Describe the Alternate gear extension mode: What happens?

• A. Relieves hydraulic pressure in the lines and releases all uplocks, gear extends by freefall (gear handle must be down to get 3 green on EICAS)
• B. Keeps hydraulic pressure in lines and extends gears electrically
• C. Extends by electrical power only
• D. Extends by mechanical force only

Answer: (A)

Alternate gear extension works by using gravity to deploy the gear when the normal hydraulic system isn’t available. When you select this mode, the hydraulic pressure in the gear lines is relieved and the uplock mechanisms that keep the gear stowed are released. With the uplocks out of the way, the weight of the gear causes it to lower into the down position—doors open as needed and the gear settles into place and locks. Once everything is down and locked and you place the gear handle in the down position, the three green indications on the EICAS typically appear, confirming that all three gears are down and locked. This backup method provides a reliable way to extend the gear even with a failed hydraulic system, though it relies on gravity and the aircraft’s weight, so it’s slower and requires the crew to verify the down-and-locked condition.