APU Doors?
 

This might seem a strange or silly question but...

I ve noticed that on BAE146 and some RJ have a set of 'clam shell' doors immediately below the rudder and these are often open whilst the aircraft is on stand.

Are they opened to allow apu cooling or for some other reason?

Can anyone shed some light?

Thanks

The 'clam-shell' doors on the 146/RJ are the speedbrakes.

Just guessing, but they might be set open for inspection on stand.

On the 125 the APU door is to stop rain collecting in the air intake when it is not running (prior to about 1985)

With a tailwind the 146 speedbrakes just blow open w/o hyd press.

There is a clip to keep the doors closed once the hydraulic pressure is low after shut down, but the clip gets a bit worn out after a while.