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C.  The engine attach fittings are described in Chapter 54, Nacelles/Pylons.
2.  Vibration Isolators
A.  The vibration isolators consist of a resilient material permanently enclosed in a metal case. As an engine vibrates the resilient material deforms slightly, thereby dampening the vibrations before they reach the airplane structure. If complete failure or loss of the resilient material occurs, the isolators will continue to support the engine.
B.  The engine forward vibration isolators are located in forward mount support fittings. A projection on each forward isolator mates with a hole in the fitting to provide positive orientation of the isolator. Vibration isolator cover plates retain the forward isolators in position. The aft vibration isolator is bolted to a fitting on the outboard flap track of the inboard flap.
3.  Cone Bolts
A.  Three cone bolts are used to attach each JT8D engine to the vibration isolators. The two forward cone bolts are identical and may be used in any forward position to support either engine. The aft cone bolts are also identical and may be used in the aft position on either engine.
500 
May 15/67  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  71-20-0 Page 1 

Vibration Isolator Engine Mounts  500 
71-20-0  Figure 1  May 01/98 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

MOUNTS - INSPECTION/CHECK
1. General
A.  Examination of the engine vibration isolators and cone bolts should be performed when the engine is removed from the airplane.
2.  Examine Cone Bolts
A.  Check cone bolts for cracks, gouges, nicks, corrosion, fretting and galling. Inspect threaded parts for crossed or otherwise damaged threads. Give particular attention to internal radii, area where thread relief and conical surface intersect and threaded shank of bolt.
B.  Magnetic-particle inspect per ASTM E 1444 or BAC 5424, Class B or alternatively perform ultrasonic inspection of the cone bolts per D6-37239, 737 Nondestructive Test Manual, Part 4, Section 71-20-01.
C.  Cone bolt acceptable repair and damage guidelines (Fig 601).
(1)  
Up to 10 percent of first three threads may be reworked to allow engagement of nut. If exceeded, discard cone bolt.

(2)  
No rework is permitted on the fused section. If damaged, discard cone bolt.

(3)  
Rework critical areas if damaged areas do not exceed 0.200 inch diameter by 0.010 inch depth, or 0.400 inch length by 0.100 inch in width by 0.010 inch depth. The total area to be reworked must not exceed 10 percent of any surface or perimeter.

(5)  
Rework non-critical areas if damaged area does not exceed 0.500 inch diameter by 0.020 inch depth, or 0.750 inch length by 0.200 inch width by 0.020 inch depth. The total area to be reworked must not exceed 15 percent of any surface or perimeter.

NOTE:  Most of the non-critical areas are forged and it is not necessary to improve the surface finish.
D.  If the wear, damage, or flaws are within the acceptable repair and damage guidelines, they may be repaired (Barry Controls OHM 71-20-03). If wear, damage, or flaws are beyond acceptable repair and damage guidelines, discard cone bolt.
E.  See Fig. 602 for cone bolt dimensions, cone bolt thread specifications and dimensions of mating surface to forward and aft isolators.
3.  Examine Forward Vibration Isolator Coverplates
A.  Examine coverplates for cracks and corrosion (Detail B, Fig 601). Check coverplate bolt holes and connecting bolts for cracks and corrosion.
4.  Examine Thrust Link Fitting:
A.  Check thrust link fittings for cracks and corrosion. Check thrust link fitting bolt holes and installation bolts for cracks, wear and corrosion.
501 
May 01/01  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  71-20-0 Page 601 

Vibration Isolator Engine Mounts Wear and Rework  501 
71-20-0  Figure 601 (Sheet 1)  May 01/98 
Page 602 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

K27147
501 Vibration Isolator Engine Mounts Wear and Rework May 01/00 Figure 601 (Sheet 2) 71-20-0 Page 602A/602B BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

 

Replace existing bushing with AMS 4640 AL-NI-Bronze bushing with interference of 0.0002
min/0.0025 max. No oversize hole or plating buildup allowed.
Ream ID of bushing to design dimension after installation.
Repair per Barry Controls OHM 71-20-03.

501  Vibration Isolator Engine Mounts Wear and Rework 
　
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