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MAINTENANCE MANUAL

D-D

Fuel Coupling in the Nacelle Strut
Figure 601 (Sheet 3)

F21273
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747-400 MAINTENANCE MANUAL
FRONT
SPAR
(REF)

COUPLING NUT
O-RING
E  SPACERFRONT SPAR
FITTING  O-RING
(REF)  RETAINER HALF (2 LOCATIONS)
SPACER
RETAINING
RING
O-RING RETAININGFRONT SPAR RING
FITTING  UNIONINBD
(REF)  FUEL TUBE (REF) O-RING
O-RINGFWD
SHROUDED COUPLING
E
(FRONT SPAR INSTALLATION SHOWN)
COUPLING
D  BODY
COUPLINGCOUPLING BODYNUT (REF) (REF)
FUEL TUBE (REF)
FRONT SPAR
OR BULKHEAD
FITTING
(REF)

WEAR ON COUPLING FITTING OR FERRULE FROM RETAINING RING OR RETAINER
1
E-E
Fuel Coupling in the Nacelle Strut Figure 601 (Sheet 4)
M04847
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 (c)
(d)

(e)

(f)

(g)

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747-400 MAINTENANCE MANUAL
 3)  If there are multiple dents, the total dent depth (individual depths added together) in any section five times the tube diameter long, must be no more than ten percent of the tube diameter.
 4)  The dents in the tubing must be farther than one diameter of the tube from the end of the tube.
 5)  The dents in the tubing must not have an area of more than
 0.125 square inch. 6) If the dent is on the outer part of a bend in the tube, the
 dent must not have a depth of more than 0.015 inch.Do an inspection for nicks. 1) The nicks in the tubing must have a rounded bottom. 2) The nicks in the tubing must not have a depth of more than
 0.004 inch. 3) You must remove all the burrs from the nick if there are
 some burrs.
Do an inspection for fretting.
 1)  Fretting must not have a depth of more than 0.004 inch.
Do an inspection for scoring.
 1)  If you find some small scoring, you can make it smooth again, but obey these conditions: a) The scoring must not be on the outer part of a bend. b) You must not remove more than 0.004 inch of metal.
Do an inspection for tubes with a cross section that is not
 fully circular (tubes with ovality).
 1) Calculate the percent ovality with this formula:

 percent ovality = [(OD Max - OD Min)/(OD Nominal)] X 100%
 - percent ovality equals [(OD Max minus OD Min) divided
 by (OD Nominal)] multiplied by 100 percent a) OD Max is the maximum outer diameter of the tube b) OD Min is the minimum outer diameter of the tube c) OD Nominal is the outer diameter of the tube at a
 position where the tube is circular or almost circular. 2) The percent ovality must not be more than 10% for tubes with a diameter of less than 2 inches. 3) The percent ovality must not be more than 5% for tubes with
 a diameter of more than 2 inches.
Wrinkles
 1)  The height of a wrinkle is the distance between a straight
 line that touches the high point of a wrinkle and a straight line that touches the low point of a wrinkle.
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MAINTENANCE MANUAL

 2)  Wrinkles must not have a height larger than the applicable
 maximum wrinkle height: ~........................................................... | Tube Diameter (inches) | Maximum Wrinkle Height (inches)| ............................................................. | less than 1 | 0.020 | ............................................................. | 1 to 1.99 | 0.030 | ............................................................. | 2 to 2.99 | 0.040 | ............................................................. | 3 or more | 0.050 | 2..........................…................................1
　
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