Are all modern commercial aircraft fitted with ram air turbines?

Question

(the propeller that spins in the wind flow to give power if engines stop)

Answer 1

I dont know of any that don't have a RAT. They are used to supply hydraulic pressure to the primary control surfaces in the event of a multiple engine failure. They usually deploy automatically.

To the other answerers.. think wind driven hydraulic pump, not jet engine!!

Answer 2

many incorrect answers here ... The RAT is for emergencies only. Most commercial airliners are equipped with them. Fewer civilian aircraft are fitted with them

A ram air turbine (RAT) is a small turbine and connected hydraulic pump, or electrical generator used as an emergency power source for aircraft. In case of the loss of both primary and auxiliary power sources the RAT will power vital systems (flight controls, linked hydraulics and also flight-critical instrumentation). Some RATs produce only hydraulic power, that is then used to power electrical generators.

Modern aircraft generate power through the main engines or an additional fuel-burning turbine called an auxiliary power unit, which is often a small tail-mounted turbine engine. The RAT generates power from the airstream due to the speed of the aircraft, and if aircraft speeds are low the RAT will produce less power. In normal conditions the RAT is retracted into the fuselage (or wing), deploying automatically in emergency power loss. In the time between power loss and RAT deployment, batteries are used.

RATs are common on military aircraft, where sudden and complete loss of power is more likely. Fewer civilian aircraft are fitted with them, although most commercial airliners are (since the 1960s on the Vickers VC-10). The Airbus A380 has the largest RAT propeller in the world at 1.63 m in diameter, but around 80 cm is more common. A typical large RAT on a commercial aircraft can be capable of producing, depending on the generator, from 5 to 70 kW. Propellers started as two-bladed or four-bladed models but military (and increasingly commercial) models now use ducted multi-blade fans. Smaller, low airspeed models may generate as little as 400 watts.

In another military use, pod-fitted units such as the M61A1 Vulcan or electronic systems (e.g. the AN/ALQ-99 TJS) can be powered by a RAT in standard operation.

In non-military use, RATs have been used to power centrifugal pumps to pressurize the spray systems on aircraft that are used as crop dusters to deliver liquid agents to cropland. The major reason for choosing a RAT is safety; using a RAT allows the FAA-certified engine and power systems on the aircraft to remain unmodified. There is no need to use an engine power takeoff to drive the pump, and the pump can be placed low or below the exterior of the airframe greatly simplifying plumbing, and being the lowest point in the plumbing, it will have gravity feed from the spray tanks and never need to be primed. In the event of a pump failure that could result in seizure, there is no effect on the flying ability of the aircraft or its systems apart from the obvious fact that the spray systems are non functional.

Honeywell and Hamilton Sundstrand are the main US suppliers of RAT systems.

Answer 3

The Ram Air Turbine (RAT) is a device to make a minimal amount of hydraulic power in case of all-engine failure.  

767, 777, 747-8, A380, etc.  have them.  

747-400 doesn't.

It's needed when the engine (in power off windmilling mode) doesn't make enough hydraulic pressure to move the flight controls.

Answer 4

Most modern commercial planes now use ram air jet engines, prop is less efficient, plus the ram air is a very useful way of supplying other equipment, for example air con, cabin pressure, ram air is used in most commercial aircraft.

Ok excuse my little knowledge on this i stand corrected ;)

Answer 5

If I remember correctly, the 747 does not have a RAT, instead using the windmilling of the four engines to provide emergency power.  I'm not sure of the details.

Answer 6

The most modern large passenger aircraft, the Airbus A-380, certainly does have a rat. The propeller diameter of this is close to five feet.

Answer 7

No.

Answer 8

Most are, but not all.  Some simply have an emergency backup battery that can provide power for about 30 minutes to minimal systems.  Considering what would be required to lose all of your other generators, 30 minutes seems like a bit of overkill to me.

Answer 9

some

Answer 10

I believe so..............

Answer 11

Samg, I believe, is correct but there was an article in the business section this week that indicated that turboprops are getting another look because of fuel efficiency considerations.

Answer 12

No

Answer 13

I cannot speak for every aircraft, but I cannot think of any commercial aircraft that don't have a RAT.

That is not to say that some do not have it...  my guess is that most do.

Sorry I don't have anything more specific to tell you.