Which component confirms landing gear status in the event of a failed indicator by a static mechanical contact?

• A. Ball nut contacting the bumper stop
• B. Gear lever position indicator
• C. Hydraulic pressure gauge
• D. Gear door position sensor

Answer: (A)

A static mechanical contact using a ball nut contacting a bumper stop provides a direct, physical confirmation of the gear’s end-of-travel position. As the gear moves to full up or full down, the ball nut rides into the bumper stop and completes an electrical path that signals that specific position. This makes it a reliable backup signal when the primary indicator fails because it does not depend on the electronics or optics of the normal indicator system; it’s a simple, fail-safe, end-of-travel contact.

Other options either rely on indicators that may be inoperative, or measure something not equal to the actual gear position. The lever position indicator reflects the cockpit control’s placement, not a guaranteed gear state if the indicator system is failed. The hydraulic pressure gauge shows hydraulic system pressure, which isn’t a direct, unambiguous readout of gear status. The gear door position sensor confirms door status, which is related but not synonymous with the gear’s actual extended/retracted position.