The RAM and the loss of all powers???

[AeroTech]

Hi,

In case of automatic deployemt of the RAT, what are the components (electrics & hydraulics, besides the main flight controls) that are provided by the RAT (we suppose the RAT provides hydraulic and electric power)

I am asking this question, because I am wondering about the landing : may be flaps up, no reversers, no spoilers, and may be no brakes (I am not sure if these components are provided or no by hydraulic, because the power of the RAT seems limited mainly at landing).
Also the battery supplies electricty to certain important flight instruments through the inverter, does the RAT provide electricity to other flight instruments or other devices? If yes, what are these intruments or devices?

I am wondering mostly about any Boeing and Airbus aircrafts fitted with RAT (preferably the recents, but other aircrafts are welcome).

Thank you.
Best regards.

[Mr @ Spotty M]

You will find the RAT only gives Hydraulic power, Electric power is from the Batteries.

[Bus429]

Aero,

Can only speak of the 757, 767, A300 series but RATonly supplies hydraulics.

[AeroTech]

Hi,

I think some RATs provide only hydraulic power, other provide hydraulic and electric power. Any feedback is very appreciated
regarding the two kinds of RAT, but mainly about the components (hydraulic and electric that are provided by the RAT).
Thank you.
Best regards

[matkat]

RAT on A320(Family)and A330 also supply electrical power.

[ICT_SLB]

Depends entirely on the aircraft. For Boeing 767, the RAT is hydraulic but is used to power an auxiliary generator at least on ETOPS aircraft. On all Bombardier aircraft (CL65, CRJ & GX) the RAT is an Air Driven Generator (ADG) that's prime use is to power the main pump for Hydraulics 3 and also provides power to all Essential & Battery Bus units up to approximately 15 kVA. In most cases the prime purpose is to provide hydraulics to power the flight controls power drive units as there is no direct manual link to the surfaces (think fly by wire with one channel prestressed cable).

Don't forget that on most aircraft the primary backup is not the RAT but, in practice, the APU which can provide at least 25 kVA. The reason it's not relied on is that it is nigh impossible to certify an APU as "Essential" such that it can be guaranteed to start & run over the entire flight envelope.

[Blacksheep]

Typically, for large air transport aircraft you get just enough hydraulics to keep the aircraft flying. They'll give you roll control through a selected few of the available spoilers and pitch through the stab trim. Emergency braking too - Gear extensions is by free-fall. Emergency electrics may run from a hydraulic generator to power only essential services - i.e. standby instruments and one radio.

The idea is to keep the aeroplane going while you try to restore power - by starting the APU for example. If you're out of fuel and the donkeys stop, the APU won't go either. It is possible to land the aircraft, as Air Canada already demonstrated with a 767, but its a heroic effort to make it work with limited flight controls and a high speed flapless landing. Still, they say any landing you can walk away from is a good one.

[AeroTech]

Hi,

Thank you guys for your posts.

Sorry guys, but the image is still unclear for me
Could be please give me confirmation about the following statements and questions (we assume the APU is not working, out of fuel):

1-Are the main flight controls(rudder, elevator, aileron) provided by the RAT?

2-Are the brakes provided by the RAT? (or they are provided by accumulator, Nitrogen)

3-It seems the flaps and the reversers are not provided by the RAT. (?)

4- Are the stab trim and the spoilers (few spoilers) provided by the RAT? Are these spoilers actuated in flight or on the ground?

5-If the RAT provides also electric power, are the flight standby intruments provided by this power?
If yes, does the battery(s) provide other flight standby instruments (or the same instruments provided by the RAT)? If other or different flight standby instruments and devices are provided, what are these instruments and devices?

6-Are the recent aircrafts provided with one battery or two (Boeing and Airbus aircrafts)? If they are provided by two batteries, the standby power will be available for 60 minutes???

Thank for your answers in advance.
Best regards.

[Blacksheep]

Answers for B767. They would be typical for other types though...

1. No, not usually. Lateral control by limited spoilers, Pitch by stabiliser trim.

2. Accumulator.

3. No flaps, no reversers

4. As per 1. Flight Spoilers, and not all of them. Only those from the hydraulic system that is powered by the RAT. In the case of a B767 for example - the centre system.

5. A Hydraulic Motor Generator provides emergency ac power - basically the standby instruments and VHF1. With the HMG running you won't deplete the batteries.

6. B767/B757 have two batteries. One is for the dc power system the other is for APU starting. There is a customer option available that allows for coupling the two together in emergency. The theory is that you get more chance of starting the APU. You wouldn't even try if you'd run out of fuel one hopes...

... because the reality is that in the extremely unlikely event of the APU failing to start, you have consumed available battery life. If you try but fail to get the APU going, don't bet on them lasting for 30 minutes, let alone 60.

Maybe you worry too much!

[aintsaying]

AeroTech
Think of the rat as your last chance. The rat will provide power (hydraulic or electric) to the Bare Minium items on that aircraft to fly and hopefully land.
So what do you need to fly? Airspeed indicator, altitude indicator, Airtfical horizon, then you'll need to talk to someone so you'll need a radio.
Everything else from then on depends on the aircraft type, gear will free fall, you might need hydraulics to power flight controls, etc.
So depending on the type of aircraft you want to talk about, you will have different setups, different requirements, etc.