This bulletin informs flight crews of the potential for fuel pump damage that could create a potential ignition source. This revision provides procedures approved by the FAA per FAA Approval Letter 140S-03-234 as an Alternative Method of Compliance to AD 2002-19-52 and AD 2002-24-51.
Inspections of Hydro-Aire fuel pumps found evidence of a chafed stator lead wire bundle that may cause the wire to contact the rotor and produce arcing, thus creating a potential ignition source. Inspections of other damaged Hydro-Aire pumps found evidence of localized overheating of parts in the priming and vapor pump section of the fuel pump, possibly due to extended dry running.
Because of these findings, the FAA issued Airworthiness Directives (AD) 2002-19-52 in September 2002 and AD 2002-24-51 in November 2002 to require flight crews to maintain certain minimum fuel levels in the center fuel tanks when operating any Hydro-Aire fuel pump.
The Operating Instructions of this bulletin provide the procedures as required by the two ADs. In response to numerous requests from operators, however, Boeing has also developed procedures that will minimize dry running of the center tank fuel pumps, while reducing the potential for large quantities of fuel remaining in the center tank. These alternate procedures have been approved by the FAA per Approval Letter 140S-03-234 and are included in the Operating Instructions below.
Boeing is revising the control logic for the center tank fuel pumps to incorporate an automatic shutoff feature to further reduce dry running of the pumps. These updates should be available second quarter 2004 via Boeing service bulletin.
These procedures have changed slightly from those previously published in accordance with AD 2002-19-52 and AD 2002-24-51. Minor changes have also been made for clarification.
The center tank fuel pump switch(es) must be selected OFF at the first indication of fuel pump low pressure any time during the flight. This includes low pressure indications that may occur because of pitch attitude changes.
The center tank fuel pump switches must be ON for takeoff if center tank fuel quantity is 5000 pounds (2300 kilograms) or greater with the airplane readied for initial taxi.
Both center tank fuel pump switches must be OFF for takeoff if center tank fuel is less than 5000 pounds (2300 kilograms) with the airplane readied for initial taxi. Both center tank fuel pumps should be repositioned ON above 10,000 feet or after the pitch attitude has been reduced to begin acceleration to climb speed, if more than 1000 pounds (500 kilograms) remain in the center tank.
Both center tank fuel pump switches must be selected OFF when center tank fuel quantity reaches approximately 1000 pounds (500 kilograms) during climb, cruise, or descent. For airplanes not equipped with a center tank scavenge system, this 1000 pounds (500 kilograms) of center tank fuel may only be used in a low fuel situation.
Note: In cruise flight, center tank fuel may be reduced to approximately 800 pounds (400 kilograms) as necessary to extinguish the FUEL CONFIG light and EICAS FUEL CONFIG message. This allows the FUEL CONFIG alert to activate for fuel imbalance or low fuel situations.
FUEL CONFIG Indication. The FUEL CONFIG light will illuminate when there is fuel in the center tank that exceeds 1200 pounds (600 kilograms) and the center tank fuel pump switches are OFF. Do not accomplish the FUEL CONFIGURATION non-normal checklist prior to or during takeoff with less than 5000 pounds (2300 kilograms) of fuel in the center tank, unless there is an imbalance between main tanks or fuel is low in either main tank. After cancelling the FUEL CONFIG message, monitor fuel quantity indications and accomplish the appropriate procedure or checklist if a main tank imbalance or main tank low fuel quantity situation occurs.
Low Fuel. In a low fuel situation, both center tank pumps may be selected ON and all center tank fuel may be used regardless of the amount of fuel remaining in the tank.
Pump Failure. If a center tank fuel pump fails with fuel in the center tank, accomplish the FUEL PUMP non-normal checklist.
Note: Both center tank fuel pump switches must be selected OFF when the center tank fuel quantity reaches approximately 1000 pounds (500 kilograms) or at the first indication of fuel pump low pressure.
Fuel Loading. For the time period that AD 2002-19-52 and AD 2002-24-51 are in effect, the zero fuel gross weight of the airplane plus the weight of center tank fuel may exceed the maximum zero fuel gross weight by up to 5000 pounds (2300 kilograms) for takeoff, climb, cruise, descent and landing, provided that the effects of balance (CG) have been considered.
This bulletin will be canceled after Boeing has been notified that the center tank fuel pump automatic shutoff feature SB 757-28A0081 is incorporated and the center tank pumps have been inspected via an approved inspection process to ensure proper wire bundle positioning.