Raising the nose wheel on take off - early jets
From fading memory, refreshed by reading some old Pilots Notes, I recall that early British designed jets required raising of the nose wheel just clear of the ground at 70-85knots during the take off run. The aircraft were then allowed to fly off the ground when ready. The DH Comet, all marks of Vampire and the Canberra are all examples of this technique. In fact, lifting the nose wheel clear of the ground at the speeds mentioned led to accidents where aircraft assumed a high nose attitude early in the take off run to the detriment of the take off distance. At night especially, the blunt nose of the Comet and Vampire single seater made visual judgement of nose attitude difficult to judge.
Modern jet airliners on the other hand, are not required to lift the nose wheel at low speed and of course as we know, have a specific rotation speed around the main wheels depending on gross weight and flap setting. I am interested why the early nose wheel lifting was a feature of the aircraft mentioned - especially as it is difficult to know exactly how far the nose wheel is off the ground. Perhaps it was because of possible winter slush where nose wheel drag could be fatal to further acceleration and the manufacturer's decided it was best to standardise all take offs in this regard - slush present or not?
The Pilot's Notes of early military types were written with the best knowledge available at the time but the universal technique of raising of the nose wheel at (say) 80 knots clear of the ground points perhaps to a general policy applicable to all jet types of the time. I recall personally from my Vampire days the mushing feeling as the aircraft sort of found itself airborne when it was ready, simply because one held the nose wheel clear of the ground at 70 knots, which set up an angle of attack ready or not, and one clawed into the air. Any wind shear made it a distinctly uncomfortable feeling.
Forgive my waffling on but here is a small extract from my Vampire PN, as an illustration why I have posed the question:
[B][I]Ease the nosewheel off the ground at about 70-75 knots IAS. Care must be taken not too get the nose wheel too high or the tail may touch the ground. The aircraft, which does not unstick cleanly, should be flown off at about 105 knots IAS.