Ram air turbine
Overview
 
A ram air turbine is a small turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

 that is connected to a hydraulic pump, or electrical generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

, installed in an aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 and used as a power source. The RAT generates power from the airstream due to the speed of the aircraft.

With the exception of crop dusters (see below), modern aircraft only use RATs in emergency — 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).
Encyclopedia
A ram air turbine is a small turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

 that is connected to a hydraulic pump, or electrical generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

, installed in an aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 and used as a power source. The RAT generates power from the airstream due to the speed of the aircraft.

With the exception of crop dusters (see below), modern aircraft only use RATs in emergency — 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, which is in turn used to power electrical generators. In some early aircraft (including airships), small RATs were permanently mounted and operated a small electrical generator or fuel pump
Fuel pump
A fuel pump is a frequently essential component on a car or other internal combustion engined device. Many engines do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank through a line or hose to the engine...

.

Modern aircraft generate power in the main engines or an additional fuel-burning turbine engine called an auxiliary power unit
Auxiliary power unit
An auxiliary power unit is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft, as well as some large land vehicles.-Function:...

, which is often mounted in the rear of the fuselage or in the main-wheel well. 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), and is deployed manually or automatically following complete loss of power. In the time between power loss and RAT deployment, batteries are used.

RATs are common in military aircraft which must be capable of surviving sudden and complete loss of power. Many modern types of commercial airliners are equipped with RATs. In the 1960s the Vickers VC10
Vickers VC10
The Vickers VC10 is a long-range British airliner designed and built by Vickers-Armstrongs Ltd, and first flown in 1962. The airliner was designed to operate on long-distance routes with a high subsonic speed and also be capable of hot and high operations from African airports...

 was one of the first types of airliner equipped with a RAT. The Airbus
Airbus
Airbus SAS is an aircraft manufacturing subsidiary of EADS, a European aerospace company. Based in Blagnac, France, surburb of Toulouse, and with significant activity across Europe, the company produces around half of the world's jet airliners....

 A380
Airbus A380
The Airbus A380 is a double-deck, wide-body, four-engine jet airliner manufactured by the European corporation Airbus, a subsidiary of EADS. It is the largest passenger airliner in the world. Due to its size, many airports had to modify and improve facilities to accommodate it...

 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. Smaller, low airspeed models may generate as little as 400 watts.

In other military uses, pod-fitted systems such as the M61A1 Vulcan or electronic systems (e.g. the AN/ALQ-99
AN/ALQ-99
The AN/ALQ-99 is an airborne electronic warfare system, found on EA-6B and EA-18G military aircraft.-System Description:The ALQ-99 is an airborne integrated jamming system designed and manufactured by EDO Corporation. Receiver equipment and antennas are mounted in a fin-tip pod while jamming...

 TJS) can be powered by a RAT in standard operation. Also, some free-fall nuclear weapons, such as the British Yellow Sun
Yellow Sun
Yellow Sun was the first British operational high-yield strategic nuclear weapon. The name actually refers only to the outer casing; the warhead was known as "Green Grass" and "Red Snow"...

 and Blue Danube
Blue Danube (nuclear weapon)
Blue Danube was the first operational British nuclear weapon. It also went by a variety of other names, including Smallboy, the Mk.1 Atom Bomb, Special Bomb and OR.1001, a reference to the Operational Requirement it was built to fill...

 used RATs to power radar altimeter
Radar altimeter
A radar altimeter, radio altimeter, low range radio altimeter or simply RA measures altitude above the terrain presently beneath an aircraft or spacecraft...

s and firing circuits; these were a more reliable alternative to batteries.

In non-military use, RATs have been used to power centrifugal pump
Centrifugal pump
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to create flow by the addition of energy to a fluid. Centrifugal pumps are commonly used to move liquids through piping...

s 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, in the case of the US, 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
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....

 and Hamilton Sundstrand
Hamilton Sundstrand
Hamilton Sundstrand, is a global corporation that manufactures and supports aerospace and industrial products for worldwide markets. It was formed from the merger of Hamilton Standard and Sundstrand Corporation in 1999. A subsidiary of United Technologies Corporation, HS is headquartered in Windsor...

 are the main US suppliers of RAT systems.

Aviation incidents

This is a list of aviation incidents involving a ram air turbine:
  • Air Canada Flight 143; better known as the Gimli Glider
    Gimli Glider
    The Gimli Glider is the nickname of the Air Canada aircraft that was involved in a notable aviation incident. On 23 July 1983, Air Canada Flight 143, a Boeing 767-200 jet, ran out of fuel at an altitude of ASL, about halfway through its flight from Montreal to Edmonton via Ottawa...

     incident
  • Air Transat Flight 236
    Air Transat Flight 236
    Air Transat Flight 236 was an Air Transat route between Toronto, Canada and Lisbon, Portugal flown by Captain Robert Piché and First Officer Dirk De Jager. On August 24, 2001, the flight ran out of fuel over the Atlantic Ocean with 306 people aboard...

  • The hijacking of Ethiopian Airlines Flight 961
    Ethiopian Airlines Flight 961
    Ethiopian Airlines Flight 961, a Boeing 767-260ER, was hijacked on , en route from Addis Ababa to Nairobi on a Bombay–Addis Ababa–Nairobi–Brazzaville–Lagos–Abidjan service, by three Ethiopians seeking political asylum in Australia. The plane crash-landed in the Indian Ocean near Comoros due to fuel...

  • Pinnacle Airlines Flight 3701
    Pinnacle Airlines Flight 3701
    Pinnacle Airlines Flight 3701 crashed on October 14, 2004, near Jefferson City, Missouri, United States. It was an overnight ferry flight from Little Rock, Arkansas, U.S. to Minneapolis-St. Paul International Airport, U.S...

  • US Airways Flight 1549
    US Airways Flight 1549
    US Airways Flight 1549 was US Airways' scheduled domestic commercial passenger flight from LaGuardia Airport in New York City to Charlotte/Douglas International Airport, Charlotte, North Carolina...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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