Some more thoughts on looping the Hawker Hunter
My copy of Pilot’s Notes HUNTER T.7 A.P. 4347G–P.N. August 1958 states on page 88.
(b) Loop 425 knots
It is recommended that until experience is gained, loops are started in the height band 10,000ft to 15,000 ft.
Rumours & News pprune post #55 .... pilot states
Having been around Hunters for a large part of my aviation career I can say it's not uncommon for a Hunter pilot to use "1 notch" of flap for maneuvering.
On these pages we are talking about an experienced display pilot starting a solo loop not at a PN recommended 10,000’, but in denser air at around 500’ agl.
My guess is that he would start the pull up at about 350 - 380 kts using full power and one notch of flap. Full power would be maintained all the way round the loop with the pilot smoothly pulling more or less ‘g’ so as to achieve the desired speeds at each point in the loop. Thus if the Hunter is slow at the top of the loop, stick pressure would be briefly slackened to enable the Hunter to accelerate to say 200kts or more and get some ‘g’ bite on the air before starting on the downward path, with a gradual increase in ‘g’ being applied with increasing speed.
A truly circular loop is never the aim: a safe loop at manageable handling speeds is the aim as fighter aircraft accelerate quickly and often lose speed very quickly when ‘g’ is pulled at lowish speeds. Thus a low level display Hunter loop is very unlikely ever to be a true round circle.
The aircraft aerodynamic capability must come first. As long as the Hunter goes up to a defined ‘gate height and speed’ to ensure a safe downward flight path, the observation that the aircraft is indeed slowish, or flying level upside down for a few seconds at the top to gain speed is not of great note to Joe Public the viewer.
The Hunter solo display pilot would use a high power setting and maintain this high power all the way round the loop pulling more or sometimes less ‘g’ as required to control the speed. A target speed plan might be around 350 - 380 kts at the start and at the finish with a desired 180 kts at the top of the loop.
Two footnotes:
Digressing to the Lightning, low level solo display loops were flown all the way round in max reheat, pulling more or sometimes less ‘g’ to control speed and shape. Safe aerodynamic control and a modicum of airfield positioning came way ahead of the impossible desire of achieving a truly round loop.
Back to the Hawker Hunter: Flying 16 or 22 Hunters in a formation loop at the Farnborough Air Show was altogether a more demanding and daunting prospect for the Leader – and those who followed him.