mr-washingtonnigelhowarth-awstpromo.jpg.crop_display.jpg Nigel Howarth/AW&ST

Industry Balks At Proposed 757 Freighter Wiring Fix

How at-risk are freighters to fuel tank-related explosions? It depends on whom you ask.

A tussle between cargo operators and the FAA over costly changes to Boeing 757 freighters that would minimize risk of fuel tank explosions has entered its fourth year, with neither side showing interest in a compromise.

The FAA in March 2012 proposed modifications to 757 fuel-quantity indication systems (FQIS) to reduce the risk of a failure creating an ignition source inside center fuel tanks. The rule would apply to aircraft not required to install nitrogen generating systems (NGS)—in other words, freighters and aircraft not operated in scheduled passenger service.

NGS, which remove oxygen from fuel tanks, are required to be installed in many U.S.-registered aircraft with center-wing tanks by late 2017—part of design changes mandated after the July 1996 inflight explosion of TWA 800, a Boeing 747. But the requirements were deemed too costly for freighter operations.

After further review, the FAA determined that a particular set of circumstances—a latent FQIS failure within a center tank and an FQIS-related failure outside the tank—posed too high a risk for explosions. As a result, the agency proposed as part of its 2012 draft rule that Boeing come up with options to mitigate the risk that are less expensive than an NGS. It could not say exactly how much less because Boeing was expected to develop the specifics during the rulemaking process. The FAA suggested that similar mandates could follow for other freighters—including Airbus aircraft—with center wing tanks.

Industry balked, calling the changes unnecessary, citing nearly 500 million explosion-free hours flown by aircraft with center wing tanks since 1996, thanks in part to 250 airworthiness directives aimed at reducing flammability. “Specifically, those ADs that prevent the dry running of fuel pumps probably have improved safety more than any other measure,” Airlines for America (A4A) argued in its 2012 comments on the proposal. “The improved safety performance provided by ignition-prevention ADs is statistically significant and attributable, and indicates that the need for the proposed AD should be reevaluated in a detailed risk assessment.”

The FAA pondered industry’s input for three years. In April 2015, it issued a more detailed proposal with a few options and extended the compliance deadline, to 72 months from 60 months. Much of industry—including Boeing—has not relaxed its opposition.

“Although Boeing has accepted the FAA’s requirement to provide the prescribed design changes, Boeing continues in its view, based on previously provided analysis, that the risk level is less than extremely improbable,” the manufacturer told the FAA last May. “The AD is not necessary since the airplane design is safe.”

While operators and manufacturers often balk at safety-focused upgrades, the FAA’s FQIS fix, which focuses on separating FQIS wires from other wires, has a few notable wrinkles. One, the agency deemed it necessary after determining that a fix with a similar goal—the NGS retrofit—was too expensive for the projected benefits. Two, and arguably more relevant, other regulators have not followed the FAA’s lead in requiring NGS or similar retrofits. The European Aviation Safety Agency (EASA) mandated them for new aircraft starting in 2012, but opted against a retrofit mandate. This, argue U.S. cargo haulers, places an unfair burden on their operations by requiring hundreds of thousands of upgrades that foreign competitors do not have to match. EASA has no plans to change its position.

In early December, representatives from five airlines and A4A met with FAA officials to express concern over the latest proposals, as well as the now-available service bulletins that detail the work.

“Airbus and Boeing indicate that service bulletins for additional modifications will be intrusive, expensive and will not significantly improve safety,” an A4A presentation made at the meeting explains. “The competitive position of U.S. freighter operators will be harmed because foreign regulators will not be requiring additional modifications,” the association adds.

As an example, UPS calculates that it has spent $35.5 million to comply with 51 flammability-reduction ADs directives that apply to its aircraft. FQIS fixes could cost it another $16 million, it projects.

Addressing the safety issue, A4A noted that the National Transportation Safety Board issued five major wiring safety and flammability-reduction recommendations in the aftermath of its TWA 800 probe. The FAA responded to each of them with mandates or certification changes, and the NTSB considered each action “acceptable.”

The National Air Traffic Controllers Association (Natca) and some freighter pilots are among those that do not think the FAA’s proposal goes far enough. Natca believes the proposed fixes are not adequate based on the FAA’s own special federal regulation issued after TWA 800. Part of the issue is FAA’s acknowledgement that Boeing’s proposed fixes will separate only 5% of the 757’s FQIS wires to the desired 2-in. minimum standard; most will be within 0.5 in. Pilots who weighed in wonder why aircraft that haul boxes should be any less safe to operate than ones that fly paying passengers.

While a mandate seems likely, it would be less costly than some feared. In 2012, Boeing suggested that it would not develop anything to meet the FAA’s general requirement for the 757 FQIS fix besides the NGS systems mandated for passenger operations—the same systems the FAA deemed too costly to justify installing on freighters. But the OEM changed its stance, coming up with service bulletins detailing testing procedures and a process for separating some of the affected wires.

The FAA puts the cost of these FQIS fixes at about $40,000 per aircraft, compared to $384,000 for a 757 NGS. The FAA’s rule lists 148 freighters and 19 other aircraft in non-passenger service that would be affected by the rule.

Despite the 90% cost reduction, industry remains adamant that the investment is not justified.

“No unsafe condition exists,” A4A argues in its presentation. “Service experience has shown that the fuel tank safety issues have been addressed with significant previous modifications and recurring maintenance. Existing improvements in fuel safety modifications, overhaul processes, repair processes, and maintenance program tasks provide the needed safety.” 

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