Airbus A350 Electrical Power Control: ATA 24 Indicating, Sources & Reconfiguration

01 · Cockpit Control Architecture

Cockpit Control Architecture: Panels 225VM, 211VM, 255VM & 222VM

The primary human-machine interface for the Airbus A350 Electrical Power System is distributed across four distinct overhead panels and two maintenance reset panels, as specified in the maintenance course syllabus. System designers consolidated operational controls on the forward overhead while isolating emergency and ground maintenance functions into segregated structural panels:

1. Overhead Panel 225VM (Electrical Section — ELEC)

Positioned in the central overhead console, panel 225VM contains all primary controls for standard flight operations. The panel is logically divided into three primary functional zones:

• Battery Control Section (Upper LH Area): Four identical bi-stable pushbuttons control the connection of the aircraft batteries: BAT 1, BAT EMER 1, BAT EMER 2, and BAT 2. In normal operation, each pushbutton is pressed in (ON position), with the white OFF legend extinguished. When released, the white OFF legend illuminates. If an internal battery or charger fault occurs, an amber FAULT legend illuminates, accompanied by an ECAM alert message on the Warning Display (WD).
• Generation & External Power Section: Controls for the four engine-driven Variable Frequency Generators (GEN 1A, GEN 1B, GEN 2B, GEN 2A) and the APU GEN (the 230 VAC starter/generator managed under ATA 49). Each generator pushbutton presents a split-legend display: an amber FAULT lamp indicating generator trip or protective opening, and a white OFF legend indicating manual disconnection. Flanking the center are the EXT 1 and EXT 2 pushbutton switches, featuring a green AVAIL legend (GPU connected with nominal frequency and voltage) and a blue ON legend (external power contactor closed to energize the aircraft network).
• Network Reconfiguration & Load Management:
  • BUS TIE P/BSW: Controls automatic cross-tie reconfiguration. When pushed (normal), the OFF legend is dark, and the Electrical System Controller automatically manages Bus Tie Contactors (BTCs). When released, the white OFF legend illuminates, opening the tie contactors to completely isolate each 230 VAC main busbar.
  • SIDE 1 & 2 ISOL P/BSW: Dedicated to the electrical smoke isolation procedure. When pushed (normal), the ON legend is dark and normal tie reconfiguration is permitted. When released during smoke drills, the white ON legend illuminates, opening tie contactors to isolate side 1 from side 2 and prevent electrical smoke propagation.
  • ELM P/B: Controls the Electrical Load Management Function (ELMF). When pushed (normal), the OFF legend is dark and the ELMF automatically manages load shedding. If an internal fault occurs, an amber FAULT illuminates; releasing the button disables automatic load management, illuminating white OFF.

2. Overhead Panel 211VM (Emergency Electrical Power — EMER ELEC PWR)

Panel 211VM houses the emergency generation controls. Its central feature is the red guarded RAT MAN ON pushbutton switch. While the Ram Air Turbine deploys automatically in flight upon total Loss of Main Electrical Power (LMES), lifting the guard and pressing RAT MAN ON forces immediate pyrotechnic/hydraulic deployment. An adjacent EMER GEN FAULT amber annunciator illuminates if the emergency generator fails to come on line or experiences out-of-tolerance voltage/frequency parameters.

3. Maintenance Overhead Panel 255VM

Located in the right-hand overhead console, panel 255VM is reserved for ground testing and maintenance procedures. It contains three critical specialized sub-systems:

• Battery Voltage Indication: A five-position rotary selector switch (OFF, BAT 1, EMER 1, BAT 2, EMER 2) connected directly to a dedicated digital LCD voltmeter, allowing line maintenance personnel to measure open-circuit and loaded battery terminal voltages directly from the cockpit without energizing the aircraft electrical network.
• ELEC REMOTE C/B CTL Pushbutton Switch: Powers the Power Distribution Maintenance Interface (PDMI) on a completely cold aircraft using emergency batteries, illuminating a blue ON legend.
• Towing on Battery Power: A dedicated POWER pushbutton switch and a three-level vertical CHARGE annunciator (HIGH green, MED amber, LOW red) that powers ground towing intercoms and external lights from Battery 1.

4. Panel 222VM (Ground Hydraulic — GND HYD) & Reset Panels

Overhead panel 222VM contains the GREEN ELEC PUMP guarded "AUTO" pushbutton switch. Because the Ram Air Turbine actuator utilizes Green hydraulic system pressure for on-ground retraction, panel 222VM provides the necessary control to pressurize the Green hydraulic circuit during ground maintenance. Additionally, maintenance reset panels 213VM and 232VM house the manual RESET pushbuttons for Transformer Rectifier 1 (TR 1) and Transformer Rectifier 2 (TR 2).

02 · Electronic Centralized Aircraft Monitoring

ECAM Indicating: ECP 135VM, SD Rotary Selector & Upper Center DU

Electrical system status, voltages, currents, and component failure alerts are processed by the Flight Warning System (FWS) and Control and Display System (CDS) and presented on the Upper Center Display Unit (DU-UPPER, CENTER). The layout and control methodology introduce a fundamental operational rule unique to the A350:

Display Partitioning on the Upper Center DU

The Upper Center Display Unit is optically partitioned into two distinct vertical display domains:

• Left-Hand Side: System Display (SD): Displays system synoptic diagrams commanded by the ECP hard keys:
  • EL/AC Key: Displays the 230 VAC and 115 VAC distribution network synoptic, showing real-time generator symbols (green triangles for online VFGs, amber crosses for tripped units), percentage electrical loads, operating voltages, frequencies, bus contactor states (green closed lines, amber open lines), and ATU step-down performance.
  • EL/DC Key: Displays the 28 VDC network, showing Transformer Rectifier outputs (TR 1, TR 2, EMER TR 1, EMER TR 2 nominal 28 V / 15 A), main and emergency battery parameters (BAT 1, BAT 2, EMER BAT 1, EMER BAT 2 nominal 27 V / 8 A), battery charge contactors, and DC busbar tie statuses.
  • STS Key: Displays the aircraft Status page, listing inoperative systems (INOP SYS) and maintenance status messages following electrical faults.
• Right-Hand Side: Warning Display (WD): Displays real-time operational cautions, warnings, and procedural checklists generated by the FWS. Electrical alerts (such as ELEC ATU 1A FAULT or battery fault warnings) appear with associated crew action items and color-coded severity levels.

03 · Ground Servicing Infrastructure

Ground Service Power & External Power Panel 925VU

To minimize fuel consumption, auxiliary power unit run hours, and unnecessary electrical system energization during ground turnaround and cabin cleaning, the A350 incorporates a dedicated ground servicing power architecture.

Ground Service Control Switches (GND SVCE CTL 1 & 2)

Servicing loads — including cabin cleaning lighting, ground utility receptacles, cargo door operation, and ground hydraulic servicing — can be energized without powering the primary flight avionics, cooling packs, or flight control computers. This is accomplished using two independent, two-position toggle switches:

• GND SVCE CTL 1 (Cabin Location): Installed inside the main passenger cabin on the left-hand frame of Door 1L (M1L). Flight attendants or cabin maintenance staff can toggle this switch to ON upon entry to illuminate cabin servicing lights directly from an available ground power unit.
• GND SVCE CTL 2 (Ramp Exterior Location): Installed on the exterior of the aircraft on the right-hand structure of the Nose Landing Gear (NLG). Ramp service personnel can activate ground servicing power directly from the tarmac without climbing into the cockpit.

Actuating either switch to ON closes the Ground Service Contactor (GSC), routing external power receptacle 1 (GPU 1) directly to the Ground Service Busbars without closing the main External Power Line Contactor (EPLC 1).

External Power Panel 925VU (Aft of NLG Bay)

The primary ground power interface is mounted at the rear of the nose landing gear wheel bay on Panel 925VU. The panel accommodates connections for two independent 90 kVA Ground Power Units (EXT PWR 1 and EXT PWR 2), a LIGHT TEST pushbutton, and four critical status indicator lamps:

04 · Multi-Voltage Architecture

Multi-Voltage Distribution Network: 230 VAC, 115 VAC & 28 VDC

The A350 electrical architecture, outlined in detail on page 18 of the maintenance manual, departs from older 115 VAC-centric designs. By adopting 230 VAC Variable Frequency generation, conductor cross-sectional area and cable weight are drastically reduced while delivering substantial power to large motor loads (such as electric hydraulic pumps, environmental control fans, and wing ice protection systems).

1. Primary Generation: 230 VAC Variable Frequency

In flight, primary electrical power is supplied by four engine-mounted Variable Frequency Generators (VFGs):VFG 1A and VFG 1B on Engine 1, and VFG 2B and VFG 2A on Engine 2. Each VFG is equipped with an integral oil sight glass for direct visual inspection of lubrication levels during pre-flight maintenance. Each VFG connects to its corresponding 230 VAC main busbar through a Generator Line Contactor (GLC):

• VFG 1A feeds 230 VAC bus AC 1A via contactor GLC 1A.
• VFG 1B feeds 230 VAC bus AC 1B via contactor GLC 1B.
• VFG 2B feeds 230 VAC bus AC 2B via contactor GLC 2B.
• VFG 2A feeds 230 VAC bus AC 2A via contactor GLC 2A.

Auxiliary 230 VAC power is provided by the APU Starter/Generator (APU S/G), which connects through the Auxiliary Generator Line Contactor (AGLC) and Starter Line Contactor (SLC). When on the ground, External Power Receptacles 1 and 2 route 230 VAC through contactors EPLC 1 and EPLC 2 to feed side 1 and side 2.

2. Secondary Transformation: 115 VAC via Auto-Transformer Units (ATUs)

Because standard avionics, flight instruments, cockpit displays, and specific fuel pumps require 115 VAC, the A350 utilizes six high-efficiency Auto-Transformer Units (ATUs) to step down 230 VAC to 115 VAC without electrical isolation:

• ATU 1A: Steps down 230 VAC from bus AC 1A to feed 115 VAC bus AC 1A.
• ATU 1B: Steps down 230 VAC from bus AC 1B to feed 115 VAC bus AC 1B.
• ATU 2B: Steps down 230 VAC from bus AC 2B to feed 115 VAC bus AC 2B.
• ATU 2A: Steps down 230 VAC from bus AC 2A to feed 115 VAC bus AC 2A.
• EMER ATU 1: Steps down 230 VAC from emergency bus AC EMER 1 to feed 115 VAC bus AC EMER 1. It also features a cross-connection to STATIC INVERTER 1 (providing 115 V backup via line 115V INV AC1).
• EMER ATU 2: Steps down 230 VAC from emergency bus AC EMER 2 to feed 115 VAC bus AC EMER 2.

3. DC Conversion: 28 VDC via Transformer Rectifiers (TRs)

Conversion from alternating current to 28 VDC is accomplished by four Transformer Rectifiers:

• TR 1: Powered from 230 VAC bus AC 1A, delivers 28 VDC (nominal 28 V / 15 A) to main bus DC 1. Resettable from cockpit panel 213VM.
• TR 2: Powered from 230 VAC bus AC 2A, delivers 28 VDC to main bus DC 2. Resettable from cockpit panel 232VM.
• EMER TR 1: Powered from emergency bus AC EMER 1, supplies 28 VDC to emergency bus DC EMER 1.
• EMER TR 2: Powered from emergency bus AC EMER 2, supplies 28 VDC to emergency bus DC EMER 2.

Specialized DC distribution buses branch from this core, including DC SHED GS 1 and DC SHED GS 2 (shed via contactors SGSC 1/2 and ESEC 3/4), evacuation buses DC EVAC 1/2, and the dedicated maintenance buses DC PDMI 1 and DC PDMI 2.

4. Battery Storage & Charging

Four 27 V nominal batteries maintain DC stability, provide cold aircraft starting, and back up flight-critical avionics:

• BAT 1: Dedicated main battery, charged via BATLC 1 from bus DC 1. Supplies the towing circuit.
• BAT 2: Dedicated main battery, charged via BATLC 2 from bus DC 2.
• EMER BAT 1: Emergency battery, charged via EBATLC 1 from bus DC EMER 1.
• EMER BAT 2: Emergency battery, charged via EBATLC 2 from bus DC EMER 2.

05 · Reconfiguration & Shedding Logic

Bus Reconfiguration, Isolation Logic & Electrical Load Management (ELMF)

The A350 power network is designed to remain fully operative under single or multiple generator failures through automatic contactor management, while providing definitive crew overrides for abnormal procedures.

Automatic Bus Tie Contactors (BTCs) & System Isolation Contactors (SICs)

Under normal flight conditions, power sources operate isolated or parallel-reconfigured via solid-state logic controllers:

• Bus Tie Contactors: Contactors BTC 1A, BTC 1B, BTC 2B, BTC 2A, BTC 3, and BTC 4 close automatically if a generator fails, transferring the unpowered busbar to an adjacent operating VFG, the APU generator, or external power.
• System Isolation Contactors: Contactors SIC 1, SIC 2, SIC 3, and SIC 4 reconfigure cross-side feeder lines to balance generator loads.

Manual Isolation Overrides

Two cockpit pushbuttons on panel 225VM can completely override this automatic logic:

• BUS TIE Pushbutton Switch: Releasing this switch to the OFF position (white OFF illuminated) locks open all BTCs and SICs. Each 230 VAC main busbar (AC 1A, AC 1B, AC 2B, AC 2A) is isolated to its dedicated source, preventing cross-feeding in the event of busbar faults or suspected short circuits.
• SIDE 1 & 2 ISOL Pushbutton Switch: Designed specifically for the cockpit electrical smoke elimination procedure. Releasing this switch to the ON position (white ON illuminated) isolates side 1 from side 2, forcing all cross-tie contactors open. The flight crew can then systematically depower one side of the aircraft to identify and eliminate the smoke source without risking total loss of the remaining healthy side.

Electrical Load Management Function (ELMF)

The ELM P/B on panel 225VM governs the Electrical Load Management Function. ELMF continuously calculates total electrical demand against available generator capacity:

• Pushed (Normal): OFF legend dark. If an engine or VFG fails, ELMF executes prioritized, sequential load shedding — disconnecting non-essential commercial loads (galley ovens, in-flight entertainment, secondary cabin lighting) to preserve full electrical power for flight controls, navigation, and fuel pumps.
• Amber FAULT: Illuminates if the ELMF software application encounters internal processing errors or loses bus sensor inputs.
• Released (Inoperative): White OFF illuminates. Automatic load shedding is inhibited, and shedding must be managed manually by the crew.

06 · Battery Operations & Ground Movement

Battery Management, Cold Aircraft Starting & Towing on Battery Power

The Airbus A350 features advanced battery health monitoring, cold aircraft maintenance access, and dedicated towing capabilities without requiring main aircraft electrical power.

Direct Battery Voltage Reading via Panel 255VM

On maintenance overhead panel 255VM, the 5-position rotary selector switch provides a hardwired, analog-to-digital measurement channel to a dedicated LCD voltmeter display. This allows line maintenance personnel to verify the static open-circuit voltage of any of the four batteries (BAT 1, BAT 2, EMER BAT 1, EMER BAT 2) prior to starting or dispatch. A nominal battery displays approximately 27.6 V to 28 V; voltages below dispatch thresholds indicate that charging or replacement is required.

Towing on Battery Power Architecture

Airport operations often require repositioning or towing an aircraft across active taxiways when neither ground power nor the APU is available. Legacy aircraft require running the APU solely to power exterior navigation lights and flight deck-to-tug intercoms.

The A350 solves this through the TOWING ON BAT POWER function on panel 255VM:

• Pressing the POWER pushbutton switch on panel 255VM activates a dedicated static circuit directly from BAT 1.
• This powers mandatory towing systems: VHF 1 radio, nose landing gear tow interphone, flight deck intercom, and external navigation/anti-collision towing lights.
• A vertical CHARGE annunciator continuously displays Battery 1 State of Charge (SOC):
  • HIGH (Green): Battery 1 has >75% charge; extended towing authorized.
  • MED (Amber): Battery 1 charge is moderate (50%–75%); towing permitted for limited duration.
  • LOW (Red): Battery 1 charge is insufficient (<50%); towing on battery power is prohibited.

07 · Digital Circuit Protection

Circuit Protection: Solid-State (SSPC/RCCB) vs. Classical C/Bs

One of the most profound evolutions in ATA 24 on the A350 is the transition away from flight deck circuit breaker walls to a dual-tier circuit protection philosophy:

Cold Aircraft Powering: The REMOTE C/B CTL Logic

A common line maintenance dilemma on modern fly-by-wire aircraft is the need to isolate circuit breakers on an unpowered aircraft during towing or ramp parking. On the A350, technicians do not need to connect an external GPU or start the APU to open electronic breakers:

1. The technician accesses cockpit maintenance overhead panel 255VM.
2. Pressing the ELEC REMOTE C/B CTL pushbutton switch illuminates a blue ON legend.
3. This energizes dedicated battery feeder contactors, connecting EMER BAT 1 and EMER BAT 2 to 28 VDC distribution lines DC PDMI 1 and DC PDMI 2.
4. The Power Distribution Maintenance Interface (PDMI) processor boots up, energizing the Onboard Maintenance Terminal (OMT) in the cockpit and exterior Portable Maintenance Access Terminal (PMAT) receptacles.
5. The technician opens, locks, or tags the required SSPCs or RCCBs directly from the screen. An automatic timer circuit prevents the batteries from draining below flight-dispatch limits.

08 · Maintenance Software Interface

PDMMF Maintenance Application: Search Mode & AMM Job Card Mode

Circuit protection management on the Onboard Maintenance Terminal (OMT) and PMAT is driven by the Power Distribution Maintenance Management Function (PDMMF) software application. PDMMF operates in two primary modes:

1. Search Mode

Search Mode is used for ad-hoc inspection and system troubleshooting. It contains two functional sub-pages:

• C/B Management: Allows the technician to search for any circuit breaker on the aircraft by entering its Functional Identification Number (FIN), ATA chapter (e.g., ATA 23, 24, 27, 29), physical panel location, or load designation. Selecting an electronic breaker displays its current electrical state (CLOSED, OPEN, TRIPPED, LOCKED, or TAGGED), current load rating, and bus supply. The technician can execute OPEN, CLOSE, LOCK, or TAG commands directly from the screen.
• C/B Config Status: Displays a comprehensive summary of all circuit breakers across the entire aircraft that are currently tripped, open, locked, or tagged. Before aircraft dispatch, technicians review this page to ensure no maintenance tags remain on flight-critical systems.

2. AMM Mode (Aircraft Maintenance Manual Integration)

AMM Mode bridges digital circuit breaker control directly with official Airbus maintenance procedures:

1. The technician inputs the specific AMM Task Number (e.g., 24-21-00-010-001) from their work card into the PDMMF interface.
2. PDMMF queries its internal database and automatically generates the complete list of circuit breakers required to be opened to electrically isolate the system.
3. The technician can select APPLY ALL to automatically open and lock all electronic SSPCs and RCCBs associated with the task in a single operation.
4. For any classical electro-mechanical C/Bs involved in the task, PDMMF displays their exact physical panel and rack coordinates in the avionics bay, prompting the technician to physically pull them and install mechanical safety clips and paper tags.
5. Upon task completion, selecting RESTORE ALL closes and un-tags all electronic breakers, returning the aircraft to its standard configuration.

09 · Emergency Generation & Ground Servicing

Emergency Electrical Power & RAT Ground Stowage Procedure

When all primary alternating current generation is lost in flight, the emergency electrical system ensures aircraft survivability via the Ram Air Turbine (RAT).

RAT Physical Location & Deployment

The RAT module is housed inside the Right Hand Side (RHS) AFT belly fairing. It deploys automatically in flight upon total Loss of Main Electrical Power (LMES), or manually when the red guarded RAT MAN ON pushbutton on cockpit panel 211VM is depressed. Once deployed, the two-blade variable-pitch turbine drives an emergency electrical generator, connecting to 230 VAC bus AC EMER 1 via contactor EGLC.

Mandatory Hub Alignment Marks

Step-by-Step RAT Ground Stowage Procedure

Ground stowage of the RAT is executed through the RAT Stow Panel, which is located inside the Green Hydraulic Ground Service Panel (GSP) in the Left Hand Side (LHS) belly fairing:

1. Manual Alignment: Manually rotate the turbine blades until the alignment arrow on the turbine hub aligns with the arrow on the gearbox forward face.
2. Pressurize Green Hydraulics: On cockpit overhead panel 222VM (GND HYD), set the GREEN ELEC PUMP guarded "AUTO" pushbutton switch to pressurize the Green hydraulic circuit to nominal operating pressure.
3. Power Stow Panel: At the Green Hydraulic GSP on the LHS belly fairing, lift the red guard and select the 28 VDC ON/OFF switch on the RAT Stow Panel to ON.
4. Command Stowage: Move the three-position STOW / LAMP TEST toggle switch from its neutral center position to the upper STOW position. This commands the hydraulic retraction actuator to hoist the RAT module into the RHS belly fairing.
5. Verify Latch: Confirm that the green RAT STOWED light on the RAT Stow Panel illuminates at the end of retraction, verifying that the mechanical latching mechanism is securely locked. Return the 28 VDC switch to OFF and lower the guard.

10 · Degradation & Failure Modes

ECAM Failure Modes: Single/Dual ATU Faults & Total Loss (LMES)

The ECAM System Display and Warning Display provide clear, definitive indications during normal and abnormal network states:

1. Normal In-Flight Configuration (Page 15)

When selecting the EL/AC key on ECP 135VM during normal flight:

• All four VFGs (GEN 1A, GEN 1B, GEN 2B, GEN 2A) display green triangles with balanced percentage loads (nominal ~34% load each).
• All six 230 VAC and 115 VAC busbars display green diamond symbols and nominal voltages (230 V on primary buses, 115 V on ATU outputs).
• Selecting the EL/DC key shows all four TRs operating at 28 V / 15 A, with all four batteries showing nominal 27 V / 8 A in trickle-charge status.

2. Single ATU 1A Failure (Page 16 Left)

If Auto-Transformer Unit 1A experiences an internal failure or thermal trip:

• The Warning Display (WD) flashes an amber caution message: ELEC ATU 1A FAULT.
• Pressing the STS key on ECP 135VM displays the inoperative system status, detailing secondary systems depowered on 115 VAC bus AC 1A.
• Pressing the EL/AC key displays the reconfigured synoptic: busbar AC 1A is cross-fed from adjacent ATUs via tie contactors, restoring essential instruments.

3. Dual ATU (1A & 1B) Failure

If both left-side step-down transformers (ATU 1A and ATU 1B) fail simultaneously:

• Dual amber caution messages appear on the WD: ELEC ATU 1A FAULT and ELEC ATU 1B FAULT.
• The left-hand 115 VAC distribution network loses its dedicated step-down sources.
• The electrical logic commands Bus Tie Contactors and System Isolation Contactors (BTC 1A, BTC 1B, SIC 1) to close, cross-feeding the healthy right-side ATU outputs (ATU 2A and ATU 2B) across the tie bus to maintain left-side flight instruments.

4. Total Loss of Main Electrical Power (LMES) & RAT Deployment (Page 16 Right)

In the catastrophic event that all four engine VFGs go offline in flight:

• All four generator displays on the ELEC AC page change to amber crosses indicating 0 % LOAD, 0 V.
• The FWS issues an emergency audio warning and displays red ELEC EMER CONFIG warnings on the Warning Display.
• The Ram Air Turbine deploys automatically into the airstream from the RHS aft belly.
• Once the turbine reaches operating speed, contactor EGLC closes.
• The ELEC AC synoptic displays the green RAT deployment symbol and dynamic electrical parameters: RAT 80 % LOAD, 115 V feeding emergency bus AC EMER 1.
• Static Inverter 1 (STAT INV 1) and the emergency TRs energize critical flight control computers (PRIMs) and Captain flight displays.

11 · Field Engineering Reference

Line Maintenance Engineer's Field Guide

When troubleshooting and servicing ATA 24 on the A350 ramp or in the hangar, engineers must adhere to several operational protocols:

• Pre-Flight VFG Inspection: Always check the physical oil sight glasses on all four engine VFGs (VFG 1A, VFG 1B, VFG 2B, VFG 2A) during walkaround. Low oil indications require servicing before dispatch.
• Cold Aircraft Troubleshooting: Remember that pressing REMOTE C/B CTL on panel 255VM powers the PDMI from EMER BAT 1 & 2. Monitor battery voltages using the 255VM rotary voltmeter to ensure batteries are not depleted below minimum starting limits during prolonged troubleshooting.
• Accessing the ECAM C/B Page: Do not search for a C/B button on the ECP. Use the SD rotary selector knob on the left of ECP 135VM to bring up the C/B page on the System Display.
• Servicing Power vs. Full Power: Use GND SVCE CTL 1 (cabin door 1L) or GND SVCE CTL 2 (NLG) to power cleaning and utility loads without needlessly clocking hours on avionics cooling fans or primary computers.
• Always Verify RAT Hub Alignment: Never command ground RAT stowage from the Green Hydraulic GSP without visually verifying that the hub and gearbox alignment arrows are perfectly aligned.

12 · Reference & FAQ

Frequently Asked Questions (FAQ)