RoseFlyer From United States of America, joined Feb 2004, 8754 posts, RR: 52 Reply 1, posted (3 years 4 months 3 weeks 6 days 6 hours ago) and read 6441 times:
The 747-8 does have a RAT unlike all the other 747s. It was required since windmilling engines do not provide enough power.
The 787 has a rat like just about every two engine jet except the 737.
If you have never designed an airplane part before, let the real designers do the work!
747classic From Netherlands, joined Aug 2009, 1789 posts, RR: 11 Reply 3, posted (3 years 4 months 3 weeks 5 days 19 hours ago) and read 6357 times:
787 :
Ram Air Turbine (RAT) , produced by Hamilton Sundstrand. The RAT provides emergency power in the unlikely event of a dual engine failure. The RAT comprises a propeller that is deployed into the air stream from the wing fairing and powers a hydraulic pump to pressurize the center hydraulic channel, and a generator to power the essential electrical bus.
747-8 :
The 747 has an RAT that provides only hydraulic power to syst #3 to meet regulation FAR 25.671(d) :
" The airplane must be designed so that it is controllable if all engines fail. Compliance with this requirement may be shown by analysis where that method has been shown to be reliable".
The main thing that changed on the 747-8 is the higher bypass ratio and higher core compression ratio of the GEnx-2B on that aircraft. The core won't windmill at a high enough rpm to run the engine mounted hydraulic pumps at a level sufficient to meet 25.671(d).
A-380 :
Ram Air Turbine (RAT), produced by Hamilton Sundstrand : The RAT provides emergency power in the unlikely event of a complete loss of engine power. The A380 RAT is the largest ever built and features a 64-inch diameter propeller that is deployed into the air stream from the wing fairing to power its 70 kVA air-cooled generator.
If AC 1, AC 2, AC 3, and AC 4 busbars are lost in flight, the Ram Air Turbine (RAT) will automatically extend and mechanically drive the emergency generator. This emergency generator supplies the AC ESS busbar with AC power at a variable frequency.
The emergency generator can supply all the electrical loads that are necessary for the remainder of the flight, and for landing.
A-350XWB
The Ram-Air Turbine (RAT) of A350-XWB (also produced by Hamilton Sundstrand) will be now localized on the belly and the generator requirement is 100 kVA.
RoseFlyer From United States of America, joined Feb 2004, 8754 posts, RR: 52 Reply 4, posted (3 years 4 months 3 weeks 5 days 17 hours ago) and read 6310 times:
Quoting HAWK21M (Reply 2):
The B737 has manual reversion on the Ailerons/Elevators & a Stby rudder PCU,so no need of the RAT.
what about the B727.
No it did not have a RAT. Manual reversion is enough to fly the plane.
Interestingly enough, the rudder requires electrical power. However in a dual engine loss on a 737, electrical power is not provided to it. They get out of this problem by considering the rudder a noncritical component since if there is no differential engine thrust, ailerons and elevators are enough to exclusively control the airplane
If you have never designed an airplane part before, let the real designers do the work!
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