While not explained in great detail in Volume II, with the flaps and slats at takeoff position when system B is lost, and provided the loss of System B is above the stand pipe level, can retract the flaps electrically, and in theory, the LEDs via the PTU. Looking at the schematic in the manual, the PTU valve opens with a loss of System B pressure.
If there is anyone going to visit the simulator, give it a try.
Fail Hydraulic System "B".
Place the Alternate Master Switch of ARM.
Trailing Edge Flap Bypass Valve closes;
LEFAS Valve associated with the Standby Hydraulic System is armed; and
the normal LED Control Valve closes.
The LEDs will remain in their current position as the Alternate Flap Switch has not been positioned to the DOWN position causing the LEFAS Valve to open.
Place the Flap Lever Up, and place the Alternate Flaps switch to the UP position which will retract the flaps electrically.
After the flaps are up, turn the Alternate Flap Master Switch off.
All valves should assume their normal positions, and via the PTU, the LEDs should retract as operation of the LEDs is a function of Flap Lever position and flap position. Looking at the schematic, it does not appear the normal LED Control cares where hydraulic pressure comes from either normal System "B", or via the PTU.
Last edited by captjns; 10th January 2009 at 15:20.