Engine flameout A/T disconnect or not on Boeing 767
 

Hi,

I'm trying to find out if the A/T will disconnect after an engine flameout in level flight on a Boeing 767.

Please provide reference.

After identifying the nature of the failure the QRH directs:

2. A/T ARM Switch...........OFF

A/T will remain active until you disconnect.

According to Boeing, when N2 reaches 9%, EEC dies and A/T should disconnect. This is engineering data. We have thrown a seized engine malfunction to get this N2=0% and could never get the A/T disconnect.

Which engine - PW4000 or CF6-80C2 FADEC? 'Stay Alive' speed for the EEC on the PW4000 is quite a bit lower than 9% - it varies a bit engine to engine but ~4% N2 is typical. CF6 is a bit higher, more like ~6% N2. In either case N2 will remain high enough to keep the EEC from dropping off line except at very low airspeeds. Further, on the CF6 the EEC is powered via the fuel switch - so long as the switch is in RUN the EEC will remain powered, even with a seized N2 rotor. The PW4000 is different and is not powered via the fuel switch unless your engines are equipped with something called an SCU (not common on the 767 except for the ones Delta bought).

So you're saying the A/T will not disconnect will engine flameout? Would you have any documentation by any chance confirming this? Need to backup my stories in front of my customers :-)

FCTM.

​​​​​​ If an engine failure occurs while at cruise altitude, it may be necessary to descend.

The autothrottle should be disconnected, thrust reference set to CON and the

thrust manually set to MCT on the operative engine

If I remember correctly, the A/T remains active. It's been a few years since I flew the 767, but if you select an altitude lower than the current one and select the engine out prompt in the FMC the rest is taken care of. The TMSP changes to CON, the thrust advances on the live engine and the commanded speed reduces back to vref 80. It then remains in pretty much level flight until the speed has reduced to vref 80 and then starts descending at the commanded speed. At some point, you should disconnect the A/T.

I think this was the simplest way of handling an engine failure in cruise scenario. That's why I can still remember it 5 years later. Can"t say the same for the Airbus.....

Going from memory here, but I think so long as the EEC is transmitting valid data, the A/T will not automatically disengage. If/when you shutdown the failed engine via the fuel cutoff switch, the EEC will do a reset which will cause a loss of EEC data for a second or so - not sure if the 767 A/T will stay connected through that interrupt or not.
I'm retired so I no longer have access to any meaningful documentation.

If you don't know the answer tell them that. Don't B.S. them and try to pretend to know the answer if you're uncertain.

Exactly, and also don't use information from an anonymous web-board as anything but unconfirmed rumors....