Originally Posted by
Blip
Take off performance:
Drag at 160 kt = 190 N
10 nm = 18520 m
Energy = 3,518,800 Joules per light.
3,518,800 J / 9.8 / 75,000 kg = 4.79 m per light.
2 x 4.79 x 3.281 = 17 ft
So after 10 nm the aircraft would be 17 ft lower than it would have been if the lights were retracted.
Rough numbers I know but it give you an idea.
In other words, the effect is negligible...