What holds the Main Landing Gear in the extended position?

• A. Mechanical over centering with down locks
• B. Hydraulic pressure only
• C. Spring loaded retraction locks
• D. PSEU control

Answer: (A)

The main idea is that the gear is held down by a positive mechanical lock once it reaches full extension. In this design, the linkage goes past the over-center point when the gear is down, and down-lock pins engage to physically latch the gear in the extended position. This mechanical over-centering with down locks provides a positive restraint that keeps the gear from retracting even if hydraulic pressure fluctuates or is momentarily unavailable. Hydraulic pressure is needed to move the gear and to unlock it, but the actual hold-down comes from the locked, over-centered position.

Other options don’t fit because hydraulic pressure alone isn’t what keeps the gear down, spring-loaded retraction locks describe a different locking approach, and the electrical control unit mentioned doesn’t physically lock the gear in the down position.