In the FCOM OF BOEING 737 HYDRAULIC SECTION I went through the part Landing gear transfer unit that it is used to raise the landing gear at a normal rate when system A EDP volume is lost.

My query is if only the hydraulic system A is lost with landing gear up position can it lowered using system B hydraulic or do we need to use manual gravity gear extension?

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    $\begingroup$ Related: this answer of the question "If the landing gear is stuck in an airliner, can the crew go down and manually open it?". It speaks about gravity extension, but nothing about the hydraulic of the B737. $\endgroup$
    – Manu H
    Jul 25, 2020 at 14:14

1 Answer 1


Normal gear extension is by the A system; alternate gear extension is by manually releasing the up-locks, allowing the gear to free-fall into place. There is no provision for any other alternate gear extension beyond that, such as via the B or Standby hydraulic systems, electrics, pneumatics, or otherwise.


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