Originally Posted by
RetiredBA/BY
Are you really saying that a jet being flown with 10,000 pounds of thrust, at full throttle, can be duplicated by a near identical aircraft using only its max thrust of 7,500 pounds of thrust. Example : pulling up for a loop at say 350 knots and 4 g.with 10 k of thrust will certainly not produce the same speed and dimensions when using only 7.5 k of thrust.
I have never flown a Hunter but the JP3 and 4 had similar thrust variations, 1750 and 2,500 pounds, simply no comparison, particularly in vertical manoeuvres. I find what you say hard to believe.. Perhaps you could explain and at least satisfy my curiosity.
For low level looping manoeuvres in a Hunter I entered with sufficient speed and used maximum thrust to exceed the gate height by a comfortable margin and to apex at a mid range speed. If I then flew a version with less thrust available I could either pull the same g and have a slightly lower apex height and lower apex airspeed or I could slacken the pull in the second quarter and make the same apex height with another airspeed reduction. Theoretically, I could enter with the higher thrust version at a lower IAS than I did and make a lower apex height and airspeed, and if I attempted the same pull up profile in a lower powered version the apex height and airspeed could be marginal for safety or even fail to make the Gate Height. However, I never entered loops in a Hunter with so little safety margin with respect to pull up airspeed or thrust; perhaps others did. The only exception to this was that for an upward half loop I was prepared to enter 20 KIAS slower in a large engine version than in a small engine one although with that amount of thrust I never really had to unless the cloudbase was marginal such that I needed an absolute minimum apex height.
With respect to pull-up heights, you can pull up for a loop from the flypast minima on your DA and AH was not below this although air display permissions will restrict the area where you can come below the SERA 500 ft minima. Obviously, if you pull up lower you need more speed to make the same apex height and airspeed.
The videos shown in court of other displays and practises by AH did not, as airsound has said, show any of the critical errors that occurred in the Shoreham accident display. However, they did show errors such as inadvertent airbrake out in the upward half of a loop, infringing display lines etc. As BV has said, we all make mistakes so everything needs to be put into context and in the case of this accident that is very complicated, and simple conclusions relating to potential CI on the accident display cannot, in my opinion, be made based upon the other videos.
The errors listed by Steve Jarvis also need to put into context. Some were errors of judgement such as the pull-up point for the manoeuvre, the angle rolled through etc. Again, these are errors that are easy to make in a display depending on the visual cues available to the pilot. Therefore, whilst there most certainly were some totally inexplicable errors made during this manoeuvre, some can be explained as known HF issues associated with display flying.
One aspect that has been commented upon very little is training related to displaying a Hunter. At the time of the accident CAP403 referred to training for 'escape manoeuvres' only as a ground training 'emergency' item. There was no requirement for a pilot to practise them during training for the award of a DA on a specific type or in a specific category, and no requirement to demonstrate proficiency in them as a requirement for the award of a DA. Unless specific training has been given regarding rolling a swept wing jet at low airspeed and then such a manoeuvre practised a pilot almost certainly would lack confidence in flying a rolling escape manoeuvre in a Hunter at 105 KIAS and, therefore, may be reluctant to do so. The AAIB report indicates clearly that a Hunter in the display configuration flown at Shoreham can be rolled safely at 80 KIAS so flying an escape manoeuvre at Shoreham was totally feasible. The report also indicates that it was possible to extend at least 4 seconds past the apex with a maximum instantaneous performance pull and then still perform a safe rolling escape manoeuvre.
With respect to Gate Heights and the requirement to respect them in looping a swept wing aircraft such as the Hunter, another essential aspect of initial display training for someone whose display experience is mainly on light aeroplanes for which a Gate Height protocol is not applicable for simple looping manoeuvres is to really emphasise this additional requirement and not to use established habit patterns from previous types.
Nothing that I have said above is new with respect to this tragic accident. However, I felt that, perhaps, it was worth refreshing upon some aspects.
Rgds
L