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Hawker Hunter Crash at Shoreham Airshow

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Hawker Hunter Crash at Shoreham Airshow

Old 31st Aug 2015, 09:42
  #561 (permalink)  
 
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Yes, Thanks for posting that link ORAC. The detail I am refering to is best seen in full screen.

OAP
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Old 31st Aug 2015, 10:00
  #562 (permalink)  
 
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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. 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
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Old 31st Aug 2015, 10:18
  #563 (permalink)  
 
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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.
Good point, well made. I'll go back under my rock and concentrate on my areas of expertise: hardcore porn and pizza.....oh, and beer....I'm multi-talented.
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Old 31st Aug 2015, 10:51
  #564 (permalink)  
 
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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.
Agree although civilian display sequences are to be briefed and I don't believe civil DA's allow random modification - obviously allowing for a necessary change being made for safety reasons.

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?
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Old 31st Aug 2015, 12:03
  #565 (permalink)  
 
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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.
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Old 31st Aug 2015, 12:24
  #566 (permalink)  
 
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Leon,
The "reserve" capability of a simple accumulator backed hydraulic system usually reflects a pump drive failure case. Leaks are different.

OAP
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Old 31st Aug 2015, 12:31
  #567 (permalink)  
 
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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
Back from under the rock for a breather. In the meantime, the Hunter notes also show:

With some types of hydraulic failure immediate reversion to Manual will result.
It goes on to say that post mod 452 (which I assume is incorporated):

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 don't claim for one moment to remember the implications of that but it would suggest that post mod 452 it is an all or nothing system i.e. you're powered or you're in manual, although I'm probably reading it incorrectly and will bow to superior knowledge.

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.
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Old 31st Aug 2015, 12:59
  #568 (permalink)  
 
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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
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Old 31st Aug 2015, 15:22
  #569 (permalink)  
 
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Originally Posted by Jayand View Post
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.
May wish to discuss that with Chuck Ellsworth.
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Old 31st Aug 2015, 15:23
  #570 (permalink)  
 
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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.
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Old 31st Aug 2015, 17:15
  #571 (permalink)  
 
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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.
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Old 31st Aug 2015, 17:34
  #572 (permalink)  
 
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Conjecture

Can the armchair experts leave analysis to the professionals everything else is pure conjecture.
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Old 31st Aug 2015, 17:40
  #573 (permalink)  
 
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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.
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Old 31st Aug 2015, 18:38
  #574 (permalink)  
 
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Can the armchair experts leave analysis to the professionals everything else is pure conjecture.
There are fast jet pilots on here (including hunter jocks) display pilots, authorizing officers, aircraft captains, people who have sat on accident boards, engineers etc etc. Also the website is called "Professional Pilots Rumour Network.

So if it is not to your taste feel free to **** off in fine pitch.
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Old 31st Aug 2015, 18:58
  #575 (permalink)  
 
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What he said

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Old 31st Aug 2015, 20:06
  #576 (permalink)  
 
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Thank you for that, TOFO.
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Old 31st Aug 2015, 21:06
  #577 (permalink)  
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@ ORAC and Onceapilot

Interesting video angle, that first vapour shot almost seems to originate from around the left aft fuselage area.

I watched G-HHUN taxy out from Bournemouth as a 4 ship on that fateful day only to return back down the taxiway with an electrical tech issue, aircraft shutdown, dropped a panel behind the where the gun pack was located, quick rectification, startup fast taxi and caught up with others en-route to Biggin.

As it left the apron it started venting fuel from the port side of the fuselage under the wing trailing edge, at the time it was thought to be normal as the aircraft departed the apron very quickly in a right hand turn, I personally witnessed the whole event up close from about 10 feet away, the rest was history.

Last edited by Above The Clouds; 1st Sep 2015 at 09:48. Reason: spelling HUNN HHUN
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Old 31st Aug 2015, 22:27
  #578 (permalink)  
 
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Hello AtC,

Would that be G-HHUN?
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Old 1st Sep 2015, 08:57
  #579 (permalink)  
 
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This photo on airliners.net shows perfectly the accident aircraft venting fuel from the starboard drop tank during a display at Biggin Hill in September 2014.

Photos: Hawker Hunter T7 Aircraft Pictures | Airliners.net
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Old 1st Sep 2015, 09:21
  #580 (permalink)  
 
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Yes Karl, that leak is apparent in many pictures.

OAP
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