FAA Demurs on New Regs For Low Fuel Indicators

Air Safety Week, May 8, 2006

Although UK air safety officials recently recommended that the FAA promulgate specific recommendations requiring low fuel warning indicators, FAA believes such a step would be redundant with its current regulations.

Largely because there are so few problems these days with low fuel conditions, aviation safety consultant John Cox believes that FAA's stance sounds reasonable. Besides, many aircraft already have indicators that are activated by the crafts' computerized flight management systems and telling the flight crew that the craft is tapping into the reserve tanks, he adds.

That point is also acknowledged by the UK's Air Accidents Investigation Branch (AAIB), adding that this is the case even though neither current regulations of FAA or the European Aviation Safety Agency (EASA) require low- fuel indicators. AAIB's recommendations for FAA arose during an investigation into a Feb. 8, 2005, incident, involving an A340-642 bound from Hong Kong to London, that had to be diverted to Amsterdam Airport Schiphol (AMS) because it appeared to the flight crew that the craft was low on fuel. In actuality, the fuel quantity indicators were not working properly, AAIB says in its February 2006 interim report and safety recommendations on the incident.

As a result of its investigations, AAIB also says FAA "should introduce into FAR [Part] 25 a requirement for a low fuel warning system for each engine feed fuel tank. This fuel warning system should be independent to the fuel control and quantity indication system."

A second recommendation says FAA "should review all aircraft currently certified to FAR [Part] 25 to ensure that if an engine fuel feed low fuel warning system is installed, it is independent of the fuel control and quantity indication system(s)." AAIB also made similar recommendations for EASA.

To those recommendations, FAA responded in a March 20 memo that there is no need for additional regulatory action. "The addition of a more specific requirement would be redundant to those regulatory objectives already covered by [FAR] 25.1309(c). Furthermore, promulgation of a more specific requirement could inadvertently impede future design innovation and would not be an efficient use of our limited rulemaking resources."

However, the same memo says that FAA will develop an interpretative guidance to clarify [FAR] 25.1309(c), and if compliance were carried out accordingly, such actions would meet AAIB's first recommendation. By press time, FAA did not respond to Air Safey Week's request for more details on the memo.

AAIB also told us they had nothing more to say on the issue than what's already in their report.

The FAA regulation in question, FAR 25.1309(c), says in full, "Warning information must be provided to alert the crew to unsafe system operating conditions, and to enable them to take appropriate corrective action. Systems, controls, and associated monitoring and warning means must be designed to minimize crew errors which could create additional hazards."

Also, under another part of the FAA regulations in FAR 25.1305, listing required powerplant instruments, there's specific mention of having a fuel quantity indicator for each tank. But this other section of FAR does not mention safety procedures.

While FAA concedes that a more specific rule would probably focus more attention on low fuel indicators, it would not relieve certificate applicants of having to comply with FAR 25.1309(c). Furthermore, "while in most instances the recommended independence constitutes good design practice, lack of such independence does not inherently render a design unsafe."

AAIB agrees that it could be argued that the general FAA regulation and its similarly worded EASA equivalent cover the need to have low fuel indicators. But the A340 incident indicates a need for more specific requirements on low fuel indicators, it says. This is partly because the A340's fuel indicator system was not working properly and the crew didn't know it.

In the A340 incident, there were readings of zero for two different fuel tanks at two separate times. Investigating one engine after the first such reading, a crew member found nothing unusual. But after the second zero reading, the commanding pilot had all the fuel crossfeed valves opened, declared a "mayday," and diverted the plane to Amsterdam. Expected indications of fuel transfer did not show up on the instrumentation, even though there were "significant quantities" of fuel in the trim, center and outer-wing fuel tanks.

"Also, with the larger aircraft, the fuel system may be used for center- of-gravity control. Fuel tank feeding sequences may be complicated and some fuel tanks may be depleted and replenished frequently during a long flight. Consequently, although fuel sequencing may be automated, deviations from the correct sequence due to automation failure may be difficult to determine simply by looking a the synoptic display. Moreover, the synoptic display ... may be congested and information difficult to assimilate unless the pilots' attention is drawn to the problem by an automatic status or failure warning."