MD-11 Fuel-Boost Pump Removal and Installation


Airline maintenance personnel occasionally experience difficulty in removing and installing DC-10 and MD-11 fuel-boost pumps. This difficulty can result in costly damage to the pumps. Using the tool and step-by-step procedure recommended by Douglas Products Division simplifies this maintenance task and decreases the potential for damaged equipment.

Douglas Products Division (DPD) has established specific procedures and identified an approved tool for the removal and installation of DC-10 and MD-11 fuel-boost pumps. Following the correct procedures and using the correct tool will enable airline maintenance personnel to complete the necessary work easily, and without damage to the airplane, pump, or tool.

The recommended procedures cover:

CORRECT TOOL
DPD recommends using the Hydro-Aire pump-removal tool to pull out and push in the pump-removal handle during pump-unit removal and installation. The tool applies a symmetrical force to the handle, reducing the possibility of breaking the handle or causing pump hang-up due to cocking of the sleeve valve.

PUMP REMOVAL
1 Open the applicable circuit breakers for the pump being removed. (See MD-11 Maintenance Manual Chapter 28-22-01 to identify the applicable circuit breakers.)

2 Remove the pump cover plate.

3 Loosen the pump-removal handle retaining screw located in the center of the pump-removal handle. (figure 1)

4 The locking lugs can now be disengaged from the groove in the housing. Disengaging the locking lugs and pulling the handle closes the pump inlet sleeve valve. Pull the pump-removal handle out approximately 1.25 inches (3.18 cm) to the positive stop. Failure to disengage both locking lugs prevents pump removal and may result in damage to the pump or housing. (figure 2)

5 Remove the lockwire from the pump bleeder plug. Place a container under the pump bleeder plug, and loosen the plug until fuel flows. When flow stops, remove the plug completely. (figure 3)

Draining the pump housing ensures that the inlet valve and outlet check valves are closed, and removing the plug prevents hydraulic lock, which inhibits pump removal.

6 After fuel is drained from the pump and locking lugs are disengaged, pull the pump out approximately 0.5 inch (1.3 cm) to the positive stop. Rotate the pumping unit approximately 30 degrees counterclockwise to the positive stop at which the unlock index marks are aligned.

7 Remove the pump unit from housing by pulling straight out. Ensure that the pump element electrical connector interfacial seal is removed with the pump. (figure 4)

The use of slide hammers or similar devices for pump extraction is prohibited. Slide-hammer action can cause damage to the housing or pump element or, in the extreme case, separation of the pump support legs before the sleeve valve is closed, allowing uncontrolled fuel flow from the tank. If free extraction is not possible, DPD recommends replacing both the pump and housing.

8 If the pump is reinstalled, replace the pump element O-ring, P/N MS29513-036, and apply a generous coat of petrolatum. (figure 5)

The pump element O-ring is intentionally stretched more than usual to reduce its cross-section. A cross-section that is too large can cause several problems, including jamming of the pump element part-way into the housing or opening of the sleeve valve, either of which could allow uncontrolled fuel flow from the tank.


PUMP INSTALLATION
1 Install the bleeder plug and lockwire before reinstalling the pump.(Use O-ring P/N MS29512-06.)

2 Inspect the pump electrical receptacle to ensure that the interfacial seal is in place and that the electrical connector is undamaged. (figure 4)

Stack-up of interfacial seals at the electrical connector can prevent the pump from being installed to a sufficient depth (within 0.125 inch, or 0.318 cm) to engage the locking lugs.

3 Check the pump housing for sharp protrusions that could damage the pump unit O-ring. Inspect the index slot of the pump element for damage, burrs, or any raised area that could inhibit pump installation.Burrs or sharp edges on the inside surface of the pump housing or index slot should be removed using crocus cloth or its equivalent. Remove residual material prior to pump installation. (figure 6)

4 Insert the pump unit into its housing. Push in and rotate the unit until the housing index pin engages the pump index slot. The unlock index marks will be aligned at the unlocked position. Push in approximately 0.5 inch (1.3 cm) until the index pin contacts the bottom of the first part of the indexing slot.

Do not exert force on the center of the pump-removal handle. Equal force should be exerted over each pin to avoid breaking the handle or cocking the inlet sleeve valve.

5 Rotate the pump unit clockwise approximately 30 degrees until the housing index pin engages the positive stop in the pump index slot. The white index marks will be aligned at the locked position.

6 Push the pump in approximately 0.5 inch (1.3 cm). Depress the finger tabs on the extended locking lugs. Push the pump handle in, using equal force over each pin to ensure symmetrical opening of the sleeve valve. Ensure engagement of the groove in the pump housing and the handle pins align with the holes in the locking lugs. (figure 7)

The pump unit O-ring may prevent free insertion of the pump to the fully seated position. Slight additional force may be required to compress the O-ring.

7 Tighten the handle retaining screw.Using the Hydro-Aire pump removal tool will help ensure application of equal force to the pump handle.

8 Replace the pump cover plate, and close the applicable circuit breakers. The pump primes automatically if the respective tank contains a minimum of 15,000 pounds (6,800 kg) of fuel.

SUMMARY
Using the tool and procedures recommended by DPD to remove or install a DC-10 or MD-11 fuel-boost pump can simplify this task for airline maintenance personnel. It also reduces the risk of incurring expensive repairs that may result from using an improper tool or incorrect procedures.

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Michael O'Toole
Customer Service Representative
Technical and Fleet Support
Douglas Products Division

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