Inverted roll with C-172????
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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
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
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The # of posts has gone down but that's not a bad thing if it drives the one-liners out.
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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?]
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?]
Last edited by Life's a Beech; 30th Sep 2007 at 12:24.
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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
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
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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".
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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.
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.
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!
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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?
Whilst this is true, how confident would one be that a tired 30 year old example would still take +3.5g?
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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.
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Barrel Rolls
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
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
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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
"Here endeth the lesson"!
SS
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!
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!
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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.
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.
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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).
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).
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Airframe failures may not happen everyday, but they do happen
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.
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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
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
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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
) 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 
I NEVER want to be in that situation
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
) 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 I NEVER want to be in that situation
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<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.
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.
Last edited by Gipsy Queen; 1st Oct 2007 at 03:27. Reason: spling mstayk