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Hawker Hunter down at Shoreham

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Hawker Hunter down at Shoreham

Old 18th Dec 2015, 17:53
  #701 (permalink)  
 
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Pilot interviewed by Police

BBC internet report this afternoon:

The pilot of the Hawker Hunter jet which crashed onto the A27 in Sussex killing 11 people, has been interviewed by police for the first time.
Officers spoke to 51-year-old Andy Hill at a police station in Hertfordshire.
Police, who did not name Mr Hill, said a man voluntarily attended an appointment and was "interviewed under caution but not arrested".


Shoreham crash: Pilot Andy Hill interviewed by police - BBC News
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Old 21st Dec 2015, 14:32
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Shoreham air crash report finds jet 'had expired parts' - BBC News

https://www.gov.uk/government/news/a...-g-bxfi-update
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Old 21st Dec 2015, 20:18
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.............

Last edited by Radix; 18th Mar 2016 at 02:20.
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Old 22nd Dec 2015, 08:44
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I think the AAIB did very well in publishing the initial report only 13 days after the accident.
That report included the radar track, peak altitude (per radar at 2600ft) and an entry height of 200ft. It also assumed from cockpit camera video that the maximum inverted speed at the apex was 100 kt and that the controls appeared to be responding the pilot's inputs.

Three cheers for the AAIB for divulging that much info so quickly!

We read from the press that the pilot has eventually been interviewed under caution (which means the police suspect that an offence may have been committed). We also read that the AAIB is still waiting to interview the pilot. Without that key input, the AAIB simply cannot speed things up, so patient we must be.

The latest report, however, concerns me as it already smacks of the big hand of over-regulation ... and it has little if anything to do with the actual cause of this accident, but that is another topic...
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Old 22nd Dec 2015, 10:14
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smacks of the big hand of over-regulation
You would expect them to do an audit of the paperwork, and that's what they've done. They appear to be suggesting that it's worth having a look to see whether some of the bureaucratic systems in place are fit for purpose, and that seems reasonable too - what use is a system which nobody can understand and/or which nobody can obey?
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Old 22nd Dec 2015, 20:11
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What gives here?? Yesterday the AAIB publish this.

In a formal representation to the AAIB, in relation to this Special Bulletin, the CAA reported that it was unclear whether a legally valid AMOC to MPD 2001-001 was in place for G-BXFI at the time of the accident. On this basis it could not determine if the aircraft met the requirements of its Permit to Fly from December 2014 onwards. The CAA indicated that it was trying to clarify the postion.

Then we get this response from the CAA today...

https://www.caa.co.uk/News/CAA-statement-on-AAIB-special-bulletin/

In relation to the validity of the alternative means of compliance (AMOC) for ongoing maintenance of the aircraft, we have already informed the AAIB that this was in place and was valid at the time of the accident.

Work under the alternative means of compliance was carried out in January 2014 with the next inspection due in January 2016 making the organisation and the aircraft compliant with the Mandatory Permit Directive.

Do these guys have each other's telephone number??!!!
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Old 23rd Dec 2015, 12:15
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This thread has naturally produced a lot of comments, some of them very good and helpful, but others have shown a limited understanding of low level aerobatics.

To help the general reader or would be pilot think a bit about what is going on when they next go to an airshow, I would like to make some comments (not specific to this accident) which apply to all aerobatic displays not just fast jets.

There are two categories of manoeuvres, those that include the possibility of something called a ‘gate’ and those that do not.

A ‘gate’ in this context is a point in the manoeuvre where it is possible to positively determine that all is well to continue and complete a downward manoeuvre without hitting the ground.

A nice easy example of such a ‘gate’ are the conditions that exist where an aircraft is upside down at the top of a loop and before the pilot carries on to flying the second half of the circle by what is called ‘pulling through’. Common sense says a minimum height will be required at the top of the loop and this will vary with the aircraft type. However the speed at this point also matters because too little and the aircraft will produce less lift on the way down, thus increasing the radius of the pull through. Perhaps surprisingly too much speed can also increase the radius of the pull through because of the extra centrifugal force involved at the higher speed. Thus the gate a pilot will look for at the top of the loop is a minimum of H feet in height and a speed between X and Y knots in the event he is outside one of these parameters then he must abandon the manoeuvre by rolling erect and carrying on as appropriate afterwards.

So a safe loop or pull through is easy eh? Well yes and no. There are many possible reasons why an aircraft is outside the gate but the pilot does not realise it. It could be he plain forgot to check, it could be the altimeter setting was wrong (remember the Thunderbirds F-16?), it could be he was distracted by some R/T that was going on at the time, or a number of other possibilities.

Please note that one thing that does not determine the safety of a loop is the height at which you start it. You could be an inch above the ground when you pull up but providing you fly up to your minimum height at the top, with your speed in the bracket, it just does not matter.

Now for the other category of manoeuvres – those that can have no gate. For me these are inherently trickier than those with a gate. Take the simple wingover as an example. This is initiated by pulling up into a climb, then pulling round in a tight turn to face the opposite direction to the original climb. This turn is overbanked so that the nose goes down during the turn and the aircraft is in a dive when rolling out on the reciprocal direction to the original pull-up. Hardly an aerobatic manoeuvre some might say – just a bit of overbanking. So easy and safe despite no gate at the top? My answer is again yes and no. Done a bit more enthusiastically (because one wants to put on a good show) the pull-up can be a bit steeper, the turn a bit harder, the overbanking a bit more and the next thing you know you are facing steeply downhill at too slow a speed and too low a height to pull out before hitting the ground. Of course the pilot avoids this by using skill, currency and being in practice. The trouble is such factors can vary from display to display unlike the loop case where checking the simple gate conditions does not require the same skill, currency or practice.

Planning, practising and executing an airshow routine involves much more than I have touched on here. Much more. Most of which is outside a simple post such as this and I would not want anybody to think otherwise.
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Old 23rd Dec 2015, 13:12
  #708 (permalink)  
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Thanks John, good advice.

We had a very interesting presentation by John Turner on demonstrating aircraft, at the ITPS flight test pilot's symposium last week, and he discussed these topics well.

As said, there's a lot more to this than can be included in a post here.

In my opinion, one of the many "dividers" of piloting experience would be: Those pilots who have been looking at oncoming ground while upside down and had to make a decision about what to do next, and those who have not.
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Old 23rd Dec 2015, 21:11
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Very good post John, succinct and hard to argue with.

We know that the donut expands with speed, so yes, entry height is technically irrelevant. And in a perfect world, it will all pan out nicely. Yet, being at the lower end of the speed band at the gate means that you have less energy to play with, less margin, and the pull-through may suddenly become less certain.

Your wingover example is good. Coming out facing the opposite direction is a downward vertical manoeuvre and the same laws of physics apply.
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Old 24th Dec 2015, 09:05
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unable to resist the "hard to argue with"
and because chrimbo is coming, I may have been on the juice a little early with my breakfast (bucks fizz goes better with egg and bacon that a pint of Murphy's.....And i am trying something I used to do at school....have a little onion marmalade with my sausages. I recall my father first introduced me to this when we were living at RAF Tengah. )

I wish you all a great x-mas, and a fantastic new year.

"Please note that one thing that does not determine the safety of a loop is the height at which you start it. You could be an inch above the ground when you pull up but providing you fly up to your minimum height at the top, with your speed in the bracket, it just does not matter. "
Agree. But is this good airmanship? Why make life tough for yourself so you have to use those superior piloting skills to get within the gate?
Most pilots familiar with aerobatics will know for types of aircraft on which they are current how much altitude they will gain in performing the first half of a loop and how much speed they will lose for a given power setting. And i would suggest this is what is normally practiced?
and....
"Thus the gate a pilot will look for at the top of the loop is a minimum of H feet in height and a speed between X and Y knots in the event he is outside one of these parameters then he must abandon the manoeuvre by rolling erect and carrying on as appropriate afterwards."
Agree. I would just add that if said pilot notices his speed is too low, and decides to roll erect too soon - ie because his speed is below stalling speed - then a roll off the top below stalling speed will bring a host of other problems.
Please remind me, from the information released so far from the AAIB. What was the speed over the top. Could you have rolled erect from this speed in a Hunter?

Back to the seasons festivities.
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Old 24th Dec 2015, 09:39
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JF,

Very well expressed.

mrangryofwarlingham,

Things are not quite as simple as you imply regarding the interaction between stalling speed, flying an escape manoeuvre and flying a roll-off-the-top as a deliberate aerobatic manoeuvre. The 'stall speed' that most people consider is the speed at which the aeroplane will stall in 1g flight. If at less than 1g the stall speed will be lower and at 0g the stall speed is 0 kts. Also, the ailerons are usually effective at a speed significantly less than the 1g stall speed so that it is possible to roll down to quite a low speed (think about maintaining wings level during a crosswind take-off and landing). In a deliberate roll-off-the-top the pilot attempts to maintain the aircraft level and straight by the co-ordinated use of elevator and rudder, for which an airspeed significantly above the 1g stall will be required. However, if the gate criteria at the top of a loop have not been met the pilot simply selects and holds neutral elevator and rudder and makes a gentle roll input. The nose will drop (with respect to the earth) as a function of true airspeed and the time that it takes to roll such that erect flight will be regained in a dive and altitude will be lost. However, airspeed will then be increasing and a controlled pull out from the dive can be made back to level flight well above the ground. Such a manoeuvre can be flown safely from starting the roll up to a few seconds past the apex so that the pilot does have time to make a decision and react.

Merry Christmas

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Old 24th Dec 2015, 09:57
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Hello LOMCEVAK

Agree that roll off the top requires greater than 1g stall speed plus some for safety margin.
Agree you can fly at below 1g stall speed if you don't need to apply 1g.
My point is this. If the gate is not met, and you are below stall 1g speed, you need to speed up before you attempt 1g.
Otherwise when the "nose will drop" during the roll to the upright- i would call it undemanded yaw - you are in real trouble if not only are you below stall speed but also you missed your gate height.
More sensible to me is to keep going through the gate for a little, apply appropriate UP recovery action.

will this be a record mild and warm winter?
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Old 26th Dec 2015, 14:50
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Do a Hover - it avoids G
 
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mrangryofwarlingham

Thank you for your post 696 re my 693

I was taught that when making a case, or introducing a topic, one should keep it as simple as possible and not stray off the subject. In my view going into the how and when of the roll erect manoeuvre in my post was not relevant to the topic of introducing the two categories of manoeuve.

Turning to the detail of your comments about the roll erect manoeuvre why did you assume that it would be carried out at a low speed? Why did you assume it would be carried out at the apex of the manoeuvre? Why did you assume the low speed of any gate would be slow in relation to the 1g stall speed for the type? In my opinion none of these assumptions is likely to be correct in the real world of display flying with pilots that hold a CAA Display Authorisation.

I disagree your comments about start height for reasons that I won’t go into for fear people will think I am trying to get at you - and I wouldn’t want that.
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Old 27th Dec 2015, 10:52
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Your point re: start height

Please note that one thing that does not determine the safety of a loop is the height at which you start it. You could be an inch above the ground when you pull up but providing you fly up to your minimum height at the top, with your speed in the bracket, it just does not matter.
Is spot on with one other element. You must be flying whatever figure accurately because stick position also has an effect. Which in relation to this accident is relevant not only in the vertical but in the rolling plane.

As you say practice and having a plan is your friend.
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Old 27th Dec 2015, 12:36
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John. You can have a go at me if you wish.
But I don't recall saying much about start height. I did agree it didn't make much difference if you made the gate. I did however question the airmanship of not caring about start height.
Why did I assume role erect would be carried out at slow speed. I didn't. I cautioned against doing so.
Why did I assume it would be carried out at the apex of the manoeuvre. I didn't. Didn't say so either. You should read what I posted.
Why did I assume the low speed of any gate manoevure would be close to the stall speed. I didn't. I don't know where you think I said that.
I did however ask the question of whether the speed close to the top of the manoeuvre performed by the Hunter as published by the AAIB was a speed at which it would be possible to roll erect.
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Old 27th Dec 2015, 14:14
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Do a Hover - it avoids G
 
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mrangryof warlingham

Of course you must be right and I must be wrong.
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Old 31st Dec 2015, 13:51
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The start height, and gate at the top are of course, elements of a successful loop which is intended to be more or less "round". If, however (and I don't know in this case) the planned location for the maneuver was being affected by winds, that upsets everything. Could the otherwise well planned entry and top gate become inappropriate of the whole maneuver were being blown out of position? The pilot, referring to landmarks, rather than invisible references to the position of the maneuver relative to the start point, and gate, attempts to suddenly tighten the loop to maintain position, and in doing so, upsets the otherwise well planned geometry and inertia?

I can say that my many years of aerobatics have been for my satisfaction, rather than a ground audience. So, as long as I was respecting airspace, traffic, and "built up areas", I was otherwise unconcerned about the geographic location of my maneuver. Placing an aerobatic maneuver in a particular geographic location, with the variable of winds, and maybe mechanical turbulence, certainly adds complexity!
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Old 8th Jan 2016, 10:49
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AAIB update 21/12/15

Everyone seems fixated on this being a pilot error. When looking at this report I would query the condition of the aircraft and what has or hasn't been done to it.


I also have a query about the hrs. According to the AAN dated 1997 the airframe had done 5566hrs and the engine had 130 remaining of 450 hrs life. Does this mean in 1997 the engine had done 320 hrs.
The sale advert around 2011 (as it states service due Jan12, seat cartridges due Jan2013) the airframe is on 5931 hrs and the engine 351 hrs.
If this is the case the airframe has done 365 hrs between 1997 and 2011 but the engine has only done 31 hrs.


Are seat cartridges given a unique serial number by the maker, so that they can confirm manufacture date and to which aircraft they were supplied and fitted to. I note that the cartridges were replaced in Nov2012 by North Weald but were due to expire Jun/Jul 2014. so only valid for about 18months not the 2yrs installed due to manufacture date. So where were the cartridges between 2008 and fitment in 2012, could they have been put in another aircraft and already been used. As it would appear cartridges are made to order hence lead time of 52 weeks, I have doubts that these were sitting around unused for 4 yrs!













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Old 9th Jan 2016, 12:35
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Everyone seems fixated on this being a pilot error
Probably because the initial AAIB interim report mentioned the pilot entering the manoeuvre below his DA floor and that the onboard footage suggested no abnormal indications present.

It will be interesting to see how the AAIB deal with the points you raise
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Old 11th Jan 2016, 14:57
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In my opinion, the specific reasons for the crash are the least important questions for AAIB to address.

Much more important questions are about the management of the airshow, approval of the display, location of the display line, and management of spectators on and off the airfield site.

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