Hello all!Easy question for those in the know:When a B-747 is parked at the ramp with the cockpit cold and dark, i.e. no hydraulic pressure: Do ground crew have to insert pins into the landing gear to avoid the gear collapsing, or does the gear have enough of an overlock to not need the pins in the first place?Cheers,- jahman.

The 747 gear locks past centre with springs, so it doesn't need hydraulic pressure to keep the gear down, which is actually true for many aircraft. Theoretically that means it doesn't need gear pins, but they are used anyway as a 'belt and braces' safety arrangement on most airliners, including the B747. They are also used when it is towed or if it is parked up for any length of time, part of the reason for doing so, is that the crew are then forced to take a look at the gear when doing a walkaround, since they have to remove the pins to go flying in the thing, and when doing that, they of course can 'kick the tires' and are more likely to spot if anything is amiss.Al

Al,Many thanks for your reply. The reason I was wondering was I've never seen the pins mentioned in any checklist...Cheers,- jahman.

The gear is also locked up, often by pins that are slid into place either hydraullically or electrically. In some aircraft the lowering cyclc begins by raising the gear slightly to take the load off the pins so they can be withdrawn before the gear is fully lowered.

That's interesting: I always wondered what kept the gear up once its hydraulics were depressurized once the gear was raised.Cheers,- jahman.