The airstairs can use gravity to extend but they require hydraulic pressure in the Yellow system for retraction. Yellow hydraulic pressure can be produced by the engine-driven pump while the #2 engine is running, or via the AC Pump when AC electrical power is available from a GPU, the APU, or the #1 or #4 engine generators.
Did you find it helpful?Send feedback
Sorry we couldn't be helpful. Help us improve this article with your feedback.