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.

Not sure, but I seem to remember from Vampire days that the consideration may have been because of a concern for nosewheel shimmy. I can remember getting that (on landing) and seeing lots of instrument panels - not nice!

Early Comet accident.

Also a related Sabre accident.

Centaurus: I agree with your recollection of the Vampire, though I can only speak for the T11, never flew the single seat version.
I think in the case of that aircraft rotorfossil has got the answer, it was prone to a nasty nosewheel shimmy.

The Venom was the same, single and twin seat N/F version, though being more powerful did not have that sinking feeling after takeoff.

However, IIRC, that was standard procedure for all those early aircraft, it certainly was with the five marks of Meteor I flew and that aircraft did not suffer shimmy.

Why this should be, apart from the shimmy problem, I never thought to ask.
Slush on takeoff is a possibility but an outside chance I feel, because I don't think we flew in those conditions often enough for there to be a standard year long procedure.
I cannot recall any accidents of the too nosehigh on takeoff variety.

Is it possible that there was also a consideration for operating off grass airfields with the early jets (fighters, not the Comet), so wishing to reduce the loading on the nosewheel?

As I recall the Trident used to do a skim take of on partially contaminated runways.

I think it was to prevent slush being thrown up by the nosewheel onto the airframe, but it was a long time ago.

Heaven knows what would have happened if an engine had failed with full thrust on the others and no steering, with the main wheels in the slush.

Happy Days!

I seem to remember that nose wheel shimmy was a concern in the Vampire FB9 we used in our advanced training.

The Jet Provost 1 take off technique was to raise the nose wheel at 60kts and the aircraft would unstick at 75 to 80 kts. Care had to be taken to avoid striking the rear fuselage on the round.

On a similar vein. It was normal practice on British jet types (sorry about vague generalisation) that the stick was held hard back on the landing run in order to create drag from the angle of attack of the wings. The nose wheel would then be lowered before the stick ran out of authority. The idea being to avoid using wheel brakes at high speeds. The question being, was this technique really effective or was it a case of every little bit of drag helps?

That's how I'll land any light aircraft, given plenty of runway, and the brakes & tires coming from my own wallet.

But to your point--before modern technology brakes, the aerodynamic braking from aft stick certainly reduces the total energy the brakes must absorb. The risk? The departure end of the tarmac may jump up & bite you...

In the Vampire/Meteor era of which we speak don´t forget that it was quite easy to burst a tyre braking at high speeds when still light on the wheels. Anti skid systems came later. Therefore it was good `airmanship´to use aerodynamic braking to kill the speed initially. This all changed with the Hunter when operated from 1600 to 2000 yard runways and with the benefit of early Maxaret anti-skid systems.

Similar technique iirc on Mks 3, 4 and 5. But wasn't Mk1 a tail-dragger? - could have sworn I saw a picture once, but I can't google anything.

Regards,
rts

Maybe you saw a photo of the JP prototype, which I believe was a tail-dragger, based on the piston provost. The JP Mk1s that first entered RAF service had tricycle undercarriage.

The Hunter F4 had no brake parachute. The landing was achieved by flying the aircraft gently on to the ground at 5 - 10 kts less than threshold speed (130 - 135 kts). PNs state "The nosewheel can be held off at speeds down to about 70kts, but the shortest run is achieved by putting the nosewheel firmly on the runway and applying the brakes."

So how did pilots judge (during take off) how far to get the nosewheel clear of the ground and to avoid over rotation? You could not use the ADI angles as the instrument was too small. Was it done on experience - or did the nose wheel stop rumbling if indeed it rumbled.

Raising the nosewheel on takeoff
 

Centaurus - Before solo on single seat Vampires, we were shown the correct attitude by sitting some guys on the tailboom, and then the attitude that would scrape the tail.
Other aircraft; noting the horizon attitude that the nosewheel stopped rumbling.
All JP's had nosewheel u/c, but the JP 1's had longer u/c legs as I think they used Piston Provost legs initially.

I have memories (from a book, of course!) of the Vulcan MK1 nose leg being lengthened so that unstick incidence could be more safely achieved. That made the leg too long for the U/C bay so the oleo shortened as part of the retraction cycle.

Lifting nosewheel on takeoff
 

That method is still widely used by eastern european crews on large commercial turboprop types (An26, An12, Il18 and the like).

If you have plenty of runway, definitely the best way to takeoff if you are way over the approved MTOW... when published V1, VR and V2 don't mean a thing anymore! :uhoh: Just watch max tyre speed...

TTF