Quote:
Originally Posted by Crockett616
Does using the ram air turbine affect the hydraulics and the feel of the controls? Are some of the flight deck equipment cut off if you have to use it? Do all airlines have one?
Not all planes have a ram air turbine (RAT). For those that do have a RAT, the services provided vary among aircraft types. On the CRJ, for example, the RAT will provide limited electrical power and also power a hydraulic pump. (Note: on the CRJ, they call it an Air Driven Generator, or ADG). On the 757 and 767s, the RAT powers a hydraulic pump. Some of these planes have a Hydraulic Drive Generator (HDG) which will provide electrical power from the RAT-driven generator.
The RAT or ADG can be deployed manually, but it will automatically deploy if both main AC power busses lose power while the plane is airborne. Once deployed, it can only be stowed by a mechanic after landing. On the 757, the RAT deploys just behind the right wing. On the CRJ, it pops out from the right side of the nose, as shown here.
In order to provide the rated power, the propeller must have a certain minimum RPM and that means that it doesn't work when the plane gets too slow (I believe the minimum speed required on the CRJ is 130 kts). This isn't a problem because the aircraft battery will provide essential electrical power for about 30 minutes. The only hydraulic demand is for the brakes and for that we have a hydraulic brake accumulator which stores enough hydraulic pressure for up to seven brake applications. For this reason, a pilot in this situation is cautioned to not pump the brakes but instead make one smooth steady application of brakes. Once stopped, the nosewheel steering won't work since it needs hydraulic pressure; the airplane will have to be towed off the runway.