Fuel Tank Inerting Harmonization Working Group Team Reports

Ground-Based Inerting Designs Task Team Final Report
9.1.4 Thermal Relief Valve
Thermal relief valves are required to relieve any pressure that may build up in the tubing due to
temperatures changes. Thermal relief valves may be incorporated into the other valves or equipment
present in the system.
9.1.5 Indication and Control
A control switch and position lamp for the isolation valve may be required. This switch and indicator
would be required to be intrinsically safe or environmentally/hermetically sealed in a manner to not
present a potential ignition source due to the potential presence of fuel. Any control hardware located near
the NEA interface would also be required to be housed or protected to not present a potential ignition
source.
9.1.6 Drain Valves
Drain valves may be required in the tubing and/or manifold where locations do not drain fuel to minimize
interference with the trapped fuel and the incoming inerting gases. Drain valves would not be necessary
where the design could be shown to always clear itself and provide the proper volume of inerting gas.
9.1.7 Placards
Placards would be affixed to those areas requiring cautionary and/or safety instructions, and placards
would be provided directly adjacent to the interface coupling servicing installation area. The servicing
coupling placard would clearly identify the certified, NEA volume to be loaded on the aircraft. Placards
would be clearly readable and of materials consistent with the usage.
9.2 AUXILIARY TANKS
Auxiliary fuel tanks would require similar equipment as the main center tanks in the aircraft. Auxiliary
fuel tanks are envisioned to be inerted through the same NEA servicing coupling as the center tanks. As
such, the auxiliary tanks could receive their inert gas from the same manifold. Depending on how the
system is designed and operated, it may require additional control circuitry for the auxiliary tank isolation
valves to control the time the auxiliary tank isolation valves are open. This would be to ensure that a
sufficient volume of inert gas is distributed to the auxiliary tank as the center tanks are being inerted. The
details of this are presented at this time due to the variability of auxiliary tank systems.
9.3 ADDITIONAL EQUIPMENT REQUIRED
Aircraft designed with crossvented fuel tanks will need to have the vent system design modified and
demonstrate methods to minimize NEA exchanges due to the crossventing configurations. This is
envisioned as a low cracking pressure bi-directional flapper check valve that is installed in all but one
vent passages used for the center tanks. These changes will need to be implemented carefully to take all
vent system design issues into account. These changes will also need to account for interaction by
auxiliary fuel tanks.
10.0 INSTALLATION REQUIREMENTS
10.1 NEW DESIGN
The design of a ground based inerting system requires the careful and balanced selection of a number of
design parameters to optimize the system’s performance versus the aircraft servicing time. The prime
requirement of the system will be to distribute the NEA to achieve a reduced oxygen concentration to
comply with the rule and the specific certification.
No major concerns are seen with the GBI inerting concept, assuming the design is launched in the early
phase of the design. During the design cycle the system would be subject to design reviews, safety
assessment, zonal analysis, etc. The manifold design, structural penetrations, wiring and service point
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