@ ICT SLB...
Like I said in my post anything is possible about the APU just no guarantees. Also the APU system on the RJ is not identical to the CL64.
Although later versions of the 604 came with the same APU as the original RJs, it could not be used at high altitude like the RJ… You cannot load it up with pneumatic/bleed and electrical power at the same time while in flight. Bleed extraction must not be used above 15,500 feet. The 604's APU does not have a retractable door like the RJ but a small fixed scoop. All small differences I’m sure but perhaps that’s why Bombardier never changed the AFM’s restrictions even after the new APU was installed.
Like I said the RAT should deploy automatically (squib releases the lock and out it goes) or manually by physically pulling on a cable that releases that same lock and yes gravity/airflow takes care of the rest. As to why it did not release in this case, well you mentioned a possibility and another possible reason is perhaps the severe G force encountered during the event that would have prevented its release.
As Globally Challenged said the RAT locking pin could have been left in placed, now that would be embarrassing.
On the hydraulics, yes there is a possibility of residual hydraulic for a very limited time but again I have to doubt about it being available through 3 or 5 rolls and a descent of 10,000 feet and this to me is the portion of this incident I’m really interested in… Time will tell.
There are no spoilerons on any Challengers (600/601/604/605/650).
Last edited by Jet Jockey A4; 11th Mar 2017 at 13:50.