The Ram Air
Turbine emergency power system, known as RAT, is one of the backup power
sources that are designed to automatically engage to ensure that those systems
needed for continued safe operation of the airplane are powered, in case a
failure of the power from both engines and the aircraft speed is above 100 Knots.
Theoretically, there is no time limitation for flying with the RAT. The Emergency Generator should remain supplying until touchdown; so the aircraft should never become 'Batteries Only'.
Theoretically, there is no time limitation for flying with the RAT. The Emergency Generator should remain supplying until touchdown; so the aircraft should never become 'Batteries Only'.
This small
generator is required in the event of power failure and should be tested before
the first flight
A ram air turbine (RAT) is a self contained turbine
unit with a hydraulic pump attached that are generally only used in emergency
situations.
RAT is deployed automatically when main system pressure
drops below a predetermined value, and could also be deployed into the airflow
by selection of a switch on the flight deck.
The RAT must be capable of operation over a broad
speed range, maintaining normal hydraulic pressure, whether the aeroplane is at
maximum speed and height or slowing for landing.
A volumetric flow control valve is usually fitted to
the RAT allowing the propeller to attain operating speed, before being loaded
by the pump, this allows full system pressure to be achieved approximately 4-5
seconds after deployment into the air stream.
In the 787 (above) the RAT is stowed in the flap track fairing. In the A350 XWB, the place of stowage was initially under the left wing as shown in this old image below, but currently is under the fuselage fairing (belly fairing).
In the
extremely rare loss of power from the engines, the RAT deploys into the
airstream and produces power for the cockpit and flight controls to safely land
the aircraft.
“We are proud
to support Airbus’ latest advanced commercial aircraft. As the world’s leading
RAT systems supplier, we strive to provide the best competitive and technical
solutions for our customers, and we’re pleased to be selected for the A350
XWB.”
Based on the
article “Airbus teste la RAT de l'A350 sur son A340-300 d'essai ” published in
AeroWeb-fr.net
Hello,
ReplyDeleteI believe there is a mistake in the article. The A350 Ram Air Turbine is not allocated under the wing, but in the fuselage (similar to the ones on Airbus single aisle aircraft). The slide you show is from 2009 and the position of the RAT has change since then.
I also don't believe that the RAT will deploy when only one engine is not operative. There would still be 2 Generators left, which would be enough to supply the A/C with power.
Apart from that, well done - it's always a pleasure to have a look on your blog ;)
Quite true.
DeleteThanks for your comments. Fixed it.
ReplyDeleteI believe the A350 RAT provides electric power, rather than hydraulic. The turbine works the same, but it spins a generator instead of a pump. A hydraulic motor can provide hydraulic power, but there are also electro-hydraulic actuators on the control surfaces.
ReplyDeleteWho here thinks that this machine seemed weird to you until you finished reading the article?
ReplyDelete