Hawker Hunter Crash at Shoreham Airshow
what should the height / speed at the apex to complete the back 3/4 of e.g. a loop, and what is is the min height drop from apex to come out wings level (ignoring margins). and how much margin would be typically added?
out of interest how does this vary by type for e.g. a hawk / typhoon etc.?
out of interest how does this vary by type for e.g. a hawk / typhoon etc.?
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I know what you mean, Newt and agree the forces would be easily manageable when low speed over the top. What I was considering was a hyd snag on the way down and control(s) reverting to manual, with the subsequent pull required to exit the 'loop' increasing as the speed increased. I could imagine Andy being more than capable of exerting the required back-stick pressure initially but, maybe, the required force to recover in the height available, as the speed increased, was just not available.
ZeBedie,
A suggestion might be that the hyds returned to life and the sudden 'snap' of pitch change that we see is the result of the stick being held back/pulled back in manual and then, suddenly, having the benefit of hydraulic power applied to flight controls. It obviously takes XXX seconds for that effect of the controls to materialise but, in the meantime, gravity continues to suck and the velocity vector stays in place.
How does that explain the large, sudden increase in pitch rate shortly before the crash, which to me, looks like the point of recognition?
A suggestion might be that the hyds returned to life and the sudden 'snap' of pitch change that we see is the result of the stick being held back/pulled back in manual and then, suddenly, having the benefit of hydraulic power applied to flight controls. It obviously takes XXX seconds for that effect of the controls to materialise but, in the meantime, gravity continues to suck and the velocity vector stays in place.
I do not wish to speculate on the accident. However, I have now seen an unusual detail on video posted at youtube. During the hard rolling break after the fast flypast, a definite trail is seen for two seconds and again, after the reversal, the trail can be seen faintly for approx three seconds. The video is jerky but, I consider the trail to be real and not an aberation.
The video can be seen on youtube under "Shoreham Hawker Hunter disaster (added material) - Tragic Hawker Hunter Plane crash". The detail I am commenting on occurs in the first fifteen seconds of the recording.
OAP
The video can be seen on youtube under "Shoreham Hawker Hunter disaster (added material) - Tragic Hawker Hunter Plane crash". The detail I am commenting on occurs in the first fifteen seconds of the recording.
OAP
I think it unlikely that its a hyd fail as the accumulators have enough energy in them to give 3 1/2 full aileron or elevator deflections before loss of pressure. So if the pilot gets a sniff of a hyd failure warning during aerobatics he would 'throw it away' and return to level flight.
The vapour trail is interesting but it could be a small fuel purge and happens a long time before the final manoeuvre. If it was hyd fluid leaking I would expect the aircraft to have warned him way before the final manoeuvre. Again, it would have meant a 'stop, stop, stop' at that point.
For JFZ90 - yes gate heights vary by type due to the physics of speed, weight, G, AOA allowance, drag and other factors. So it will be different between Typhoon and a Hawk.
LJ
The vapour trail is interesting but it could be a small fuel purge and happens a long time before the final manoeuvre. If it was hyd fluid leaking I would expect the aircraft to have warned him way before the final manoeuvre. Again, it would have meant a 'stop, stop, stop' at that point.
For JFZ90 - yes gate heights vary by type due to the physics of speed, weight, G, AOA allowance, drag and other factors. So it will be different between Typhoon and a Hawk.
LJ
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I think it unlikely that its a hyd fail as the accumulators have enough energy in them to give 3 1/2 full aileron or elevator deflections before loss of pressure.
to me I think it was a factor of a modified 1/4 clover and then an oblique pull through that meant that the normal gate height would probably have been too low. Normally a 1/4 clover would be from 90 degs from the crowdline but the position of Lancing and Lancing College make this difficult. That's always been my opinion of civilian authorised displays compared to military authorised displays - the military ones are 'set piece' and not for modification, whereas, the civilian displays can be modified as required by the pilot. I remember watching a very experienced ex-mil pilot put an extra roll in his display over-sea and he did not recover. The UK military PDA regime is far more restrictive and modification to the authorised 'full', 'rolling' and 'flat' displays is not allowed as far as I'm aware.
That's my theory, anyway. Don't think it will be G-loc or overstress looking at the numerous videos. If he lost his engine at the top of the vertical manoeuvre then he would have rolled out and then gone for a FL towards the field, if he lost the engine going downwards then he would have been at idle anyway. But, hey, here's hoping the AAIB release something soon to stop speculation and actually report facts - rather than our best guesses. Of course something could have gone wrong with the jet, but I don't see any significant evidence to support that.
I do think the CAA have been right to enforce the restrictions they have - I don"t see them as 'knee jerk' as some have opined.
That's my theory, anyway. Don't think it will be G-loc or overstress looking at the numerous videos. If he lost his engine at the top of the vertical manoeuvre then he would have rolled out and then gone for a FL towards the field, if he lost the engine going downwards then he would have been at idle anyway. But, hey, here's hoping the AAIB release something soon to stop speculation and actually report facts - rather than our best guesses. Of course something could have gone wrong with the jet, but I don't see any significant evidence to support that.
I do think the CAA have been right to enforce the restrictions they have - I don"t see them as 'knee jerk' as some have opined.
I don't agree that the CAA restrictions were well thought out. If special measures are needed for "vintage jet aircraft" then having highlighted that these may need special attention, it follows that any unwinding of these restrictions will come with a solid explanation. Its the same with any wider air display review.
To take some brief examples. If you read this:-
http://www.caa.co.uk/docs/33/CivilAi...eforPilots.pdf
I don't see how any review can conclude anything especially new or revealing in that and if you read this:-
http://www.caa.co.uk/docs/33/CAP%204...l%20events.pdf
Page 23, read item 3.25 and suggest how that was arrived at... So now the CAA have put these things in focus how do you ever redo those numbers without effectively ending airshows?
Leon,
You make some good points there that prompted me to consider your point about 3 1/2 full deflections. From the point of the apparent vapour (which I agree is likely to be fuel) there are only a handful of partial aileron and elevator deflections. Do you recall what would trigger hyd warnings? If a pressure threshold, could that occur a significant time after the actual failure - I'm thinking of residual pressure here.
You make some good points there that prompted me to consider your point about 3 1/2 full deflections. From the point of the apparent vapour (which I agree is likely to be fuel) there are only a handful of partial aileron and elevator deflections. Do you recall what would trigger hyd warnings? If a pressure threshold, could that occur a significant time after the actual failure - I'm thinking of residual pressure here.
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I think it unlikely that its a hyd fail as the accumulators have enough energy in them to give 3 1/2 full aileron or elevator deflections before loss of pressure
With some types of hydraulic failure immediate reversion to Manual will result.
When mod. 452 is embodied a revised wiring and switching arrangement is applied to the aileron and elevator pawl release units so that Manual is automatically selected if any pawl disengages even though momentarily. The aircraft can therefore be flown only with Power correctly engaged or in Manual
I couldn't find out the hydraulic pressure required for a warning but it does say that below 200 psi the system switches automatically to manual.
Maybe with OAP's vapour being a hydraulic leak the system could be intermittent and, perhaps, go hand-in-hand with my earlier suggestion that the rapid pitch-up just before impact was normal hydraulic controls being restored, even momentarily, but still to late to change the aircraft's vector.
Pontious,
I said I would not speculate, and I will not. However, I will just say that the Hunter hydraulic system, and its possible failure modes, is quite complex-for a "simple" hydraulic system, IMO.
OAP
I said I would not speculate, and I will not. However, I will just say that the Hunter hydraulic system, and its possible failure modes, is quite complex-for a "simple" hydraulic system, IMO.
OAP
It has been suggested in some corners that the pilot may have blacked out during the high energy manoeuvre. Whilst this is pure speculation it does raise the question should display pilots have an upper age limit? Is it right a 51 yr old was performing a high g manoeuvre? Do display pilots undergo strict annual medicals, ECG, blood tests etc? Flying military spec, even fifty year old jets is demanding and perhaps not for the more mature pilot? You don't see many fifty year old pilots in active FJ service very often, you dont see F1 drivers of that age.
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May I ask why anyone is talking about the Hunter hydraulic system, and associated failures, when there is absolutely NO evidence to suggest that this aircraft had suffered from a hydraulic failure.
Equally, there is no evidence that it suffered from and engine failure, or malfunction of any type.
Until there is some positive and reliable evidence as to a possible cause, let us wait.
Equally, there is no evidence that it suffered from and engine failure, or malfunction of any type.
Until there is some positive and reliable evidence as to a possible cause, let us wait.
It was the normal joke when flying a passenger in the Hunter.....
'I will put the controls over to you'... Switch the power controls off...
'it's yours'
'Oh, not stong enough to fly it?'
...'Hang on, I;ll take control back' ...turn on power controls.
...'can't see the problem'
Repeat as long as you like.
A manual reversion is like putting control locks in. The ac can only be flown using the trimmer. ..more or less.
'I will put the controls over to you'... Switch the power controls off...
'it's yours'
'Oh, not stong enough to fly it?'
...'Hang on, I;ll take control back' ...turn on power controls.
...'can't see the problem'
Repeat as long as you like.
A manual reversion is like putting control locks in. The ac can only be flown using the trimmer. ..more or less.
Thanks for the reply LJ, I'd be interested to know the specific gates height and speeds as they vary with e.g. entry speed for different types in say a loop. Perhaps a typhoon is classified, so how about some numbers for a hawk, jaguar and phantom? Did a Jag have enough puff to do a loop?
Maybe this should be posted / responded to in the gates thread.
Maybe this should be posted / responded to in the gates thread.
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Can the armchair experts leave analysis to the professionals everything else is pure conjecture.
So if it is not to your taste feel free to **** off in fine pitch.
