Fuel Tank Inerting Harmonization Working Group Team Reports

Ground-Based Inerting Designs Task Team Final Report
failures that will prevent the system from allowing the tanks to be inerted. In the case of the more likely
failures, i.e., failure of the shut off valve, maintenance procedures can be devised which will still allow
the airplane to be dispatched with the tanks inerted. This aspect is considered further in the Safety
Analysis Team Appendix H and the Airline Operations & Maintenance Team Appendix F.
6.7 SYSTEM COSTS
System costs are examined in detail in the Estimating and Forecasting Team Appendix G.
6.8 ENVIRONMENTAL ISSUES
The GBI system may introduce additional VOCs to the atmosphere as a result of the ullage washing
procedure. Since the center tanks would be inerted every flight, the ullage and its associated VOCs from
residual fuel would be exhausted out the vent system at each turn around whether the center tank was
utilized or not. The detailed environmental analysis of this GBI system is beyond the scope of the Tasking
Statement and is not addressed here.
7.0 GROUND SUPPLY REQUIREMENTS
7.1 NEA PURITY
Nitrogen Enriched Air (NEA) purity effects a number of different aspects of the ground based inerting
system, however the primary effect on the aircraft system is one of varying the volume of NEA required
to be loaded. The precise volume would be determined during development (analysis and testing) testing
of the particular aircraft model and would be for a particular purity of NEA. NEA purity can also have an
effect on the initial design to support the desired turn times to inert the aircraft. NEA 95% (95% nitrogen
and 5% oxygen) was recommended for use in this inerting study in the beginning. Later, it was
determined that NEA of slightly higher nitrogen concentration of 97 % or 98 % may be more desirable
from overall cost and commercial standpoint. (See Figure 7.1-1 below). The cost of the gas is slightly
higher for the higher purity, but the volume required to inert the fuel tank would be less. Consequently,
the price of the total load of NEA may be lower.
C-9