AAIB investigation to Hawker Hunter T7 G-BXFI 22 August 2015

[Tay Cough]

Originally Posted by falcon900

Taycough, it is the AAIB who are saying it wasnt his usual rotation speed.

From the comments on this thread by Hunter pilots, the AAIB may be mistaken.

[Onceapilot]

Quote:
Originally Posted by deadheader View Post
At 04 seconds it passes directly between the sun and the camera; the exhaust is highlighted as a result. Just my two penn'orth...
I totally agree, having played with hunters there's no fuel or fluid drain in the lower rear fuselage(aft of the transport joint). There's nothing in that area that would give you a plume, and it doesn't show up on other images.

Regarding the AAIB not reporting on things we think significant, I will paraphrase a qote from a retired AAIB inspector who was presenting at a course I was on. "AAIB reports report the findings and analysis relating to an accident or incident, they do not provide a comprehensive description of every line of enquiry That was considered and dismissed during the course of the investigation". I imagine if they did that this report would be considerably larger.

Great! As it happens , I don't agree with either of you. What I see is a considerable liquid trail from the fuselage that occurs seconds before the accident, is clearly shown in that clip and, is not commented upon by the report. I cannot understand that omission.

[Lemain]

I agree with your interpretation however cameras DO lie (lens aberrations, reflected light etc.) When you slow that image right down in a movie clip editor it looks as though only some kind of vapour or liquid trail could have caused it. As you say, the odd thing is it's not detailed in the report. Since we could never determine that, the next question is "If it is fuel/vapour then where might it have come from?" And the next question is "How might that have affected the performance or the pilot?"

[Tailspin Turtle]

Back to the beginning of the accident maneuver: there was an additional gate besides the speed (very important) and altitude (in my opinion, not so important because one should fly a loop so as to be able to come out of it above the starting altitude; you then finesse the pull out to come down to the height above ground desired at its completion), That third gate is the point at which to begin the bent loop so as to come out on a line parallel to the show line. He may have begun the pull up late since it appears that he wasn't far enough west as he was coming down its back side. If on the run-in, he realized that he was past the point where he should have started up, he may have glanced at the airspeed indicator and decided, as hard as it is to believe, that he was going fast enough to begin the maneuver.

[H Peacock]

To be perfectly honest, I don't really get this 'bent' loop business. If you're after a small change in heading (he was) why not just make a very minor correction going over the top or even 3rd quarter to roll out pointing along the required datum. If you need a bigger change of heading, surely you put the roll in the upward vertical. Any errors in your roll will not make any change to the height that you then peak at, in addition, the fractional pause in your pull-up means you'll easily achieve you're apex gate height/speed. If you roll too early during the 1st quarter you're almost into barrel roll territory but with not enough height to half-loop out of.

[DaveReidUK]

Bending a loop at the apex will result in a different track over the ground compared to bending it (by the same amount) in the vertical.

[Onceapilot]

Quote Lemain:

I agree with your interpretation however cameras DO lie (lens aberrations, reflected light etc.) When you slow that image right down in a movie clip editor it looks as though only some kind of vapour or liquid trail could have caused it. As you say, the odd thing is it's not detailed in the report. Since we could never determine that, the next question is "If it is fuel/vapour then where might it have come from?" And the next question is "How might that have affected the performance or the pilot?"

My real point here is that the report fails to identify this important and unusual evidence.
Here is the link again, the trail is visible at around 04 seconds after the start.

https://www.youtube.com/watch?v=Mr4POEBz81s)

[bront]

What about the possibility of the ASI reading incorrectly i.e. over reading?


The result would be rotation too early and entry to manoeuvre too slow.


Falcon 900 mentioned 'He misses it, interestingly by roughly the same % margin as missed his target rotation speed on takeoff....'

[Lemain]

Originally Posted by Onceapilot

Quote Lemain:



My real point here is that the report fails to identify this important and unusual evidence.
Here is the link again, the trail is visible at around 04 seconds after the start.

Yes, I agree. I loaded the vid into one of my video editors and looked at it frame by frame. It doesn't look like a light aberration to me. However the res isn't as good as one would like. It looks like a condensation trail. An experienced Hunter pilot on this thread said it's unlikely - obviously he has detailed knowledge of the airframe and engine. If a con-trail, what is condensing? Unburnt fuel? Water? Smoke (i.e. a mix of combustion products)?

[Blacksheep]

You want to help maximise the life of components and keep the vehicle running.

If that was what he was trying to do he failed to achieve his aim, big-time. The AAIB investigation was as objective and professional as always and their conclusions are clear and evidence based.

[dynamics]

Given the historic facts and evidence, perhaps the direct way to prevent this particular tragedy happening again is to ban high-speed, low-level split-s/vertical loop maneuvers. The common denominator in all such accidents. I for one would favor this over further type or location restrictions.

In addition to the Thunderbird crash and Typhoon near miss posted above, here are two more unfortunate examples that spring to mind where neither the pilot's experience nor platform's capabilities were in-doubt.

Hawk, 1999
https://www.youtube.com/watch?v=nBF52ai6ivc

Blue Angels, 2016
https://www.youtube.com/watch?v=N4WKX1yVHhQ

Time and time again we witness the lethality of such an unforgiving maneuver. Perhaps we humans need to concede that it's just a little beyond us and that it's just not worth it, anymore...

[sycamore]

OAP/Lemain; cooling air outlet from the conditioner pack as it was a hot day,or further back is an access panel to the rear tank contents switchery...?

[Onceapilot]

Sycamore: I do not know what that trail is but, it seems to have been missed in the report. Strange that the other far less significant "mist" from the wing tank area merited coverage! I suspect that this fuselage trail was overlooked!

[Tailspin Turtle]

Originally Posted by H Peacock

To be perfectly honest, I don't really get this 'bent' loop business. If you're after a small change in heading (he was) why not just make a very minor correction going over the top or even 3rd quarter to roll out pointing along the required datum. If you need a bigger change of heading, surely you put the roll in the upward vertical. Any errors in your roll will not make any change to the height that you then peak at, in addition, the fractional pause in your pull-up means you'll easily achieve you're apex gate height/speed. If you roll too early during the 1st quarter you're almost into barrel roll territory but with not enough height to half-loop out of.

It took me a couple of viewings of the video when it was first available to figure out what the maneuver was and moreover, what its purpose was. One shortcoming is that you roll away from the venue and put it behind you as a reference point for lineup, potentially delaying your increase in pull on the back side momentarily while you looked for it. If I was to bend a loop with a roll, I would prefer to do it on the back side so that the show-line runway was always in sight. However, if a low pass down the show line was to be made coming out of the loop, that would require displacing the initial run-in farther to the east, adding time between the opening pass and the next maneuver. It was also informative to see all the restrictions to altitudes and overflights on the map in the AAIB report, which may have dictated the bent loop as flown.

[RAT 5]

If I was to bend a loop with a roll, I would prefer to do it on the back side so that the show-line runway was always in sight.

Indeed. All aeros I've been trained in, or seen demo'd, the loop is simple and any line correction is made after the apex on the way down. If the climbing loop is combined with rolling it is a proper quarter roll, or more usually a half roll, even full roll to a predetermined datum then pull through. A line adjustment on the climb seems a guess at best.
Many questions, so few answers.

[Chronus]

Another hypothesis for the roll could be that he did realise he was too slow and low and twitched the stick for an escape with a slight roll which bled off more of the precious little energy left, then thought he would have a better chance on the descent. Having got over the top and nosed it into the descent, eye balling the proximity of the ground, realised he had little height to spare and the only way to turn the betting odds in his favour might be by going straight down for the deck.
All that RAT 5 suggests is true, but only so if sufficient height and energy remains in hand. In this case neither were present.
David Learmount has published opinion on his web site. Here is the link:
https://davidlearmount.com/tag/bent-loop/
I tend to agree with him on all his comments. Makes a lot of sense. Especially those about faulty components.

[H Peacock]

In addition to the Thunderbird crash and Typhoon near miss posted above, here are two more unfortunate examples that spring to mind where neither the pilot's experience nor platform's capabilities were in-doubt.

Dynamics, I didn't know GW who was displaying the Hawk 200, but I suspect his lack of relevant experience (LL display flying) was the main cause of the 1999 accident.

[McDuff]

HP, GW was Graham Wardell, a former test pilot (and the first foreigner to fly the F117) who had, we have to assume, had a proper workup in the Hawk for the display. It would have been in BAe's interests to assure the proficiency of its display pilot for an aircraft that it was trying to sell. When I spoke to fellow Flt Ops individuals, there was no hint that Graham was anything other than proficient.

[Hebog]

an anyone tell me what the red flash is on the top of the aircraft is in this clip at 2:28.


https://www.youtube.com/watch?v=JnczDEiFFN4

[LOMCEVAK]

McDuff,

Graham Wardell was the first RAF pilot on an exchange tour on the F-117 but he was not the first foreign/British pilot to fly it (2 had flown it in 1986)

H Peacock,

For a given pitch rate in the upward half of a loop, any roll introduced before the vertical up line will reduce the apex height (just geometry). The correct technique, as you have said, is to reduce the pitch rate whilst rolling (or even to maintain a pure up vertical line) and then the apex height will be the same or greater. However, in the Shoreham accident it appears that maximum instantaneous pitch rate was maintained throughout the upward half, including during the roll. Appendix H of the report covers this.