Imagine flying at 30,000 feet when every single engine unexpectedly quits—a terrifying, but incredibly rare, scenario known as a “flameout.” While modern airliners have multiple backup systems, there is one unsung hero, a last-ditch power source that can mean the difference between disaster and a safe glide to the runway: the Ram Air Turbine (RAT).
What is this hidden propeller, and how does it manage to harness the air to power critical systems? In this deep dive, we’ll pull back the curtain on this vital piece of aviation technology, explain its purpose, and review a recent, high-profile incident involving an Air India flight.
What is a Ram Air Turbine (RAT)?
The Ram Air Turbine (RAT) is essentially a small, retractable wind turbine installed in an aircraft’s fuselage or wing. When all primary and auxiliary power sources fail—such as a catastrophic loss of engine and Auxiliary Power Unit (APU) power—the RAT is automatically or manually deployed into the fast-moving airstream.
Once deployed, the turbine’s blades spin rapidly, harnessing the ram pressure (the force exerted by the air due to the aircraft’s speed) to generate power.
- Key Components: The turbine blades are connected to a central hub, which drives either a hydraulic pump or an electrical generator, or sometimes both.
- Size and Output: According to aviation standards, typical RATs on large commercial airliners can generate anywhere from 5 to 70 kilowatts (kW) of power, though this is entirely dependent on the speed of the aircraft.
The Critical Use of the Ram Air Turbine
The RAT is not a backup for convenience; it is a dedicated emergency system designed for one purpose: to power the bare minimum of systems required to control and land the aircraft safely. It is the definition of redundancy in aviation.
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Powering Flight-Critical Systems
In a total power failure scenario, the RAT immediately supplies energy to the most vital components, ensuring the crew can maintain control:
- Flight Controls: It provides hydraulic pressure to operate the essential ailerons, elevators, and rudder—the surfaces needed to steer the plane.
- Essential Avionics: It powers a dedicated emergency bus-bar to run critical flight instruments, navigation systems, and at least one communication radio.
- Standby Systems: It can also power certain essential pumps and instruments required for basic operation.
The goal is to provide just enough hydraulic pressure and electricity to transform the aircraft from a heavy glider into a controllable one. While the aircraft’s battery bridges the gap between power loss and RAT deployment, the RAT is designed to operate for the entire remainder of the flight.
Latest Incident of Ram Air Turbine Deployment in India’s Aviation
While RAT deployment is incredibly rare, it makes headlines when it happens. A notable recent incident involved an Air India Boeing 787-8 Dreamliner flying from Amritsar to Birmingham (AI117) on October 4, 2025.
The Ram Air Turbine unexpectedly deployed on its own during the aircraft’s final approach at a low altitude (around 400 feet) near Birmingham.
- The Anomaly: Crucially, Air India reported that all electrical and hydraulic parameters were found to be normal despite the RAT’s automatic deployment.
- Regulatory Response: India’s aviation safety regulator, the Directorate General of Civil Aviation (DGCA), launched a detailed probe into the “uncommanded RAT deployment.”
- Pilot Concerns: The Federation of Indian Pilots (FIP) noted that the aircraft’s monitoring system detected a fault in a Bus Power Control Unit (BPCU), suggesting an underlying electrical issue may have incorrectly triggered the emergency system. This incident highlights the rigorous, investigative focus on system reliability, even when a flight lands safely.
Aviation Safety in Motion
The Ram Air Turbine stands as a testament to the layers of redundancy baked into modern aviation safety. While its deployment is a loud, clear signal that all primary systems have failed, its successful activation is always a successful demonstration of engineering saving lives. The RAT ensures that even the most dire emergencies are survivable, providing the flight crew with the power needed to execute a safe landing.
FAQs on Ram Air Turbine Deployment
Q1: Is a Ram Air Turbine always deployed when an engine fails?
No. Modern airliners have multiple power sources, including the remaining engine(s) and an Auxiliary Power Unit (APU). The RAT is deployed only if all primary and secondary power sources (like all engines and the APU) are lost.
Q2: How much power does a RAT generate?
A typical commercial airliner RAT can generate between 5 and 70 kW of power, but the exact output is dependent on the aircraft’s speed and altitude (ram pressure). The slower the plane, the less power is produced.
Q3: Can a pilot manually deploy the Ram Air Turbine?
Yes. In most modern aircraft, the pilot can manually deploy the RAT from the cockpit as a precautionary measure, even if the automatic deployment system has not been triggered.
Q4: Does the RAT increase drag on the aircraft?
Yes. Deploying the RAT exposes a small fan into the airstream, which significantly increases aerodynamic drag. This means the aircraft’s glide distance is reduced, requiring the pilots to adjust their emergency landing plan accordingly.
Q5: What is the most famous incident where a RAT was used?
The most famous example is the “Gimli Glider” incident in 1983 (Air Canada Flight 143), where a Boeing 767 ran out of fuel mid-flight. The RAT deployed successfully, providing the necessary hydraulic power for the crew to control the aircraft and perform a non-fatal glide-landing.
