f. Static Leak Detection in Airframe Lines and Fuel Cells. If only the airframe mounted fuel lines and con-
nectors, 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
(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 light 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 lights 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 light 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 con-
forming to MIL-PRF-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 or JP-8 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
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.