Ram Air Turbine (RAT): The Complete Guide — and Where to Buy, Exchange or Sell One

Technical Guides · 11 min read · Published 2026-07-19

A ram air turbine (RAT) is a small wind-driven turbine that deploys into the airflow to generate emergency electrical and/or hydraulic power when an aircraft loses its main engine-driven and auxiliary power sources. Driven only by the aircraft's forward speed, it powers essential flight controls, instruments, and critical systems long enough for the crew to fly and land safely. RATs are fitted to most transport-category aircraft (A320, A330, A350, 737, 777, 787, 747 and others) and are inspection- and cycle-driven components — tested on a schedule and overhauled or exchanged at defined intervals, which is why a steady aftermarket exists for serviceable and overhauled units.

Key Takeaways

A RAT is a last-line-of-defense backup: it needs no fuel, no engine, and typically no pilot action to deploy — only forward airspeed.
Electrical RATs drive a generator, hydraulic RATs drive a pump for a priority hydraulic system, and combined units do both — but all power essential systems only.
Deployment is automatic on triggers like loss of all AC power or dual-engine flameout; restowing is a ground maintenance action, not an in-flight one.
RATs and their subassemblies (governor, generator, pump, actuator) are inspection- and cycle-driven, creating constant aftermarket demand for NE, OH, SV, and AR units.
For a six-figure rotable like a widebody RAT, verified trace paperwork (FAA 8130-3, removal tag, back-to-birth where applicable) is what separates a sellable unit from shelf stock.

What Is a Ram Air Turbine?

The name comes from "ram air" — air rammed into the unit by the aircraft's forward motion. A ram air turbine is a small two-bladed turbine (visually similar to a propeller) mounted on a fold-out strut, stowed behind a door in the fuselage belly or wing root. When deployed, the airstream spins the turbine, and the turbine drives a generator, a hydraulic pump, or both.

The core idea is simple: every other power source on the aircraft ultimately depends on the engines or the APU. The RAT depends only on the aircraft moving through air — which a gliding aircraft is always doing. That makes it the last line of defense for powered flight controls and essential instruments. It needs no fuel, no engine, and, on most types, no pilot action to start.

What a RAT Powers (and What It Doesn't)

RAT output is small — enough for what matters and nothing else. Depending on the design, a RAT is one of three types:

Electrical RATs drive a generator that feeds the essential AC/DC busses — flight instruments, key avionics, and flight-control computers.
Hydraulic RATs drive a pump that pressurizes a priority hydraulic system, keeping primary flight controls moving.
Combined units do both — for example, powering a hydraulic system that in turn drives an emergency generator.

What it does not power: galleys, cabin systems, most lighting, and anything else non-essential. The design goal is control authority and situational awareness for the crew — enough power to fly the aircraft and land it, not to run it normally.

How and When a RAT Deploys

Deployment is automatic on most transport aircraft when defined triggers are met — typically loss of both engine-driven generators plus the APU generator, dual-engine flameout, loss of all AC power, or on some types a critical hydraulic system loss. Flight crews also have a manual deploy control.

Deployment is a one-way action in flight: springs or an actuator drive the unit into the airstream, and it cannot be easily restowed airborne. Restowing the RAT is a ground maintenance task performed after the event, which is one reason every deployment — real or from a functional test — touches the maintenance and parts ecosystem around these units.

RAT Components

A complete RAT installation is a system of individually serviceable subassemblies, and each of them is traded in the aftermarket in its own right:

Turbine and blades — the two-blade rotor that extracts power from the airstream.
Governor — a constant-speed control that pitches the blades to hold the turbine at its rated speed across the airspeed envelope.
Generator and/or hydraulic pump — the actual power producers, driven by the turbine.
Deployment actuator — extends the strut and locks the unit into the airstream; ram air turbine actuators are a frequent overhaul and exchange item.
Control and monitoring hardware — deployment logic, sensors, and indication.

Because these subassemblies wear at different rates (governor drift, pump seal wear, actuator seals), operators often source or overhaul them individually rather than replacing the complete unit.

RATs by Aircraft Type

Most transport-category aircraft carry a RAT, but the location, type, and part numbers differ by family. Applicable part numbers depend on the specific airframe effectivity and modification status — contact us with your MSN for the applicable part number for your aircraft.

Airbus A320 family (A318/A319/A320/A321) — hydraulic RAT powering the Blue hydraulic system, which in turn supports emergency electrical generation. We source serviceable and overhauled units and cores for this family — see the A320-family Ram Air Turbine part page and the RAT actuator.
Airbus A330/A350 — RAT-equipped widebodies; the A350's unit is among the larger RATs flying.
Boeing 737 — notably does not use a deployable RAT; standby power comes from batteries and the APU. Buyers searching "737 RAT" are usually looking for standby power or air-turbine starter components — send the part number and we'll confirm what fits.
Boeing 777 — combined hydraulic/electrical RAT in the wing-to-body fairing.
Boeing 787 — RAT-equipped; deploys automatically on loss of both engines or all electrical power.
Boeing 747 / Airbus A380 — RAT-equipped widebodies with type-specific units.
Regional jets — most modern regional families (E-Jet, CRJ) carry an air-driven generator or RAT variant.

We source serviceable and overhauled units and cores across these types, subject to per-request availability confirmation.

RAT Testing, Overhaul and Exchange

RATs are scheduled-maintenance components. Operators run periodic functional and deployment tests, and complete units go through overhaul on defined intervals or on condition — typical drivers are governor drift, generator or pump wear, and actuator seal degradation.

In the aftermarket, buyers see four condition codes on RAT units and subassemblies:

NE — New: unused, full OEM trace.
OH — Overhauled: disassembled, restored to spec, zero-timed by a certified repair station.
SV — Serviceable: inspected and tagged serviceable without full overhaul.
AR — As-Removed (core): removed without post-removal inspection; the input stock for the overhaul cycle.

This cycle — test, remove, overhaul or exchange, return to service — is why a steady aftermarket exists for these units, and why cores hold real value. For condition-code details, see our guide to New vs Overhauled vs Serviceable parts.

Buy, Exchange or Sell a Ram Air Turbine

Three paths, depending on which side of the transaction you're on:

1. Buy or exchange a serviceable/overhauled RAT. Need a RAT or RAT subassembly for an AOG or a scheduled swap? We source verified, physically-confirmed units with complete trace paperwork (FAA 8130-3, removal tag) — not ghost stock. Availability is confirmed per request. Send your part number and effectivity for a same-day quote.

2. Sell your RAT or RAT cores. Have removed, serviceable, or as-removed RATs on the shelf? We buy and broker RAT cores and complete units. Tell us what you're holding for a buyback range.

3. RAT exchange program. If your unit is due overhaul but the aircraft needs to keep flying, an exchange puts an overhauled unit on the aircraft now and your removed unit enters the overhaul cycle as the core.

Whichever path: paperwork decides value. A unit with a current 8130-3, removal documentation, and clean trace is a different asset from the same hardware without it — our guides on verifying 8130-3 tags and reading trace documentation cover exactly what to check.

Frequently Asked Questions

What does a ram air turbine do?

A ram air turbine deploys into the airflow to generate emergency electrical and/or hydraulic power when an aircraft loses its main and auxiliary power sources, powering essential flight controls and instruments so the crew can fly and land safely.

Has a ram air turbine ever been used in a real emergency?

Yes. In several well-documented dual-power-loss events, the deployed RAT provided the electrical and hydraulic power that kept flight controls working until landing. It is a proven last-resort system, which is why it is tested and maintained on a strict schedule.

Does a Boeing 787 have a ram air turbine?

Yes. The 787, along with the A320, A330, A350, 777, 747, A380 and most transport-category aircraft, is fitted with a ram air turbine as an emergency backup power source. The Boeing 737 is a notable exception — it relies on batteries and the APU for standby power instead of a deployable RAT.

How much does a ram air turbine cost?

Cost varies widely by aircraft type and condition — from a few thousand dollars for a core or an actuator to six figures for an overhauled complete unit on a widebody or current narrowbody. Pricing is quoted per part number, condition (New, Serviceable, Overhauled, As-Removed), and the trace documentation supplied with the unit.

Can a ram air turbine be restowed in flight?

Generally no. Once deployed, restowing a RAT is a ground maintenance task performed by maintenance personnel, not an in-flight action available to the crew.

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