scheduled hot end internal inspections is limited. Refer to table 2-3 notes. Continued use of leaded aviation gasoline or
jet fuel in excess of 1% of aviation gasoline, may cause failure of the vaporizing tubes and subsequent turbine blade
damage resulting in a safety-of-flight hazard. The continued use of jet fuel contaminated with less than 1% of aviation
gasoline is permissible in these aircraft. If the permissible accumulated operating time is exceeded, a special cleaning
and inspection becomes mandatory. The cleaning and inspection may be delayed for 10 operating hours provided only
recommended fuel is used during the delay. A fuel mixture which contains over 10% leaded gasoline shall be identified
as all-leaded gasoline on DA Form 2408-13, Aircraft Inspection and Maintenance Record.
e. Gasoline containing TCP (Tricresyl Phosphate) in addition to TEL (Tetraethyl Lead) is more detrimental to
combustor parts than gasoline containing TEL only. Deterioration of combustor parts occurs at least twice as fast when
TCP is added to leaded gasoline. Operating time on gasoline with TCP is therefore limited to one-half the time allowed
on leaded gasoline without TCP and shall be clearly indicated in the fueling records. Whenever fuel with TCP is used,
special cleaning and inspection of combustor parts is mandatory.
f. For information concerning the cleaning of combustor parts after the use of emergency fuels, refer to the
applicable maintenance manuals.
g. See footnote in table 2-3 for limitations and precautions with emergency fuel.
Record emergency fuel flight time on DA Form 2408-13 block 17. When DA Form 2408-13 is
removed from the log book, transfer the emergency fuel data to DA Form 2408-15 for the
engine and record both that days flight time on emergency fuel and a total flight time on
2-7. Detection of Leaks.
a. Introduction. Dyed fuel may be used for static leak detection of JP-4 fuel cells and complete fuel systems.
Inflight tests to detect leaks, which cannot be detected by static or engine runup test may be used. However, the use of
inflight tests requires special approval of the maintenance officer.
b. Preparation of Dye Solution. The quantities of liquid dye to be used and the mixing ratios are as specified in
c. Mixing in Servicing Vehicle. The dye can be blended in a refueling vehicle that has been reserved for servicing
dyed fuel. The required quantity of dye should be determined before starting. To insure proper mixing of dye in fuel,
partially fill the trailer to about 10 percent and then add the appropriate amount of dye slowly to the contents of the trailer
while the trailer is filled with . remaining fuel.
d. Static Leak Detection in Fuel Cells. Use a diagram of the leaking fuel cell which shows al' connections.
(1) Transfer the fuel into another cell or defuel as necessary. Pour the liquid dye into the leaking cell and fill to
the 1/3 level with JP-4 fuel.
One third level is determined from the known capacity of the cell; for example, 100 gads
added to a 300 gallon cell.
Allow the dye solution to set in the cell for approximately 6 hours or until the dye solution comes through the drain.
Should the dye appear, there is a leak within this level.
(2) Repeat the procedure at the 2/3 level and full level, as necessary. A full cell should be allowed to set for
approximately 12 hours.
(3) When a leak is detected, connections should be checked, the cell defueled, and residual fuel removed with
cloths and drained from the sump. Type MA-1 explosion proof blower may be used to remove fumes. Remove all
connections, pull fuel cell down, and check for dye stains on exterior of the cell. These stains are easily detected, thus
pinpointing the leak. Rarely is any maintenance necessary other than replacing seals and retorquing connections.
(4) Check for defective cells (blisters, layer separations, etc.) in accordance with the applicable fuel cell and/or
aircraft maintenance manual.
(5) After closing the fuel cell, the dye solution may be transferred into the fuel cell once more to the three
levels: 1/3, 2/3, and full, thereby ascertaining whether or not the cell still leaks.
(6) After completion of fuel cell leak detection operation, the aircraft may be flown with yellow dyed fuel. Red
dyed fuel can be used provided it is diluted 10 parts to 1 part with undyed