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The Care of LORD 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:

1. 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.
2. Visually inspect all bonded steel parts for cracks and excessive nicks, scratches, or gouges.
3. Inspect all nut locking wires for looseness and tighten as necessary.
4. When applicable, measure all drift indicators in each mounting assembly for excessive deflection.
5. Whenever any of the conditions detailed above in steps (1), (2), and (4) 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 & Inspection

1. Wipe oil and dirt from bonded mountings, but do not dip in cleaning solvents.
2. 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.
3. 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.