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EDFZ
8th Oct 2012, 15:47
Hi guys,

why does the FD on a 737 initially pitch down to about -10 till passing 60kts and then comes up again to 15 NU. Does anybody have an idea?

Thanks!

BOAC
8th Oct 2012, 15:54
Possibly to stop you following it below Vr?

EDFZ
8th Oct 2012, 16:14
Well, you obviously cant follow any vertical profile/path when still rolling on the ground.
But why does it start moving at 60kts? I could understand if it at least started moving at/close to Vr or at V1 already...
If you change the FD to x-Bars the lateral bar remains centered. It's only the horizontal needle I'm talking about...

And, if you regarded the 10 ND as a command, you

downwind
10th Oct 2012, 03:22
I had asked this question before to a tech pilot, they *believe*, that it is a cue to help show the flightcrew that the control column should have light forward force applied for nosewheel steering affectivness as indicated below by the b737 FCTM, then transition to a nuetral stick force around 80 kts (but this does not co-incide with the FD vertical re-positioning back up at 60kts??

"Light forward pressure is held on the control column. Keep the airplane on
centerline with rudder pedal steering and rudder. The rudder becomes effective
between 40 and 60 knots. Maximum nose wheel steering effectiveness is available
when above taxi speeds by using rudder pedal steering."

"Above 80 knots, relax the forward control column pressure to the neutral position."

de facto
10th Oct 2012, 05:01
Another of urban legends im afraid....