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View Full Version : Is the Ram Air Turbine considered an AC source?


MohBadawi
28th Nov 2018, 08:26
Hello fellow pilots,
This question might be type specific. However I appreciate general philosophy but I'm concerned more about the Embraer E190/170.
We have a company policy states that with a single AC source functioning onboard we shall declare emergency. the conflict then rises which is whether to declare emergency over single IDG ,with both otherside and apu gen inop, or not since we still have one more emergency source (RAT).

hans brinker
28th Nov 2018, 16:33
Hello fellow pilots,
This question might be type specific. However I appreciate general philosophy but I'm concerned more about the Embraer E190/170.
We have a company policy states that with a single AC source functioning onboard we shall declare emergency. the conflict then rises which is whether to declare emergency over single IDG ,with both otherside and apu gen inop, or not since we still have one more emergency source (RAT).

A320, same setup AFAIK. I was dispatched with number 2 GEN INOP, so we flew with the APU running and the APU GEN providing the second source. On leg 2 we had an auto-shutdown of the APU in cruise. I decided to divert, and asked for priority handling. No emergency was declared, and the company agreed with my decision. I would not continue on one GEN because I think the RAT is not a totally valid source of AC power as it will only power certain systems and not all the time (on the A320 you lose the RAT around 140kts, so there is a chance yours screens will go blank during the approach...). as far as your company policy goes, if it is required to declare an emergency when you are down to one source, I would take that as one REGULAR source and not count the RAT. If your company writes black and white policy about when to declare emergencies, they really need to write black and white guidance about what is considered a valid AC source.

Check Airman
28th Nov 2018, 17:02
Agree with hans. I wouldn't go off knowing that the RAT is my only backup.

Peter Chube
29th Nov 2018, 07:13
Does the RAT not load shed, on the Embraer, at around 130kts? If so I wouldn’t consider it a reliable AC source!

vilas
29th Nov 2018, 15:38
on the A320 you lose the RAT around 140kts, so there is a chance yours screens will go blank during the approach. Only very old A320s Rat used to stall on lowering the gear but not so anymore. 140kts is minimum approach speed for Rat it will guarantee it's operation all the time. Decision to divert will depend on some factors as the duration of the flight and maintenance at the next station. CRTare lost only at 50kts during roll out.