> The power to operate a transponder may have come from a Hydraulic Motor Generator (some 767's have three of them, one on each hydraulic system).

Qavion; actually some 767's have one HMG (now called HDG by the new Boeing books). The HMG comes on-line automatically (after a 10-15 second delay) with the loss of both left and right AC buses. To power the HMG the center hydraulic system's ADP (Air Demand Pump) is signaled to operate (the selector must be in Auto).

The HMG powers 7 buses. The Left (#1) transponder is powered, as is the Captain's flight instrument bus for a full EFIS compliment.

Uptrim Disable,

MMEMatty is correct when he says that min drag speed would give you best glide ratio. As to where to find it, it would be very close to best holding speed or best angle of climb speed, both of which are available from the FMC. Best hold speed is also available in the perf manual. A deviation of + or - 20kts or so would probably have little effect and I personally would shoot for about 240kts in a 737, which may be on the high side but would give better windmilling and a little more energy for turning, etc.

On a 747, I would go for 240 - 280kts, depending on weight.

"Qavion; actually some 767's have one HMG (now called HDG by the new Boeing books). The HMG comes on-line automatically (after a 10-15 second delay) with the loss of both left and right AC buses. To power the HMG the center hydraulic system's ADP (Air Demand Pump) is signaled to operate (the selector must be in Auto)."

Agreed, "None"... but since there is probably insufficient bleed air in this scenerio to run an ADP, I only mentioned the 3 HMG-type 767. The windmilling engines and the EDP's are more likely, however, to provide power to the HMG's on the L & R Hydraulic systems (or have I overlooked something obvious?).

Regards.
Q.

>but since there is probably insufficient bleed air in this scenerio to run an ADP, I only mentioned the 3 HMG-type 767. The windmilling engines and the EDP's are more likely, however, to provide power to the HMG's on the L & R Hydraulic systems (or have I overlooked something obvious?).


To my knowledge, there are no 767s with 3 HMGs. For ETOPS 767s, there is one HMG (Hydraulic Motor Generator, now Hydraulic Driven Generator), powered by the ADP, which receives air from the Center Pneumatic Duct. The source of the air is whatever is pressurizing the center duct.

The electric hydraulic pumps are A.C. powered.

"To my knowledge, there are no 767s with 3 HMGs."

Qantas has three on their -300's and one of their -200's. I'm sure they are not unique in this respect.

Regards.
Q.