Are all modern commercial aircraft fitted with ram air turbines?

many incorrect answers here ... rat emergencies only. commercial airliners equipped them. fewer civilian aircraft fitted them

ram air turbine (rat) small turbine , connected hydraulic pump, or electrical generator used emergency power source aircraft. in case of loss of both primary , auxiliary power sources rat power vital systems (flight controls, linked hydraulics , flight-critical instrumentation). rats produce hydraulic power, used power electrical generators.

modern aircraft generate power through main engines or additional fuel-burning turbine called auxiliary power unit, small tail-mounted turbine engine. rat generates power airstream due speed of aircraft, , if aircraft speeds low rat produce less power. in normal conditions rat retracted fuselage (or wing), deploying automatically in emergency power loss. in time between power loss , rat deployment, batteries used.

rats common on military aircraft, sudden , complete loss of power more likely. fewer civilian aircraft fitted them, although commercial airliners (since 1960s on vickers vc-10). airbus a380 has largest rat propeller in world @ 1.63 m in diameter, around 80 cm more common. typical large rat on commercial aircraft can capable of producing, depending on generator, 5 70 kw. propellers started two-bladed or four-bladed models military (and increasingly commercial) models use ducted multi-blade fans. smaller, low airspeed models may generate little 400 watts.

in military use, pod-fitted units such m61a1 vulcan or electronic systems (e.g. an/alq-99 tjs) can powered rat in standard operation.

in non-military use, rats have been used power centrifugal pumps pressurize spray systems on aircraft used crop dusters deliver liquid agents cropland. major reason choosing rat safety; using rat allows faa-certified engine , power systems on aircraft remain unmodified. there no need use engine power takeoff drive pump, , pump can placed low or below exterior of airframe simplifying plumbing, , being lowest point in plumbing, have gravity feed spray tanks , never need primed. in event of pump failure result in seizure, there no effect on flying ability of aircraft or systems apart obvious fact spray systems non functional.

honeywell , hamilton sundstrand main suppliers of rat systems.

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

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