PMDG 737-800 landing with autothrottle - yes or no?

[SquadronLeader 62]

With the Fenix A320 the plane's computer 'instructs' you to retard when at 20 feet above the runway. What is the correct procedure for the 737-800. Does the pilot cut the auto throttle? - at or around 20 feet above the runway - or does the auto throttle cut itself off when the main wheels touch the runway? 

Thanks in advance

[SAS443 1,746]

37 minutes ago, SquadronLeader said:

at or around 20 feet above the runway - or does the auto throttle cut itself off when the main wheels touch the runway?

During autoland:
throttles retard at 27ft RA
AutoThrottle disconnect 2 seconds after touchdown.

[SquadronLeader 62]

Thanks SAS443

I usually do manual landings in the PMDG 737-800 - but use the auto throttle to manage the speed - so that being the case, any movement of my throttle (reduction in power) does not override the auto throttle  - and I do not experience the throttles (assume auto throttles) retarding at 27 feet RA. 

Any other thoughts or suggestions?

 

[Fiorentoni 4,464]

Boeing explicitly recommends to NOT use AT when handflying the final approach. There have been several incidents where flying manually with AT on has made the pilot flying "forget" to look out for speed (e.g. the Asiana crash at KSFO with a 777 a couple of years ago) or AT reacted far too late or pilot flying had a misunderstanding about how AT works in certain situations. It's much more natural and much safer for any pilot to use yoke and throttle when manually flying, because that's how they learned their basics. I find it absurd to land a 737 with AT on and at the same time moving the yoke and trimming the aircraft.

Now on the Airbus it's different, mostly because the pilot flying is already "disconnected" from the aircraft due to the sidestick flying by wire. Also Airbus has a pretty extensive low speed protection (alpha floor), which does a great job (but has other problems; a large part of the "What is it doing again?!"-Airbus-meme comes from the alpha floor protection and the pilots' failure to understand it).

Here's the link to the Asiana crash for anyone interested:

 

Edited November 3, 2022 by Fiorentoni
Added link

[SquadronLeader 62]

Many thanks Fiorentoni - that is very helpful - and I will go and give it a try

[Bobsk8 12,934]

I spent about 8 hours total in a Airline 767-400 ER Level D sim with one of the Airline Check Pilots that had over 20,000 hours. He told me to leave the autothrottle on, on approach. He said you would be looking for traffic, the runway, etc, and the last thing you needed was to be focusing on the airspeed indicator, which the AT would take care of. 

Edited November 3, 2022 by Bobsk8

[sniper31 651]

That is some good insight and info Fiorentoni, thanks! I fly both the PMDG 737 and the Fenix A320, and I am always trying to learn the subtle differences between the two. The obvious differences are easier to see the more you fly them in the sim, but some of these little nuances are nice to confirm. Good question SquadronLeader 🙂 

[Fiorentoni 4,464]

Just now, Bobsk8 said:

I spent about 8 hours total in a Airline 767-400 ER Level D sim with one of the Airline Check Pilots. He told me to leave the autothrottle on, on approach. He said you would be looking for traffic, the runway, etc, and the last thing you needed was to be focusing on the airspeed indicator, which the AT would take care of. 

I don't know when you had that sim session, but after the Asiana triple seven crash in 2013 most airlines changed their SOPs for Boeings to AT off when handflying. Also the check pilot could have told *you* as a non-airliner pilot specifically because he didn't want you to worry about that aspect while trying to land a 767, which would be reasonable.

[regis9 4,044]

I’ve always disconnected the auto throttle at the same time as the AP on the 737.  I understand this is standard at most (but perhaps not all) 737 operators.  

Edited November 3, 2022 by regis9

[Gazzareth 842]

17 minutes ago, regis9 said:

I’ve always disconnected the auto throttle at the same time as the AP on the 737.  I understand this is standard at most (but perhaps not all) 737 operators.  

From a conversation a few weeks ago I am sure I saw someone saying that some operators leave it on, but their pilots have to have specific training on the method.

I turn it off unless autolanding, certainly worked out if left on in p3d though - never tried it in MSFS.

 

G

[ahsmatt7 1,213]

1 hour ago, SquadronLeader said:

Thanks SAS443

I usually do manual landings in the PMDG 737-800 - but use the auto throttle to manage the speed - so that being the case, any movement of my throttle (reduction in power) does not override the auto throttle  - and I do not experience the throttles (assume auto throttles) retarding at 27 feet RA. 

Any other thoughts or suggestions?

 

If you the autopilot is not on, you aren’t going to have the thrust levers automatically retard to idle. The 27’ RA thing is an auto land feature. 
 

Edited November 3, 2022 by ahsmatt7

[Bobsk8 12,934]

52 minutes ago, Fiorentoni said:

I don't know when you had that sim session, but after the Asiana triple seven crash in 2013 most airlines changed their SOPs for Boeings to AT off when handflying. Also the check pilot could have told *you* as a non-airliner pilot specifically because he didn't want you to worry about that aspect while trying to land a 767, which would be reasonable.

Yes it was many years ago around 2002 if I remember correctly. 

[TurboKen 222]

The iFly 737 in P3D will cut the throttle at touchdown, but for some reason the PMDG in MSFS will not, (assuming its a bug) so because of this I just cut off auto throttle when I shut off the rest of the auto pilot. But maybe there is a step I am missing?

Edited November 3, 2022 by TurboKen

[threexgreen 3,160]

4 hours ago, Fiorentoni said:

Boeing explicitly recommends to NOT use AT when handflying the final approach.

I recall reading that for the 737 the recommendation was changed by Boeing with a newer software to leave autothrottle on when landing manually as it had been much improved in its response to speed fluctuations resulting from wind. The airline I know this from doesn't mandate following this recommendation though but still leaves it to the pilots as do most airlines that don't specifically require the autothrottle to be disconnected with the autopilot off I'm guessing (or require it to be left engaged for that matter).

3 hours ago, ahsmatt7 said:

If you the autopilot is not on, you aren’t going to have the thrust levers automatically retard to idle. The 27’ RA thing is an auto land feature. 

I'm aware of what you do as a job so I'm wondering if this is a software version difference as I've read it does retard thrust even when flying manually (see above)? The source is a pilot for a US carrier.

Edited November 3, 2022 by threegreen

[ahsmatt7 1,213]

4 hours ago, threegreen said:

I recall reading that for the 737 the recommendation was changed by Boeing with a newer software to leave autothrottle on when landing manually as it had been much improved in its response to speed fluctuations resulting from wind. The airline I know this from doesn't mandate following this recommendation though but still leaves it to the pilots as do most airlines that don't specifically require the autothrottle to be disconnected with the autopilot off I'm guessing (or require it to be left engaged for that matter).

I'm aware of what you do as a job so I'm wondering if this is a software version difference as I've read it does retard thrust even when flying manually (see above)? The source is a pilot for a US carrier.

Now you have me wondering! My airline frowned against A/T being left when hand flying because of what you mentioned above with the older software. I’ll start digging.