Originally Posted by
invisible
I have several questions on fact that it landed without landing gear and flaps:
- How long before landing and what altitude flaps and lending gear is released? At my recollection, minimum 20 min before landing, no?
- Does release and locking of landing gear gravity based or is it powered?
- If plane lost power on both engines, does auxiliary RAT engine sufficient to provide enough power to release landing gear?
- What kind of event might cause BOTH flaps and landing gear not being able to deployed?
Thanks
- Depends on the regulations you work under, however, as a general rule the aircraft shall be fully established (on speed, on glide slope, gear & flaps down) by 1000 feet AGL. For most cases, that means flaps start to come out at around 2000 ft followed by the gear at around 1500 ft. That is to say, you start configuring around 3-5 minutes before landing. If you’re flying into a really busy airport where holding is required and speed control is in effect, you could end up in a situation where flaps would be extended if ATC commands you to maintain a speed that is less than minimum clean speed. That could well be 20 minutes out (looking at you, Heathrow), but that’s the exception.
- Landing gear is normally extended using hydraulics, with the hydraulic pumps being run by the engines. Some aircraft have electrical back-up pumps, which can be driven by the APU or RAT. Some aircraft, including the 737, have a completely manual reversion (if all else fails), whereby the gear can be extended using gravity.
- A total loss of hydraulics will cause the flaps to remain in stowed position.