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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.? |
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.
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 |
Video from above.
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Yes, Thanks for posting that link ORAC. The detail I am refering to is best seen in full screen.
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 |
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. 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. |
Leon,
The "reserve" capability of a simple accumulator backed hydraulic system usually reflects a pump drive failure case. Leaks are different. 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 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 |
Originally Posted by Jayand
(Post 9098381)
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. |
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. |
Conjecture
Can the armchair experts leave analysis to the professionals everything else is pure conjecture.
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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. |
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. |
What he said
:D |
Thank you for that, TOFO. :ok:
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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. |
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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 |
Yes Karl, that leak is apparent in many pictures.
OAP |
KarlADrage 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. |
The accident has yet to make the monthly aviation magazines, with Flypast and Aeroplane going to press before it happened.
I will be interested to see how it is covered, but as much of the aviation media never likes to report bad or controversial news I suspect it will along the lines of 'we won't comment on anything until the report is published'. This is the polar opposite of the feeding frenzy in the national media, and if so will be in my eyes as unacceptable. As an event that will have a huge impact in aviation in the UK, airshows and the general perception of vintage aircraft, I hope the specialist press will come out all guns blazing to report the event soberly, offer a reasoned, balanced viewpoint and refute the sensationalist crap in the dailies. I know it is preaching to the converted but these magazines are on sale in public venues and if just a handful of people pick one up out of curiosity, read something sensible and learn about what happened it might help. Just a thought. |
Martin
The aviation mags do report accidents but don't in general have all the grim imagery. And the reason it gets a reasonable report in magazines is that some of us (that did once work) in aviation publishing and some of the editors knew the victims on several occasions. V1 |
Was AH flying the jet in the RHS? I saw a photo in one of the papers last weekend where I thought I could see a bone dome. Not sure if my eyes are playing tricks on me. Anybody else see anything?
P.S. I think it was the Daily Mail and the article related to the people who has a near miss. I have been out of the country since Saturday so any news on AH? |
Inquest
Just heard on the radio that the inquest into the deaths started today. Although all answers will not be forthcoming at least the process has started. My thoughts are with the families of those killed.
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The coroner has promised the families a 'full and fearless inquiry' with the inquest expected in June 2016.
http:///www.bbc.com/news/uk-england-sussex-34117125 |
Fine Pitch
Suggest you read article by Jon Whaley who really does know his stuff. Better to remain silent and appear a fool than to open the mouth and remove all possible doubt. You will note than Jon refuses to speculate a view which I thoroughly respect. Remain in coarse pitch!
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'fearless'
was that the word actually used by the coroner? Is it just me, or is that an unnecessarily emotionally loaded adjective? Makes him/her sound like a right ****, with some kind of premeditated bias. |
According to the Beeb lunchtime news the coroner was a she, and she ordered that police and AAIB investigations be concluded before her next report in 6/2016.
I am sure the AAIB will take no notice and proceed with their customary diligence. |
Some more thoughts on looping the Hawker Hunter
My copy of Pilot’s Notes HUNTER T.7 A.P. 4347G–P.N. August 1958 states on page 88.
(b) Loop 425 knots It is recommended that until experience is gained, loops are started in the height band 10,000ft to 15,000 ft. Rumours & News pprune post #55 .... pilot states Having been around Hunters for a large part of my aviation career I can say it's not uncommon for a Hunter pilot to use "1 notch" of flap for maneuvering. On these pages we are talking about an experienced display pilot starting a solo loop not at a PN recommended 10,000’, but in denser air at around 500’ agl. My guess is that he would start the pull up at about 350 - 380 kts using full power and one notch of flap. Full power would be maintained all the way round the loop with the pilot smoothly pulling more or less ‘g’ so as to achieve the desired speeds at each point in the loop. Thus if the Hunter is slow at the top of the loop, stick pressure would be briefly slackened to enable the Hunter to accelerate to say 200kts or more and get some ‘g’ bite on the air before starting on the downward path, with a gradual increase in ‘g’ being applied with increasing speed. A truly circular loop is never the aim: a safe loop at manageable handling speeds is the aim as fighter aircraft accelerate quickly and often lose speed very quickly when ‘g’ is pulled at lowish speeds. Thus a low level display Hunter loop is very unlikely ever to be a true round circle. The aircraft aerodynamic capability must come first. As long as the Hunter goes up to a defined ‘gate height and speed’ to ensure a safe downward flight path, the observation that the aircraft is indeed slowish, or flying level upside down for a few seconds at the top to gain speed is not of great note to Joe Public the viewer. The Hunter solo display pilot would use a high power setting and maintain this high power all the way round the loop pulling more or sometimes less ‘g’ as required to control the speed. A target speed plan might be around 350 - 380 kts at the start and at the finish with a desired 180 kts at the top of the loop. Two footnotes: Digressing to the Lightning, low level solo display loops were flown all the way round in max reheat, pulling more or sometimes less ‘g’ to control speed and shape. Safe aerodynamic control and a modicum of airfield positioning came way ahead of the impossible desire of achieving a truly round loop. Back to the Hawker Hunter: Flying 16 or 22 Hunters in a formation loop at the Farnborough Air Show was altogether a more demanding and daunting prospect for the Leader – and those who followed him. |
Suggest you read article by Jon Whaley who really does know his stuff Moreover, rather than slinging out random insults, if you read the thread in detail you will quickly find that as regards the actual accident, most "good" contributors have followed exactly the same stance as JW - discussion good; speculation bad. Of course there are the misguided, judgmental etc...it's the internet FFS. Most of the disagreement on the thread relates to air displays and their conduct in general. This tragedy is only an element in that discourse and for many of us who have been around aviation a long time, it was an inevitable accident waiting to happen. Frankly the outcome of any AAIB report will have very little bearing on many peoples opinions of air displays, whichever side of the debate they sit on. I think the larger air display debate on this particular thread is... healthy timely not speculative largely well informed mostly professional welcome There are other "troll-infested" threads around pprune running about this accident and the air display consequences, which are far from the above. If you just want to slag people off, you could pop on to one of them and have a dig. |
Hunter pilots often use "1 notch" of flap for maneuvering
...... it's not uncommon for a Hunter pilot to use "1 notch" of flap for maneuvering.....
http://www.radfanhunters.co.uk/Opera...op_1960_PM.jpg |
Aerobatics with tanks on too
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As shown in post #403 :oh:
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and bigger engine.....
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JFZ90
Makes him/her sound like a right ****, with some kind of premeditated bias. |
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