Fuel, Main Transfer System - Right Side Induced or Return Flow Blocked

TASK 28-26-00-810-813-A
Fuel, Main Transfer System - Right Side Induced or Return Flow Blocked

WARNING: OBEY THE FUEL SAFETY PROCEDURES.

1. Possible Causes

a blockage caused by unwanted material (debris)
STRAINER-JET PUMP R, CENTER TANK [221QM]
JET PUMP-R, CENTER TANK [158QM]
discharge check valve
fuel pipe between the R JET PUMP STRAINER (221QM) and the right-side check valve

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 28-11-00-810-810-A	Fuel - Unwanted Material (Debris) In The Center-Tank Fuel Installation
AMM 28-26-00-210-001	Manually Operate the Transfer System Discharge Check Valve on RIB1 and Check For Full and Free Movement
AMM 28-26-00-710-001	Operational Test of the Main Transfer System
AMM 28-26-41-000-001	Removal of the Center Tank Jet Pump
AMM 28-26-41-400-001	Installation of the Center Tank Jet Pump
AMM 28-26-42-000-001	Removal of the Jet Pump Strainer
AMM 28-26-42-400-001	Installation of the Jet Pump Strainer
AMM 28-26-44-000-001	Removal of the Main-Transfer-System Clack Valve
AMM 28-26-44-400-001	Installation of the Main-Transfer-System Clack Valve

3. Fault Confirmation
Subtask 28-26-00-710-072-A ** ON A/C NOT FOR ALL

A. Introduction
(1) Read all of this Para. before you start Para. 3.B.
(2) The jet pump system operation.
(a) In normal operation.
1 When the transfer control valve is open, the two wing-tank fuel-pumps supply sufficient primary (pressurized) fuel-flow through the jet-pump to cause a suction in it. This suction moves the fuel from the center-tank to the related wing-tank. The suction of the fuel can stop:

when one pump is used to feed both engines at high power
if there is a leak in the primary fuel flow to the jet pump
if the primary fuel flow to the jet pump is blocked
when the related engine is gravity fed.

(b) In unusual operation (or during maintenance).
1 If the surface of the fuel in a wing-tank drops below that of the center-tank, gravity causes the fuel to flow from the center-tank to that wing-tank.
(c) Possible defective operation.
1 If the check-valve (installed at the end of the transfer pipe on the outboard side of Rib1) becomes unserviceable in the closed position, it stops a jet-pump driven and a gravity fuel transfer.

NOTE: A check-valve, flap-valve or clack-valve are other names given to types of non-return valve.

Subtask 28-26-00-710-062-A ** ON A/C NOT FOR ALL

B. Test
(1) Do the Operational Test of the Main Transfer System AMM 28-26-00-710-001.
(a) If the right side main transfer system:

operates as specified, no troubleshooting work steps are necessary
does not transfer fuel by jet pump or gravity, do Para. 4.A.

4. Fault Isolation
Subtask 28-26-00-810-062-A ** ON A/C NOT FOR ALL

A. Procedure
(1) Get access to the jet pump strainer 221QM AMM 28-26-42-000-001.
(a) Do an inspection of:

the jet pump strainer 221QM.
the fuel-tank floor adjacent to the strainer 221QM.

(b) Look for a blockage caused by unwanted material (debris).
(c) If unwanted material is:

found, do step (2)
not found, do step (3).

(2) Do the steps that follow before you do step (3).
(a) Remove all the unwanted material (debris).
(b) Replace, if necessary, the STRAINER-JET PUMP R, CENTER TANK [221QM] AMM 28-26-42-000-001 and AMM 28-26-42-400-001.
(c) Do the TSM procedure for unwanted material (debris) in the center-tank (Ref. TSM TASK 28-11-00-810-810).
(3) Do a check of and replace, if necessary, the JET PUMP-R, CENTER TANK [158QM] AMM 28-26-41-000-001 and AMM 28-26-41-400-001. Make sure that the (butterfly flap-type) check valve (in the secondary inlet) of the jet-pump:

is (usually) held closed (by a torsion spring)
can open (to let the fuel out of the center-tank during a transfer).

(a) Do the test given in Para. 3.B.
(4) If the fault continues:
(a) Get access to the main transfer system, right-side discharge check valve AMM 28-26-44-000-001.

NOTE: The left and right discharge check valves are not FIN coded items.

(b) Do a check of the discharge check valve AMM 28-26-00-210-001.
(c) Replace, if necessary, the discharge check valve AMM 28-26-44-000-001 and AMM 28-26-44-400-001.
(d) Do the test given in Para. 3.B.
(5) If the fault continues:
(a) Do a check of the fuel pipe between the R JET PUMP STRAINER (221QM) and the right-side check valve.
(b) Look for damage, a leak, a blockage or incorrect installation.
(c) Repair (or replace) all the unserviceable pipes and connections.
(d) Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:28:48 UTC