Hi,

 

I have always been accustomed to the MD-80 systems as I fly them for a living. While flying the 737NG on long flights I take the time to catch up on subtle differences between the two. Either system or operational wise.

 

One of these is the auto throttle retard system. On the Mad Dog, the throttles retard at 50'. Does not matter if you're doing a full coupled ILS or a visual approach with no active VHF signals tuned, and/or no GPS/NAV/FMC input.

But I see from the 737 that it auto retards at 27' ONLY if you are executing an autoland. In other words, if I approach an airport in HDG SEL, VERT SPD, I will not get retard functionality. The A/T will try to maintain MCP speed during my flare if I do not disengage the A/T.

 

Am I correct?

 

Thanks,

 

Xander

Correct. The minimum use height of the A/P in single channel is 158' AGL or 50' below MDH whichever is higher. With A/P disconnected, the A/T must also be disconnected.

 

I don't know about the MD80, but flying manually with the A/T, except in TO/GA or CLB thrust, is very problematic due to the pitch moment of the thrust line compared to the drag line due to the engines being underslung.

With A/P disconnected, the A/T must also be disconnected.

 

This is actually not a restriction, but a heavy recommendation by Boeing.

 

Anyway without dual or triple channel autoland, AFDS will not arm the retard mode of the A/T, you have to retard yourself.

This is actually not a restriction, but a heavy recommendation by Boeing.

That is quite correct. However, in my defence and in the cold light of day, recommended practice is effectively standard practice unless there is a good enough reason to do different - pretty much the same for mandatory practice really

I agree with you. I treat it as if it were a restriction. In fact if it is treated as such in company manuals, which is quite possible, it is just as binding to the pilot as if it were Boeings hard limit.

 

I just clarified for the benefit of those readers who might take your "must" as a sign of hard restriction.

Thanks to both !

 

In the MD-80 the autothrottle is left on from the start of the takeoff roll until touchdown if all limitations are complied with.

At 50' AGL the RETARD mode activates and upon nosewheel strut compression the autothrottle disengages.

This irregardless of single or dual channel, coupled, FD or raw data approaches.

 

Xander

In the MD-80 the autothrottle is left on from the start of the takeoff roll until touchdown if all limitations are complied with.

At 50' AGL the RETARD mode activates and upon nosewheel strut compression the autothrottle disengages.

This irregardless of single or dual channel, coupled, FD or raw data approaches.

The same in the DC-10, G5 and G550. The DC-10s I flew didn't have auto-land installed(too Mx intensive$$$). The auto-throttles started a smooth power reduction as the radar altimeter passed 50ft if left on during landing. The 10 had the same issues with the wing engines as the 737. Adding power pitches the nose up and reducing power lowers the nose due to the engines being below the CG. Because of this, we taught guys to turn off the auto-throttles when hand flying in turbulence and gusty winds. The auto-throttles could be left on from takeoff to landing. There were two things not recommended as far as auto throttle use. One, autopilot on and auto throttles off. This can get you in trouble real fast. The other was auto throttle landing during touch n goes. The throttles would drop off as you actuated thrust reverse. If you didn't disconnect them, they would fight against you as you pushed them up during the touch n go.