Hello,

I have a question based on the Aircraft Systems Manual II p399 for ACCEL HT and I hoped someone could help.

"This is the Acceleration Height for flap retraction for all engines or one
engine out at which VNAV guidance will decrease pitch and begin
acceleration toward the target speed"

When the acceleration height has been entered into the CDU (TAKEOFF REF page 2 => ACCEL HT), does the flight director bar descent in pitch when the inputted altitude has been reached ? Or only if VNAV is engaged meaning VNAV is engaged before acceleration height ? The take off procedure of the Manual part III P35 only states to "Call for "VNAV" at flap retraction altitude.

I have done many tests but but it is not obvious that the bar descent.

Thank you for your help.
Mathieu

As i am observing the FD in 757 it follows my pitch movements instead of as it should be opposite... I am afraid it is far from correct logic as of now.

As far as I can see VNAV takeoff logic is not implemented in this simulation.

Use TOGA mode instead and bug up manually and engage VNAV after flaps up, then it works better.

Thanks for you reply !

FYI here is my takeoff profile.

LNAV preset if an LNAV departure.

When taking off add power to 1.10 EPR let the engines stabilize then press EPR.

Complete the take off roll, V1 -> rotate -> Positive rate -> gear up

At 400' AGL select or verify the roll mode. Either press heading select or just verify that LNAV is active.

At 1000' AGL select VNAV or FLCH if needed (you control the speed at this point).  If you select VNAV the plane will then pitch for the acceleration, clean up the flaps then climb away with the pitch command following the VNAV programming in the FMC