Hawker Hunter Crash at Shoreham Airshow
Originally Posted by Daily Telegraph
Shoreham Air Show plane crash: Pilot was too low, official report reveals
Air Accidents Investigation Branch publishes interim report into crash that killed 11, showing loop-the-loop began at 200ft when pilot Andy Hill was licensed to perform such manoeuvres at 500ft and above
Air Accidents Investigation Branch publishes interim report into crash that killed 11, showing loop-the-loop began at 200ft when pilot Andy Hill was licensed to perform such manoeuvres at 500ft and above
I think one of the points pittsextra was trying to make was that if the DT headline is indeed incorrect, why has nobody in an official capacity corrected or clarified it.
I might be wrong though, it's hard to know what points he's trying to make
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I must admit I am getting seriously bored by what in my mind has become a rather stupid circular argument. I am only amazed that PittsExtra hasn't shifted the argument to the entry speed of the manoeuvre, which in some reports suggested it was too slow. However this of course was not part of the DT headline.
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LlamaFarmer
In that case...
is incorrect and misleading.
I think one of the points pittsextra was trying to make was that if the DT headline is indeed incorrect, why has nobody in an official capacity corrected or clarified it.
Originally Posted by Courtney Mil View Post
So, AS FAR AS WE KNOW AT THE MOMENT, he pulled up from a 200 foot pass into a quarter clover, which is both safe and legal and approved.
So, AS FAR AS WE KNOW AT THE MOMENT, he pulled up from a 200 foot pass into a quarter clover, which is both safe and legal and approved.
In that case...
Originally Posted by Daily Telegraph
Shoreham Air Show plane crash: Pilot was too low, official report reveals
Air Accidents Investigation Branch publishes interim report into crash that killed 11, showing loop-the-loop began at 200ft when pilot Andy Hill was licensed to perform such manoeuvres at 500ft and above
Shoreham Air Show plane crash: Pilot was too low, official report reveals
Air Accidents Investigation Branch publishes interim report into crash that killed 11, showing loop-the-loop began at 200ft when pilot Andy Hill was licensed to perform such manoeuvres at 500ft and above
I think one of the points pittsextra was trying to make was that if the DT headline is indeed incorrect, why has nobody in an official capacity corrected or clarified it.
The aircraft then pitched up into a manoeuvre with both a vertical component and roll to the left, becoming almost fully inverted at the apex of the manoeuvre at a height of approximately 2,600 ft amsl.
So are we now suggesting the authorities chase every newspaper to correct their inadequacies to type the facts ?
I don't own this space under my name. I should have leased it while I still could
ATC, indeed, I am sure most people will have noticed that a correction or apology is usually buried in the right hand column of page 2 or 4 and wholly insignificant when compared with a previous 'sensational' leading article.
Who knows, maybe a correction was printed.
DaveU may wish to confirm this industry method of hidden apology.
Who knows, maybe a correction was printed.
DaveU may wish to confirm this industry method of hidden apology.
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CM: Is that enough?
I’m almost afraid to post here for fear of being ridiculed by a few vociferous and largely nameless (in the latter respect, not you CM) experts who seem to delight in shooting down anyone with lesser knowledge or experience, but I’ll take my chance and pose what I believe is a reasonable question. Apologies in advance if I am typing out of turn, and shouldn’t even be visiting your ever so holy forum.
Leaving aside for a moment Lomcevak’s previous red herring which, in his defence, I recall as being the “guidelines” we worked to in my display flying days (long since passed), I have a question that someone with better maths skills than me could hopefully answer.
If we assume that the AAIB are correct in their determination that the aircraft reached a peak altitude of 2,600 (let’s call that AGL as the field is almost SL), and at the apex while inverted the IAS was noted by the AAIB as being 100kts, one might reasonably conclude that the aircraft had 2,100 feet within which to complete the manoeuvre. It might be argued by some that he actually had more than this, but unless it was another red herring Lomcevak also stated that “descent below the approved aerobatic height (500 ft in the case of this pilot, in the Hunter) to the approved fly by height is permitted once certain capture of the aerobatic display height.” (Assuming you lot have no objections therefore, I propose to use 2,100 feet for the purpose of my question).
With the limited information we have to go on at this point in time, would 2,100 feet have been sufficient in a Hunter – and without exceeding the aircraft limitations, or it leaving the envelope?
The approximate fuel load and weight of the aircraft has been determined, and the Permit to Fly flight test report will have recorded a recent un-accelerated 1G stall speed of the actual aircraft at a specified weight. From this it is easy to determine pretty accurate unaccelerated and accelerated stall speeds for any G value. (Pittsextra knows that). We also know that from the inverted the aircraft had to achieve a radius of 1,050 in order to meet the display floor, but we don’t know what thrust was used, or if indeed all of it was available. That stated, with the thrust normally available to the type, and forgetting the wind on the day, did the aircraft have sufficient space within which to meet the display floor limit of 500 feet, keep within the envelope, and was it possible to do so without exceeding any airframe limits for the configuration it was in?
I’m not entirely sure that it is possible to make a precise calculation (****, I'm not a military pilot), but surely we can narrow the field down a bit. For example, at 100kts (small radius) the manoeuvre would not have been possible – the required acceleration would have exceeded the flight envelope and the aircraft would have stalled. Similarly had excessive thrust been used (if it was even available), the radius would have exceeded the space available. Clearly there IS a balance of thrust versus pull required in order to achieve the smallest radius, but is it possible to calculate it – and align these figures to see if what was attempted was actually possible within a radius of 1,050 feet?
Ready for incoming!
I’m almost afraid to post here for fear of being ridiculed by a few vociferous and largely nameless (in the latter respect, not you CM) experts who seem to delight in shooting down anyone with lesser knowledge or experience, but I’ll take my chance and pose what I believe is a reasonable question. Apologies in advance if I am typing out of turn, and shouldn’t even be visiting your ever so holy forum.
Leaving aside for a moment Lomcevak’s previous red herring which, in his defence, I recall as being the “guidelines” we worked to in my display flying days (long since passed), I have a question that someone with better maths skills than me could hopefully answer.
If we assume that the AAIB are correct in their determination that the aircraft reached a peak altitude of 2,600 (let’s call that AGL as the field is almost SL), and at the apex while inverted the IAS was noted by the AAIB as being 100kts, one might reasonably conclude that the aircraft had 2,100 feet within which to complete the manoeuvre. It might be argued by some that he actually had more than this, but unless it was another red herring Lomcevak also stated that “descent below the approved aerobatic height (500 ft in the case of this pilot, in the Hunter) to the approved fly by height is permitted once certain capture of the aerobatic display height.” (Assuming you lot have no objections therefore, I propose to use 2,100 feet for the purpose of my question).
With the limited information we have to go on at this point in time, would 2,100 feet have been sufficient in a Hunter – and without exceeding the aircraft limitations, or it leaving the envelope?
The approximate fuel load and weight of the aircraft has been determined, and the Permit to Fly flight test report will have recorded a recent un-accelerated 1G stall speed of the actual aircraft at a specified weight. From this it is easy to determine pretty accurate unaccelerated and accelerated stall speeds for any G value. (Pittsextra knows that). We also know that from the inverted the aircraft had to achieve a radius of 1,050 in order to meet the display floor, but we don’t know what thrust was used, or if indeed all of it was available. That stated, with the thrust normally available to the type, and forgetting the wind on the day, did the aircraft have sufficient space within which to meet the display floor limit of 500 feet, keep within the envelope, and was it possible to do so without exceeding any airframe limits for the configuration it was in?
I’m not entirely sure that it is possible to make a precise calculation (****, I'm not a military pilot), but surely we can narrow the field down a bit. For example, at 100kts (small radius) the manoeuvre would not have been possible – the required acceleration would have exceeded the flight envelope and the aircraft would have stalled. Similarly had excessive thrust been used (if it was even available), the radius would have exceeded the space available. Clearly there IS a balance of thrust versus pull required in order to achieve the smallest radius, but is it possible to calculate it – and align these figures to see if what was attempted was actually possible within a radius of 1,050 feet?
Ready for incoming!
CliveWatson,
Give me a while to go through your post and address your points.
For now, let me just say this. The regulars here don't normally shoot people down for asking questions about their understanding of topics such as this, although I quite understand why you might get that impression at times. Folk here get pissed off and a little harsh when people come here full of attitude and keep bashing away at issues that they do not understand in a way that becomes intolerable or try to score points or criticise or draw unfounded conclusions.
To come here and present a reasoned argument that does not state assumptions as facts and to ask for opinions or explanations is what the forum is all about. In my opinion.
I've scanned your post and my initial thought is that I'm not sure that 2600 was the apex, but that's just from memory. I thought that was the highest altitude recorded on radar - I'm not sure if the aircraft peaked higher between sweeps. I doubt the difference is that much and it's close to what I think MAY have been his top gate.
I'll get back to you an this and there will be others here that will certainly be able to comment.
Give me a while to go through your post and address your points.
For now, let me just say this. The regulars here don't normally shoot people down for asking questions about their understanding of topics such as this, although I quite understand why you might get that impression at times. Folk here get pissed off and a little harsh when people come here full of attitude and keep bashing away at issues that they do not understand in a way that becomes intolerable or try to score points or criticise or draw unfounded conclusions.
To come here and present a reasoned argument that does not state assumptions as facts and to ask for opinions or explanations is what the forum is all about. In my opinion.
I've scanned your post and my initial thought is that I'm not sure that 2600 was the apex, but that's just from memory. I thought that was the highest altitude recorded on radar - I'm not sure if the aircraft peaked higher between sweeps. I doubt the difference is that much and it's close to what I think MAY have been his top gate.
I'll get back to you an this and there will be others here that will certainly be able to comment.
Hard not to think that if he had started the maneuver at 500 feet vs 200 feet (assuming the 200 foot figure is in fact, accurate), the outcome might have been quite different.......
Hard to think that he could fly the planned manoeuvre from the planned entry height and not crash. Hard to think that if all aero displays were flown to a 5.000 ft base height they might all get away with it.
I can't deny that additional energy at entry could make the manoeuvre safer. But then what is the point of air displays? Hard to think we'd not be safer without them. And Formula 1. And ski jumping. And Rugby. It would be a dull old world, but safer.
I can't deny that additional energy at entry could make the manoeuvre safer. But then what is the point of air displays? Hard to think we'd not be safer without them. And Formula 1. And ski jumping. And Rugby. It would be a dull old world, but safer.
Courtney,
You might be a little busy with thoughts about min radius turning at the mo but, I think you may find that major league motorsport has largely cleaned-up its safety, on international circuits at least. That process required major revisions in run-off areas and spectator proximity to high speed vehicles. I expect that similar restraint will inevitably come to future FJ public display flying (such as may survive).
OAP
You might be a little busy with thoughts about min radius turning at the mo but, I think you may find that major league motorsport has largely cleaned-up its safety, on international circuits at least. That process required major revisions in run-off areas and spectator proximity to high speed vehicles. I expect that similar restraint will inevitably come to future FJ public display flying (such as may survive).
OAP
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Dave Unwin. Welcome !
Good to have a positive minded journo here.
Clive Watson.
Very good question very clearly put.
FL
I see irony in an establishment legal figure asking people to moderate behaviour which is not prohibited.
Reverser bucket
What makes you think AH has an account to give to anybody? Enough posts have alluded to the fact that with trauma it's not uncommon for there to be amnesia.
Good to have a positive minded journo here.
Clive Watson.
Very good question very clearly put.
FL
I see irony in an establishment legal figure asking people to moderate behaviour which is not prohibited.
Reverser bucket
What makes you think AH has an account to give to anybody? Enough posts have alluded to the fact that with trauma it's not uncommon for there to be amnesia.
Clivewatson,
A well worded post with sensible questions. To answer some of them:
The Hunter is not cleared for intentional stalling and so 1g stall speeds are not assessed on airtests. Even if they were, the lift curve of the wing varies with Reynold's number, effectively true airspeed, (and Mach number but that would not be relevant below about 0.5M) and so a straight mathematical calculation of an accelerated stall speed at a given g would not be totally reliable. And if you don't know either the g and the speed around the manoeuvre then you cannot calculate radius. Even if someone finds the data sheets for the wing section it would be almost impossible to calculate an accurate theoretical value of lift coefficient for the whole wing. This data may exist in the BAES archives but access may not be easy.
I have never seen a performance manual that deals with looping radius and pilots often have their own numbers for use in ACM or aerobatic practise but these normally are rough figures for guidance and then have a safety margin built in. I hope that this helps a little.
A well worded post with sensible questions. To answer some of them:
The Hunter is not cleared for intentional stalling and so 1g stall speeds are not assessed on airtests. Even if they were, the lift curve of the wing varies with Reynold's number, effectively true airspeed, (and Mach number but that would not be relevant below about 0.5M) and so a straight mathematical calculation of an accelerated stall speed at a given g would not be totally reliable. And if you don't know either the g and the speed around the manoeuvre then you cannot calculate radius. Even if someone finds the data sheets for the wing section it would be almost impossible to calculate an accurate theoretical value of lift coefficient for the whole wing. This data may exist in the BAES archives but access may not be easy.
I have never seen a performance manual that deals with looping radius and pilots often have their own numbers for use in ACM or aerobatic practise but these normally are rough figures for guidance and then have a safety margin built in. I hope that this helps a little.
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Pittsextra
I agree.
It's taken a few years but I knew we'd agree about something eventually.
Perhaps because while there is still an ongoing investigation it would be an irresponsible thing to do and it is better and wiser to let the official investigation take its course.
In accident investigation, accuracy is far more important than speed.
The headline is misleading because it gives the impression that an official report found that the pilot was "too low". Closer examination of the article reveals that it did not.
Too low for what?
According to the journo: "lower than his licence allowed".
David Learmount, described in the article as "a leading aviation expert", saw fit to say that the AAIB Special Bulletin showed that the pilot had been “unwise” and made a “misjudgement”.
Such comments are, as he knows (being a journalist himself), good fodder for the press, but it is not what the Bulletin says.
I worked with experts extensively for decades. I didn't, and wouldn't, use anyone claiming to be an expert who was prepared to express conclusions before all the relevant evidence was available.
In my experience, those worthy of the description are never prepared to do that. They may comment in very general terms about procedures, the aircraft type etc but they will never comment upon causation - far less presume to attribute blame - until all the facts are known.
The media are in the business of publishing 'shock horror' stories. It's not difficult to work out why the same 'experts' appear regularly. Entirely understandably, the media are not interested in using experts who, sensibly, decline to comment because there is insufficient information.
How often do we read or hear:
That wouldn't make a a good story so, understandably, the media use experts whom they know will.
.
Personally the law and its consequences as it may apply to anyone involved here are less interesting than understanding the thinking behind the wider process of what is and is not accepted and who or what takes precedence.
It's taken a few years but I knew we'd agree about something eventually.
I'd have thought that when the Sept 2015 AAIB bulletin printed some numbers that got turned into headlines that someone from the CAA, BADA or individuals involved with delegated authority could have put those numbers into some sort of context.
I've not seen that done to date. Why?
I've not seen that done to date. Why?
In accident investigation, accuracy is far more important than speed.
I find clarification is needed because it led to these headlines:-
Shoreham Air Show plane crash: Pilot was too low, official report reveals - Telegraph
Shoreham Air Show plane crash: Pilot was too low, official report reveals - Telegraph
Too low for what?
According to the journo: "lower than his licence allowed".
David Learmount, described in the article as "a leading aviation expert", saw fit to say that the AAIB Special Bulletin showed that the pilot had been “unwise” and made a “misjudgement”.
Such comments are, as he knows (being a journalist himself), good fodder for the press, but it is not what the Bulletin says.
I worked with experts extensively for decades. I didn't, and wouldn't, use anyone claiming to be an expert who was prepared to express conclusions before all the relevant evidence was available.
In my experience, those worthy of the description are never prepared to do that. They may comment in very general terms about procedures, the aircraft type etc but they will never comment upon causation - far less presume to attribute blame - until all the facts are known.
The media are in the business of publishing 'shock horror' stories. It's not difficult to work out why the same 'experts' appear regularly. Entirely understandably, the media are not interested in using experts who, sensibly, decline to comment because there is insufficient information.
How often do we read or hear:
Aviation expert refuses to comment!
"X Y, a leading aviation expert, said it was far too early to make an informed comment and he was not prepared to speculate."
"X Y, a leading aviation expert, said it was far too early to make an informed comment and he was not prepared to speculate."
.
Last edited by Flying Lawyer; 8th Feb 2016 at 19:24.
CliveWatson,
It is actually fairly simple to do an approximation to the mathematics of a loop. Acceleration is a vector, so the acceleration due to gravity can be separated from the centripetal acceleration of the loop.
If we assume the loop is a perfect circle of radius R, the distance from the top of the loop to the bottom of the loop is S, and the velocity at the top of the loop is v, and the time from top of loop to bottom of loop is t, then we find that t=pie*R/v, and 0.5gt^2+2R=S. Substitute t, and we get a quadratic equation for R. Solve that, and put in the actual figures you quote, then we can work out out that the centripetal acceleration at the top of the loop would be 1.9g, so (subtracting gravity) he would have had to pull 0.9g at the top of the loop, which is pretty reasonable and would not have risked an inverted stall (though I don't know the stall speed of a Hunter so can't be sure of that). As the aircraft descends, potential energy is converted into kinetic energy so that o.5V^2=gS+0.5v^2, where V is the velocity at the bottom of the loop. Chug away at the maths of that and he would have been doing about 250knots at the bottom of the loop and would have to pull about 9g to maintain a constant radius loop, which is quite high.
Now note that I said "constant radius" loop. This is not necessarily the case. Also, drag would have varied around the loop as different elevator inputs were used, so V might be a bit lower. But nevertheless, i think he might have found himself in a situation where he was having to pull a lot of g at the bottom of the loop, which is more or less what is observed in the videos.
Does anybody know approximate stall speed of the Hunter at the mass and configuration of the day? I can use it to work out how close to the stall he would have been at different bottoming out scenarios (i.e. 500ft, 200ft, 0ft).
It is actually fairly simple to do an approximation to the mathematics of a loop. Acceleration is a vector, so the acceleration due to gravity can be separated from the centripetal acceleration of the loop.
If we assume the loop is a perfect circle of radius R, the distance from the top of the loop to the bottom of the loop is S, and the velocity at the top of the loop is v, and the time from top of loop to bottom of loop is t, then we find that t=pie*R/v, and 0.5gt^2+2R=S. Substitute t, and we get a quadratic equation for R. Solve that, and put in the actual figures you quote, then we can work out out that the centripetal acceleration at the top of the loop would be 1.9g, so (subtracting gravity) he would have had to pull 0.9g at the top of the loop, which is pretty reasonable and would not have risked an inverted stall (though I don't know the stall speed of a Hunter so can't be sure of that). As the aircraft descends, potential energy is converted into kinetic energy so that o.5V^2=gS+0.5v^2, where V is the velocity at the bottom of the loop. Chug away at the maths of that and he would have been doing about 250knots at the bottom of the loop and would have to pull about 9g to maintain a constant radius loop, which is quite high.
Now note that I said "constant radius" loop. This is not necessarily the case. Also, drag would have varied around the loop as different elevator inputs were used, so V might be a bit lower. But nevertheless, i think he might have found himself in a situation where he was having to pull a lot of g at the bottom of the loop, which is more or less what is observed in the videos.
Does anybody know approximate stall speed of the Hunter at the mass and configuration of the day? I can use it to work out how close to the stall he would have been at different bottoming out scenarios (i.e. 500ft, 200ft, 0ft).
Last edited by Trim Stab; 8th Feb 2016 at 19:48. Reason: To ask a question about stall speed
Originally Posted by DSqdrn...
Dave Unwin. Welcome !
Good to have a positive minded journo here.
Good to have a positive minded journo here.
Flying Lawyer,
An outstanding post. You managed to say in three paras exactly what I've been trying to say in five months!!! THANK YOU.
The AAIB Special Report does not mention doing a 'loop-the-loop' that is the Daily Telegraph's and other tabloids interpretation, the actual report if you follow the link states.
https://assets.digital.cabinet-offic...015_G-BXFI.pdf
So are we now suggesting the authorities chase every newspaper to correct their inadequacies to type the facts ?
https://assets.digital.cabinet-offic...015_G-BXFI.pdf
So are we now suggesting the authorities chase every newspaper to correct their inadequacies to type the facts ?
I'm not proposing or suggesting anything... I was merely stating I think that was what pitts was trying to say but others were attacking him about his other points without acknowledging this point
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How often do we read or hear:
Quote:
Aviation expert refuses to comment!
"X Y, a leading aviation expert, said it was far too early to make an informed comment and he was not prepared to speculate."
Quote:
Aviation expert refuses to comment!
"X Y, a leading aviation expert, said it was far too early to make an informed comment and he was not prepared to speculate."
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Having survived my question, and further to Lomcevak's response, I found this:
http://people.clarkson.edu/~pmarzocc.../AE-429-12.pdf
I'm not sure how to turn it into a link, or post it as a pictures for all to see but on page 5 one will see "pull up" and "pull down" turn radii calculations.
I wouldn't know where to start with these because I'm not very adept at sums, but surely someone here would have an idea, and might even be able to put some rough examples together. (eg an average 5 or 6G pull down at an average TAS at say 225 or whatever).
Also, the "pull down" chart has an interesting annotation. It's perhaps obvious when one thinks about it, but due to the increasing speed the rate is reduced and the radius is enlarged in the case of a "pull down" when compared with a "pull up."
Maybe food for thought when reviewing DA's?
http://people.clarkson.edu/~pmarzocc.../AE-429-12.pdf
I'm not sure how to turn it into a link, or post it as a pictures for all to see but on page 5 one will see "pull up" and "pull down" turn radii calculations.
I wouldn't know where to start with these because I'm not very adept at sums, but surely someone here would have an idea, and might even be able to put some rough examples together. (eg an average 5 or 6G pull down at an average TAS at say 225 or whatever).
Also, the "pull down" chart has an interesting annotation. It's perhaps obvious when one thinks about it, but due to the increasing speed the rate is reduced and the radius is enlarged in the case of a "pull down" when compared with a "pull up."
Maybe food for thought when reviewing DA's?
If you want to describe (for example) a loop or a part thereof in numbers, you will find it a very complex excersise. The examples you show in your link are snapshots. The reality is a continuously changing set of variables as, most significantly, speed changes and gravity acts at at a different angle to the z axis. At least with a loop you don't (or shouldn't) need to worry about all that cosine bank angle stuff. But you also need to consider the change in control effectiveness and control authority with changing airspeed - very relevant for the F-16 as an example.
In practice, the equations give way to known loop dimensions for given speeds, hence the use of gates - essentially known parameters at various, critical points in the display. Pilots flying the displays are well versed in the theory of flight, but it's not a very practical way of designing or flying a display sequence.
In practice, the equations give way to known loop dimensions for given speeds, hence the use of gates - essentially known parameters at various, critical points in the display. Pilots flying the displays are well versed in the theory of flight, but it's not a very practical way of designing or flying a display sequence.