Tbur

Manual landing with or w/o autothrottle engaged

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Hi,

please apologize this possibly very often asked question !

 

I'm interested to hear what is the common practice when hand landing the 747-400 as you have to do e.g. at St. Maarten (TNCM) using auto throttle or not.

My experience as PC pilot is of course that it can be  very convenient because you get rid of some workload. But I want to know when it is recommended to do so or are there some issues maybe because safety is affected to be advised manually control throttle settings.

Some information from the reality  and common practice if there is one as well is appreciated. Thank you.

regards

 

Thomas Burchard

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In the 747-400, the autothrottle should be disconnected whenever the autopilot is disconnected. There is a significant pitch/power couple which makes manual flight with A/T engaged at best uncomfortable (pitch up - speed reduces - A/T increases thrust - aircraft pitches up due to extra thrust - aircraft pitches up even more - pilot pushes forward to counter pitch up - speed increases - A/T reduces thrust - nose pitches further down - ad infinitum...). Not to say that it's impossible, but not recommended.

In any event, you will have to take the A/T out at some point in order to flare!

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51 minutes ago, skelsey said:

Not to say that it's impossible

I have made at least a 100 flights now with the Queen, with AP off, A/T engaged, without any issues whatsoever managing flared landings at Vref but after reading some other posts re:hand-flying the approach and landing, have started following the 'recommended' way

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1 minute ago, vc10man said:

I have made at least a 100 flights now with the Queen, with AP off, A/T engaged, without any issues whatsoever managing flared landings at Vref

Out of curiosity (haven't tried it myself and away from my home PC at the moment) - does the PMDG 747 A/T reduce power to idle in the flare when you are hand-flying?

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23 minutes ago, skelsey said:

Out of curiosity (haven't tried it myself and away from my home PC at the moment) - does the PMDG 747 A/T reduce power to idle in the flare when you are hand-flying?

Right Simon, the A/T does act as expected during flare; however, I find it easier to land without A/T.  Much the opposite of the 777.

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There is very little pitch power couple in the pmdg. Besides it's beneficial in every way to get back to the basics. Your a pilot not an automation manager :D

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20 hours ago, downscc said:

Right Simon, the A/T does act as expected during flare; however, I find it easier to land without A/T.  Much the opposite of the 777.

I concur, with you, Dan, as until the last few recent flights, I was leaving the A/T on set at Vref30+5, but now, actually hand-fly and land without A/T and AP. Incredible how PMDG have replicated this so realistically.

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My 2 cents worth... A manual landing was tried in a big simulator in England with only the A/T engaged to see what would happen and there was no idle during flare.

I can't say for sure, however, that the 747-8 with the NG FMC would also behave like this. The NG does have a well-documented idle mode during flare with the A/P not engaged.

Cheers

JHW

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I forget the details, but the reduction to idle at the flare by the A/T is not a full reduction for a short period and this can affect your landing if you are not used to it and it will slightly delay the deployment of spoilers. Maybe the English simulator captured that effect? I remember this discussion during beta but not the details; however, the details were discussed and it was apparent that PMDG got this right.  In real world, you can land with or without A/T and I'm sure there are valid arguments for either procedure.

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21 hours ago, downscc said:

but the reduction to idle at the flare by the A/T is not a full reduction for a short period

Sorry, not sure what you mean, Dan. You get a slower retard rate? Or the throttles don't go all the way to idle before you touchdown? I believe the A/T goes dormant on touchdown (or thereabouts), so if the throttles are too slow to retard, you won't get autospeedbrake operation.

The reports of the behaviour have been so contradictory, one desktop sim made it optional (to please everyone). Perhaps thrust reduction occurs simply because the aircraft is in ground-effect and less energy is required to maintain speed?

Anyway, I don't think Boeing will be approving this technique for landing for the 744 anytime soon :D


Cheers

JHW

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