(7) Hold the fitting in its position and tighten
the nut against the boss.
b. Use this procedure to install universal fittings
without backup rings. (See figure 5-1.)
(1) Run the nut on the fitting end back until the
washer face is aligned with the upper inner comer of
the seal groove.
(2) Lubricate seals used on oil, anti-icing, and
bleed air tube fittings with lubricating oil (item 7,
table 2-2). Lubricate seals used on fuel tube fittings
with lubricating oil (item 8, table 2-2). DO NOT lubri-
cate seals used on fuel system control air tube fittings.
Place the seal in the seal groove.
(3) Screw the fitting into the boss until the seal
barely touches the boss.
(4) Turn the fitting and nut together until the
nut touches the boss.
(5) Put a wrench on the nut to prevent its turn-
ing, and position the fitting by turning it in up to 270°
or unscrewing it up to 90°.
(6) Hold the fitting in its proper position and
tighten the nut against the boss.
5-4.1. Airframe/Engine Interface Connection.
Refer to table 5-1 for the recommended torque values
of airframe fittings installed into the engine at the
airframe and engine interface.
Table 5-1. Recommended Torque for Airframe/
Engine Interface Connections.
5-5. Rigid Tube Installation.
Failure of engine pneumatic or fuel tubes
due to faulty maintenance practice could
cause flameout, power loss, or overspeed.
The practice of tightening lock nuts with
tube assemblies installed can cause tube
damage and failure of the tube assembly.
a. Tube assemblies must fit and be aligned with the
mating flare tube fittings to the degree that at both
ends of the assembly the flares shall uniformly seat in a
free state on the cones of the mating fittings. The fit
shall be without distortion or stretching of the tube
assembly and to the degree that the nuts can be fully
engaged up to the final one-half turn with light finger
b. In the event a tube does not align with the mating
fittings, reposition the mating fittings to the degree
that proper alignment may be attained. Final tighten-
ing of these fittings must be accomplished before the
tube assembly is connected.
c. If proper alignment cannot be attained by reposi-
tioning mating flare tube fittings, bend the tube suffi-
ciently to provide alignment in the free state as spec-
ified. Accomplish all bending with the tube removed
from the engine. Adjustment of the fit may be accom-
plished by bending by hand at principal bends. In the
event the tube cannot be bent by hand, the tube must
be clamped in a fixture or device which will not scratch,
indent, crimp, or mark the surface of the tube during
the bending operation. The flattened effect of the cross
section of the tube as a result of the reforming opera-
tion must not exceed 15 percent of the tube OD.
d. When proper free-state alignment is attained
complete the tubing installation by simultaneously
securing the coupling nuts and tightening them to
proper torque. Always use a backup wrench on the tube
fittings when tightening the tube coupling nuts.
e. When a component to which rigid tube assem-
blies are attached is replaced, remove all interfering
tube assemblies to permit easy removal and reinstalla-
tion of the component. This precaution will prevent
subsequent damage to the tube assemblies.