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On airplanes with the electric CWT scavenge pump, all of the remaining 3,000 pounds (1,360 kilograms) of fuel will be scavenged and can be considered usable fuel.
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Operations Manual Bulletin No. ILF2-41(R5), Dated April 1, 1999 (continued)
On airplanes with jet scavenge pumps, some or all of the remaining fuel may not scavenge. With 3,000 pounds (1,360 kilograms) of fuel remaining in the center wing tank, it is likely the jet scavenge pumps will activate, but not until later in the flight when there may not be sufficient time to scavenge all remaining fuel. It will take approximately 2 hours to scavenge 3000 pounds (1,360 kilograms) of fuel. Initially, the 3000 pounds of fuel should be considered unusable. Operator experience may provide a different value of unusable fuel.
In the above cases, the 7,000 pounds (3,200 kilograms) or 3,000 pounds (1,360 kilograms) of CWT fuel would normally be considered as “fuel in lieu of payload” as described in the Weight and Balance Manual, Section 1-22-01. Boeing has reviewed the certification conditions for the 747-400 and determined for AD T98-25-52 only, CWT fuel up to 7,000 pounds (3,200 kilograms) need not be considered as fuel in lieu of payload.
Boeing Service Bulletin 747-28-2226 (December 22, 1998) provides an alternate means of compliance that allows use of the CWT override/jettison pumps after specified inspections/repairs. With the incorporation of this Service Bulletin, the CWT override/jettison pumps may be used normally.
These pumps are also used in the horizontal stabilizer tanks. Selecting the stabilizer tank pumps OFF with fuel remaining in the stabilizer tank results in unacceptable display of the EICAS caution message FUEL STAB XFR and violates the certified structural loads analysis. Therefore, fueling and use of the horizontal stabilizer tank is prohibited.
The FAA has approved an alternate means of compliance with AD T98-25-52 through inspection procedures contained in Boeing Service Bulletin 747-28-2225 (December 22, 1998 Rev 2). Upon completion of the required inspections/repairs, horizontal stabilizer fuel pumps may be used normally.
Pump damage may be accompanied by tripped fuel pump circuit breakers. Therefore, a tripped CWT fuel pump or horizontal stabilizer pump circuit breaker should not be reset.
Operating Instructions
Fueling and use of the horizontal stabilizer tank is prohibited until inspections/repairs required by SB 747-28-2225 have been accomplished.
The following CWT restrictions apply until inspections/repairs required by Service Bulletin 747-28-2226 have been accomplished:
If the CWT override/jettison pumps are required for flight, the center wing tank
must contain a minimum of 17,000 pounds (7,700 kilograms) prior to engine start. If CWT fuel is less than 50,000 pounds (22,700 kilograms) prior to engine start, select both CWT override/jettison pumps OFF at the first occurrence of any of the following:
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Operations Manual Bulletin No. ILF2-41(R5), Dated April 1, 1999 (continued)
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at or before CWT fuel reaches 7,000 pounds (3,200 kilograms), or
.
when either CWT fuel pump low pressure light illuminates with CWT fuel
below 7,000 pounds (3,200 kilograms); FUEL OVRD CTR L & R EICAS
messages may be displayed, or
.
when either FUEL OVRD CTR L or R EICAS message displays with CWT fuel below 7,000 pounds (3,200 kilograms).
The flight crew may select the CWT Override/Jettison pumps ON in stabilized cruise, then select them OFF when CWT fuel reaches 3,000 pounds (1,360 kilograms).
If CWT fuel is greater than or equal to 50,000 pounds (22,700 kilograms) prior to engine start, select both CWT override/jettison pumps OFF at the first occurrence of any of the following:
.
at or before CWT fuel reaches 3,000 pounds (1,360 kilograms), or
.
when either center tank fuel pump low pressure light illuminates with CWT fuel below 3,000 pounds (1,360 kilograms); FUEL OVRD CTR L & R EICAS messages may be displayed, or
.
when either FUEL OVRD CTR L or R EICAS message displays with CWT fuel below 3,000 pounds (1,360 kilograms).
WARNING: Do not reset a tripped CWT override/jettison or horizontal stabilizer transfer/jettison pump circuit breaker.
NOTE:
.
The CWT fuel quantity indication system must be operative to dispatch with CWT mission fuel.
.
The center wing tank may be emptied during emergency fuel jettison.
.
In a low fuel situation, both CWT pumps may be selected ON and all CWT
fuel used.
Upon completion of the three Service Bulletins specified in this Operations Manual Bulletin, CWT override/jettison and horizontal stabilizer transfer/jettison pumps may be used normally.
Administrative Information
Insert this bulletin behind the Bulletin Record Page in Volume 1 of your Operations Manual. Amend the Bulletin Record to show bulletin ILF2-41(R5) IN EFFECT (IE).
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