Questions for 737NG pilots

[Virtual738]

1. Can the autopilot ( CMD ) be pressed while on the ground ? If yes........What would be the reason(s)

2. Should the N1 button light automatically light up at thrust reduction altitude even if N1 has not been pressed ? (automatic thrust reduction)

Thanks for any answers.
I am a very keen flight simulator enthusiast and am not sure about these because it does not mention them in the FCOM's

[STBYRUD]

1) Any button can be pressed on the ground. Coincidentally the AP will go into CMD even on the ground. No particular reason.

2) The A/T will go into N1 at thrust reduction, otherwise it could not set climb thrust.

[M.82]

About 2)

With auto-throttle engage, the N1 button will iluminated when the aircraft reach the reduced thrust altitude that you put on the FMC.
-So, you take off:
A) You push TOGA
B) N1 and TOGA are shown on the Flight Mode Annunciator.
C) At 80 kts, you will see THR HOLD, instead of N1 in the FMA.
D) Them you will see ARM instead of TRH HOLD in the FMA.
E) At reduced thrust altitude, you will see N1 again in the FMA and will also iluminate the N1 switch. And you will also see CLB in the Thrust Mode Annunciator.

You can also set the climb thrust value manually (with auto-throttle disengage) that figure at the N1 limit page (CLB) by switching L4 from the CDU.


I hope it helps you!

[Virtual738]

Thanks for the answers guys !
They have helped understand things much better.

I guess one use for the autothrottle being armed on the ground would be to press CMD and get a feel for the controls to see when they would disengage the autopilot. It would also help to make sure the FD bars show correctly by selecting Heading Select and Alt Hold.

I just find it strange that Fcom 1&2 do not mention these things.
That is why I was so unsure about the N1 button light. I know it obviously comes on with Level Change but the Fcom says nothing about it as regards automatic thrust reduction.

Might have another question or two soon.

Thanks again for your responce.

[CancelIFR]

Well, N1 does not illuminate if you are flying an aircraft without the auto thrust reduction option, certain companies have a call in their SOP for the PM to press N1, usually at 1000' or 1500' AGL ("climb thrust, set climb thust, N1" etc.)

[SKYWRITER1]

I seriously doubt the autopilot can be engaged on the ground "to see how the controls feel" or to test the flight director bars. Who the hell checks the flight director bar function ( not even sure an engineer would).

I would find it a lot more useful to have the autopilot still engaged after an autoland with rollout capability perhaps???

[pilot999]

Skywriter why bother posting to something you know nothing about!!!!!

The Autopilot can easily be engaged on the groundin CWS and after an autoland the autopilot will revert to CWS if you do not disengage the autopilot with the associated consequence of pitch trim winding full forward etc.

[Denti]

You can engage the autopilot on the ground in all modes, not only CWS. And what happens after touchdown in an auto land depends on bought options, auto-rollout is available and works extremely well.