Al the FBW aircraft types have a RAT.The A320 RAT deploys automatically in the
case of a double AC power failure. Not dual engine failure, as many "experts"
write, although this will usually trigger the RAT deploying by default when the
generators wind down. Pedantic, maybe, but accurate. (The speed also has to be
above 100kts but now I am nitpicking).The A320 RAT is available for both
emergency electrical power and also emergency hydraulic power if required. It
can also be manually deployed by two guarded pushbuttons, one on the overhead
electrical panel and the other on the hydraulic panel. Pushing the button on
the HYD panel drops the RAT but only powers a hydraulic pump connected to the
"BLUE" system.The button on the ELEC panel powers up the emergency generator
only and leaves the hydraulics alone. This is a much lower power generator than
the main ones (understandably, as it's only driven by a windmill) hence the
aircraft switches to its "emergency electrical configuration" which sheds a lot
of electrical load so it can successfully power essential systems. One example
if load shedding is it will also only power the Captain's screens (also only
VHF#1, ILS#1,VOR#1 etc) so the Capt has to give it some of that pilot s***
whilst the FO runs the drills and the other switchery. Only one overhead
reading light is powered but that's kindly given to the FO as he has to do the
reading. Clever, eh?If you can get the power restored by switching on the APU
then the APU generator, which is pretty much fully rated, can restore most
electrical systems, giving the FO his screens back (and the Capt his reading
light) and hopefully an autopilot. The restoration of almost normal electrical
power is invariably accompanied by huge sighs of relief all round. )This
situation, needless to say, never happens in any simulator session. Ever). Simon
-------- Original message --------From: Robert Ditchey via Mifnet
<mifnet@lists.mifnet.com> Date: 18/06/2025 00:56 (GMT+02:00) To:
mifnet@lists.mifnet.com Cc: rob...@ditchey.com Subject: [Mifnet 🛰 72772] Re:
RAT, Flight Control, and Hydraulics Here’s a You Tube that
applies:https://www.youtube.com/watch?v=V48IcswGLYg It says that the Miracle on
the Hudson case depended on the RAT for final flight control. So that aircraft
type has the RAT. From: rob...@ditchey.com <rob...@ditchey.com> Sent: Tuesday,
June 17, 2025 2:48 PMTo: 'mifnet@lists.mifnet.com'
<mifnet@lists.mifnet.com>Subject: RE: [Mifnet 🛰 72762] RAT, Flight Control, and
Hydraulics I found a partial answer to my question. As concerns the B737 and
the Jeju accident, the B737 does not have a RAT.  See the attached for much
more. I suppose that I’ll find something similar for the A320/321. But I still
have more questions unanswered. For example, why did the recorders fail for
Jeju? For Jeju, from battery power, the electric driven motor pumps for the
hydraulic system likely powered the flight control actuators, provided the
battery was OK. But the recorders? Bob Ditchey
--------------------------------------------------------------------------
Revised: 20250507
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