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

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

Old 7th Mar 2017, 20:06
  #321 (permalink)  
hum
 
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Originally Posted by LOMCEVAK View Post
hum,

re your #272, the accident report which you quote relates to a P-LOC/A-LOC event. These factors and total G-LOC were discounted in the Shoreham report.
The the Red Arrow accident investigators had the benefit of an ADR; faced with inappropriate & abnormal control inputs leading to a tragic crash they concluded after careful analysis that transient cognitive impairment was a possible cause.

The shoreham investigators had go-pro camera footage showing the back of the pilot's helmet. Faced with a remarkably similar pattern of inappropriate and abnormal control inputs leading to an even greater tragedy they concluded that the pilot "appeared alert and active throughout the flight" ... Remarkable...
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Old 7th Mar 2017, 20:09
  #322 (permalink)  
 
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Originally Posted by bvcu View Post
Read that Lemain , quite scary as couldn't imagine signing that out as airworthy as it should have a duplicate inspection {independent} but that would cost two licenced engineers . So if done correctly shouldn't have been a serial number error . I'm guessing that a static leak at that altitude would have some effect but not as much as at altitude .
As the pilot had flown a few hundred miles shortly before probably fairly low level (VMC/VFR) on a fine day enjoying the flight, thinking of his display routine he might not have noticed any small deviations. I can think of 3 plausible scenarios:

1. Small leak in static line from the pitot-static tube(s) maybe in the wing section

2. Someone bashed the pitot-static head, while on the ground and didn't fess-up (Happened to me once and I nipped to ironmonger to buy Araldite Rapid so I could fly, I had a Special Cat CofA). It was a licensed engineer who bashed it for certain, and he'd buggered off for the weekend. It happens.

3. Something odd about that second servo-altimeter which must presumably share the same (one and only) static? Might there have been a connection problem between the two Alts?

Suppose there was a slow leak from the static in the port wing section. Might there be a venturi effect that decreased the static pressure line or, on the contrary, a positive pressure in the wing section that increased the static? If that was the case - and the Report states that the investigators could not determine that connection due to accident damage, then the venturi or increased pressure would, I imagine, be dependent on true airspeed and angle of attack of that wing section. It might result in some very odd indications on both of the altimeters and the ASIs. I realise there is the GoPro evidence but when I read that through for the third time it sounded a bit like water divining. Either you can read the instruments or you can't. They couldn't and they made assumptions.

The pilot was a senior captain with huge experience and respected by everyone in the industry. Obviously he can't remember - retrograde amnesia which I once had after a car crash. So I can relate to this pilot's situation. This pilot is not likely to have flown a display if he felt out of sorts. Yet they imply this highly respected pilot failed to enter his manoeuvre at the appropriate speed and altitude. Feels suspicious to me.
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Old 7th Mar 2017, 20:32
  #323 (permalink)  
 
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Static leak at that altitude not really an issue , would only have a small effect , no venturi action on a static , some light a/c have a static source in the cabin for unpressurised types. Cant disagree with the logic of the findings on this system in the report with the information given . Would be of the opinion that a guy of this experience and multiple types and display flying of lighter slower types would be aware of any major altimeter errors visually , so although a posibility don't think its relevant.
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Old 7th Mar 2017, 20:39
  #324 (permalink)  
 
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Originally Posted by Lemain View Post
Yet they imply this highly respected pilot failed to enter his manoeuvre at the appropriate speed and altitude.
... or in the right place.

Feels suspicious to me.
Yep, but the static system doesn't affect the pull up location and that was also out by a margin, although few people seem to have noticed.

Last edited by Tay Cough; 7th Mar 2017 at 20:51.
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Old 7th Mar 2017, 21:11
  #325 (permalink)  
 
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Whatever happened to the engine on the entry and/or the way up to the top of the loop is a red herring. Whether you have 6700/7000/7200 on the WAY UP is irrelevant. When you fail to make your gate at the apex, you are either going to die or you initiate Plan B and convert to a Half Cuban. As a current operator (sic) you will know how to deal with these events. That's why you've been chosen to display (from a cast of ....). We used to practice 1 in 1's on the Hunter and were examined on them. Did AH ever do one single PFL in a Hunter?? Not his fault - the CAA allowed him to think he was infallible. He wasn't. End of.
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Old 7th Mar 2017, 21:12
  #326 (permalink)  
 
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bvcu
"JPT and engine RPM do not correspond to thrust on 100 series Avon . It does if no faults."
Make your mind up mate. Engine with open bleed valve problem runs higher JPT. Whatever, I am not here to armchair the issue.
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Old 7th Mar 2017, 21:48
  #327 (permalink)  
 
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Originally Posted by bvcu View Post
Static leak at that altitude not really an issue , would only have a small effect , no venturi action on a static , some light a/c have a static source in the cabin for unpressurised types. Cant disagree with the logic of the findings on this system in the report with the information given . Would be of the opinion that a guy of this experience and multiple types and display flying of lighter slower types would be aware of any major altimeter errors visually , so although a possibility don't think its relevant.
I'm not explaining myself as well as I should and re-reading my posts I see that I could have explained myself better.

Consider an aerofoil section of wing. This wing is not hermetically-sealed so the pressure within the wing section will be the sum of the static and dynamic pressures. The dynamic pressure will be dependant on the ram-effect of air entering the leading edge and the venturi effect from the trailing edge.

As an imaginary thought experiment, imagine putting a meteorological barograph into the wing section during flight. Imagine how the needle would fluctuate according to not just altitude but also to true airspeed and angle of attack. Control surfaces might also have an effect albeit this is a fairly simple wing section, the movement of flap and aileron will affect our hypothetical barograph.

The dynamics of this will be in some 1950s yellowing file somewhere, not in an ops manual. Nobody cares or cared, other than the aeronautical engineers who designed the wing section.

Let us now consider the pitot-static head. I suppose it is the traditional two-tube type? On the leading edge of the pitot head there is an orifice. On the trailing edge of the pitot head there is another hole shaped to reduce venturi? I think that's the arrangement on this a/c. The head itself is presumably heatable by electricity? On that day at those altitudes the pitot heating is unlikely to be an issue. So leave the idea of 'freezing' because it seems so unlikely.

From the pitot-static head we have two tubes. One is connected to the forward facing pitot-static head assembly orifice and the other is connected to an orifice on the same assembly in a place where the dynamic pressure expected to be negligible -- i.e. the static vent.

Suppose one of those tubes had a leak. The report states that there had been no recent leak-test. As you said, an a/c being flown aerobatically would be leak-checked regularly if not before every flight. This a/c had not been checked. Furthermore, there is, from the report, a question about the maintenance of one of the components in that system (Alt2 with the wrong serial No.)

In a fast jet being flown aerobatically for performance dynamics might be significant.

These two tubes were so badly damaged in the crash the investigators could not determine whether they had been intact at the time of the final flight of this a/c. This is stated in the report. All they could do was to bench-test the visual display indicators (the instruments). Obviously if the instruments did not get accurate input then they would not have shown an accurate indication. The pilot depends on the indication to fly the a/c.

This possibility does not seem to have been addressed by the AAIB.
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Old 7th Mar 2017, 21:57
  #328 (permalink)  
 
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hum,

Unless you have seen the GoPro recording from the Shoreham accident you cannot know what can be deduced from it about the pilot's awareness state. Also, the data presented in the Shoreham report indicates that a maximum instantaneous pitch rate was maintained throughout the downward half of the accident manoeuvre in order to achieve the altitude loss that occurred. This would not be consistent with any A-OLC/P-LOC immpairment.
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Old 7th Mar 2017, 23:09
  #329 (permalink)  
 
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Lemain

The pilot flew from North Weald to Shoreham and maintained his assigned course and altitude without any significant deviation as recorded by ground radar.

Calculations generated from ground footage of the display and cockpit video footage where the airspeed was visible are in close agreement.

The pipework connecting the instruments to the pitot tube was too damaged in the crash to be able to test it, but even after the crash, the somewhat damaged instruments still performed almost to specification.

Every indication is that the instruments were working correctly and any errors displayed, such as the left hand altimeter lagging and under reading slightly, would act as a cue to the pilot to fly higher and faster, if anything.

You are grasping at straws pursuing this as a possible reason for the accident.

What may be of relevance and something that was glossed over in the report is that a GPS device was fitted in the cockpit. Is it possible that this was being used as a quick source of positional reference by the pilot rather than doing a proper cockpit scan? Now that would make sense if the GPS was being used to assess ground speed. The difference between miles per hour and knots would account for the low entry speed into the bent loop manoeuvre. I believe the GPS display was mounted higher on the instrument panel and would have been more immediately visible glancing back and forth between outside and inside the cockpit. Shouldn't be used as a reference, we all know that from the sorry tales of pilots attempting unapproved GPS letdowns in bad weather, but the temptation is there.

I believe that this is a far more likely scenario than faulty airspeed and altitude indicators with a pitot problem, when every test that could be conducted suggests that they were working normally.
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Old 7th Mar 2017, 23:16
  #330 (permalink)  
 
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Originally Posted by G0ULI View Post
You are grasping at straws pursuing this as a possible reason for the accident.
Or, to put it another way, Occam's Razor applies just as much here as it does in any other circumstances.
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Old 7th Mar 2017, 23:18
  #331 (permalink)  
 
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Something about forest and seeing trees comes to mind....

* Incorrect speed
* Incorrect altitude
* Lack of recognition
* Lack of recovery

That's about it.
Really.
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Old 7th Mar 2017, 23:28
  #332 (permalink)  
 
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G0ULI --
You are grasping at straws pursuing this as a possible reason for the accident.
My dad, who flew right through the fifties and sixties, said the conclusion of every AAIB was written before the inspectors arrived. Pilot error. So when everyone gangs up against a highly experienced and respected pilot I like to consider the alternatives.

I've contributed all I can to the discussion here but will follow the case with interest and concern.
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Old 7th Mar 2017, 23:46
  #333 (permalink)  
 
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Lemain

I appreciate the sentiment. That said, just because you are highly experienced and respected doesn't mean you aren't capable of making a mistake.

One hopes that modern accident investigators have learned from the lessons of the past and don't approach an investigation with a conclusion in mind. In this case, the sheer volume of the report and the assistance sought from independent sources suggests that no stone has been left unturned in the search for a mechanical cause.

That just leaves human factors as a possibility and no doubt there will be much debate in the future about physiological, psychological and hidden medical conditions that can contribute to a complete disconnect between a person's perception and the reality of an emergency as it unfolds.
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Old 8th Mar 2017, 07:51
  #334 (permalink)  
 
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One of the most highly respected Display Pilots killed himself in what should have been a simple slow/barrel roll, HP. P.38, Duxford.
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Old 8th Mar 2017, 07:52
  #335 (permalink)  
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Originally Posted by Tay Cough View Post
... or in the right place.



Yep, but the static system doesn't affect the pull up location and that was also out by a margin, although few people seem to have noticed.
I agree, he seems to have been a little "lost" with his ground references while entering this pull up. Which could have resulted in a big distraction.


Not a fact, just an impression I have.
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Old 8th Mar 2017, 08:13
  #336 (permalink)  
 
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To display pilots: if you are not so current, and perhaps there has been quite a break since your last rock & roll, if you have the opportunity at your departure airfield would you fly a couple of manoeuvres to check the a/c and yourself: get you and your beast 'in the mood'? If so, then perhaps any malfunctions might be apparent. Is it worth it?
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Old 8th Mar 2017, 08:18
  #337 (permalink)  
 
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Rat 5, I'd imagine with early fast jets, if you also have a significant transit, endurance might be an issue.
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Old 8th Mar 2017, 08:32
  #338 (permalink)  
 
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Something that hasn't had much coverage is just how close he came to flying away. Extrapolating the flightpath and perusing the data from the AAIB test flights suggests the margin by which it impacted the ground was about the same as the margin by which the Typhoon at RIAT missed it. 50ft at the apex and the outcome would likely have been very different, in either case.

If he'd flown away, we could have learned everything we've learned from this, and probably much more, without any of the tragic consequences. It does beg the question of why we didn't seemingly learn it from the Typhoon incident.
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Old 8th Mar 2017, 09:25
  #339 (permalink)  
 
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Originally Posted by G0ULI View Post
Lemain

I appreciate the sentiment. That said, just because you are highly experienced and respected doesn't mean you aren't capable of making a mistake.

One hopes that modern accident investigators have learned ..... from independent sources suggests that no stone has been left unturned in the search for a mechanical cause.

That just leaves human factors as a possibility and no doubt there will be much debate in the future about physiological, psychological and hidden medical conditions that can contribute to a complete disconnect between a person's perception and the reality of an emergency as it unfolds.
Hi G0ULI, That's what's troubling me. This isn't one "mistake". It's a significant spatial disorientation. The pilot becoming unwell is one plausible explanation. The report doesn't produce any evidence to support that but neither does it produce any evidence against. We all get thrown when instruments play up. Then we mistrust the dials. Very disorienting.

Hi Sillert, they have JetA1 at Shoreham. It's quite a decent little airport. They've also got a live webcam at Live Webcam of the Runway | Brighton City Airport, Shoreham I'm watching the pigeons lining-up for T/O right now.
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Old 8th Mar 2017, 09:35
  #340 (permalink)  
 
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I know nothing about aerobatic display flying: Do such pilots have to pass 6 monthly aerobatic flying exams in the SIM and/or the real aircraft? We, (normal airline pilots), do, though not aerobatics !

Secondly, just because someone is highly respected and very experienced, does not mean that they somehow magically retain their fine flying skills for ever, i.e, reaction times, hand-eye coordination and SA during unusual attitudes. At some point in our lives, our brain power starts to diminish.

I would hope that display aerobatic pilots are very rigorously checked indeed - including medically, for example proper eyesight examinations and their 'g' resiliance.
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