Inverted roll with C-172???? [Archive]

englishal

26th Sep 2007, 23:33

After all, the perfect barrel roll is only a 1G manoeuvre.
Not quite, you need to pull up into it ;)

I'm sure you could roll a 172 (flying through the wake of an A320 nearly did it to us once).....but you'd be a bit stupid to do it deliberately....the 172 is NOT APPROVED for aerobatics. When it goes tits up and the wings fall off, remember this on the way down - just hope these people don't take anyone else with them.

In one of the aerobatic books I have got, it has a nice diagram of an aeroplane at 60 degrees nose down with 17 second (I think) written beside it. This is the time till impact at 120kts (I think) at 3000'. It also has a pic of one in the vertical with something like 12 seconds written beside it......

One thing I didn't know before starting to learn aeros is that in a roll (not barrel), in a typical aeroplane (without symetrical wing), the nose will drop approx 60 degrees, which is why you pull up 30 degrees before you start the roll......

Contacttower

26th Sep 2007, 23:33

I was reading the Safety Matters section of Pilot magazine today and there is a story in there entitled:

"Baron broke up during aerobatic manoeuvre"

Cloud Basher

27th Sep 2007, 01:18

Any aircraft can be aerobatted. However ONLY those aircraft that are certified for aerobatics should be aerobatted. You are a fcukwit if you aerobat anything that is not approved for aero's. Yes that means I am calling those on this list that aerobat spamcans not approved for it. All this is, is an ego thing and shows the poorest lack of airmanship.

Also it usually seems to be those who are not trained in aerobatics that do this! As most aerobatic pilots I know would never aerobat anything but those approved (there will always be exceptions and perhaps I chose to hang around with those who know their own and the aircrafts limitations).

Pilot DAR I am glad you are in Canada as there is very little chance of me ever hiring a non-approved aircraft you have aerobatted but for the sake of others here, can you please list the rego numbers and types of non approved aircraft you have aerobatted so I can make sure that I NEVER fly in them. Whilst you are at it can you also list the numbers of those your mates have aerobatted as well.

Whilst you may think you haven't done any damage it is cumulative and some day some poor sod will be flying the aircraft, hit a bit of turbulant and then wonder why his wings clap above his head.

Pure idiocy.

As for a barrel roll being 1G that is also false. It is +ve G the whole way and you have to pull up into it and out of it, which is greater than 1G. Have a think about it, the aircraft is accelerating vertically and so there HAS TO BE more than 1G applied!!!!!!!! Basic friggen physics.

And I agree with Pitts 2112, it was a CRAP 8 point hesitation roll if the maps on the back seat never moved!

Baccalaris

27th Sep 2007, 03:08

I had one character boast about how he had a friend with a tiger moth who would let him take it for a fly, even though he was unlicensed, and how he performed outside loops in it. Im hoping to locate this tiger moth for the next moon shot....:E

Life's a Beech

27th Sep 2007, 06:22

Almost any aircraft can be rolled (positive roll. Can't see a 172 being capable of an outside roll, pathetic roll rate). If it goes well there will be no harm done to aircraft or pax by a barrel roll. However if it is not done correctly then it might spin (not bad in a 172, but not good in other aircraft) or more likely the nose might come down too far, risking either exceeding VNE or overstressing to avoid doing so.

Don't do it people.

P.S. Cloudbasher is right. It always annoyed me when people described the barrel roll as a 1g manoeuvre.

muffin

27th Sep 2007, 07:00

When I was doing my IMC rating many years ago in my elderly C172, the instructor/examiner (who was a very well known and experienced individual) was demonstrating the effects of gyros toppling and to my horror proceeded to execute a perfect barrel roll. It was actually totally undramatic and the maps etc stayed put on the back seat.

KZ8

27th Sep 2007, 07:28

The C172 Manoeuvring Speed is about 104 kts, so if you apply full aileron above this number, you may/will overstress the wings in torsion.
That, as well as all the other reasons, is why it is a bad idea.
KZ8

BackPacker

27th Sep 2007, 07:43

For those that haven't done any aeros, and don't know the difference between a barrel roll and an aileron roll:

A barrel roll is like a "corkscrew" in a roller coaster. Yes, there is some initial vertical accelleration ("g") when you pitch up, possibly up to 2 or 3g, but during the manoeuvre the "g" is pretty constant at around 1g. In any case it'll be somewhere between 1/2g and 2g. So it is a manoeuvre that falls well within the range of what any aircraft is capable of, IF (and that's a big IF) it is executed properly. For a barrel roll to be executed properly, you have to pitch up and roll in perfect harmony, while the speed is decaying, in order to be "on top" in both axis (pitch and roll) simultaneously. And keep the harmony going while the aircraft is accellerating again in the second half of the manoeuvre. It is far harder than executing the perfect chandelle. And if you do it improperly, well, number of things that can happen. You can fall out on top and end up in an inverted spin. Drop out the bottom and exceed Vne, or have to pull too many "g"s to recover. So although it looks simple (especially if you see one of those videos of people pouring coffee while doing it) but it is fraught with danger. In fact, at our club the barrel roll is considered an advanced aerobatic manoeuvre and is not taught in the basic aerobatics course.

An aileron roll is a manoeuvre with, in principle, no vertical accelleration. You follow a horizontal flight path, roll the aircraft with the ailerons while using pitch and rudder opposite gravity to keep the flight path horizontal. So from the normal +1G you go to a sideways force (through full rudder) with 0G in the vertical (aircraft) axis at 90 deg, then to -1G at 180 deg, then again 0G and a sideways force at 270 deg. Two things important here: most aircraft cannot maintain their horizontal flightpath with the rudder while being on the side, so most rolls use a more or less ballistic flightpath instead of a straight horizontal one. How ballistic this needs to be depends on the roll rate but about 30 degrees up at the start of the manoeuvre is usually enough. And if you don't have an inverted fuel/oil system, you lose engine power halfway through. The good news is, however, that there is not a lot of vertical accelleration throughout the manoeuvre, so the speed stays more or less constant. But if you have loose items in the back, they will be all over the plane. In fact, without an inverted fuel system, the engine will stop, the speed will decay because of the drag, and all items in the back will float forward. Not funny.

A hesitation roll is an aileron roll where the aircraft is momentarily fixed in position, by stopping the roll, at 45 degree, 90 degree etc. angles (in case of an 8-point). So at 8 times during the roll, the aircraft seems to hesitate.

So, yes, any aircraft might be able to perform the perfect barrel roll without being overstressed, or even drinks being spilled all over the place. But it takes a very skilled pilot to do it properly. And an improperly executed barrel roll will leave you without options (or even without wings) in a very short time.

Don't do it people.

Get a proper aerobatics instructor and a proper plane. I can tell you from experience it's a lot of fun but the easiest-looking manoeuvres are usually the hardest to fly.

Oh, and 4g just means that the sweat runs off your face and back four times as fast.

Wrong Stuff

27th Sep 2007, 08:09

What spoilsports! Pulling g in a tourer (http://www.alexisparkinn.com/photogallery/Videos/torn-off-wings.wmv) looks such fun! A bit of background reading here. (http://www.alexisparkinn.com/too_many_gs.htm)

stiknruda

27th Sep 2007, 08:31

Words fail me!

(And that doesn't happen very often!!)

Runaway Gun

27th Sep 2007, 08:33

I'm glad that some sensible people have made themselves obvious here, by pointing out that it is wrong to brag about aerobatics in a non-aerobatic type of aircraft.

Even detailing supposed bragging methods of how it was done in a 172, 185 or similar type, is simply stupid. Surely you realise that it is encouraging someone else to try. And there's a fair chance that they won't be as super skilled as you are, and will f*ck it up.

If you don't kill yourself doing it, you will be responsible for the death of innocent people when you overstress the aircraft, and it breaks up on a later normal flight.

I'm simply astounded, and disgusted. Grow up people. :*

IFollowRailways

27th Sep 2007, 08:35

Can you tell us all where and when you'll be flying in the future so we can avoid your airspace, please?

Actually, I'm not too worried about sharing the airspace - I'd be more concerned about sharing the ground below!

luigi_m_

27th Sep 2007, 08:48

Here's a video of a C172 doing a roll (about 1:00 in) ( http://www.youtube.com/watch?v=GxNgw8_y0nc ) . It shows that is it possible. Even so, I would not encourage aerobatics in a touring aircraft, and you will never find me doing anything more than a steep turn in the 172 I fly. That video of the P68c loing its wings after passing VNE is word enough against not doing aerobatic manouevers in a tourer for me...

clearfinalsno1

27th Sep 2007, 08:57

Shocking video. 8.3G - what did he expect?

I think this sequence should be shown to all newly qualified PPLs or certainly incorporated into CAA safety evenings.

Spruit

27th Sep 2007, 09:24

That video's awful, luckilly I'm at work and haven't watched with the sound on, just the images made my stomach turn!

A chilling lesson to those who push beyond their own and their aircrafts limits!

Spru!

FullyFlapped

27th Sep 2007, 10:27

That video's awful, luckilly I'm at work and haven't watched with the sound on, just the images made my stomach turn!

You're absolutely right. Now get some bl**dy work done ! ;):ouch::p

FF :ok:

Spruit

27th Sep 2007, 10:45

Now get some bl**dy work done

Work??? I don't come here to do that, only come here for the conversation! :O

Anyway, back to the thread!

Spru!

carbheathot

27th Sep 2007, 12:35

I once had a sausage roll in the flying club that went inverted.Does that count?

Brooklands

27th Sep 2007, 12:55

Backpacker wrote:
In fact, at our club the barrel roll is considered an advanced aerobatic manoeuvre and is not taught in the basic aerobatics course.

Indeed. In an article in Flyer magazine a few months ago Brain Lecomber described it an exceedingly dangerous manoeuver - its killed a few very experienced pilots.

There was a similar thread on the Flyer forums a week or two ago about aerobatting a PA-28 (http://forums.flyer.co.uk/viewtopic.php?t=36679), with similar conclusions: DON'T DO IT

Brooklands

strake

27th Sep 2007, 13:24

<Indeed. In an article in Flyer magazine a few months ago Brain Lecomber described it an exceedingly dangerous manoeuver - its killed a few very experienced pilots>

He was right...for the sort of people he mixed with. They were the types who'd consider 50ft a touch high for entry....

EvilKitty

27th Sep 2007, 14:02

It's enough to put you off ever using a club aircraft again, as you never know what the person before you did in it :ooh:

And if looking to puchase an aircraft, how can you check if the airframe has been overstressed previously? (or for an aircraft approved for such manouvers is still within its limits?) Is something that would be picked up when checked by an engineer?

Merritt

27th Sep 2007, 15:55

:eek:

This thread is a good demonstration of why it bothers me to rent club aircraft...

You never know what the previous occupant has been doing.

:uhoh:

Steve

slim_slag

27th Sep 2007, 16:13

Airframe failures are very uncommon. Most always due to pilot error of the pilot flying the thing at the time. Big problems are flight into thunderstorms, and inadvertent flight into IMC -> spiral dive -> Vne. Also flying into the ground due to dumb manouvers at 50ft. I cannot see any evidence that the pilot before you stressing the airframe is much to worry about, I'd be more worried about me doing something stupid.

I wouldn't have the nerve to roll a C172. The roll rate is atrocious, expecially once you have rolled something a little sexier, and the sexy beasts aren't much more expensive to fly anyway. Some of them are even cheaper :ok:

Pilot DAR

27th Sep 2007, 16:15

Yes, I concede that an 8 point roll might not be perfect if the maps on the back seat did not move, but the ease and grace of the maneuver was so gentle and smooth that it seemed very pleasing to me.

As for the lists of registrations, do you really do feel that your privilege to know outweighs the privacy of the respective aircraft owners?

Were I to consider issuing such a list however, for it to have the value you apparently seek, I would also have to include all of the aircraft which I am aware have encountered severe turbulence, rough runways, prolonged pounding on the water as a float plane, abusive landings as flight trainers, mismanaged unusual attitude training recoveries, prolonged low level flights as a patrol or sightseeing aircraft, and on and on…. I can assert that a well flown roll is much less strenuous on the airframe than a lot of the aforementioned, and probably happens much less frequently!

Skillful flying of aircraft within their operating limitations is not damaging to aircraft, either immediately, or in the long term. That’s why the limitations are there! I know of light aircraft with total times nearing 20,000 hours, still in service, and they still conform to their design standards, or how do they continue to pass inspections?

This thread reminds me of a previous one in which contributors asserted the dangers of zero G flight in a Piper Cherokee. And by the way, maintaining maneuvering speed or less during maneuvering only protects the aircraft from damage in the pitch axis, not roll and yaw.

A Cessna 172, can be easily rolled by a skilled pilot, well within it’s structural limitations. An untrained pilot would very likely risk both his, and the aircraft’s safety attempting such a maneuver, and should not do so at all.

Pilot DAR

Runaway Gun

27th Sep 2007, 17:16

Slim-slag says "I cannot see any evidence that the pilot before you stressing the airframe is much to worry about, I'd be more worried about me doing something stupid."

May I suggest that you talk to an aeronautical engineer, particularly in regards to micro-fails etc (basically every successive G loading produces tiny failings in metal, on a logarythmic scale). Pull twice the G allowed, and you will easily expend ten times the amount that should have been. Wing spars and other rather important pieces of metal do have a finite fatigue life. Rolling G-forces - where the upgoing wing is pulling even more G than you are, also accentuates the problem.

Consequently, the wing might just stay attached during your last stupid Superman manouvre, only to be destroyed next time an innocent pilot pulls into a 45 degree turn, or hits moderate turbulence.

Bottom line is simple - Dont do it in a non-aerobatic aircraft.

slim_slag

27th Sep 2007, 17:23

How many light aircraft have had airframe failures when an "innocent pilot pulls into a 45 degree turn, or hits moderate turbulence"?

Inexperienced people are getting all worried about renting airplanes and what I said was addressed to them. I didn't say it cannot happen, I said I think there are far more important things to worry about.

Runaway Gun

27th Sep 2007, 17:29

I dunno - but I reckon that one is too many.

More important than the wings clapping? I doubt it very much.

I can handle most emergencies and failures - in fact have so far - but falling to earth like a broken dart is something well beyond my pilot capabilities to fix.

slim_slag

27th Sep 2007, 17:43

Every time you get into a light aircraft you trust people you have never met before. If you are going to worry about what happened last month you should stay on the ground. All you can do is your best. Also, I think one is not too many, there will always be deaths when people do things slightly interesting.

Runaway Gun

27th Sep 2007, 18:26

Not to get into a debate about it, but that's not exactly my point. I'm more concerned with people glamorising it, saying it's a non-event piece of doddle to do, and even talking about their techniques.

It will kill entice somebody, and will kill them one day. Which one of your family (except perhaps for an ex-missus or mother-in-law) would you not be worried about if they were killed in such a way? No answer required - just making a point.

tmmorris

27th Sep 2007, 18:42

You can aileron roll a 777. Or at least, you can the full-motion BA-owned simulator at Heathrow...

Tim

BackPacker

27th Sep 2007, 20:59

Airframe overstress may not give any signs that would be picked up on a simple visual inspection. One reason why pilots need to report events that may have led to an overstress.

There's a few obvious signs of serious overstress, but you've had them during PPL training. Buckling/denting/cracking of skin is the most important one. For landing mishaps, check the welds on the engine/nosewheel mounting frame, if you can.

On our aerobatic R2160 we perform one additional check. Squat down about two meters behind the aircraft, exactly on the centerline. Look at the place where the top line of the elevator intersects the wings. This should be completely symmetrical. If it's not, somebody bent the plane, typically through torsional loads due to side loads on the rudder (eg. flick roll at too high a speed) or through the wing root bending effect: rolling while pulling serious g's, which increases the g loading of the wing going up, but is not reflected on the g meter in the panel.

I don't know of any other checks that you can use to visually check for overstress. It's very insiduous, as mentioned before.

Pitts2112

27th Sep 2007, 21:29

What I find most interesting in these posts (and you can find this same topic discussed ad naseum on an innumerable number of other threads) is that genuine aerobatic pilots don't ever brag about doing aerobatics in non-aerobatic airoplanes. They know the issues involved and they know what they should/can do in different types of aircraft. I take that to mean the people that actually know what they're talking about are not doing it. That ought to be reason enough for anyone else to do the same.

I always question the judgement of non-aerobatic pilots who claim you can do this or that in a C172 or PA-28. I think it's mostly ignorance and bravado talking and I'll leave it at that.

Pitts2112

stiknruda

27th Sep 2007, 21:38

I'm v much with 2112.

I've been aerobatting Curtis Pitts' designs since '94. I've continually owned one since '99. I've competed and won medals. I display (legally).

In '07, I eventually got around to learning how to barrell-roll. This really is a figure fraught with danger. Go figure.

G-EMMA, pls don't abandon Pprune because of some of the ill-educated self-opinionated arses on here. You'll find that most of us post less with "hours on Pprune".

It doesn't take too long to work out who is not worth reading.

KZ8 - infrequently posts. One of the most qualified aeronautical engineers in the UK - his advice is priceless.

Stik

Say again s l o w l y

27th Sep 2007, 21:40

Don't go Emma, we need someone to help shoot daft ideas down in flames!!

Again, I can't believe this has come up again and that some people think it is acceptable to do things that are not prescribed in the POH.

Anyone who thinks of aerobatting an non aerobatic tourer like a 172 is an idiot. Plain and simple.

You are a fool who will either kill yourself (no great loss) or someone else who is unlucky enough to fly the machine after you.

As I've said before, if I caught a member at one of our clubs doing this, then they'd be booted out faster than you cn imagine. I would also follow this up by calling all the other local schools and clubs and explaining that they really don't want this person in their membership.

That isn't an over-reaction as I believe anyone who does this sort of thing hasn't got the common sense required to keep themselves and their passengers alive for long.

It aint big, clever or impressive. If you want to turn an aircraft upside down, go and fly something suitable. It's not difficult to find a machine to do it in.

Pilot DAR

27th Sep 2007, 21:55

An over stressed airframe has the potential to be unsafe (though Cessnas in particular seem extra safe it this respect). Skillfully executed maneuvers, which might include aerobatics, can be conducted well within the stated stress limits.

Stress not exceeded, so strain not exceeded, and no fatigue cycle life limits (on a 172 anyway), means no harm done, no matter how many times done, means fly with confidence.

I have had inflight structural failures in aircraft, but they were most certanly not the type caused by previous pilot inflight operating techniques.

I fly with confidence, and I would (and have) willingly fly a previously rolled 172, if the pilot who rolled it left it for me to fly. I've flown much worse!

Pilot DAR

Say again s l o w l y

27th Sep 2007, 22:15

No it doesn't.

I would suspect that anyone stupid enough to do these sort of manouevers in a 172 isn't an experienced aero's pilot.

So the likelihood of a stuff up is that much greater. If you are stupid enough to do it then you are unlikely to have the brains to have had proper training.

The next step in the argument will be something like "Bob Hoover does it blah blah blah..." the difference being that Bob Hoover is one of the most skillful and experienced pilots to have ever flown and he understands it fully and cut his teeth on aerobatic machines. I reckon he might think an inexperienced showoff PPL would be a d*ck for trying it.

Whilst the 172 aerobatting idiot might like to think he has Bob's skill, I'll tell you right now that he doesn't.

It's funny, but as 2112 has already mentioned, of all the posters here, all of those with good aero's experience such as Stik and Edd who probably could be trusted to pull off a safe manouevre in a 172, have said what an stupid idea it is.

That for me sums up the argument. Just don't do it and if you suspect it has been done, then ground the aircraft until it is properly inspected. The lives you save could be your own and your family's.

It just isn't worth it.

slim_slag

27th Sep 2007, 22:21

Jeeze you guys just crack me up. Slim Slag - airframe failure is rare?

http://www.pprune.org/forums/showpost.php?p=3604996&postcount=31

What I said was that it is very uncommon, and that you have more important things to worry about. I stand by that. The figures back me up.

In 2003, in the GA fleet, there were 16 fatal accidents in the US where the first thing to go wrong was identified as the airframe. Thats out of a total of 352 fatal accidents, or less than 5%. Approx 26 million hours were said to have been flown that year, with 1.34 fatal accidents per 100,000 hours. 5% were airframe, that means an airframe failed and caused a fatal accident on average approximately every 1,500,000 hours.

To me, that is very uncommon. And yes, you do have more important things to worry about. I suspect that the UK figures would be similar, though I suspect the sample size is smaller so might not be as valid.

Runaway Gun

27th Sep 2007, 22:36

Ah fair enough slim-slag, you've completely changed my mind.

Send your sister around tomorrow, and I'll take her up for some loops and flick rolls in my Piper Cub. Probably nothing will go wrong, and you can sleep well knowing that you are indeed wise.

Stick, I was just being sarcastic...you know that right?

stiknruda

27th Sep 2007, 23:08

SAS,
I fear that you are wasting your breath, slim_slag, pilok-DOAH are just too good for us. I'm happy to fly with 2112 a foot away from my wingtip. (We have photos from August, I believe). I'm sure after a brief, coffee and 14 doughnuts Ed would be just as comfy there, too.
I shan't post again on this subject, my parting words (in simple Merikun) : if it ain't cleared and you ain't trained - don't do it. You might kill somebody else.
Fekwits
Stik

editted cos the other guy phoned me to say he was being sarcastic and my sister is too ugly to have sent 'round.

slim_slag

27th Sep 2007, 23:23

Well, if I'm going to be called a fekwit for simply pointing out that airframe failures are v uncommon (and having the temerity to back my claim up with real figures) I may as well throw my toys out of the pram like the rest of them and refuse to post any more either. lol

Say again s l o w l y

27th Sep 2007, 23:35

Airframe failures may not happen everyday, but they do happen.

Why knowingly increase the chances of it happening? How much of a plonker do you have to be to push 20,000 hour airframe that may have a dubious history.

The basic principles of airmanship dictate that actions like this are stupid. It doesn't matter if only one accident or death could be attributed to overstressing an airframe. It is still too many.

However, I suspect the numbers are a lot higher than just 1.

Stik, you are probably right, but I'll bang on until some sense prevails. I haven't got a lot else to do at the moment since I can't fly!

Final 3 Greens

28th Sep 2007, 00:27

Cloud Basher

28th Sep 2007, 00:55

Pilot DAR stated:
"Were I to consider issuing such a list however, for it to have the value you apparently seek, I would also have to include all of the aircraft which I am aware have encountered severe turbulence, rough runways, prolonged pounding on the water as a float plane, abusive landings as flight trainers, mismanaged unusual attitude training recoveries, prolonged low level flights as a patrol or sightseeing aircraft, and on and on…. I can assert that a well flown roll is much less strenuous on the airframe than a lot of the aforementioned, and probably happens much less frequently!

Skillful flying of aircraft within their operating limitations is not damaging to aircraft, either immediately, or in the long term. That’s why the limitations are there! I know of light aircraft with total times nearing 20,000 hours, still in service, and they still conform to their design standards, or how do they continue to pass inspections?"

You sir are a hypocrite.
You state skillfully flying an aircraft within its operating limitations is not damaging anything. Well I have flown a shed load (hangar load?) of C-172's and I am yet top see one with its POH in the limitations section which says anything other than acrobatics (sic) prohibited. To the way I have been trained this means no aerobatics and yet you say doing aerobatics is within its operating limitations.

I know what you are getting at; you are simply referring to g loadings. Well you say above you won't list tail numbers for privacy reasons and if you did you would have to list all those who have encountered severe turbulence etc. Well it may come as a surprise to you but aircraft are stressed for turbulence, hard landings etc. The designers know that this will happen to the aircraft and as such are designed for it. Take a look at the relevant FAR's and you will see various gust design loads listed.

What the aircraft has not been designed for and tested for is aerobatics. They are prohibited for a reason. You think G loading is the ONLY force an aerobatic aircraft experiences? You REALLY need to go out and get some aerobatic instruction in an appropriate aircraft to learn a little more about it.

And if you are an aerobatic pilot then you are a fool hardy one, who as I said previously, is only feeding your own ego and nothing else.

Let me put it another way. A VFR pilot continues into IMC and subsequently dies from loss of control. Why did he continue, well probably a case of press-on-itis. At least he has an excuse (not a good one but one is there anyway) There is NO excuse for doing aero's in a non rated aircraft. NONE!!!!

And you keep coming back and saying they can be done by a skillful pilot. I agree with you but this is NOT THE POINT!!!!!!!!

The aircraft is not rated for them so IT SHOULD NOT BE DONE. You really don't have a clue... I hope for your sake that no one is injured or worse if or when an aircraft falls apart that you and your mates have aerobatted.

As to being able to detect overstressors, well there isn’t too many outwards signs. You can look for ripples on the skins, popped rivets and black aluminium oxides coming back from lose rivets, but most of our 20-40 year old training fleet has these anyway!

But don't let this worry you too much, as has been said structural failure in light aircraft is rare by comparison to other failures statistically, but I would hate to be the poor sod that flies in one of Pilot DAR's aircraft and has a structural failure. Accident report would probably read pilot failed to maintain control and overstressed aircraft when in fact Pilot DAR or his mates were the ones who did the real damage. Just some other poor soul pulled a 2G steep turn at the wrong time. Let me put it another way. The odds of winning lotto are 35M+ to 1; essentially you will never win it. But alas, someone each (most) week does...

Rant Off
CB

englishal

28th Sep 2007, 03:24

G limitations.....

Something I didn't know (or think about) before I did some aerobatics with an instructor and read some books is G limitations.....The ones quoted in the POH ONLY apply to inputs on one axis only. So if I pull hard back on the stick in the Bulldog, I can go to 6 G. However, during a rolling manoeuvre, for example a barrel roll, when you have back stick and aieleron then the G limitations drop to half....so the 6G bulldog now becomes 3G.

Now apply the same to a 4.5G C172 in the utility cat. 2.25G? Hmm, it'd be easy to exceed that during a botched recovery of a barrel roll.

I may be wrong, not being very experienced in aero's, but to me it looks like the margins are pretty tight for a "normal" aeroplane (we have all probably pulled 2g during PPL training).

slim_slag

28th Sep 2007, 08:13

G-EMMA, Stik & SAS
I think you are being a little unfair on Slag (who is normally an opponent of mine in some interesting debates.)

He isn't condoning rolls in Cessnas nor recommending them, but only pointing out that in flight break ups are a low probability for accidents and not perhaps the foremost thing to worry about when renting an aircraft.

And I agree with him.Thankyou F3G, I think you have summed it up very well, and thankyou for taking the time to read into what I said.

In fact, I made no comment on the guy/gal who rolled the 172, all I said is that I wouldn't have the nerve to do it myself. I would like a little more info before I judge, though I am definitely leaning to the opinion that he is a fekwit.

EvilKitty said "It's enough to put you off ever using a club aircraft again, as you never know what the person before you did in it"

Student pilot G-EMMA (MEng - Here to learn not to inform) has jumped on me before and got it wrong, but when she said "Probably the scariest thread I've read on PPrune so far.."

I thought I would just say a little to perhaps reassure them.

And that is

Airframe failures are very uncommon

i.e even if you rent an airplane that has been rolled before, the chances of you coming a cropper is low. Not zero, but low. When you walk up to that rental aircraft, make sure you do a preflight, but the chances of you being killed by it falling apart because of some fekwit before you is lower than the chances of you being killed because you did something wrong yourself. Statistically, you have more important things to worry about

Well. I slept on it, and my mummy put all my toys back into the pram during the night, but I don't care - I'm throwing them out again. Cocky student pilots I can handle, seen loads of them, don't bother me. But if somebody with the calibre of stik starts having a go it's time to realise that it's time to move on. This place ain't what it used to be. I ain't posting again!

BEagle

28th Sep 2007, 08:35

After a fatal accident involving a PA 28, the AAIB recommended as follows:

Safety Recommendation 2003-98

The CAA should review the current training syllabus for the Private Pilot's Licence and the literature available to pilots generally, with respect to raising the awareness of the significance of manoeuvre speed, and clearly make it known that flying at or below manoeuvre speed does not provide protection for the aircraft structure from damaging stresses for all possible combinations, and reversals of, control inputs.

That doesn't seem to have happened yet. So, for those simpletons who have yet to accept it:

Aerobatics conducted by untrained fools in non-aerobatic aircraft are likely to cause death.

Anyone stating that it is in any way 'safe' to conduct barrel rolls in spamcans such as the C172 should cease flying forthwith.

Say again s l o w l y

28th Sep 2007, 08:45

S_S, I wasn't having a go at you, so I don't mind helping you clear up the teddies!

Whilst structural failures are rare, they do happen. What does happen on a more regular basis, is that aircraft owners find unknown damage that has to be put right, usually at massive cost to them.

However, flying is risk management and we should do all we can to minimise the chances of killing ourselves or others.

Doing impromptu Aero's in an unsuitable machine doesn't exactly follow that philosophy.

Even experienced pilot's in aerobatic machines make mistakes and that is what can damage a machine fatally if it isn't built to take it.

Yes, pilot error and things like CFIT kill more people than structural failure, but it doesn't mean to say we should ignore it and try to wipe out the mentality that says that this sort of thing is acceptable.

stiknruda

28th Sep 2007, 09:08

"This place ain't what it used to be. I ain't posting again!"

I agree that this place is not what it used to be, previously threads like this would not have reached so many pages of tripe, before it became obvious that aerobatting aircraft not designed for aeros by the untrained was plain stupid, dangerous and irresponsible. Statistics never killed anyone, bad airmanship has killed numerous people, the promotion of bad airmanship will continue to increase the death toll.

So S-S, whether you post again or not, I could not care a fig. I post far less here than I used to because I believe the quality/tenor has fallen. However on threads like these, I do become motivated to type as I really hope that I can positively influence people NOT to try looping and swooping in a C172/PA28.

Aviation mistakes tend to be costly. Three brave men died whilst I was at Reno, earlier this month. My chum died in a Hurricane at Shoreham the same week.

If you want to try aeros, go find somebody to teach you in something cleared for aerobatics. Please, please please don't teach yourself in a rented 172.

Stik

Final 3 Greens

28th Sep 2007, 09:10

However, flying is risk management and we should do all we can to minimise the chances of killing ourselves or others.

That's the sanest comment I've read for a long time :ok:

Pilot DAR

28th Sep 2007, 09:57

Well Beaver Diver,

It appears to me that your original question has probably been very thoroughly answered here. Though there has obviously been some disagreement, it is clear to me that all of the contributors agree that competent aerobatic training is vital before aerobatics are attempted in any aircraft. That training will have to be appropriate to the aircraft type in which the training is conducted. I completely agree that a pilot could receive competent training in a Cessna Aerobat, but not yet have anywhere near the skill to fly a purpose built aerobatic aircraft. I have never flown such an aircraft, and would never attempt it without training.

I am by no means a skilled aerobatic pilot, and as such, would always defer to those who are, in discussions on aerobatics in "aerobatic" aircraft. I am, however, a competent general aviation pilot with enough skill to gently enter unusual attitudes, and gently recover, without reaching any of the limiting values for the aircraft. As suggested, doing so, places me at the edge of my skill set, not in the middle. So like flying in poor VFR weather, when IFR is not possible (neither I or the aircraft are properly equipped), when we fly at the edge of our skill set, we do it with great caution, after suitable training.

After competent basic aerobatic training on a privately owned 150 Aerobat more than 20 years ago, I have regularly flown loops and rolls in my privately owned, G meter equipped, 150 ever since. I feel that not doing so would allow my skills to slip away somewhat. Like spins, or crosswind landings, I don’t really enjoy it, but it must be done. I have never "aerobatted" a plane I did not own, (and I've only owned the one), and I have never been "aerobatted" in a plane, other than by that plane's owner.

I can tell you that the flying that I am required to do during design approval test flying is often much more stressful on the aircraft than even the sloppiest aerobatics I have experienced. A spin in a fully loaded, float equipped Cessna 185, with external equipment fitted, will get you a lot closer to the G limit and Vne than a skillfully executed roll in the same aircraft. This I can say with certainty! I took off with two paddles firmly in place, and landed with one! And before the outcry about spinning the 185, it was required by Transport Canada Flight Test Department, over my objections of being a valueless exercise, which needlessly endangered the aircraft.

Fly after training, fly with caution, and fly with skill (if you’ve managed all of that, try for fly with grace too!). But know that the “flying with skill”, is really only happening if you also practice at the edges of your skill, at safe and appropriate times. I once test flew a 172 with it’s owner as my passenger. When I told him I was going to spin it (required by TC again, for no good reason), he was shocked, and asked when I’d last spun a plane… “Last week” I replied. “Oh, I have not spun since I learned to fly 5 years ago”. Would I send the aforementioned sister flying with him? I’m not so sure…

I hope that the many answers to your question have helped you take aviation very seriously,

Pilot DAR

IO540

28th Sep 2007, 11:14

"This place ain't what it used to be. I ain't posting again!"

From my fairly short memory of pprune, it used to be a lot worse.

I think that pprune has grown up a bit in the last few years, with quite a lot of people bothering to write more than 1 or 2 lines - more than one can say about other pilot forums.

The # of posts has gone down but that's not a bad thing if it drives the one-liners out.

The best way to deal with trolls is to ignore them.

BeechNut

28th Sep 2007, 13:04

I'm all for aerobatics as long as the aircraft is certified for it. There may be many reasons why an aircraft isn't certified for specific manoeuvers. Overstressing may be one, but inability to recover from a ham-fisted manoeuver may be another. Try spinning a Grumman AA1 to see what I mean.

That said: I have spun every aircraft I have ever owned which include: C150, PA28-140, Beech 77 (Skipper) and my current Beech C-23 (Sundowner 180). However, they were all cleared for, and placarded for spinning in the Utility Category. The worst of the lot was the Skipper; standard recovery resulted in an incipient spin in the other direction. Something good to know though. My current plane simply doesn't spin very easily and it has a tendency to degrade into a spiral dive, quickly building up to Vne.

I have also looped my Beech C23...and before the outcries, I have one of the rare ones that has the aerobatic kit installed and is cleared for spins, aileron, barrel and snap rolls, loops, Immelmans and split-S. It must be in the acrobatic category: all-up weight cannot exceed 2030 lbs (normal gross is 2450 lbs), no passengers in the rear seats, and no negative-G manoeuvers (no inverted oil/fuel systems). In acrobatic category, it is stressed to +6/-2 g's. It is specially equipped for aerobatics: quick-release doors, g-meter, extra ventral fin on the tail, increased stabilator surface, and nose strakes, in addition to some strategic structural reinforcements.

I haven't rolled it because I haven't been taught that manoeuver. I have since stopped doing aerobatics in it because it is no longer legal in that category: I had to replace the door hinges and rather than going through the trouble and expense of fitting quick-release hinges, I went the "cheap" route and got regular hinges; I primarily use the plane as a touring aircraft. That it also happened to be aerobatic was just luck.

Hat's off to you for having the guts to spin a 185 on floats. TC can be weird some times. I recall hearing a story about when the DC-10 was certified in Canada, TC wanted a fully developed stall on it. Douglas said "but it has a stick shaker and stick pusher". TC insisted, Douglas had a big order from CP Air so had no choice. They ended up with structural damage in the tail.

Say again s l o w l y

28th Sep 2007, 13:04

Just because you "own" an aircraft, doesn't make it any more acceptable to go against the POH.

Aerobatting a bog standard 150 isn't sensible. I don't care if you learnt to Aerobat in an 150 Aerobat (!!!!!) the simple fact is that you are operating your own a/c contrary to the POH.

What part of that's a stupid idea don't you get.

Spinning an aircraft doesn't put as much stress on a machine as badly flown aerobatics. It is the recovery that loads an aircraft, not the spin itself.

As has already been mentioned, recoveries from badly executed aero's is likely to put all sorts of stresses in lots of different directions, rolling loads etc. Something that your average spam can isn't able to take. Even Aero's a/c and military jets have restrictions on rolling loads compared to "straight G".

Normally flown Spin recoveries don't have a rolling load, but loads in the directions where an aircraft is strongest.

So trying to compare spin recoveries in a/c cleared for spinning and recovered using the correct techniques cannot be compared to even basic aerobatics, let alone badly flown ones with fudged recoveries.

Shaggy Sheep Driver

28th Sep 2007, 19:14

And it's not just about 'G' limits - control authority and other factors come into it.

I just can't believe anyone would be daft enough to roll a 172. Especially a barrel roll. It's not a 1 'G' manouvre - you have to pull up into it and pull level after it. And it is a VERY difficult manouvre to get right consistantly - and when you get it wrong, 'G' and speed, especially rolling 'G', will rapidly increase to levels way beyond what would break a 172.

SSD

Sir George Cayley

28th Sep 2007, 20:40

Oi, Stik!

Picture of your Sis if you please.:ok:

Beuty t'is in the eye of the boulder!:p

Sir George

shortstripper

29th Sep 2007, 07:58

The # of posts has gone down but that's not a bad thing if it drives the one-liners out.

But more than one line may expose my inexperience ... damn!

Life's a Beech

29th Sep 2007, 09:01

Might I suggest to some of the people here that they actually read the posts they are replying to, before criticising the poster? Then Slim Slag might not have taken (quite legitimate) umbrage at the comments directed at him. He never advocated flying aeros in an unsuitable aircraft. Nor did he deny the damage that could have been caused to an airframe by this. He simply pointed out that the probability of this having happened to an aircraft we fly and causing a structural failure is low enough that it should not stop us from hiring aeroplanes of unknown history. he backed his view with statistics.

Shaggy

I would add that a 172's lousy aileron authority, especially as it loses speed as it would over the top, makes it an especially unsuitable craft to roll

P.S. I once decided that, next time I flew it I would roll the Navajo, knowing that with the decent roll rate it is capable of and the excess power when empty it would go nicely; I was always good at barrel rolls. That decision is only one of the many reasons we don't fly drunk. I am still convinced I could roll the aircraft, but feel no need to prove it now I am sober.

[edited: How did the font change on this post?]

dublinpilot

29th Sep 2007, 16:02

I for one will be sorry to see slim go. His posts were always well thought out, and usually accurate.

In this thread, I also have to agree with him. He didn't say that it's a good idea to roll a C172. If you actually read his posts, what he said was that when I go rent a C172, my mind should be focused on stuff like:

Weather? Is it really suitable today?
Fuel systems. Have I properly checked for water, and cleared any fully?
Am I properly current on this aircraft?
Do I know my speeds?
Have I practiced PFL's recently? Could I do one safely (for real) on this flight if necessary?
What are my options for an engine failure on take off?

These issues and others, are far far far more likely to kill me, than what someone else may have done before me in the aircraft.

All slim said, was that while it may not be clever to roll a C172, our mind should be focused on things more likely to kill us, than what someone else did before us.

Think about it slim.....there's no need to go. I too have been subject to personal attacks here......stick it out and argue your case.....you are right ;)

dp

SkyHawk-N

29th Sep 2007, 17:41

Last time I was in the USA I noticed a very tidy 172 sitting in a hangar and spoke to a mechanic about it. He explained that they were awaiting a report on it's structural integrity and whether or not it was a write-off. Apparently it was hit by a micro burst while airborne and had been flipped inverted. I was shown how the whole aircraft was out-of-true and the many cracks on the wings and fuselage. The pilot, who owned the aircraft, got it checked out straight away, if it were a rented aircraft maybe this wouldn't have happened and may still be flying. Ok, this had been a pretty sudden (maybe violent) manoeuvre but it shows that the commonal garden runaround Cessna/Piper is not that strong when it comes to "aerobatics".

SkyHawk-N

29th Sep 2007, 17:44

Oi, Stik!
Picture of your Sis if you please.
If she comes from the fens don't expect much! :eek:

Gipsy Queen

30th Sep 2007, 02:43

I find it extraordinary that this thread (like the TAP/Airbus display) should have been able to maintain sufficient life to enable it to stagger on for so long. Even more extraordinary is my actually reading it all! And yet more astonishing is my adding my four cents . . .

I should be worried about those who think aerobatting an unsuitable/non approved aircraft is in some circumstances (skill, experience etc.) acceptable. If their judgment is warped to this degree on something relatively uncommon, what is the quality of their thinking likely to be in more mundane circumstances involving things like controlled airspace, weather etc.? Even being on the ground is unsafe with them about.

And full marks to whoever it was who suggested that contrary to commonly held belief, the barrel roll is not the piece of cake that many mistakenly think it might be because almost any aircraft can be made to do one. Bob Hoover and his Pinot Grigio '57 have much to answer for! It is a difficult manoeuvre to execute well and when performed less well, one likely to put considerable stress on the airframe. I did a few a couple of weeks ago in a S-2A and made a complete nonsense of one - I'm a trifle rusty!; recovery registered 3,5 on the meter. Nothing out of the ordinary for a +6/-3 aircraft but what if the same attitude had been adopted in a 172? 3,5 on the Richter scale!

Absolutely bloody stupid.

GQ.

bookworm

30th Sep 2007, 09:52

I did a few a couple of weeks ago in a S-2A and made a complete nonsense of one - I'm a trifle rusty!; recovery registered 3,5 on the meter. Nothing out of the ordinary for a +6/-3 aircraft but what if the same attitude had been adopted in a 172? 3,5 on the Richter scale!

3.5 g is within the positive limit manoeuvring load factor for the C172, which has to be at least 3.8 g for certification of aircraft under about 4 tons for normal and commuter category.

Final 3 Greens

30th Sep 2007, 11:21

Life's a Beech

30th Sep 2007, 12:29

I'm sure it would take it. However I am a lot less sure that the 172 would have remained with only 3.5g, given its lousy roll rate and less overall control authority compared with the S-2A, and certinly given a less experienced pilot than Gipsy Queen who appears at least to be rusty rather than untrained. Also 3.5g with roll is worse than 3.8 symmetrical.

rodthesod

30th Sep 2007, 12:32

I've just noticed this thread so I'm a bit late posting: I'm quite surprised it's gone so far but feel obliged to contribute.

I was taught barrel rolls in the RAF in the Jet Provost and later taught them as an A2 QFI on the same type. I have to agree with those who say that, properly executed, a BR can be flown in almost any aircraft, and have myself done so in many suitably certified gliders and powered aircraft.
Whether the manoeuvre should be flown in an aircraft just because it can be is a different matter entirely, and in this respect I'm with Brian Lecomber, stiknruda, Pitts2112 and BEagle entirely.

The barrel roll is NOT a simple manoeuvre and certainly not a 1g affair. Pitch and roll inputs constantly vary throughout the roll as airspeed reduces on the way up and increases on the way down. If the aircraft is not pitched up sufficiently and the roll rate lags behind, the subsequent recovery is the BIGGEST potential height loser of ANY aerobatic manouvre. Some aircraft may not be able to achieve an adequate roll rate at low speed in such a situation. I would not clear a student to fly the BR solo unless I had very sound evidence of their capabilities.

27 years after the event I still have a vivid memory of a Biggin Hill airshow. I had completed my Pitts display with the Rothman's Aerobatic Team and was enjoying a beer in the pilot's enclosure when the A26 Invader displayed. I personally never rated its pilot much and felt he had been 'walking on water' for a long time. His demise (sadly with passengers who were not all seated) was a co**ed-up barrel roll (insufficient initial pitch up and the nose way too low in the inverted). Rather than take the ignominious option of aileron rolling off the display line (throwing away the manoeuvre), he chose to 'use' the valley. The A26 tentpegged almost vertically very close to a housing estate - I estimated he probably needed at least another 5,000ft to recover without pulling the wings off. Despite my personal dislike of the man, the pilot was a VERY experienced display pilot, not a weekend C172 flyer.

rts

shortstripper

30th Sep 2007, 17:04

Having watched the "Untouchables" the other night, Sean Connery's quote is most appropriate to the last post, and hopefully this thread ....

"Here endeth the lesson"!

SS

BEagle

30th Sep 2007, 17:24

There's only one thing more potentially lethal than the barrel roll - and that's the so-called 'Victory Roll'....

Enter at relatively high speed, probably in trim and level flight. Pitch up slightly and start to roll with a large aileron movement and probably some rudder in the same direction.

The aircraft now starts to decelerate due to imbalance, drag due to roll and the climbing attitude. After 90 deg, the effect of the rudder is to cause a descending vector - or at least to reduce the climb rate. Half way round, with the nose now (at best) on the horizon instead of pushing to maintain the climb, back pressure is relaxed and the second half of the so-called manoeuvre begins - with ever more aileron, drag and deceleration. Nearing roll out, the aircraft is descending, out of trim and at a much lower speed than at entry. Large, uncoordinated aft stick is then frantically applied as the ground rapidly rises up to meet the aircraft and occupant for one final embrace......

If you want to fly aerobatics:

1. Ensure you're taught properly. The AOPA course, at least.
2. Only use an appropriate aeroplane.
3. Never be too ambitious...

All aeroplanes will bite if provoked!

rmac

30th Sep 2007, 18:27

A number of people have used the example of spins as justification. I have never found that spins produce much in the way of G load, even centrifugally ?

It would appear that its not the G potential of the manoeuvre which is the threat, rather the G potential of recovering a botched manoeuvre, which I would suppose is more likely in an aircraft not designed for aerobatics (e.g. smaller control surfaces for a start !)

Anyway, my main point is that we have two C172's in the hangar, which have just been un-crated and are waiting to have the wings put on. If anyone is in the area and would like to see the (small) size of the two bolts on each side which actually hold the wings on, you are welcome to have a look. Give me a decent wing spar for aeros anytime.

But for some of you I guess that out of sight is also out of mind.

Shaggy Sheep Driver

30th Sep 2007, 20:26

3.5 g is within the positive limit manoeuvring load factor for the C172, which has to be at least 3.8 g for certification of aircraft under about 4 tons for normal and commuter category.

Whilst this is true, how confident would one be that a tired 30 year old example would still take +3.5g?
-------------------------------------------------------
I say again - consider ROLLING 'G', far more destructive than is straight loading - and it's rolling 'G; you pull trying to recover from a less than perfect barrel roll.

Also, inadequate control response in a non-aerobatic aeroplane means much more chance of screwing up and then not being able to execute a quick recovery before speeds and rolling 'G' reach and rapidly exceed Cessna-breaking levels (in just seconds).

DX Wombat

30th Sep 2007, 22:18

Airframe failures may not happen everyday, but they do happen. I have only one thing to say to that, - G-DELS (http://www.aaib.dft.gov.uk/publications/bulletins/december_1996/pierre_500558.cfm). The pilot's final words make chilling reading.
I have been fortunate enough to spend some time this year helping at BAeA Aerobatic competitions. People such as Ed (and many others) know what they are talking about, you would do well to listen to them. It would also be a good idea to adhere to the recommendations made in the aircraft's POH. How many of you who think it is clever to do stupid things actually bother to read it? Having said that, there will always be the raving lunatic who knows better than everyone else including the manufacturer, CFI, FI, AAIB etc. I met one such fellow student when I was doing my PPL training. He mocked me for saying that if I found a wrinkle in the aircraft I wouldn't fly it until it had been thoroughly checked by a properly qualified person - "Yes, well you would say that, you are too cautious when it comes to checking (as in preflight check) aircraft." I told him about G-DELS and he just gave me a pitying look and walked away. I then found the report and, with the CFI's permission , made him read it from end to end. His comment? "Are they (the AAIB) sure that's what happened?" Words almost failed me. I can't remember exactly what I said, but it was polite, short, and very much to the point. I would never even think of flying with him.

stiknruda

30th Sep 2007, 22:21

I have PM'd S_S about his desire to self exclude. Having given the entire thread some thought, I was going to publish my thoughts on the S-S resigns/condolences thread - however that has evaporated.

Nevertheless, trivialising the consequences of someone £ucking-up will lead to complacency!

rmac - if you really want to learn about spin spin behaviour, there are a couple of quite readable references available. They all start by explaining A:B:C couples and the the effect of overcoming inertia and something to do with E=MxV(squared) vis a vis coefficient of liftxhalf rho squared x size of the lifting body.

Chap I know quite well, ex mil: bajillions of hours- span his new £200,000 aerobatic a/c, forgot that to check that tip tanks were empty and it took him 7,500' to recover. Just one more turn before he felt authority return and he and the pax were going to hit silk.

Aerobatting is my passion - but it can bite fools. Anyone doing it without training or in an a/c un-certified or trivialising the consequences of such, IMHO is a fekwit - far worse than a fool!

Stik

englishal

1st Oct 2007, 03:14

The GDELS report does indeed make chilling reading, but the report also states that the damage sustained should probably have been visible in a metal aeroplane as opposed to wood and fabric..

Anway I'd be sad to see SS leave, he is a useful contributer and knows his stuff well.......So I hope he comes back. At no time did he support "unauthorised" aerobatics....I don't blame him though.....

Regarding wing spar failures, in one of my books it goes on about one of the memebers of the British Aerobatics team in the early 70's (I forget who :O) who was practicing without a parachute on. He pulled 5 G's and snap, the wing started to fold up. Luckily, and with a lot of skill, he very quickly realised that the wing was only folding up under +ve load due to makeup of the wing, so he rolled inverted and the wing popped back into place. He climbed and tried rolling upright again, and again the wing started to fold up.....In the article in the book it is now described how he was shaking like a leaf and thought that he was about to die......had he had a parachute on, he would have climbed and bailed out....but he didn't. He knew he had about 10 minutes to sort this out before the engine stopped due to running inverted for so long so he decided to make an inverted approach, and at the last minute rolled upright - it is reported that the wingtip cleared the ground by 6 inches. As he rolled upright the wing folded up and it settled onto the ground.....he walked away :D

I NEVER want to be in that situation := :)

Gipsy Queen

1st Oct 2007, 03:24

<quote>3.5 g is within the positive limit manoeuvring load factor for the C172, which has to be at least 3.8 g for certification of aircraft under about 4 tons for normal and commuter category.</quote>

This is an arbitrary figure and at only 0,3g more than the figure I gave, hardly more than academic.

The accelerometer is accurate only when the forces are applied perpendicularly to the instrument datum i.e. the lateral horizontal (y) axis of the aircraft. The barrel roll generates many forces acting upon the airframe and these can be of appreciable magnitude; this magnitude being amplified to a significant degree when the manoeuvre goes askew. As Life's a Beech has observed, the maximum load recorded by the g-meter will be in a condition symmetrical with the instrument datum. Loads tangential to this may be recorded but, obviously, will be shown as a lesser value and as a function proportional to the "offset". Thus it easily would be possible for the 172 to indicate 3,5g but in fact, have a frame/spar loading closer to or perhaps in excess of 4,0g. I'm not suggesting that the aircraft necessarily would fall apart at this higher figure - the question is of no interest to me - the point I'm making is that to voluntarily approach these limits of structural performance is just stupidly foolhardy and ultimately, a totally pointless exercise unless you are a qualified test pilot performing required manoeuvres.

And the fact that the book/certification might say 3,8 is not much of a guarantee of anything. I have logged quite a few hours in the wonderful Z526 (and yes, it was a few years ago - hence the rust!); this was an aircraft rather stronger than the 172 and whose raison d'etre was to be thrown around the sky but I was rather more circumspect in my application of control forces after Neil Williams's spar failure.

And in making upright/inverted transitions, one had to factor in the momentary power loss as the engine coughed its way from one carburettor to the other, but I must stay away from Memory Lane . . .

GQ.

rmac

1st Oct 2007, 06:58

Englishal,

I guess you are referring to Neil Williams, who was later to die in a CFIT accident.

Stiknruda,

Thanks for the references, have a spin or five under my belt in a variety of Zlins and Extras but never looked at the actual physics calculations, never felt anything likely to pull the tail off even after a well developed six or seven turns. Never pulled more than 3G even in a botched recovery, and i've had a few over aggressive recoveries in the early days with the 142/242. My point was to emphasise that spin forces rarely equal the forces in other aerobatic manoeuvres. Now if we want to talk about things likely to break the aeroplane, how about opening a thread on tailslides :eek:

As for your tip tanks story, I have one of my own. I once had a Zlin242 shipped to Archerfield, Brisbane and left it with the owner of a local flying school to look after. Well known aerobatic pilot and ex RAAF fighter pilot, but a bit of an arse, anyone reading this from Archerfield will know exactly who I am referring to. When I got back to Australia, he rather heatedly described the aircraft as dangerously designed as it had nearly killed him and a student with a late spin recovery and was getting quite excited until I pointed out the placard which said, no spins with fuel in the tip tanks :ugh:

Runaway Gun

1st Oct 2007, 08:14

Yes, that was Neil Williams. In fact, I recall that the wingtip left a gouge in the grass - so he judged it extremely well !!

Shaggy Sheep Driver

1st Oct 2007, 09:19

It was the wingtip nav light that left a mark in the grass during the roll - and the glass didn't break. So.... very well done!

Runaway Gun

1st Oct 2007, 13:35

Just read a bit of Neil Williams' book, and I noted the following point that would emphasise the nature of stress and microfails etc.

The Zlin aerobatic aircraft had an airframe life of 2200hrs when subjected to +6 and -3G aerobatics.
The same aircraft, when flown to higher unlimited aerobatic standards of +8 and -6G, was reduced to an airframe life of only 100 hrs.

Added for your interest.

draccent

1st Oct 2007, 15:01

OMG! You can roll a 172???? :eek:

hoodie

1st Oct 2007, 15:48

OMG! You can roll a 172???? :eek:

Very nearly all the way around, it would appear. :E

This thread should be awarded the "PPRuNe :ugh::ugh::ugh: Award 2007" I reckon. :hmm:

foxmoth

1st Oct 2007, 16:07

in flight break ups are a low probability for accidents

Whilst this may be true, when I first arrived at the flying club to do my Flying scholarship (many moons ago:}) all the school staff were away at the funeral of a member who had died - he had been doing aeros in a (non aero) C150, since then I have heard of a number of instances of non aero aircraft breaking up whilst being turned intentionally upside down - I now teach aeros but I have never done it in a non aerobatic machine and never will - and when there are so many better aircraft for doing aeros in, why bother doing it in such a machine?:ugh:

jamestkirk

1st Oct 2007, 16:16

....AGREE with all of you who say, 'unless your trained, in an aerobatic aircraft, in good flying practise and are showing good airmanship and preperation before the proposed aerobatic flight'...then don't do it.

I have regularly seen people in busy class g (yes i know its a free for all) who have not 'advised' anyone of their aerobatic intentions and have come very close to other aircraft out for a less exciting site seeing trip. Trained pilots or not? I have no idea.

Its just a small example that rolling and looping etc. should be part of a well thought out flight.

Shaggy Sheep Driver

1st Oct 2007, 18:54

Soon after I passed my PPL back in the late'70s, one of the guys who'd instructed me (and had since got a job flying with Loganair) was killed, along with another club member, aerobatting a Luton Major (non aerobatic). The right wing seperated in flight.

knox

2nd Oct 2007, 01:49

Quote: "But a properly executed barrel roll is a positive manouvre and the great Bob Hoover demonstrated it with a glass of water perched on the coaming all the way through".

Actually an aileron roll.

Aileron roll explained:

Aileron rolls are flown with the rudder and elevator in the neutral position during the roll. The aileron is fully deflected in the direction of the roll. This is the easiest of the rolls to fly.
The aileron roll is started by pulling the nose up to 20 - 30 degrees above the horizon. The elevator is then neutralized and the aileron fully deflected in the direction of the roll. The controls are maintained in that position till the roll is completed. After the roll is completed the nose is usually 20 - 30 degrees below the horizon.

Barrel roll explained:

The Barrel roll is a combination between a loop and a roll. You complete one loop while completing one roll at the same time. The flight path during a barrel roll has the shape of a horizontal cork screw. Imagine a big barrel, with the airplanes wheels rolling along the inside of the barrel in a cork screw path. During a barrel roll, the pilot always experiences positive Gs. The maximum is about 2.5 to 3 G. The minimum about 0.5 G.

Not my descriptions, pulled from IAC website. http://www.iac.org/begin/figures.html#Aileron%20Rolls

Knox

IFMU

2nd Oct 2007, 02:34

The great Bob Hoover definitely did a barrel roll with his iced tea pitcher trick. He had a glass on the panel, and poured iced tea in the glass all through the roll with one hand, while flying with the other. This requires positive G's all the way around. Or, in your description, a barrel roll.
It's at the end of this video:
http://www.youtube.com/watch?v=tOZEgKXJMCE
If I was Bob Hoover, I'd do inverted rolls in a C172. But I'm not. So I won't.
-- IFMU

draccent

2nd Oct 2007, 03:58

ok so while I would freaking LOVE to roll a 172.....NO! Its stupid. A 172 is not designed to do rolls and ****. Its a point a to point b machine. I fly one....and although it has come close to putting me in tears....I like it now. I also know...it is not made to do rolls and loops. Your kidding me!

knox

2nd Oct 2007, 04:30

Quote: The great Bob Hoover definitely did a barrel roll with his iced tea pitcher trick. He had a glass on the panel, and poured iced tea in the glass all through the roll with one hand, while flying with the other. This requires positive G's all the way around. Or, in your description, a barrel roll.

Watched it again and definitely not a barrel roll.
If you watch carefully, as he enters the maneuver his ref point is the mountain range, as he comes through the inverted the same mountains are still ahead, he would have to be 90 deg to that point for it to be a barrel.
In a barrel roll you also need to apply back pressure on the yoke as you roll, (corkscrew manner), if you look carefully Bob applies no back pressure on the yoke.

An aileron roll is a positive 1G maneuver, so pouring the liquid is still possible.

Knox

Definitely wouldn't roll a C172. Craziness!!

Captain_djaffar

2nd Oct 2007, 04:46

structural damage due to aircraft over-stressing.Can be done...but not for the prudent and safe pilot....less you hold specific training and modified 172 aircraft.

Dan Winterland

2nd Oct 2007, 05:31

I think we have people from different continents argueing about their continent's definition of a roll.

But wherever you're from, a barrel roll isn't a 1g manoeuvre - It's a positive g manoeuvre. Even Bob Hoover couldn't fly a barrel roll at 1g -it's impossible. And an aileron roll is just that - a roll actuated by ailerons only. And in nearly all types, this will leave you nose low when completed. A slow roll is where the nose points at a spot on or above the horizon without deviating, the aircraft completes the manoeuvre without height loss. To do this, at some stage you will be flying inverted and be at -1g. This is not an elevator or rudder neutral manoeuvre - co-ordinated use of all controls is necessary to keep the aircraft level.

Some people think that barrell rolls are difficult. They are a lot easier that slow rolls. At a school I instructed at, the barrell roll was the second aeroabtic manoeuvre (after the loop) taught to the students, the slow roll coming much later. It can't have been that hard as they were usually cleared to fly them solo by 30hrs total time.

But whatever you call your rolls, anyone who aerobats a C172 is a ###t!

draccent

2nd Oct 2007, 07:01

Ok...to all those who think they can roll a 172: GO TO WAL MART AND BUY A LITTLE TRICYCLE. ITS THE ONLY THING YOU SHOULD BE ALLOWED TO OPERATE.

BackPacker

2nd Oct 2007, 07:22

Knox, you may have missed something here and there. Have you ever done barrel rolls and aileron rolls yourself?

You lifted this quote from the IAC website:

Aileron rolls are flown with the rudder and elevator in the neutral position during the roll. The aileron is fully deflected in the direction of the roll. This is the easiest of the rolls to fly.
The aileron roll is started by pulling the nose up to 20 - 30 degrees above the horizon. The elevator is then neutralized and the aileron fully deflected in the direction of the roll. The controls are maintained in that position till the roll is completed. After the roll is completed the nose is usually 20 - 30 degrees below the horizon.

But what you missed is that almost everybody who flies aerobatics competitions on a serious level (what the IAC is all about), flies aircraft with symmetric aerofoils and inverted flight systems, and expects to be inverted about 50% of the time. Because of this, they TRIM the aircraft for 0g (yes, zero, so requiring a positive pull to maintain straight and level) before starting the aeros sequence.

So when they "neutralize the elevator", they actually start flying a ballistic, 0g flight path. With a roll rate, typically, approaching or even exceeding 360 degrees per second it's good enough to pitch up, center the elevator and rudder and just roll the aircraft with the ailerons. For a slow/hesitation roll however, or to prevent the nose from wobbling (through torque effects, p factor and whatnot), little deflections of both elevator and rudder make the manoeuvre neater, but also induce sideways forces and negative g's. Definitely something that makes you spill your drinks.

Bob Hoover did not do an aileron roll. And I also don't think he did a proper barrel roll, but it's very hard to tell from the video. What it looks like, to me, is what we call a "students roll". It looks almost the same from the ground, you experience the same positive g throughout, but it doesn't require the same precise coordination between pitch and roll as a barrel roll. It goes like this: dive to get some speed (130 knots), pull straight up to 60 degrees (about a 2-3 g pullup), once at 60 degrees (you are below Va then) neutralize the pitch (but I'm still at the level where we trim for 1g, so at this point I'm just doing 1g), then roll with all your might. Stop the roll, then pull out of the 60 degree dive.

Watch the video and look at the way the sun shines on the magnetic compass. It's pitch up first and only with his nose high does he start the roll.

The students roll is not an official aerobatics manoeuvre, but it is used to get used to the physical sensations of rolling and is later developed into a slow roll or a barrel roll. Or we do a stop on top to get used to the force needed for inverted flight, the physical sensation of being inverted, and learning the reflex reaction on what to do when the engine stops (our R2160 doesn't have an inverted flight system).

knox

2nd Oct 2007, 08:56

Quote: Have you ever done barrel rolls and aileron rolls yourself?
Yes many.

Yes it is hard to tell exactly what he is doing but the pitch looks fairly normal for a aileron roll but its not a classic (text book) barrel roll either.
I do understand that he more than likely has his own very unique style.
He is a legendary pilot.

I think the point i'm trying to emphasize is that a lot of people that utilize this forum do get the two maneuvers confused.
Before I started aero's i didn't know the difference.

Knox

D SQDRN 97th IOTC

2nd Oct 2007, 11:27

Knox

"a lot of people that utilize this forum do get the two maneuvers confused."

err.....

I don't think so.

Also not sure how anyone can do a proper aileron roll with a glass of water on the cowling still intact after the manoevure.

chrismkii

2nd Oct 2007, 16:36

back to the original quote ! a 172 did a roll today over norwich now with the outstanding roll rate of the mighty spam can it nodout took all day to get round it ! p.s got a pic of cerne abbas giant with hommer simpson next to it.

Zulu Alpha

2nd Oct 2007, 21:30

My mate Dave sez its possible for a properly trained pilot to do a loop in a VP1 as long as you really tighten the seatbelt so you don't fall out and put some chewing gum over the pitot so that you don't break the ASI in the dive to get enough airspeed.
What d'ya think? VP1's are quite cheap so we could club together to get one and try it!

Hasn't this thread run for long enough?!!!

ZA

eharding

2nd Oct 2007, 21:46

...and what does your mate Dave use to make sure the oil dipstick doesn't come loose in the VP1 while he's looping it? :E

Are you coming down to Lasham to for the Glidder vs Poorer match? I hear rumours of Pies....

DX Wombat

2nd Oct 2007, 21:51

...and what does your mate Dave use to make sure the oil dipstick doesn't come loose in the VP1 while he's looping it?Probably a chunk of old blutak :} :eek: :*
Are you sure it's pies EH? Not curry? Have a great time down there, I have a prior commitment so can't be there. :{

Zulu Alpha

2nd Oct 2007, 22:08

Ed,
In a properly looped VP1 the dipstick doesn't move.
Not coming to Lasham......... I can get pies up here in East Anglia, also its probably best to stay clear of the pies before looping a VP1.
(actually I'm showing my son around universities....and I wasn't invited!!)
ZA

stiknruda

2nd Oct 2007, 22:25

ZA - you wasn't inviyed, mate, sniff. I woz!

Any way, looping the Veep was a breeze, it was lom-choo-vac-ing the bugger that caused the prop thingy to go west (and east).

After that it was easy-peasy-lemon-squeezy - Vne on the dial covered a wide arc, so I went for the high end and then played lawn darts. Big flare at 50' and I got her down in three pieces.

Soz, you won't be at lash 'em. Ergo - I win!

Stik

Zulu Alpha

2nd Oct 2007, 22:28

Vne on the dial covered a wide arc,
So you're still using the Mach meter then.
Are you competing ? If so VP1 or Peeeets?
ZA

Heliport

2nd Oct 2007, 22:40

What an interesting thread.
Not so much the content as the way some people have reacted to those with whom they disagree - or think they disagree because they didn't take the trouble to read a post properly. (eg Some responses to slim-slag's posts.)

Politely pointing out why (in your opinion) others are completely wrong is far more effective than resorting to 'idiot, feckwit, clown' abuse, more conducive to good discussion and enables people who want to learn to do so - a valuable part of PPRuNe.

If G-EMMA chooses to flounce off from PPRuNe because she doesn't like what she reads, let her go IMHO. :rolleyes:

draccent ok so while I would freaking LOVE to roll a 172.....NO! Its stupid. As a 35 hour student pilot, some might think you'd be stupid to try rolling anything unless under supervision.

H.

eharding

2nd Oct 2007, 22:43

Any way, looping the Veep was a breeze, it was lom-choo-vac-ing the bugger that caused the prop thingy to go west (and east).

Do the Lom-choo-vac, and put the freshness back? I'd say that was just plain Ruade. Anyway, my Mulleroids have been playing up something chronic, have to go and see the doc in the morning....you know the one - small glasses, always wears a Cravat.....

knox

2nd Oct 2007, 23:14

Quote:
D SQDRN 97th IOTC speak for yourself
Knox

"a lot of people that utilize this forum do get the two maneuvers confused."

err.....

I don't think so.

Also not sure how anyone can do a proper aileron roll with a glass of water on the cowling still intact after the manoevure.

Yes I will speak for myself... thats what a forum is all about.

Maybe you'd like to write a brief description on each maneuver?

I wouldn't know about doing a "proper" aileron roll with a glass of water on the cowling.... don't see the point really and plus its already been done by bob hoover.

I'll also let my aeros instructor know that he hasn't taught me a proper aileron roll and will also suggest that he returns some of his trophies.:rolleyes:

Knox.

draccent

2nd Oct 2007, 23:49

no Im just making the point that I have like no time and have enough sense to know you don't roll 172's.

eharding

3rd Oct 2007, 00:14

I'll also let my aeros instructor know that he hasn't taught me a proper aileron roll and will also suggest that he returns some of his trophies.

The rule is that you have to return the trophies at the end of the year, anyway...unless you win the one shaped like a Zlin in knife-edge, in which case you're entitled to a smaller version to keep forever.....

englishal

3rd Oct 2007, 00:47

An aileron roll is a positive 1G maneuver, so pouring the liquid is still possible.
Never heard that before. I know when I do an aileron roll it is defintely goes through -1g or thereabouts !!!

I was taught, pull up about 30 degs (> +1g) , centralise all controls, then stick hard left or right (< 1g) and hold it until until wings level, then centralise again, recover from the nose drop after wings level (> 1g).

A barrel roll on the other hand goes a bit like this.....30 degrees of heading off where you want to end up, nose down to accelerate to entry speed (if nescessary) then back sick (>> 1g) and aileron...In many books it is classified an advanced maneuvre.....

D SQDRN 97th IOTC

3rd Oct 2007, 06:39

Knox
you asked how I would do an aileron roll.
Two ways.
You can do a quick (but lazy) one in the way englishal describes.
The water will be lost off the cowling doing a roll this way because the speed of the rotation will make the glass slide off.
Or you can do a slow one like this: and you can put as many hesitation points in as you wish
no pull up
stick left or right as you wish
full or partial deflection as you wish
as the roll starts, the nose will start to drop
pick the nose up with some rudder. rudder use will be opposite to the stick deflection so you need to think about the secondary effects of yaw (from stick) and roll (from rudder).
the glass of water has long gone by this stage.
keep the roll going. less rudder is needed as you go inverted but you now need to push forward on the stick to keep straight and level.
still keeping the roll going, you will start to need some rudder again to pick the nose up, but this time the secondary effects of yaw and roll will be acting together in a different way from when the controls were crossed.
you having a good teacher, perhaps he can advise you on this?
and BTW, having a good teacher doesn't make you a good student.
I could have been taught by John Taylor or Andy Cubin, doesn't mean I'll ever be as good as them.
In neither scenario does the glass of water remain intact.
I think you're a bluffer Knox............

Mad Girl

3rd Oct 2007, 07:17

as the roll starts, the nose will start to drop
pick the nose up with some rudder. rudder use will be opposite to the stick deflection so you need to think about the secondary effects of yaw (from stick) and roll (from rudder).
the glass of water has long gone by this stage.
keep the roll going. less rudder is needed as you go inverted but you now need to push forward on the stick to keep straight and level.
still keeping the roll going, you will start to need some rudder again to pick the nose up, but this time the secondary effects of yaw and roll will be acting together in a different way from when the controls were crossed.
you having a good teacher, perhaps he can advise you on this?
and BTW, having a good teacher doesn't make you a good student.
I could have been taught by John Taylor or Andy Cubin, doesn't mean I'll ever be as good as them.
In neither scenario does the glass of water remain intact.
I think you're a bluffer Knox............

Only a student - so be gentle - that sounds like a slow roll to me...not an aileron roll...... :O

stiknruda

3rd Oct 2007, 07:46

I'm with you MadGirl!! Axial/slow roll.

Large 60+ pitching component in the barrell prior to the roll....

waldopepper42

3rd Oct 2007, 08:33

Ed: you know the one - small glasses, always wears a Cravat.....

Isn't that the guy who directs the aero comps? With a hotel in Derbyshire...?

DX Wombat

3rd Oct 2007, 09:39

Could also be one of the competitors except he doesn't have a hotel (as far as I know).
EH - hope you are soon feeling more comfortable and pain-free. :ok:

stiknruda

3rd Oct 2007, 09:41

Aaah, that doc - what a jewel!!

old,not bold

3rd Oct 2007, 09:52

To reinforce those posts saying that it's effin stupid to fly an aircraft outside its limits, regardless of whether or not it's "possible" to do that.........

Some years ago a pilot towed a glider to 4000' with an Auster, on a gusty, turbulent day with small active cumulus clouds and a lot of thermal activity.

He released and started back down to get on the ground for the next as soon as possible.

At about 1500' the port wing broke off.

The investigation found that he had a habit of setting the flaps at what he called "trail". The flaps were operated by a handle on the top LH side of the cabin, hinged at the back end, and could be set in one of 3 (from memory) positions, achieved by a slotted quadrant and a little lever operated by a spring-loaded button at the foreward end of the lever. The "trail" position was in fact loose between 0 flap and the 1st position. The pilot reckoned that this gave him the best rate of descent while maintaining a much higher speed than would be permitted with flap set to position 1.

The Auster was high wing, and had a strut from the bottom of the fuselage to a point about 1/3rd along each wing. About halfway along this strut was a small vertical "jury" strut, going up to the main spar..

What the pilot didn't know was that the point where this strut joined the main spar was the point of maximum lift with flap, which is why the strut was there.

The sequence of events, the AIB concluded, was that as he descended in the rough air, the handle fell into the 1st position and locked there, as it would. Since he was descending at well over the flap limit speed, the jury strut became massively overstressed, and failed, almost certainly in a gust giving a temporary speed increase of 10-20Kts.

Sod's law then took over, as it always will when you are in extremis. The main strut mounting depended on a weld (either welded to the fuselage, or at the bottom of the strut, perhaps an Auster owner will know).

The weld, it was found from the wreckage, had insufficient penetration. The stress caused by the jury strut failure, combined with a momentary airspeed increase caused by a gust above the already excessive speed (with flaps in position 1) , caused the main strut to fail and the wing to fold up and break off.

And that was that. Speed and manoeuvring limitations are there because if they are exceeded the safety margin is lost and the airframe may break up. The cause of the Auster wing breaking off was the failure of the strut due to exceeding flap speed limitations. The poor weld was a possible contributory factor, ie the strut would probably have failed anyway, once the jury strut had failed.

Of course you can do anything with an aircraft that its handling characteristics allow you to do. Equally, you can break it up while doing that, and you'll never even work out why on the way down.

scooter boy

3rd Oct 2007, 11:40

This sounds vaguely reminiscent of the Beech Baron fatal accident this year during an inpromptu aerobatic display. Stupid for the pilot to kill himself while showing off but unforgivable to take others with him.

Yes, sure, loop and roll it once I've got out, I'll just stay on the ground at a safe distance and watch, if that's OK with you, life is dangerous enough.

SB

gasax

3rd Oct 2007, 11:47

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

3rd Oct 2007, 14:38

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

3rd Oct 2007, 18:04

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

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

3rd Oct 2007, 19:38

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

3rd Oct 2007, 20:18

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.:ugh:

DX Wombat

3rd Oct 2007, 20:31

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

3rd Oct 2007, 20:57

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. :ugh:

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

Enough said, I think.

Knox.

Pilot DAR

4th Oct 2007, 00:18

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

4th Oct 2007, 03:01

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

4th Oct 2007, 07:56

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

4th Oct 2007, 09:29

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

5th Oct 2007, 03:40

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.

:bored:

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

5th Oct 2007, 19:58

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

5th Oct 2007, 21:06

BD,

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

BackPacker

5th Oct 2007, 21:52

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

5th Oct 2007, 22:24

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

5th Oct 2007, 22:38

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

5th Oct 2007, 22:52

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

5th Oct 2007, 23:14

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

Yes
ZA

IFMU

6th Oct 2007, 01:49

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.

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