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!