Action
Final rule; request for comments.
Summary
We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires repetitive testing for correct functioning of the engine indication and crew alerting system (EICAS) to ensure that it receives both the LOW FUEL and FUEL CONFIG discrete signals from the fuel quantity processor unit, and alerts the flightcrew of a low fuel situation, and if the test fails, troubleshooting to find wire faults and damaged equipment, and corrective actions if necessary. This AD was prompted by a report that the EICAS failed to alert the flightcrew of an improper fuel system configuration during flight. Later in that flight, the EICAS failed to alert the flightcrew that the fuel in the left- and right-hand main tanks was depleted below the minimum of 2,200 pounds. We are issuing this AD to detect and correct a single latent failure of the FUEL CONFIG discrete signal, which disables both the FUEL CONFIG and LOW FUEL messages. Such failure, combined with a flightcrew error in configuring the fuel system, could lead to depletion of the fuel in the main tanks and possible flame out of both engines. A dual engine flame out could result in inaccessibility of the remaining fuel in the center tank due to loss of electrical power to the pumps, consequent unrecoverable dual engine shutdown, and forced landing of the airplane.