TB 55-9150-200-24
fuel-in the fuel cell or cells. If dilution is not possible, the aircraft will be defueled of dyed fuel which will be stored in a
bulk storage tank.
e. Static Leak Detection for Fuel System Including Lines and Engines. Leakage checks of airframe mounted lines
and connectors, and of integral wing and auxiliary fuel tanks may be undertaken using any of the dyes authorized herein.
However, when red dye is used the engine shall not be operated, and the aircraft shall be defueled of the dye fuel
following testing. Residual yellow dyed fuel need not be removed.
f. Static Leak Detection in Airframe Lines and Fuel Cells. If only the airframe mounted fuel lines and connectors, or
integral wing and auxiliary fuel cells are to be tested, allow the dyed fuel to stand in the aircraft 6 to 8 hours before
performing leakage testing.
(1) Examine all accessible fuel cell interconnects, fuel cell access covers, drains, boost pump mounting
points, and fuel line connections. Follow periodic instructions given in applicable aircraft maintenance technical manuals.
(2) If the aircraft has not had an engine run-up, operate fuel boost pumps keeping main fuel shutoff valve
closed. Check for leaks in the lines upstream of the main fuel shutoff valve.
g. Leak Detection for Engine Run-Up. If engine run-up or test flight is programmed, the leakage test may-be
conducted any time after the aircraft has been fueled. Only yellow dyed fuel may be used for engine run-up testing on
the ground, after an engine change, or for test flights after a periodic or phased inspection. The dyed fuel is particularly
useful in checking for leakage near the engine hot section area, where high temperatures prevent leaking fuel from
leaving a wet spot. When the dyed fuel evaporates from a surface, the dye remains as a deposited residue.
(1) Perform engine run-up or test flight in accordance with applicable directives.
(2) Upon completion, carefully examine main fuel line shutoff valve connections and all other connectors
downstream from it. Any dye deposit indicates leakage.
(3) When a leak has been repaired, remove the dye stain with the aircraft fuel or dry cleaning solvent
conforming to P-D-680 and repeat the applicable test. Recheck repaired areas to verify leakage has been stopped.
h. Disposition of Dyed Fuel. JP-4 fuel dyed with yellow dye may be left in the fuel system, following leak detection
operations, and used in normal operations.
(1) Yellow dyed fuel which must be removed from the fuel system may be placed in bulk storage and used
without dilution or mixed with other dyed fuel which has been diluted.
(2) JP-4 fuel dyed with red dye liquid will be diluted in the aircraft 10 to 1 with undyed fuel and used in normal
operations or removed from the aircraft and placed in bulk storage where it is diluted 10 to 1 with undyed fuel. This fuel
may then be issued to base assigned aircraft for normal use.
(3) The bulk tank in which the dyed fuel is stored or mixed with standard fuel will be marked with signs 4"' x
12", black letters on white background, which will be prepared using wood or similar material. The signs will read: THIS
TANK CONTAINS LEAK DETECTION DYED FUEL. These signs will be temporarily attached to the receiving and
issuing valves. When all of the dyed fuel has been issued, the signs will be removed. This should be accomplished in
order to avoid confusion with colored gasoline.
(4) Any excess liquid stain on aircraft, fuel cell, or storage equipment may be removed by wiping with a cloth.
The dye will lose color over a short period of time; therefore, it is not necessary to take special measures to remove all
stains.
i. Servicing Procedures to Transient Aircraft. Dyed fuel stored in bulk storage facilities will be serviced to locally
assigned aircraft. It will not be serviced to transient aircraft. The presence of dyed fuel in transient aircraft could be
falsely construed by air crews and maintenance personnel as contaminated fuel. If emergencies arise requiring servicing
of dyed fuel to transient aircraft, the crew will be advised and note made on aircraft form that aircraft was serviced with
dyed fuel.
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