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Hawker Hunter Crash at Shoreham Airshow

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Hawker Hunter Crash at Shoreham Airshow

Old 8th Feb 2016, 20:49
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FL - bang on.

AP, you'll never read/see it - because that's not what the mainstream media wants. I ran Today's Pilot for 10 years, and despite several invitations the only time I ever went on TV was to do a kids show (don't ask!) For a few years after the magazine was launched the BBC/ITN/Daily Mail etc etc would ring whenever there was a GA prang. Eventually, my secretary got so tired of me telling her to tell them "he says he wasn't there and doesn't have enough information to comment" that she stopped telling me they'd phoned, and just said "he wasn't there."

PN - there's a lot of variables that decide the size and location of the correction/apology. I did my best not to screw up in the first place, but when the ball was dropped (even if it wasn't strictly my fault) I always put my hand up. As Editor, the buck stopped with me.
People who know just a little but insist on pontificating on the radio or TV (mostly for their own self-aggrandisment) really annoy me. And I've always been very wary of self-professed experts - we all know that an ex is a has-been, and a spurt is a drip under pressure!

Finally, BPF - have you ever considered a career with the AAIB or NTSB?
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Old 8th Feb 2016, 20:54
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Clivewatson,

The maths in your link is sound but there are some assumptions. The pull up and pull down equations assume constant speed. They assume that the maximum coefficient of lift vs angle of attack relationship is constant at all speeds (which invariably it is not). They ignore the radial component of thrust.

In order to calculate radius the airspeed would need to be known (and often it changes quite extensively around a loop) as would the load factor, n, which also changes during the manoeuvre and, if thrust effects were to be taken into account, the engine thrust and AoA.

I hate to say it but if a mathematical calculation of the radius of a loop was easy to do, it would have been done a long time ago on this thread!
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Old 8th Feb 2016, 20:58
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...but only by a test pilot or a QWI. And a QWI would assume that a QFI would probably prefer to do that sort of thing. And the test pilot would be too busy flying a jet he'd never seen before. So it never gets done.
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Old 8th Feb 2016, 21:00
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If I may add one thought on how to deal with questions about an accident .....

A friend of mine had a nose gear stick up in a very high profile aircraft type. He landed successfully, lowered the nose gently onto the runway and slid to a halt in a bow wave of sparks. He made a successful emergency egress to be met immediately by a star rank senior officer who had rushed to the aircraft. "What happened?" said the VSO. My friend replied "I don't know - I've only just got here!".

I am still waiting for the opportunity to use it!
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Old 8th Feb 2016, 21:07
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Like it!

A QFI, a Test Pilot and a QWI go into a bar and order a round of drinks.

QFI says, "I've prepared a brief on the back of this beer mat to decide who pays."

TP says, "Who cares, someone will pay. Let's just drink the beer."

QWI say, "OK."
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Old 8th Feb 2016, 21:15
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Lomcevak - genius! Pure, unadulterated genius.
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Old 8th Feb 2016, 21:21
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Agreed. Superb!
I wish I could think as quickly as that.



D SQDRN

FL

I see irony in an establishment legal figure asking people to moderate behaviour which is not prohibited.

(1) I don't.

(2) I don't think of myself as "an establishment legal figure" although I can understand why others might regard me as such.

(3) I post as a PPL/aviation enthusiast who also happens to be a lawyer with decades of experience dealing with aviation fatal accident cases, both civil and military.

.

Last edited by Flying Lawyer; 8th Feb 2016 at 21:34.
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Old 8th Feb 2016, 21:29
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As recounted by a German TP (and one time 'Космонавт'):

"We sell an aeroplane to Germany, Britain and France, with all its paperwork. Each country decides that it wants to do something special with the aeroplane...."

"Ach, we cannot find the requirements in the manual's procedures section, so we cannot do this - it is not permitted!", said the Germans.

"Hmm, can't actually find anything in the limitations prohibiting it, so we'll just get on with it!", said the Brits.

And what about the French?

"Pardon - mais, qu'est que c'est un 'Manual'?"
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Old 8th Feb 2016, 21:30
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D Sqdn....

FL is a straight talking forum member, who only posts about things he understand and gives us a valuable insight into the legal aspects of matters we wouldn't normally get. Probably little or no virtue in challenging him on what he says or his motives.

BEagle,

French pilots to a tee. Shame they can't carry that refreshing approach over into their domestic politics. But I still love them.
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Old 8th Feb 2016, 22:29
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This thread appears to have been reinvigorated somewhat since the news that the 'JP incident' at the Southport Display is also being looked into as part of the ongoing inquiry. A fair mixture of views have appeared with the usual (for PPRuNe) spread of overly aggressive posts from some. The dynamics of the display sequence have never been too far away.

Turning to the 1/4 clover/loop debate; I have to opine that it was neither in its pure form, but rather (as the AAIB stated) a rolling and pitching manoeuvre. A pure 1/4 C with a 90 roll once in the upwards-vertical is followed by 3/4 of a loop and does require a lot of height at the apex. Now albeit a little lighter, the similar power/weight ratio of the Hawk flown at GH altitudes needs about 4000ft to complete a loop from a level 300kts entry, reducing to about 160kts over the top. In the thicker air lower down when display flying I dare say an 'aggressive' loop could be completed in 3-3500ft, but certainly not 2600ft that the Hunter is alleged to have peaked at. Even the JP/Tucano used about 2000ft of sky.

The change of axis required after the Hunter's initial flypast and Derry Turn at Shoreham could equally have been achieved with a variety of profiles; a 1/4 clover; a skewed loop (a touch of roll input during the manoeuvre resulting in a noticeable heading change); a modified barrel roll where the pitch rate somewhat leads or lags the roll rate again resulting in the aircraft exiting on a noticeable different heading to that upon entry; another Derry Turn / Canadian break. I'm sure most of us in the military have at some stage flown these 'skewed' loops or barrel rolls quite unintentionally - I know I have. (I can still hear the Wonderful Bill Brewer sat next to me to this day!)

Now, any manoeuvre terminating in a significant looping element (like the 1/4C) needs the corresponding amount of vertical space for successful completion, but a modified barrel roll could produce the required change of heading needed with a lot less of a vertical displacement. The required gate heights (ignoring IAS) could probably be between 3600ft for the 'loop' down to as low as say 1500ft for the 'barrel roll'.

I don't know what Andy was attempting on the day, but it appears from the video that the Hunter, once inverted, was effectively trying to complete the last half of a loop with very little if any change of axis, hence roll. He may well have achieved the planned gate height if he was planning on being at the apex of the manoeuvre off-axis and hence pitching and rolling (i.e. barrelling) out onto the A axis where much less altitude is needed. However, whether he momentarily lost his SA (dazzling sun, A27 v rwy 02/20) or he simply misjudged it, he was left with insufficient height to complete the half-loop manoeuvre with such tragic consequences.

I'm afraid you may well need to get your hands out to 'fly' the profiles elaborated on above, and as a QFI I have little doubt the QWI(s) will already have left the bar and gone to bed or fallen asleep in the corner!!!
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Old 8th Feb 2016, 23:08
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H Peacock,

Great to see a factual post here for a change and well explained (even if only using one colour!). You're right that i had left the bar and was, in fact, dreaming about a particularly tricky off-boresite aiming solution, but was woken by my QWI dog alerting me to your post.

Just one point on the loop height, and you are right to describe the latter stage of the manoeuvre in question as the back side of a loop for practical purposes, although the reference to a (very exaggerated) barrel roll is relevant. I think your estimate of 3500 feet is a bit over the top - if you see what I mean. Let's disregard my memory of both Hawk and Hunter loops for a moment, in the manoeuvre in question the aircraft's velocity vector was very close to horizontal at impact - another few feet and he would have missed the ground. If you truncate a 3500' loop 900' from the bottom, the VV would be (I'm guessing here) minus 30 degrees or more? I don't think it was that much.

I'll check my notes tomorrow for the Hawk loop - I'm pretty sure I don't have that number for the Hunter. My memory says considerably less, but I won't publish an inaccurate guess here lest the vultures grab the wrong number and infer dangerous untruths.

Thanks for your excellent post and the descriptions.

Courtney out.
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Old 9th Feb 2016, 04:58
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Courtney

Don't think I have challenged FL on his motives or substantially on what he has said.
But he most assuredly is an establishment legal figure. (And very well respected too.)
I see irony, he doesn't.

Reality is that the law doesn't deter certain posts. You can argue here on pprune with some people or remind them that their posts go beyond decency but they won't change or moderate their behaviour.

This thread however is about Shoreham, not whether it is right or wrong for people to speculate about the causes of crashes. That has been done to death on other threads.
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Old 9th Feb 2016, 09:02
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H Peacock,

If I may add just one comment to what you have said. You cannot really have a meaningful gate height for a barrel roll because the minimum height required at the apex for safe completion is a function of the pitch attitude used in the second half. Personally, in a barrel roll I always look for being wings level when I reach the inverted straight and level attitude (which will be nose slightly above the horizon) at the top of a barrel roll and height only becomes an issue in maintaining separation from any cloudbase above. I do tend to fly relatively shallow barrel rolls with a low apex height because I always feel that steep nose attitudes in the second half from a high apex height are very uncomfortable!
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Old 9th Feb 2016, 15:22
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I’ve given up trying to calculate the required looping radius – as has been pointed out there are sooo many variables that it is a pointless exercise. Nevertheless a few other things have puzzled me, and not least of them was the appearance that something happened at about the time the aircraft was pointing vertically downwards. Others here noted an apparent reduction in the pitch rate, and when reviewing the clip below it is seems to occur between 20 and 23 seconds in, just when the sun glints off the wings. I had originally thought that the sun may have distracted the pilot, or possibly he was searching for the display line and paused his pitch momentarily while getting his bearings.

Shoreham air crash: Man films Hunter hitting A27 road - BBC News

I guess we will never know for sure, but either way it seems that someone with the pilot’s credentials would have managed both of those distractions.

Moving on though I looked back at some previous posts that mentioned use of flaps as a “normal” procedure when displaying the Hunter to improve its manoeuvrability. It seems that the consensus here is that the manoeuvre in question was flown throughout with flaps extended, but when I dug up a copy of the Pilots Notes I read that with flaps extended beyond zero and up to 38 degrees the aircraft is limited to 300 kts/M0.9. I doubt that it is “normal” to deliberately exceed the flap limit when displaying (or is it?!), but it seems that the benefit of flap for manoeuvrability comes with a pretty hefty penalty - especially when the Pilot Notes suggest 425 kts as the recommended entry speed for a loop. I assume that those experienced on type could manage a loop with quite a bit less than this, but my first question is whether sub 300 kts realistic? And my second is whether it’s common to be re-configuring during a display to offset the limit – assuming that it is not ignored?

Still on the subject of flaps, I also read a few poster comments on the consequences of over speeding with them extended. Lomcevak noted that the flaps retract as the airflow increases, but the pilot notes suggest that they will not retract completely. Of more interest to me though were additional notes included in Chapter 2, Handling in Flight – Flaps. Here both over-speed scenarios are highlighted, first the case when exceeding the Mach limit of 0.9, (not considered for obvious reasons) and the second details high airspeed consequences, both of which are entirely different limits for entirely different aerodynamic reasons:

“If the IAS limitations for the use of flap are inadvertently exceeded, the flap angle is limited according to the air load to prevent damage, but sufficient flap will be extended to create a strong nose down change of trim. This can result in elevator jack stalling and tail plane actuator clutch slip. In this event not only is longitudinal control lost, but the aircraft cannot be trimmed nose up by either the main or standby systems. In extreme cases the air loads may force the tail plane to move in opposition to the actuator thereby causing an additional nose down change of trim.”


I obviously have no idea what IAS had been achieved while the aircraft was pointing vertically down, but from the inverted at 100kts, with possibly full thrust and not much in the way of pull (at that point anyway) it seems likely that the aircraft would have been gaining speed at a brisk pace, does it not?

I know that a little knowledge is a dangerous thing, so please don’t hesitate to site my comments as an endorsement for the expression if you think I may be barking up the wrong tree!
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Old 9th Feb 2016, 16:16
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Posted previously by LOMCEVAK in response to a similar question:

It is exceeding 0.9M that results in the uncontrollable pitch down; exceeding 300 KIAS when below 0.9M is fully controllable. The limit is always promulgated as M0.9/300kts but the reasons for the M and IAS limits are different. To put this into the context of display flying, please note that M0.9 at ISA, sea level is 595 kts.
Which differs from your quote. Haven't read the pilot's notes but if that's what they say there seems to be a discrepancy.
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Old 9th Feb 2016, 16:43
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If memory serves me, 100kts in the Hunter is centralise and wait. Maybe that is the pause noted on recovering to a vertical dive and completing the manoeuvre.

To keep a fast jet display within the boundary of a small airfield is not possible - so positioning manoeuvres will be over assorted bits of the surroundings.


A bit of flap is 'de rigueur'

That will do. Mustn't speculate.
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Old 9th Feb 2016, 16:44
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Deefer Dog,

There is no discrepancy there. Lomcevac was addressing the pitch down at high, subsonic mach nos. above M0.9 where the pitch down issue starts. 300kts is not an issue for pitch control at low altitudes. The airspeed limit is linked to a note concerning airloads decreasing flap angle above 350kts and nose up trim change.

Looks like youre trying to find something else to argue about. There is no argument to be had.



Out.

Last edited by Courtney Mil; 9th Feb 2016 at 16:59.
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Old 9th Feb 2016, 18:16
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I'm sure LOMCEVAK will explain the facts and without the agressive tone.
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Old 9th Feb 2016, 18:23
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deefer dog's quote of mine from an earlier post was written from memory and I have since re-read the Aircrew Manual, including the section that clivewatson quoted in his post and, yes, I was wrong and have re-learned something. The folk lore was that it was fully controllable if below 0.9M but at high IAS it obviously isn't. However, the Aircrew Manual gives no clue as to the IAS at which this occurs and I have never heard of anyone having this problem other than when exceeding 0.9M.

With respect to the apparent reduction in pitch rate passing the down vertical, this could have been caused by a visual illusion when viewing a loop head on because the eye perceives pitch rate as a function of rate of change in apparent fuselage length, and this is a function of sine pitch attitude and therefore non-linear (I have posted this point on another thread already).

The 425 kt loop entry speed in the Aircrew Manual is way in excess of what is needed for an aircraft in a low level display and was typical of the margin applied for inexperienced pilots in recommended Pilot's Notes speeds from documents of that period. The selective use of flaps during a display is quite usual and the display teams such as the Black Arrows and Patrouille Suisse used flap to generate more drag to give better throttle control over the top of loops. I always respect the 300 KIAS limit for the flap; I cannot comment on what others do.
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Old 9th Feb 2016, 18:59
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LOMCEVAK
The selective use of flaps during a display is quite usual and the display teams such as the Black Arrows and Patrouille Suisse used flap to generate more drag to give better throttle control over the top of loops.
Here is a good example showing the Hunter using flap as LOMCEVAK explained.

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