"On earlier 200 and 300 series aircraft the Authrottle will disconect once you select the Alternate Flaps to Flap 5. On newer aircraft there is no mention in the QRH to disconnect the Autothrottle and the Autothrottle will not disconnect with Alternate Flap selection."
Interesting. I've just been told that in our -200/-300 QRH, no mention is made of disconnecting the A/T. It must have something to do with specific harware/software P/N's & S/N's.
As I recall, (older?) 767's have less-than-accurate cockpit flap position indications during Alt Flap extension (particularly noticeable at larger flap settings).
Also, according to my notes, the A/T will disconnect if no position information is available from the FSEU(Flap/Slat Position Module) when in SPD mode, N1 mode in flight, or VNAV SPD mode.
I'm trying hard to link the two, but not having much success.
If the A/T is using the same position data as the cockpit flap position indicator, then I could see how alpha computations would be affected, but.... I don't see why the A/T should disconnect, especially at 5 units.
Regards.
Q.