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Engine Mount (Lord) Frequently
Asked Questions
How do I take care of my engine
mounts
Where a component maintenance manual is available for a system, its
requirements take precedence.
General Comments
Bonded sandwich assemblies are natural rubber or specially blended
synthetic compounds bonded to two plates. The normal installation
requires four assemblies, each consisting of two sandwich mountings and one
spacer. Satisfactory performance requires that the spacer be
designed to the correct length to precompress each mounting to guarantee proper
positioning of the mountings. When properly installed, these
mountings provide excellent isolation of engine vibration, resulting in
smoother, quieter flight. Always order replacement mounting by the mounting
assembly number to insure the correct spacer.
Visual Inspection of Installed Mountings
At each annual inspection and at FAA required inspections of the
aircraft's engines, all mounting assemblies should be visually inspected
in their installed state while supporting the engine's weight. The correct
visual inspection procedure is as follows:
- Inspect all bonded sandwich mountings for metal-to-rubber bond
separations, flex cracks, rubber deterioration due to exposure to fluids,
and mechanical damage such as cuts in the rubber surface.
- Visually inspect all bonded steel parts for cracks and excessive nicks,
scratches, or gouges.
- Inspect all nut locking wires for looseness and tighten as necessary.
- When applicable, measure all drift indicators in each mounting assembly
for excessive deflection.
- Whenever any of the conditions detailed above in steps (a), (b), and (d)
are found, remove the mounting assembly from the engine, disassemble,
inspect, and repair it as described in the maintenance manual.
CAUTION
Whenever the aircraft engines are cleaned during a normal
inspection, cover each mounting assembly to protect it from
contamination by cleaning fluids or solvents. This also applies to engine
lubricants. Should any such materials accidentally get on a
mounting assembly, wipe it off thoroughly as soon as possible with a clean rag.
Disassembly
To remove mounting assemblies from the engine/aircraft, it is necessary
to remove the engine weight from the mountings by the use of a
chain hoist or equivalent, and disconnect the nuts and bolts which hold the
mountings in place. In general, removal of one mounting at a time
can be accomplished, if necessary, without removing the engine weight from the
mountings.
Cleaning and Inspection
- Wipe oil and dirt from bonded mountings, but do not dip in cleaning
solvents.
- Steel bolts and spacers should be inspected for cracks or damaged
threads. Examine spacers for crushing of ends caused by excessive tightening
torque on bolt. Replace if either condition is apparent.
- Examine bonded rubber mounting for oil swelling, bond or rubber
separation, and shear or compression set. Bond separation, oil swelling, or
flex cracks in the surface of the rubber is cause for rejection. The affects
of shear and compression set are determined by measuring the dimensions
shown in Figure 1. Reject parts which have an eccentricity greater than
dimension "A" or an overall thickness less than dimension "B" as shown in
Table 1.
Figure 1.
Table 1.
| Mounting Series Number |
Eccentricity Max. "A" inch. |
Thickness Min. "B" inch. |
|
J1552 |
0.05 |
0.29 |
|
J2245 |
0.06 |
0.45 |
|
J3049 |
0.07 |
0.71 |
|
J6113 |
0.05 |
0.39 |
|
J7401 |
0.06 |
0.75 |
|
J7530 |
0.06 |
0.75 |
|
J7649 |
0.06 |
0.75 |
|
J7763 |
0.08 |
1.02 |
|
J8381 |
0.06 |
0.75 |
|
J9555 |
0.06 |
0.75 |
|
J9612 |
0.08 |
1.22 |
|
J10533 |
0.10 |
0.80 |
|
J10776 |
0.10 |
1.01 |
|
J12165 |
0.20 |
1.00 |
|
J12397 |
0.20 |
0.86 |
|
J12454 |
0.20 |
1.30 |
|
J12799 |
0.20 |
1.28 |
|
J13051 |
0.23 |
1.40 |
|
J15199 |
0.40 |
1.60 |
|
J7763-34(BTR-II) |
0.14 |
1.02 |
|
J9612-30(BTR-II) |
0.14 |
1.20 |
|
J9612-32(BTR-II) |
0.12 |
1.20 |
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