Jetdoctor From United Kingdom, joined Aug 2001, 257 posts, RR: 0 Reply 6, posted (10 years 3 weeks 4 days 9 hours ago) and read 4619 times:
The ERJ is so reliable that it doesn't need any RAT backup system......... hahahahahaha.
OK, all jokes aside the ERJ does have manual gear deployment, and there are 2 electical hydraulic pumps that can run off the battery, but as how long those batteries can last? I would not bet very long. Leave them on at the gate for more than 10 minutes, and they are dead enough to not start the APU.
Break ground, and head into the wind. Don't break wind and head into the ground.
Ramper@iah From United States of America, joined Dec 2001, 240 posts, RR: 1 Reply 7, posted (10 years 3 weeks 2 days 8 hours ago) and read 4514 times:
Basically, the EMB-145 would have to be out of gas in order for it to need backup hydraulic and electrical power in the form of an RAT. It has five 400 amp generators, two on each engine, and one on the APU. It has four seperate hydraulic pumps, one on each engine and two DC electric pumps. So even with both engines flamed out, every single system on the aircraft would work (assuming the APU is operartive).
Avt007 From Canada, joined Jul 2000, 2132 posts, RR: 5 Reply 8, posted (10 years 3 weeks 1 day 19 hours ago) and read 4485 times:
Rampers post brings up another question- can the ERJ APU operate in flight?
Not necessarily a dumb question, the Dash8 APU is disabled in flight, and the F28 APU runs, generator too , but the bleed air is disabled. So I'm curious about the ERJ.
Ramper@iah From United States of America, joined Dec 2001, 240 posts, RR: 1 Reply 9, posted (10 years 3 weeks 1 day 17 hours ago) and read 4472 times:
Yes, the APU on the EMB-145 can operate during flight and in some cases, it is required to be running (i.e. MEL'd generator on aircraft with the Integrated Standby Instrument System). It can handle the full electrical load as well as cabin pressurization.
Fr8tdog From United States of America, joined Feb 2000, 120 posts, RR: 0 Reply 13, posted (10 years 2 weeks 2 days 6 hours ago) and read 4327 times:
The "RAT" on the CRJ is called the ADG(air driven generator) that contains a ram air turbine and frequency is governed from a variable pitch 2 bladed impeller.
The ADG has two ways that it can be deployed, if loss of all AC power and the prox sensors are not indicating WOW it will deploy or it can be manually deployed by pulling the ADG man deploy handle on the lower center pedestal.
The CRJ's electrical sys. consist's of AC and DC pwr.
The AC pwr generation consist's of 2 IDG's and 1 APU gen. Each IGD (integrated drive generator) is driven off of the turbine engines and produces
3 phase, 115v, 400hz and 30 Kva. The APU gen is also 3 phase, 115v, 400hz and 30kva
The 28v DC pwr is supplied by 5, 100a TRU's (transformer rectifier units) located in the forward avionics bay, ahead of the flight deck.
ChallengerDan From Canada, joined Sep 2003, 167 posts, RR: 0 Reply 14, posted (10 years 2 weeks 1 day 18 hours ago) and read 4309 times:
The situation you described is why RAT or "ADG" exist. Double engine flame-out with the APU off-line. Let's put it in a simple way: If the aircraft looses all its regular sources of AC power, is it still flyable? On the CRJ, no, as the flight controls are hydraulically powered so you need the Air driven generator to power the Emergency hydraulic pump (3B).
I'm not familiar with the ERJ, but i suppose, if it doesn't have a RAT, its
has DC hydraulic pumps, with are powered by the battery on the emergency or direct bus.
It could also be in a situation with double Ac generators going offline at the same time, for some reason. As the APU is generally not runnig during normal cruise, the ADG would deploy to power the systems while you start the APU and get the APU gen online. Wouldn't want to be in a ERJ in this situation if you can't restart the APU in flight, altough i agree these are highly unprobable situations.
It's all a matter of electrical system architecture.
if your flight goes MX in YUL, I might be called to fix it!
Ramper@iah From United States of America, joined Dec 2001, 240 posts, RR: 1 Reply 15, posted (10 years 2 weeks 1 day 1 hour ago) and read 4262 times:
You can start the APU while in flight on the EMB-145. The only time a dire situation would exist is during a dual flameout with an unsuccessful APU start. In this case, aileron and rudder control would be accomplished by manual reversion and pitch control would be unaffected. Gear extension is also still possible via a manual control. The batteries would power essential aircraft instrumentation for up to 45 minutes.
The chances of having all four hydraulic pumps unavailable are slim. The likelihood of five DC generators being unavailable is slim to none.