Cricri From France, joined Oct 1999, 581 posts, RR: 6 Posted (15 years 2 months 4 weeks 1 day 5 hours ago) and read 1203 times:
Good morning all...
Here is my question : how much time does it takes for the windmill (RATT) to extract itself from the fuselage and supply emergency power when needed?
I don't need an "at the second precise" answer, just an idea of the average time would be fine.
I already know a bit about the required conditions to let it work properly (speed, etc...) but by reading a story of a near crash, i was surprised to see that it toke quit a long time.
If u have a little bit time more, then could you tell me too what power it supplies exactly, how long it lasts and any other info have.
Thanks in advance.
Heavyjet From , joined Dec 1969, posts, RR:
Reply 1, posted (15 years 2 months 4 weeks 20 hours ago) and read 1127 times:
Just a couple of seconds is all that's needed.
On the B757 it deploys automatically inflight after a dual engine failure. On the A300/310 it has to be deployed manually by one of two RAT handles (one by the Capt and one by the FO). The accident you read about probably required the crew to manually deploy the RAT and might explain the time delay. Whether deployed automatically on the Boeings or manually on the Airbuses, it only takes about 2-3 seconds for it to supply normal hydraulic pressure to at least the primary flight controls (elevators, ailerons and rudder).
If the crew is able to start the APU and supply the aircraft with normal electrical power from the APU generator, the electric hydraulic pumps will operate and supply normal pressure to the flt controls. The RAT requires a speed above around 130kts (depending on aircraft) to supply sufficient pressure.
Bigscrew From , joined Dec 1969, posts, RR:
Reply 2, posted (15 years 2 months 3 weeks 6 days 14 hours ago) and read 1096 times:
The RAT is deployed automaticali in flight if both
AC-Busses are offshedulled and the speed is more than
100kt (Airbus A319/320/321) you need no Hydr. or Electric. The RPM is a constant 5400rpm what gives 2800PSI with 45 l/min at a speed of 130kt. In the training thei told us, the RAT is faling out very fast.
The A300/310the RAT has to extend manualy by one of two handles in the cockpit (Capt. or First Off.).
Thats the info I can give you.
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 20
Reply 3, posted (15 years 2 months 3 weeks 5 days 23 hours ago) and read 1074 times:
Hi Cricri, Buzz here. Let's see. the 757 and 767 takes about 2 seconds (as they previously said), and if you're working under the airplane the door will shove you aside as it comes down. HOWEVER on an L-1011 the RAT springs down suddenly, about a half second deploy..... it's hurt people. We had 6 of them at UAL, never really got used to the old Pan-Am airplanes. Let's see, it takes a couple seconds on the A320 also.
On the 757 it runs the center hydraulic system, so you have some basic flight control functions and on ETOPS '57's it'll power a small AC generator. Similar set up on the A320.
Humorous story from a bad incident:
20+ years ago Eastern had an L-1011 leave Miami, have all 3 engines with problems, and return, narrowly avoiding a water landing. The RAT deployed, and it was hanging down between the main landing gear. Somebody asked what that "thingy" was, a quick witted mechanic said it's the "trolling motor", you get 3 knots while fishing....... (grin)
Buzz Fuselsausage, Line Mechanic by night, DC-3 Crew Chief by choice.