Eliminate flammable fuel/air vapors in fuel tanks on transport category aircraft. "The issue before us is totally unacceptable," said NTSB member Ellen Engleman-Conners. Specifically, the short-term recommendation issued nine years ago, to modify operations "to reduce the potential for fuel-air mixtures in the fuel tanks of transport category aircraft" was closed by the NTSB after it became apparent that the FAA would not act on it. This recommendation basically involved near term actions to reduce the temperature in center fuel tanks (such as by loading them with chilled fuel).
The NTSB also called for "design modifications such as nitrogen-inerting and insulation between heat-generating equipment and fuel tanks." In response to this recommendation, the FAA developed an inerting system using nitrogen- enriched air three years ago, but it took until Nov. 14 for the FAA to issue an NPRM suggesting that the system be deployed on new and existing airplanes with heated center wing tanks, about one-third of the fleet [this NPRM will be discussed in the next issue of ASW]. Airplanes without heated center wing tanks, i.e., without heat-generating air conditioning packs under the tanks, will not need to be inerted. This caveat applies to wing tanks as well, which avoids the issue that overheated or faulting fuel pumps can occur in any tank (the scenario involving the fuel tank explosion in a Phillipine Airlines B737 in 1990). It also ignores dangerous electrical arcing outside the tank, whose energy may find its way into a low-power circuit within the tank (the likely scenario regarding the center wing tank explosion on a TWA B747 in 1996).
The NTSB's resident expert on fuel/air flammability, Bob Swaim, noted that the European Aviation Safety Agency (EASA) plans to mandate inerting as a production cut-in in 2008, but that does not include the Airbus A380, which does not feature a heated center wing tank, and no retrofit of inerting to the existing fleet is planned. "The EASA recommendation will cover 300-400 airplanes, and the safety board disagrees with the position taken on the A380," he noted.
Because the FAA took no action on the short-term recommendation, it was closed as unacceptable action.
Recommendation: complete rulemaking efforts to preclude the operation of transport-category airplanes with flammable fuel/air vapors in the fuel tanks on all aircraft. Status: "Open - Acceptable Response." The recommendation has a yellow color-coded timeliness classification, signifying that the response is acceptable but progressing too slowly.
Improve aviation audio and data recorders and require cockpit video recorders. The NTSB wants five things: (1) retrofit 30-minute cockpit voice recorders (CVRs) to 2-hour CVRs, (2) provide 10-minutes of independent back up power for recorders, (3) fit aircraft with fore and aft dual-redundant CVRs and flight data recorders (FDRs), (4) provide additional recorder parameters for the B737 to better discriminate between pilot control inputs and system flaws in the event of rudder reversals, and (5) equip aircraft with cockpit image recorders.
It's a lot, and so far the FAA has delivered very little. In February 2005 the FAA issued an NPRM calling for 2-hour CVRs to be retrofitted (see ASW, Feb. 28). However, the NPRM called for the 10-minutes of independent backup power to be installed only on new aircraft, and it did not call for dual redundant CVRs/FDRs.
Jim Cash, the NTSB's recorder expert, noted that the new Embraer EMB-190 and the Boeing B787 will have, or at least sport as options, both fore and aft recorders.
The FAA is now digesting comments submitted on the NPRM and is expected to issue a final rule in 2006.
The FAA has yet to issue requirements, proposed or otherwise, on B737 FDR parameters, although the FAA has not decreed that the rudder system redesign of the B737 meets the safety board's standard for "reliable redundancy."