The A350 stores fuel in left wing, right wing, and center tanks, managed by dual FQMS computers.
Tank Wall Data Concentrators (TWDCs) digitize capacitance probe signals at the tank boundary, dramatically reducing airframe wiring mass.
Higher delivery pressure from center tank pumps automatically prioritizes center tank burn before wing tank consumption for structural wing relief.
The Fuel Tank Inerting System (FTIS) supplies Nitrogen Enriched Air (NEA) into the tank ullage to eliminate flammability risks.
Video Chapters & System Sequences
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Technical System Guide & Source Grounding
The Airbus A350 Fuel System (ATA Chapter 28) stores, monitors, conditions, and feeds kerosene to the two Rolls-Royce Trent XWB turbofans and the Honeywell HGT1700 APU. Incorporating digital Tank Wall Data Concentrators (TWDC), full-tank inerting (FTIS), and automated center-of-gravity calculation, the system combines high efficiency with fail-safe reliability.
1. Tank Layout & Capacity Architecture
A350-900 vs A350-1000 Capacities and Vent Tanks
Fuel is contained within the wet-wing structure and the center fuselage section. In addition to the three main storage tanks, two outboard surge/vent tanks protect the structure from thermal expansion overpressure and capture venting vapor during rapid climb or descent.
Total fuel capacity on the standard A350-900 is 138,000 liters (approx. 108 tonnes), whereas the stretched A350-1000 incorporates an enlarged center wing box holding over 156,000 liters (approx. 127 tonnes).
Figure 1: Airbus A350 fuel tank geometry and structural center wing box allocation.
2. Fuel Quantity Management System (FQMS) & TWDCs
Digital Boundary Architecture and Sensor Redundancy
The FQMS calculates fuel mass by measuring dielectric capacitance across dozens of submerged probes. Because fuel density varies with temperature and crude oil batch, ultrasound densitometers provide density compensation.
Tank Wall Data Concentrators (TWDCs) located adjacent to each tank convert analog sensor frequencies into digital packets, connecting directly to the dual-channel FQMS computers via the AFDX data network.
⚠ Fuel Scavenge Jet Pump Operation
When center tank quantity drops to low levels, jet pumps driven by motive fuel flow transfer residual unusable fuel from structural recesses into the pump intake bays, ensuring complete fuel extraction.
3. Fuel Tank Inerting System (FTIS)
Nitrogen Enriched Air (NEA) Explosion Prevention
To comply with FAA/EASA fuel tank flammability reduction rules, the A350 features a permanent catalytic Fuel Tank Inerting System. Conditioned air passes through permeable hollow-fiber membranes inside the Air Separation Module (ASM).
Oxygen molecules permeate through the fiber walls and are exhausted overboard, while nitrogen-enriched air (with oxygen content below 12%) is piped into the fuel tank ullage space, rendering the atmosphere completely non-explosive.
The Airbus A350 ATA 28 system represents the benchmark in commercial transport fuel management—providing automatic mass balance, autonomous nitrogen inerting, and high-rate gravity/pressure cross-feeding.
Technical Review & Part-66 Comprehension Check
Q1: Why does the Airbus A350 burn fuel from the center tank before the wing tanks?
Q2: What is the primary role of the Tank Wall Data Concentrators (TWDC)?
Q3: What safety mechanism ensures the fuel jettison system cannot accidentally dump all onboard fuel?
