1. Airbus A350 Ram Air Turbine Stowage Overview
In the Airbus A350 electrical power architecture (ATA 24), emergency AC power is provided by the Ram Air Turbine (RAT) generator in the event of total normal AC electrical generation loss. To protect the assembly during normal flight regimes and preserve clean aerodynamic airflow, the entire RAT module is stowed inside an enclosed bay in the fuselage belly fairing.
The stowage system comprises the structural mounting frame, the deployment and retraction actuator, aerodynamic fairing doors, the ground service RAT Stow Panel 7215VU, mechanical uplock latches with position microswitches, and hydraulic lines connected to the aircraft Green hydraulic system. Stowage and retraction are performed strictly on the ground following scheduled maintenance deployment tests or in-flight emergency extensions.
2. Component Location & Structural Installation (Zone 192)
According to the Airbus A350 Technical Training Manual, the Ram Air Turbine stowage hardware is installed in the forward-to-mid section of the right-hand belly fairing:
Zone 192 (RH Belly Fairing)
The RAT module is installed in Zone 192 on the right-hand belly fairing structure. Mechanically, the module spans longitudinally between fuselage Frame 44 (FR44) and Frame 47 (FR47).
Door 192KB & Door 192FB
The RAT deploys downward through bottom fairing door Door 192KB. For ground servicing, access to the RAT stow panel 7215VU is provided via Door 192FB, located on the right-hand belly fairing at Frame 45.
The structural layout and access mechanisms are summarized in the maintenance reference table below:
| Hardware Component / Unit | Designation | Aircraft Location | Access / Operating Means |
|---|---|---|---|
| RAT Module Assembly | RAT Module | RH Belly Fairing, FR44 – FR47 (Zone 192) | Door 192KB (Bottom Fairing) |
| RAT Stow Panel | 7215VU | RH Belly Fairing, Frame 45 | Door 192FB (Hinged Access Door) |
| Retraction Actuator | Actuator Cylinder | Inside RAT Compartment (FR44–FR47) | Green Hydraulic System |
| Uplock Latch Mechanism | Mechanical Uplock Hook | Internal Upper Bay Structure | Position Microswitches & STOWED Light |
3. RAT Stow Panel 7215VU: Controls & Annunciators
The RAT Stow Panel 7215VU is the primary ground maintenance interface for re-stowing the Ram Air Turbine following extension. Located behind hinged access door 192FB on the right-hand belly fairing at Frame 45, the panel integrates dedicated actuation switches and visual status lamps.
Panel Controls (Switches)
- RAT RETRACT Switch: A spring-loaded multi-position switch that defaults to the OFF position. When pushed and held in the RETRACT position, electrical command is sent to the retraction control valve, directing Green hydraulic pressure into the actuator cylinder.
- LAMP TEST Switch: A momentary test switch that illuminates both the STOWED and PRESS lamps to verify filament integrity prior to starting the retraction sequence.
Panel Annunciators (Indicators)
- STOWED Indicator: Illuminates green when internal position microswitches verify that the RAT module has reached its full upper travel limit and the mechanical uplock hook is fully latched.
- PRESS Indicator: Indicates that sufficient operating hydraulic pressure is available from the Green hydraulic system to power the retraction actuator.
4. Actuation Mechanics: Green Hydraulic Retraction & Ejection Springs
The Airbus A350 RAT deployment and stowage architecture utilizes an asymmetric energy design to guarantee fail-safe emergency deployment in flight while restricting retraction exclusively to ground operations:
In-Flight Deployment (Mechanical / Spring Energy)
In flight, RAT deployment requires zero hydraulic or electrical power. Releasing the uplock hook allows powerful internal ejection springs and gravitational/aerodynamic forces to immediately push the RAT assembly out through door 192KB into the external slipstream.
Ground Retraction (Green Hydraulic Power)
Re-stowing the RAT requires overcoming the high-force ejection springs. Ground retraction is performed exclusively by hydraulic pressure supplied by the Green Hydraulic System. Pressure is generated on the ground via an electrically driven hydraulic pump (powered by GPU) or an external ground hydraulic power cart.
Hub & Gearbox Alignment Mark Verification
Prior to commanding hydraulic retraction, ground personnel must verify that the alignment mark (arrow) on the turbine hub is correctly aligned with the alignment mark on the gearbox casing. Proper blade indexing is required so the turbine blades pass through the fuselage cutout and settle flush inside the bay without contacting structure or doors.
5. Step-by-Step Ground Retraction Procedure
According to the maintenance instructions in the A350 Technical Training Manual, maintenance technicians follow a strict sequential workflow to safely re-stow the RAT module:
Hydraulic System Pressurization
Pressurize the aircraft Green Hydraulic System using the ground electric motor pump or a connected ground hydraulic cart.
Blade Alignment & Access Door 192FB
Confirm that the turbine hub and gearbox alignment arrows are aligned. Open access door 192FB at Frame 45 on the right-hand belly fairing to access RAT Stow Panel 7215VU.
Lamp Test & Hydraulic Pressure Check
Actuate the LAMP TEST switch on panel 7215VU to verify lamp filament continuity. Confirm that the PRESS indicator confirms available Green hydraulic pressure.
Actuate and Hold RAT RETRACT Switch
Move and hold the spring-loaded RAT RETRACT switch in the RETRACT position. Green hydraulic pressure enters the actuator cylinder, pulling the turbine up against the ejection springs.
Uplock Latch Verification & Panel Closure
Maintain switch selection until the mechanical uplock engages and the green STOWED annunciator light illuminates steadily. Release the switch to OFF, verify fairing door 192KB is fully flush, and close and latch access door 192FB.
6. Technical Source Traceability & References
In strict adherence to technical grounding requirements, every factual statement, aircraft zone, frame station, door identifier, and panel control described in this article is traceable to the original source: