A B757-200 had a wing tank fuel quantity inoperative affecting the totalizer and an EICAS system self-generating an incorrect 'FUEL LOW' alert. The air carrier attempted to have two flight crews accept the aircraft in an unairworthy condition.

Narrative

Aircraft had multiple defects involving determination of onboard fuel quantity. Fuel quantity indication for the right wing fuel tank was inoperative. As a byproduct; the total fuel quantity indication was also inoperative. The manual fuel measurement system for the right wing fuel tank had a missing component (a drip stick was missing). And finally; the computerized warning system (EICAS) was reported as intermittently generating a 'LOW FUEL' caution. Without exception; a 'LOW FUEL' caution requires landing at the nearest suitable airport. On a standalone basis; an unreliable 'LOW FUEL' caution is not deferrable; and even less so in combination with other fuel anomalies. A legal deferral with an inoperative fuel quantity indicator requires a reliable EICAS computer with no provision allowing a flight crew to ignore fuel warnings or cautions generated by the system. Prudence dictates that; before departure with an inoperative fuel quantity indicator; a flight crew must verify fuel quantity by all rational means. This would include use of the manual fuel measurement (drip stick) system. My air carrier maintenance department rationalized that; in compliance with regulatory restrictions; the EICAS computer was probably operating reliably as both a 'LOW FUEL' caution and an inoperative quantity indicator were consistent with a defective fuel probe (notwithstanding the absence of diagnostics to confirm a bad probe.) Therefore; even though the EICAS output was inaccurate; it was the official position that since the fault might not be internal to the computer the aircraft was legal and airworthy. This loose interpretation of regulatory requirements left unanswered how the unreliable 'LOW FUEL' caution itself was deferrable or what response air carrier management contemplated from a flight crew confronted with the fault. In accordance with his regulatory responsibility; a Captain considered the aircraft unairworthy and refused to operate it. Audaciously undaunted; the air carrier attempted to find another Captain to accept the aircraft. Based on my experience I also judged the aircraft to be unairworthy and was the next Captain to refuse it. I urge the FAA in conjunction with my air carrier safety personnel to review the appropriateness of indiscriminately shopping mechanically compromised aircraft to various Captains; and whether my air carrier can be trusted with such latitude as currently structured. (Refused aircraft may be shopped without authorization from a pilot manager; current and qualified as a Captain on the aircraft in question.) Indiscriminate aircraft shopping is permitted by the airline's flight operations manual as accepted by the FAA states 'Refusal of an airplane for a particular flight segment by one Captain does not imply that the airplane is unacceptable for all flight segments.' Each Captain is required to determine if the airplane is acceptable based on operational considerations. The resulting indiscriminate aircraft shopping undermines the safety margin contemplated by Federal Aviation Regulations; which dictate that a Captain must make an independent determination that an aircraft is suitable for the flight. Aircraft shopping dilutes this safety margin to the lowest possible denominator according to whether any captain will accept the aircraft. For example; a deadheading captain familiar with this aircraft type advocated for acceptance of the aircraft in this case! It's also worth noting that a Federal Judge censured my air carriers' pilots for refusing to operate aircraft with legally deferrable mechanical defects. With the onus on pilots to demonstrate a legal flaw in a deferral; aircraft shopping may find a captain who; although concerned about the aircrafts airworthiness; is unable to identify a legal flaw and thusly feels obligated to operate the aircraft in accordance with the Judges order.