Aircraft Accidents and the RAT

I once wrote an article about the dangers of heavy reliance on technologies. I don’t usually read the criticisms of articles I write; my mentor, Bill O’Brien told me not to. I also NEVER EVER respond; it’s a surefire way to get into arguments that are endless and pointless. But a responder wrote a comment that was heavy on ‘you-don’t-know-what-you’re-talking-about’ and with a good dose of the ‘technology-is-the-best-thing-since-sliced-bread’ lecture.
I don’t know why I did it; I immediately regretted it from the moment I hit SEND, but I wrote back, “Tell that to Sully.” Later that day the commenter wrote another page long response ending with “… and he had a RAT.”
I didn’t write back, convinced the commenter heard the term ‘RAT’ somewhere and used it as a weapon to make his/her point.
The acronym RAT stands for Ram Air Turbine; Douglas employed a similar device called an Air Driven Generator (ADG). It is used to power systems on a crippled airliner during emergencies. The RAT/ADG deploys from the fuselage into the airstream, its turbine or propeller catching the rushing air to turn it. The RAT or ADG turn this air energy into mechanical energy that powers the hydraulics or electronics of the aircraft. I had been trained on the A300 so I know Airbus employed them. However, I didn’t read the USAir 1549 report or see the movie ‘Sully’, so I’m not sure if he deployed the RAT in flight.
But I can think of reasons he would or wouldn’t.
Would: he would have gained hydraulic pressure for maneuvering. The RAT enables either hydraulics or electronics, but not both. The hydraulics would have enabled them to steer easier. They would have been able to use standby gauges – of the analog type, not digital – to track the aircraft’s rate of descent, altitude, attitude and direction.
Would not: the aircraft at that moment with no engines becomes a flying rock; it has a glide ratio, but without the altitude needed, the glide ratio only works best with the wind helping. To deploy the RAT creates drag. The fully loaded aircraft (full fuel, passengers and luggage) needed two things to stay aloft: altitude and speed, otherwise it gives out to gravity and drag. Adding an air driven unit into the airstream adds drag. And then there’s the question of the aircraft moving fast enough to make the RAT usable; it was a glider with a slow speed, perhaps not sufficient to turn the RAT enough to benefit from it.
And then the question of what happens when they hit the water. The RAT would surely break free; it could puncture the fuselage, decreasing the precious time to evacuate considerably. The RAT could also have become a missile propelled back by the airliner’s forward momentum to pierce the fuselage and bounce around the cabin. And yes, it has happened where something as soft a seagull broke through the metal and took out a pilot.
I’m going to have to find time to read that report.

One thought on “Aircraft Accidents and the RAT”

  1. Read the NTSB report and see the movie. The RAT deployed automatically. They also started the APU. The movie depicted the simulator pilots skipping that step and saving a few seconds. Clint Eastwood used the A/A simulator. The pompous NTSB civil servants were depicted nicely, but probably incorrectly, in the movie. They didn’t like the movie. A lot of it was fictionalized for ticket sales.

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