my guess
0 RA reperesents distance calculated at touchdown,LG extended,from the antena in use .After landing ,the struts are compressed,also the antena position is lower (more or less depending of its position on the fusselage forward or aft) ,so that's why the negative measurement.At touchdown,due to landing angle of the fusselage,the antena is a little bit higher than after landing,fusselage aprox horizontal.
On a 737 is around -2 /-4 ft.
On the 757 (which is longer) if the antena is close to the forward part of the fusselage,the deviation can be up to -20 ft,as said by BB.(I don't fly the 757 ,it may be less than this.It can be calculated if you know the angle at touchdown and distance from main gear to the antena,I think.)
Brgds Alex
Last edited by alexban; 17th June 2004 at 19:07.