Framer,
The access door has a microswitch that sends an electrical signal to the manual extend solenoid valve in the landing gear selector valve which moves the bypass valve in the selector valve to the bypass position connecting the hydraulic system to the return side. When you pull the manual extension handles in the cockpit they are mechanically connected to the landing gear uplocks, and you physically release the uplocks, allowing the gear to free fall to the down position. Without the bypass valve connecting the hydraulic fluid to the return side you would create a hydraulic lock when you manually release the gear to lower, as the fluid would not have anywhere to go.
The door switch has nothing to do with the lever lock. They are two very separate things. The lever lock solenoid is there to stop inadvertent repositioning of the gear lever in the wrong configuration (on ground - gear up). It is a physical barrier in the lever assy itself which is electrically powered to remove the lock when the aircraft is in the air to allow handle movement to the up position.
Last edited by Gas Bags; 18th Sep 2013 at 22:22.