Safetypee,
Good info, as you say BAe spent thousands of pounds tying to cure the howl, this wasn't just on the RJ but on the original 146 as well. The RJ (not BAe 146)series were fitted with flap track covers which help to reduce some noise. These sometimes get stuck in the down position when the flaps are retracted at the end of the flight, this often leaves inexperienced FOs scratching their heads during walk-rounds. Whilst this does not present the pilots with a problem/issue the noise in the cabin is increased. The cure for this is a spot of grease - the same solution as an airbrake which keeps deploying itself on the ground when the hydraulics are selected off.
