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Old 24th Jun 2015, 13:11
  #6341 (permalink)  
John Farley

Do a Hover - it avoids G
 
Join Date: Oct 1999
Location: Chichester West Sussex UK
Age: 87
Posts: 2,206
Engines

so the exit speed will be low, giving a low pitch rate at exit
Interesting point that you mentioned about pitch rate at ramp exit.

The fact that the ramp induces a pitch rate on the aircraft really made me lose the plot when I was first asked my opinion about Doug Taylor’s idea for a ramp take off for the Harrier back in 1976. I had just walked into my office after a couple of weeks with the USMC watching them fly from an LPD. On several of their STOs the pilots had the stick pinned on the forward stop for a couple of seconds trying to control a pitch-up as they entered the upflow of air that is ahead of any ship’s bow (which was increasing their AoA). So when the Kingston performance man rang me up to tell me about this ramp idea, the poor (good) bloke got the full benefit of my jetlag plus a real earfull about adding pitch rate to an aircraft which already had inadequate controllability off a flat deck.

However the next day after a bit of thought it was clear there were many advantages to the ramp idea if we improved longitudinal control. In the event further thought made it clear that after the nose wheel left the ramp the aircraft had a split second or two with the main wheels still on the ramp and pushing like mad up behind the CG. A couple of sums suggested this effect would just zero the ramp induced pitch rate on the aircraft. Since there is an aeronautical god that is indeed how it worked out. Bottom line – higher weights and higher speeds did not give (Harrier) greater pitch rates at launch, because as speed increased up the ramp the g also increased and in turn increased the nose down moment in play after the nose wheel left the ramp.

Clearly for any given type the issue is gear position/CG position/longit inertia related but the sums are not rocket science. Dunno about the B but I am sure plenty do.
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