Table 2-8. Approved Fuels (Continued)
Emergency Fuel. Avgas is emergency fuel and
subject to 150 hour time limit.
2-91. USE OF FUELS.
Fuel is used as follows:
Fuel Mixture. Standard and alternate fuels may
be mixed in any ratio. Emergency fuels may be mixed
in any ratio with standard and alternate fuels, however,
use of the lowest octane rating available is suggested.
Use of emergency fuel is subject to a 150 hour time
Use of Kerosene Fuels. The use of kerosene
fuels (JP-5 type) in turbine engines dictates the need for
observance of special precautions. Both ground starts
and air restarts at low temperature may be more difficult
due to low vapor pressure. Kerosene fuels having a
freezing point of minus 40 degrees C (minus 40 degrees
F) limit the maximum altitude of a mission to 28,000
feet under standard day conditions.
Mixing of Fuels in Aircraft Tanks. When
changing from one type of authorized fuel to another, for
example JP-4 to JP-5, it is not necessary to drain the
aircraft fuel system before adding the new fuel.
Fuel Specifications. Fuels having the same
NATO code number are interchangeable. Jet fuels
conforming to ASTM D-1655 specification may be used
when MIL-T-5624 fuels are not available. This usually
occurs during cross country flights where aircraft using
NATO F-44 (JP-5) are refueling with NATO F-40 (JP-4)
or Commercial ASTM Type B fuels. Whenever this
condition occurs, the engine operating characteristics
may change in that lower operating temperature, slower
acceleration, lower engine speed, easier starting, and
shorter range may be experienced. The reverse is true
when changing from F-40 (JP-4) fuel to F-44 (JP-5) or
Commercial ASTM Type A-1 fuels. Most commercial
turbine engines will operate satisfactorily on either
kerosene or JP-4 type fuel. The difference in specific
gravity may possibly require fuel control adjustments; if
so, the recommendations of the manufacturers of the
engine and airframe are to be followed.
2-92. SERVICING OIL SYSTEM.
An integral oil tank occupies the cavity formed
between the accessory gearbox housing and the
compressor inlet case on the engine. The tank has a
calibrated oil dipstick and an oil drain plug. Avoid
spilling oil. Any oil spilled must be removed
immediately. Use a cloth moistened in solvent to
remove oil. Overfilling may cause a discharge of oil
through the accessory gearbox breather until a
satisfactory level is reached. Service oil system as
Table 2-9. Standard, Alternate and Emergency.