An aircraft's normal hydraulic landing gear extension system fails during approach, and the pilot must use the emergency extension system. Which of the following best describes the typical operating principle of a manual emergency gear extension system?
- AIt engages an auxiliary electric motor that drives the hydraulic pump at a higher pressure than normal
- BIt uses a mechanical hand pump or release mechanism that bypasses the normal hydraulic system to allow gravity or spring force to extend the gear
- CIt automatically extends the gear using a barometric switch that senses low altitude
- DIt requires the pilot to manually pump hydraulic fluid at higher pressure into the same lines used by the normal system
Show answer & explanationAnswer & explanation
Correct answer: B. It uses a mechanical hand pump or release mechanism that bypasses the normal hydraulic system to allow gravity or spring force to extend the gear
Most emergency gear extension systems work by mechanically releasing uplocks and disconnecting the gear from the normal hydraulic system, allowing gravity, air loads, and/or springs to freely extend and lock the landing gear, often assisted by a hand pump or a free-fall mechanism, independent of the failed hydraulic power source.
Why the other options are wrong
- A. An auxiliary electric-driven hydraulic pump is not the typical emergency method; it still depends on the hydraulic system.
- C. There is no automatic barometric-triggered emergency gear extension system in typical light aircraft.
- D. Using the same hydraulic lines would not help if the failure is within that same hydraulic system.
Emergency Landing Gear Extension
A backup mechanism that bypasses the normal hydraulic/electric gear system, using mechanical release and gravity, airloads, or springs (sometimes aided by a hand pump) to extend and lock the landing gear.
- Bypasses failed normal hydraulic/electric system
- Relies on gravity, air loads, or springs for extension
- May require manual hand pump or crank to complete the process
Memory trick: When hydraulics fail, gravity becomes your co-pilot