Expert: Roberto Gomes - 11/19/2008

Question
Hello, I'm hoping you can answer a question that I've been wondering about for quite some time.

I travel quite often, on many different airlines.  Whenever I travel Spirit airlines, usually to Vegas or Orlando, we fly on the exact same kind of plane, an Airbus, the longer of the two that Spirit flies.  

It never fails that, right after boarding, before any ground movement, from deep in the belly of the plane comes a series of strange hydraulic noises.  I'd describe the noise as that of the sound a robot makes moving it's arms or legs.  I always look to see, but it never appears to be anything on the wings.

I fly Northwest, Frontier, etc., and have never heard this sound on any other plane.  

Do you know what it could be?

Thanks!  

Cal.

Answer
Dear Cal,

As strange that it should be, the sounds that you hear may come from different sources.

One of them, may be the internal baggage loading system. Some airlines used it although it represents an "extra" weight to the aircraft basic operating weight, but helps in order to make faster turnarounds.

Other source can be the baggage doors being closed or even the conveyor belt used to load/unload bags.

The movement related to the wings is (when after push-back) sound of the flaps being set by the crew for take-off.

Hope this helps,
Best Regards,
R. Gomes