DALLAS — The European Union Aviation Safety Agency (EASA) has agreed with the Federal Aviation Administration (FAA) on design changes to the body of the Airbus A321XLR.

The European regulator insists on changes to the A321XLR Rear Center Tank (RCT), claiming that the tank needs to be redesigned to avoid serious fire risks in the event of a survivable crash.

The EASA document comes in response to the FAA's request that Airbus make some changes to the fuselage of the A321XLR. Because the RTC tank is located in the lower fuselage area, which partially replaces the rear cargo compartment in older generation planes, the FAA states that Airbus will be required to lower half of the fuselage near the longitudinal RCT area. The aviation body also suggested the area should be made fire-resistant.

On its part, EASA requests that the fuel tank be installed in a specific aircraft fuselage area that was "not likely to fail or rupture in a survivable crash condition exceeding the applicable existing emergency landing conditions.”

The European regulator added that Airbus should consider including a bladder and crushable structure around the tank area to help mitigate the effects of impact and scraping on the ground, "including contact with obstacles."

The EASA document released on December 8, 2022, reads as follows, “EASA identified the need to prescribe special detailed technical specifications (named Special Conditions) to ensure adequate occupants protection against the risks of external fire and burn-through, fuel vapour ignition and fuel tank explosion as well to ensure crashworthiness of this fuel tank so that no fuel is released in sufficient quantities so to start a serious fire in an otherwise survivable crash event,”

Fuel Tank Installation

US standards found in the § 29.967 Fuel Tank Installation document state the following:

• Each fuel tank must be supported so that tank loads are not concentrated on unsupported tank surfaces. In addition -
  • There must be pads, if necessary, to prevent chafing between each tank and its supports;
  • (The padding must be nonabsorbent or treated to avoid the absorption of fuel;
  • If flexible tank liners are used, they must be supported so that they are not required to withstand fluid loads; and
  • (Each interior surface of tank compartments must be smooth and free of projections that could cause wear of the liner, unless -
  • There are means for protection of the liner at those points; or
  • The construction of the liner itself provides such protection.

• Any spaces adjacent to tank surfaces must be adequately ventilated to avoid fuel accumulation or fumes in those spaces due to minor leakage. If the tank is in a sealed compartment, ventilation may be limited to drain holes that prevent clogging and that prevent excessive pressure resulting from altitude changes. If flexible tank liners are installed, the venting arrangement for the spaces between the liner and its container must maintain the proper relationship to tank vent pressures for any common flight condition.

• The location of each tank must meet the requirements of § 29.1185(b) and (c).

• No rotorcraft skin immediately adjacent to a major air outlet from the engine compartment may act as the wall of an integral tank.

How do Manufacturers Test Aircraft Tanks?

The exact regulations governing an aircraft's fuel tanks are determined by a variety of factors such as engine type and number, construction material, mounting method, number of passengers, aircraft gross weight, and so on.

However, the 14 CFR 23.965 - Fuel tank tests document provides a good overall set of requirements. Pressure testing, vibration, sloshing, inertia loads, venting, duration and number of cycles of each test, and so on are all included.

Also, the aforementioned 14 CFR 23.967 (thru 23.101) - Fuel tank tests guidance provides additional criteria, including requirements for components such as access panels, fuel sensors, filters and strainers, lines, pumps, drains, valves, jettisoning, etc.

The question still remains: How do you test the A321XLR tank so you can ensure no serious fuel-fire risk in survivable accidents occurs? Be sure to leave your comments on our social media channels!

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Featured image: A321XLR. Photo: Airbus