an aerobatic enthusiast to compete in Intermediate Category which is usually Pitts territory. The aeroplane is finished so there will be another article before long about its flying characteristics.

 

The Citabria is still available new from the factory today. Still with the original certification basis and 5 g limit. The spar is quite a bit lighter than in my Decathlon but even the wing on the Decathlon is not really suitable for aerobatics at 6g despite the certification at +6 and -5 g. Plenty of Citabrias operating around the world doing aerobatics - a few schools in Australia use them. A long history with few problems so no need to change the certification basis. The factory has even re-introduced the original Champ as an LSA, still with the 5g limit.

 

 

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Individual aircraft types are permited to do CERTAIN manoeuvers only and there will be a specified max weight. IF you botch these manoeuvers you could easily "break" most utility derived aircraft. Beware of the stated "G" capability of some planes. In some cases the load will be the failure load and others it will still have a margin. All aerobatic aircraft that are used for aero's are subject to more inspections and have reduced component life. They may be required to incorporate mods to components. ie The DH 82 had a braced fuselage if it was to do flick manoeuvers. Aerobatic aircraft, are fitted with a "G"meter that notes the highest "G" encountered till it is cancelled. Engine overspeed is supposed to be recorded and appropriate service action taken. Engines that can run inverted (oil system and fuel) are not universal, so if you are gliding inverted you must keep the throttle closed and wait for the oil pressure to come back in aircraft like a Chipmunk, after you are right side up. The normal Rotax 912 will vent copious amounts of oil out of the normal tank with negative "G". because of the breather location. Nev

 

 

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The problem is that RAA operations specifically prohibit aerobatic operations.

Dunno about that, the RAA logo itself kinda promotes aerobatics. 022_wink.gif.2137519eeebfc3acb3315da062b6b1c1.gif

 

 

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