Can you safely invert a Cessna (say) 172?

[Dave T-S]

Having a discussion about this on another bulletin board.

I seem to remember reading somewhere in the dim and distant past that a Cessna 172/152 etc's wings are not designed to take the loadings that inverted flight can cause leading to the wings detaching.

Or would it have to be in a high G situation - a loop but not barrel roll etc.

True or false?

Thanks in advance:)

[Semaphore Sam]

Only in China (but don't fly straight & level).

[Captain Stable]

Dave, it simply is a matter of the manufacturer's loading limits. If the Manual says "+5g - -0g" (for example), then it may not be flown inverted.

You also need to consider the engine fuel supply. Most light aircraft do not have a fuel system that can supply fuel to the engine whilst inverted. It all then goes horribly quiet.

To pick up on another point in your post, both a loop and a barrel roll, performed correctly, are positive-g manouevres.

That the Book of Words states that only Split-S's, Chandelles and Lazy-8's may be performed may have a bearing on the matter, though, since if you do something more ambitious and bend something, then the insurance is invalidated.

[DB6]

As the good captain says it depends on the g limits. A C152 Aerobat has +6-3g capabilty so can do an outside loop if required, however the engine won't produce power while you're doing it. A 172 or standard 152 on the other hand has utility category limits (+4.4/-2ish) which are quite adequate for aeros however they are not permitted by the certifying authorities. Other things to be borne in mind are a) neither aircraft has inverted fuel or oil systems so the engine will stop and b) non-aerobats have lapstrap/inertia reel harnesses so you will end up with your nose squashed up against the roof and coffee in your hair :eek: .

[GoneWest]

Dave - as they say, G and fuel system....so to actually answer your question...

Can you safely invert a Cessna (say) 172?

Yes: But not for very long!!

[dick badcock]

Chief Test Pilot Tex Johnston barrell rolled a B-707 once at a flight display ('selling the aircraft' as he put it) and at some stage was inverted. The airplane, however, had no idea it was inverted. The maneuver was performed such that it felt like 1g at all times.

As for sustained inverted flight, I suppose if Cessna fitted a recirculating oil pump and fuel pumps on a 152, you could fly inverted (at least aerodynamically it would be no problem) although not as efficiently as when flying normally. Unless you had a symmetrical wing profile, of course. Legally the aircraft would have to be certified to at least -1g, though.

[Dave T-S]

Thanks for the replies so far guys:)

This was one of those semi theoretical conversations ;) so whilst the carburation/oil point is a good one, it is purely a wing loading question.

Anyone know what the manufacturers +/- G limits are for (say) a C 172?

[Tinstaafl]

Utility category ie loaded within the more restrictive limits: no rear seat occupants, nothing in the cargo area & within the utility CoG limits, flaps UP.

+4.4, -1.76

Normal category:

+3.3, -1.52 note: +2 with the flaps extended.

[FormationFlyer]

a C172 what?! There are a number of models - not all C172 are equal... for instance is it a C172P?

Always check the flight manual for a specific aircraft..NEVER use generalisations - *especially* when considering aerobatic manoeuvres.

Remember folks - play safe....the flight manual/poh was written for a reason :)

[Lawyerboy]

Don't have the manual on me, so don't know about the G- limits, but are we saying then that on an a/c with a fuel pump (such as the PA38) you could roll it inverted so long as kept within limits?

[Lowtimer]

Lawyerboy,

"but are we saying then that on an a/c with a fuel pump (such as the PA38) you could roll it inverted so long as kept within limits?"

No. A fuel pump does not in itself enable the engine to run under negative G. A fuel injected engine will run, but not for long unless it also has a negative G lubrication system.

In any case, rolling aerobatics are not permitted by the POH for the PA-38, as far as I am aware.

But it's not as simple as what the engine can do and the G limits for the airframe. Some aircraft, (Chipmunk, Tiger Moth, Spitfire, Hurricane) are permitted to fly inverted for short periods, e.g. a proper slow roll or roll off the top of a loop, but the engine will cut under the negative G. As the negative G comes on you throttle back in any case so that when fuel comes back, later in the roll, you do not give the bearings too much of a belt during a period of marginal lubrication.

Some aircraft, like the Beagle Pup, are certified for aerobatics with a +4.4G and (I think) -2g limit, while lots of others have the same G limits in utility category and are not allowed aeros. Some are allowed to aerobat in certain countries (the Europa and Vans RV6 and RV8 spring to mind) but not in others.

[Oscar Duece]

Hell I'm not crazy enough to fly a PA38 in any phase of flight.

:eek: :eek: :eek: :eek: :eek: :eek:

[eyeinthesky]

The short answer is : Yes you can fly a 172 inverted provided you do not exceed positive (or negative) design G limits and provided you keep it under positive G all the way round (e.g. Barrel roll or Loop).

Whether it would be sensible and whether a 172 would have enough inertia and engine power to take it over the top of a loop still in positive G without exceeding Va at the bottom is different question.

I did hear a story about someone who had learned to fly on something like a Fuji and then hired a Cherokee and proceeded to barrel roll it. He had not realised that the Fuji is somewhat special in being approved for aerobatics. Apparently the only damage done was oil all over the engine compartment from the breather pipe!!:D

[Dave T-S]

eyeinthesky
That's the answer I was looking for!

Cheers:)

[poetpilot]

Not a cessna, but I have seen a film sometime where Bob Hoover rolled a Shrike Commander (I think) with a cup of coffee on the dashboard, retaining all the coffee and not moving the cup. Don't try this at home...

[EchoKiloEcho]

I've heard about this. Any idea where I can find the video, or have you got the name of the film?

[FlyingForFun]

A fuel pump does not in itself enable the engine to run under negative G. A fuel injected engine will run, but not for long unless it also has a negative G lubrication system.Not entirely sure about this. The fuel pump will try to pick fuel up from the bottom of the tank - so unless you've got very full tanks, you won't get any fuel into the injectors. But I'm not going to volunteer to try it on any aircraft which isn't certified for aeros!

FFF
-------------

[Windy Militant]

You can, but you may not!
Any fixed wing aircraft can be barrel rolled. A favorite trick with early Canberras was seeing if you could do it smoothly enough so that the navigator didn't notice. However what you have to consider is if it all goes pear shaped is the airframe strong enough to withstand the forces that would be imposed on it during the recovery.

Echo kilo Echo.
The Bob Hoover clip was used in one of the Episodes of 'Reaching for the skies' made by the BBC back around 1986- 87 might still be on Discovery.

[Aerohack]

Bob Hoover not only rolled and looped the Shrike, but did it with both engines shut down, culminating in a deadstick 'Tennessee Waltz' landing and silent roll back to his parking spot. His party piece was to put a glass of iced water on the centre console, and never spill a drop. I rode right seat with him once (without the water trick) and it was an extraordinary experience sitting in a big, serious business twin and watching the world revolve with those Hartzells feathered. I also rode with him during his aerobatic routine in a Commander 114. Had to sit in the back to get wide-angle pictures of him at work, and that wasn't such fun with only a lapstrap.

[Zlin526]

Can I look forward to seeing this topic featured in a future issue of the AAIB bulletins?




Captain Stable,

a properly performed loop will not be +ve all the way round, only if you fly an egg shape, which is not a perfect loop. A properly performed barrell roll should maintain 1G all the way round, and as people have rightly said, has been performed in such aircraft as the 707 and Islander. If you get it wrong though, gawd 'elp you.....

[Flash0710]

Zlin Please.

The pupose of the original post was to enquire not to encourage.

Don't start assuming we are all going to jump in our respective tin and try it.

Ya never know unless you ask!

[ozplane]

Don't know about the coffee but I saw Bob Hoover do the barrel roll in the Commander at Reno 1999...but with both engines stopped. And he still had enough momentum to land (on one wheel purposely) and taxi up to his parking spot, jump out and wave to the crowd. Amazing stuff. He calls it Energy Management.

[My names Turkish]

Can't give to many details for fear or recrimination but..

I know about two CFIs in Cessna 152 going out to do their spin training and being full of adrenilin after performing a couple of spins, decide the next step was to do a loop. Put the 'plane into a high speed dive and pulled the loop off. The only scare was their baggage in the back hitting the ceiling when they were upside down. How do I know its true? I was watching from a pre-arranged vantage point.

Before anyone gets upset, I am not condoning this behaviour. I think its especially dumb, especially without five point harness and the proper training.

[CamelPilot]

For what it's worth.

You have to know something about aerobatics - that is the first requirement. Next you have to recognise the aeroplane's own limits. It is within THESE limits that you manouver ANY aircraft.

So.......it is possible to aerobat a 172 but only in positive G configuration. You can do it in other types also - but I witnessed the wings fold on a Turbulent in a loop at Biggin. I have seen and A26 barrel roll and crash - also at Biggin - and others too. ALL WERE FLYING OUTSIDE KNOWN LIMITS.

As far as flying inverted is concerned, a fuel pump will NOT help you round a roll through the inverted. If the engine has not got inverted capability to keep running it will stop if you stop the roll - so you have to keep it going. It will certainly cough and splutter a good deal. And even this has been known to cause a catastrophic lapse in concentration and nerve resulting in a collision with the ground. The initial requirement is therefore: Correct entry speed and a properly executed 360 degree roll - INSIDE limits.

The answer to the original question is NO if you do not have the following. The ability. The full knowledge of the aircraft's manual, and HEIGHT! And by golly you had better know your aeroplane!

[Shaggy Sheep Driver]

I'd agree with Camel Pilot - and add that if you do it in a non-aerobatic aeroplane you'd better be bloody good to ensure you stay within the (narrow) limits.

I'm no aeros ace, but I've a few years experience of basic aeros in Chippy and Yak 52. Usually, a barrel roll is a nice, lazy, low 'G' manoever. But sometimes, if I'm having an off day, it can degenerate into a horrible nose-low exit with far more speed, height loss, and 'G' than I intended. Still well within the limits of Chippy or Yak and my 2000 foot minimum height limit of course, but it could have the wings or tailfeathers off a 172.

I also witnessed, at a Barton air show a long time ago, a 'midget Mustang' do exactly this. His aeroplane was strong enough for the roll even when it went wrong, but he did it at display height and I can still hear the sickening thump and remember the fountain of earth as he went in.

SSD