Inverted roll with C-172????

[gasax]

old, not bold

I'm sure you posted the above in good faith however there are more than a few things about it which smack of urban myth and junk science.

In the UK there has only been a single wing failure on an Auster in the last 25 years - it was in 1993 and the investigation blamed steep manoeurves at low level. That was hotly disputed by family and friends if I remember accurately - but is perhaps germane to this thread.

The function of a jury strut is to stop the wing struts buckling whilst under negative g. So they do not 'see' the torsional loadings which would result from exceeding the flap limiting speed. On the other hand they would get a real work out in a gliding environment if heavish landings are occurring. however in normal (positive gee) flight you do not need the jury struts.

Still if nothing else this thread clearly demonstrates how much many of us really know - be it design, limitations or even what the maneourves look like!

[old,not bold]

I'm sure you posted the above in good faith however there are more than a few things about it which smack of urban myth and junk science.

Well no, actually. The accident certainly happened more or less as recalled in my post, and until quite recently I had the accident report stuffed somewhere in the junk in the attic; it might still be there.

I'm not sure you are wholly correct about the jury strut function, but if so the negative G could have resulted from unusual accelerations in a gust. It's quite possible that my recollection of that part of the accident report is faulty!

If the accident you mention is the only one since 1982 or so, then the one I'm talking about happened before that. It is history, as is the Auster, pretty much, and the point was to illustrate how easy it is to exceed design limitations with a combination of factors starting with ignoring the placards, and the possible nature of the consequences of doing so. It seems from what you say that the 1993 accident may have been another case.

[Caullystone]

Fit A G Meter

This is one of the most scary thread I have read so far on here....
I use rental aircraft

Would it not be possible to fit a G Meter to all aircraft and especially to all rental aircraft which shows the Max and Min G that the Airframe has been subjected to since it was constructed.

Sure it would need be tamper proof but it must be possible.

Then the rental organisations could check G Meter after each flight to ensure that some Ass*h*le has not flown it to excessive G

[bjornhall]

So how does the airframe stress from a reasonably performed barrel roll compare to the stress from a somewhat "spirited" stall/incipient spin recovery? Furthermore, what about the stress from the occasional (once every few years?) barrel roll when some lunatic got hold of the aircraft compared to the accumulated strain from taking students on stall practice almost every day for, say, three decades?

The '79 C172N I'm usually stuck in for training has probably pulled a dozen accumulated G's daily during its 25+ year training career, and it hasn't shed any wings that I'm aware of... Sure agree with previous posters that there might be more urgent things to worry about...

[foxmoth]

So how does the airframe stress from a reasonably performed barrel roll compare to the stress from a somewhat "spirited" stall/incipient spin recovery?

Stress from a "reasonably performed" barrel roll is not a big problem, but as has been already stated, most competent aerobatic pilots stick to doing it in proper aerobatic aircraft because they know the likelihood and consequences of it going wrong (plus they normally have the chance to do it in an aircraft that is more fun for doing this sort of manoeuvre so do not bother in a 172), so the chances are that if this is being done in a 172 it is by someone not that competent and hence more chance of a screw up/overstress.

[DX Wombat]

Why, oh why do people think they know better than the aircraft's manufacturer? If the manufacturer says it isn't suitable, or the aircraft is prohibited from performing aerobatics then it is unsuitable / prohibited. What do people think the POH is for? Extra ballast? Spare toilet paper? An exercise to keep someone in a job writing? Something for the FI to give the students to read on a rainy day or when they can't be bothered to do anything else? A good excuse for the FI who doesn't know the answer to say to the student - "Look it up in the POH" ? If the manufacturer says DON'T do it then you should NOT do it. Why is it so difficult to understand that? I was taught to read the POH, not just a condensed version, of a new-to-me type of aircraft before I ever went near it. It is something I shall continue to do as I wish to stay alive as long as possible.

[knox]

Quote: I think you're a bluffer Knox............


Well it looks like I have been outed. Just thought I'd mix it up a little.

This forum has gone from the sublime to the ridiculous. I can't believe that people have left this forum and pprune because what has been said here.

Its really simple, if the a/c is not designed to do aeros..... guess what.... DON'T.

Enough said, I think.


Knox.

[Pilot DAR]

Wow,

Lots of chatter here, but have people forgotten to read the original question? It was not "should I attempt a roll?", or "how do I roll a 172?", or "what are the different types of rolls?". The original question was: Is it possible?

Yes, It's possible, but unwise, not approved, and potentially very unsafe.

It is my opinion that most of the responders here seem to be caught up in the discussion of related, but different topics. Perhaps it would be appropriate to start two more threads: Should I attempt rolls in non-approved types?, and What are the type of rolls?

With those questions, the answers could all fall neatly where they belong, and people would probably stop being abused, and feeling personally attacked!

This is a forum for those flyers with a "professional" attitude, right?

Is there a thread drift alarm anywhere around? It would appear that another thread, derrived directly from this one, merrited complete deletion...

Pilot DAR

[Gipsy Queen]

Good heavens! Is this thread still going?

The flap control on the Auster was indeed pulled down with the pilots left arm but, as far as I recall, you had to pull the black plastic grip on the pipe forward to disengage the spring-loaded detent system. Whatever . .

Now this jury strut thingy . . . To be frank, and with respect, Sir, its purpose could not be as Old Not Bold describes it. In terms of the resolution of forces applied to the rest of the wing geometry, it is an irrelevance and has no part in flying/landing loads. The jury strut can act only in compression or, more effectively, in tension but to transmit wing spar or other loads loads to a point more or less in the middle of the main strut and where the resultant reaction can only be one of unresisted bending in a beam sense is a dynamic which would be avoided by a first year physics student.

May I respectfully suggest that the purpose of the jury strut is to control beam flexure by effectively halving the resonant length of the main strut by tying it to the main spar? This I could understand. Furthermore, it could explain why some models of Auster had both struts controlled in this way and other models had the jury strut applied to the forward main strut only. I shouldn't be surprised if, having removed the jury strut, the main strut started to vibrate or misbehave in some other way at critical loads/airspeeds.

GQ.

[LowNSlow]

The jury strut serves two puposes:

a) It stops the wing to fuselage struts bending under negative g-loads as they are long, slender struts which would flex if the wing was pushed downwards relative to the airframe. This could happen due to aerodynamic loads (turbulence or a deliberate negative g manoeuvre) or the negative loads found when taxiing across rough ground.

b) They prevent in flight vibration of the aforementioned long. slender struts.

I'm sure Genghis the Engineer can give us the specifics on this if he pops his head into this fairly daft thread.

Back on topic I think anybody who operates an aircraft outside of the specified limits, unless it's to rescue a potential disaster, is taking their lives and potentially the lives of others in their hands.

PS The Auster flaps do require a forward pull on the grip at the end of the handle to release the pawl in the flap selector quadrant. It is possible to leave the flap disengaged and allow it to "float" between the flaps up and position 1 although why anybody would do it is beyond me. If the aerodynamic loads were sightly eased however the flap lever, being quite heavy, would drop the flaps into position 1 for which the limiting speed is 70mph. I use 65mph in defrence to the fact that the wing the flap is attached to is 61 years old!

[old,not bold]

Thanks for all the reminders about how the flap lever operated on an Auster...I last flew one in 1966, according to my logbook, after 300 hours on the type!

And for all the information about the jury strut; illuminating, to say the least. We live to learn.

But my original point wasn't really about Austers; it was about deliberately flying outside the limits, and the way that Sod's law turns silliness into a fatal error.

And that applies to rolling a C172.

[Gipsy Queen]

The point hadn't gone unnoticed o,nb.

Those with any proper understanding of the subject have all been saying the same thing ad nauseam, which is why I wonder at the longevity of this thread.



GQ.

PS Thanks LowNSlow for (unwittingly?) correcting me.

In my earlier post I remarked that the jury strut played no part in "flying/landing loads". Clearly, -g in flight would put the main strut in compression and requiring the control of the jury strut. Similarly, heavy landings and the like would impose negative loads on the same strut so my previous assertion was incorrect in this particular respect. I'm obliged to you. Your moniker suggests you might be an Auster owner? LowNSlow it is; not much choice if you've got the Cirrus Minor engine!

I don't know why it should, but mention of the flap control reminded me of the park brake mechanism. Made by Bluemels, I think, and used on the contemporary Ford Popular and Prefect amongst others. Elevator trim handle ex-Vauxhall 10/12/14 window winder by Wilmot Breeden.

Why is it that I find myself blankly staring at a shelf in Sainsburys, wondering why the hell I'm there but have no difficulty in remembering this useless trivia from fifty something years ago?

[Beaver diver]

OK guys ,a lot of things learned and reviewed. Since I have started this thread I will finish it in the same manor with a few juicy questions that we're never described in any POH or explained to us at the time when we we're still "student pilots" regarding everyday flying. Some of the questions are;
1.) How does the plane react if you are stalling with 4 people on board and max baggage?
= Answer: I don't know ( usualy you are in the plane with your instructor and no baggage)
2.) How does the plane react in a full flap config stall while carying 4 people (C172) and max baggage while on 500 feet final?
= Answer: I am confused (usualy you do this exercises on 3000 feet plus...)
3.) They say that some of the airplanes are not "Spin" authorised; does that means that If I inadvertently end up in a spin, I can't recover the airplane or do they just say ;"Well, If it brakes apart while recovering it It is your fault since we have said it is not made to do any spins???"
= Answer; I hope I will never end up in a spin...
There are many more things that I would like to explore and get answers to, but for now, let's believe that C172 can't make a barrel roll, can't be "spinned", can't stall at 500 feet with full load and lets believe to the POH references. Anyways It is safest for all of us.

[Runaway Gun]

BD,

Check your dictionary, and compare the words "Can't" and "Don't".

[BackPacker]

My guesses at answers:

1. As long as you are within fore and aft CofG limits, stall behaviour should be more or less the same as stalling with just you and an instructor. At MTOW, expect the stall to happen exactly on the bottom of the green arc, instead of some knots below it, and expect a little more altitude loss than what happened in training. Depending on balance, there might also be a more severe wing drop. Oh, and loose baggage might shift, obviously.

If you are outside CofG limits, all bets are off. Best case might be that the aircraft doesn't stall properly but you run out of elevator travel and the aircraft just mushes down. Worst case might be a very severe stall without any warning, severe wing drop, spin, whatnot.

2. If it's a fully developed stall at MTOW, 500 feet might not be enough for recovery especially if your recovery technique is rusty. As for stalling (at a safe height) with full flaps - why not try this with an instructor on board? As long as you don't exceed Vfe I do not see a reason the airframe won't be able to handle this. (But do check the POH and clear it with an instructor first!) Do note the altitude loss though - that's what you wanted answered after all.

But at 500 feet, regardless of configuration or actual weight, always recover at the first signs of a stall (stall warner and/or buffet). You can always go around.

(Some aircraft have a real twitchy stall warner. DA-40 comes to mind. You get used to this: if it chirps, you check the airspeed first. If you're still well above the bottom of the green or white arc and you are essentially in non-accellerated, non-turning, normal 1g flight like on final, you continue the approach anyway.)

3. All light aircraft (at the very least all CofA aircraft - I don't know about PFA) have to be spin tested and have to exhibit more or less normal spin characteristics. The exact anti-spin procedure is in the POH. So you should be able to stop the spin even in aircraft that are not authorized to be spinned with an established procedure, usually by unloading the elevator and applying opposite rudder.

After the spin, you end up in a dive. Most of the spam cans we fly are not slippery enough to reach Vne in such a dive without adding power. But even if you do reach Vne, rest assured that again for certification purposes, a dive faster than Vne is mandatory. So to recover from the dive, make sure throttle is closed and gently (key word is gently as you might be above Va) pull out of the dive until speed reaches normal cruise flight levels.

The fact that an aircraft is authorized to spin means that you can spin it all day without adverse long-term conditions. If an aircraft that is not spin-certified ends up in an inadvertent spin anyway (through a botched stall practice, for instance), the airframe will most likely survive but it is one of those things that you tell maintenance afterwards so that they can do some checks. Just like exceeding Vne is, or a hard landing, or exceeding Vfe with flaps extended, or exceeding g limits.

By the way, if you've never spun an aircraft, I do advise you to try it out once. My club regularly (tomorrow, incidently) organizes an "unusual attitudes" day, where you go flying with an experienced aerobatics instructor, in an aerobatics capable plane, to explore some of these unusual attitudes. The program includes various stalls (high-speed stalls, full power stalls, stalls in turns), a spin, very steeply banked turns (75 degrees or more) and a spiral dive. It gives you an appreciation on what an airframe can and cannot handle, and how to recover from these situations, as some recoveries (spin, mostly) are not intuitive.

Any school which has access to an aerobatics capable plane should be able to organise such a lesson. And if you enjoy this unusual attitudes thingy, it becomes your first aerobatics lesson. Mine was half a year ago, I've done the aerobatics course over the summer and I hope to do my solo aerobatics checkflight next week!

[stiknruda]

Gents, I refer you to my first post #17.
Words fail me!
--------------------------------------------------------------------------
Stall warners on two identical factory built a/c, under identical loadinds/flight regimes will go off at different times! It is all down to how Hiram and Jose screwed it onto the leading edge (Cessna/Piper/Pitts/Robin). A millimetre more north or south makes a difference. A lick of paint will make it behave differently!!
IF YOU KEEP THE AIRCRAFT IN BALANCE, USING YOUR FEET, IE - THE BALL IS CENTRALISED, YOU WILL NOT SPIN.
We can get in to the semantics of what that means, but let's not.
Is this the thread that deserves to die, but just won't?!

[Zulu Alpha]

Is this the thread that deserves to die, but just won't?!

Yes

All light aircraft (at the very least all CofA aircraft - I don't know about PFA) have to be spin tested and have to exhibit more or less normal spin characteristics. The exact anti-spin procedure is in the POH. So you should be able to stop the spin even in aircraft that are not authorized to be spinned with an established procedure, usually by unloading the elevator and applying opposite rudder.

Yes, but no but yes but.... The spin testing only requires recovery after half a turn if the aircraft is certified as "spinning not allowed". Thus if it goes beyond a half turn you become the test pilot.

Is this the thread that deserves to die, but just won't?!

Yes

[eharding]

Originally Posted by ZA, S&R

Is this the thread that deserves to die, but just won't?! ...yes

Oh come on....this has to be the most entertaining thread since the "Bomber Circuits - A Study In Onanism" incident.

[Zulu Alpha]

Is this the thread that deserves to die, but just won't?!

Yes
ZA

[IFMU]

Originally Posted by Beaver Driver

1.) How does the plane react if you are stalling with 4 people on board and max baggage?

Barry Schiff had an excellent article on this topic a couple of months ago in AOPA. Said a young instructor had asked him how do people inadvertenly stall? Nose is way high, you are pulling hard on the yoke, stall horn blaring, you would have to be asleep not to see it coming. So, they got a couple more young instructors interested in the same airplane, loaded up the 172 to a hair under max gross and just within the CG envelope, and did stalls. The airplane stalled a lot easier, lot less force on the yoke, and with a much lower pitch attitude. It was like a totally different airplane.

Originally Posted by Beaver Driver

2.) How does the plane react in a full flap config stall while carying 4 people (C172) and max baggage while on 500 feet final?

Well, the same as it does at 3000 feet. But it sure looks different out the window. So, the airplane is not dispositioned to do anything differently, but the pilot might.

-- IFMU