As I understand it, usually the way it is done in the real 737ng, on approach:-

 

when the autopilot is disengaged for a manual landing, the pilot calls for speed mode to be disengaged also - the autothrottle switch is still in the on position.

The reason, as I understand it for this, is so the autothrottle's safety features are still available during the approach and for a go around if required.

 

The problem is that although during normal flight, I can disengage and reengage the speed mode (by pressing the speed button on the MCP) okay,

during an approach with the autopilot off, pressing the speed button on the MCP fails to disengage the speed mode of the autothrottle.

 

What am I doing wrong or is what I am attempting not possible with the PMDG NGX ?

 

Advice would be appreciated.

 

 

Fergus

What does your Flight Mode Annunciator say?

MCP SPD is announciated on the PFD during manual landings - gear is down, flaps 30 etc etc autopilot is off

 

- at about 600 ft on the radio altimeter I call "select speed off" using FS2CREW (this command works fine if I use it during cruise)

 

- the first officer confirms the command and I hear the click as the first officer presses the speed button on the MCP

 

- but the announciators should change to ARM, but dont - speed mode won't disengage

 

I then press the speed button myself on the MCP - same result - nothing happens ??

 

Eventually, I have to disengage the autothrottle completely - which, I understand is not realistic procedure.

 

What am I doing wrong ?

 

 

 

Fergus

I've solved it -

 

on an approach-

 

- above 400 ft above the ground, it is possible to disconnect the speed mode of the autothrottle, but keep the autothrottle armed.

 

- but once below 400 ft above the ground, its no longer possible to disconnect the speed mode of the autothrottle without turning off the whole autothrottle.

 

Everybody else probably already knew this. Anyway, this info might be useful to someone.

 

 

 

Fergus

Does somebody know, if this is a bug or a feature?

 

I have already searched the FCOM, but nothing found so far.

 

Thanks.

400ft almost sounds like a feature. How does the MCP button light behave?

How does the MCP button light behave?

 

The SPD light on the MCP stays illuminated; also no changes at the FMA. Tested with Honeywell and Collins and each time with single and dual AP.

 

By the way, the other way round behaves the same: So, when you are already in ARM mode it is not possible to (re-)active SPD under 400ft.

 

I also believe that this is feature, but I am still searching for a plausible explanation why Boeing do not want this last-second-user-change ...