Vibration is a useful diagnostic tool. Initially it is a common symptom of parts or systems which require service. If the vibration is permitted to develop because the source is not identified and corrected, the continued vibration may cause rapid wear and fatigue damage.
NOTE:  Vibration associated with control surfaces must be diagnosed and repaired quickly to assure continued safe operation.

Vibration can be caused by multiple factors. Vibration and noise associated with acrodynamics can be expected when external irregularities and gaps are created by mis-rigging and missing seals. This type of vibration and noise usually increases with airspeed. Vibration associated with control surfaces usually decreases when the surfaces are loaded aerodynamically; unloaded surfaces readily vibrate within their free-play range. Vibration associated with mechanical excitation can be expected for all devices which rotate (engines, pumps, wheels, etc.), and can be improved with balance.
These procedures are suggested to identify the vibration problem, as it may
be reported by the aircrew. The isolation procedure is intended to guide the diagnosis, usually from the simple to the more complex, but emphasis on safety is maintained. The cause and action are consistent. The references give more explicit instructions or further details.
Vibration Symptom and Maintenance Action - In-flight Vibration Figure 201 (Sheet 21)
H52948
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 OVERWEIGHT LANDING - MAINTENANCE PRACTICES
__________________________________________ (CONDITIONAL INSPECTION)
________________________
 1. General
_______
 A. Overweight Landing
 (1)  When the airplane lands at a weight that is above the maximum-design-landing weight (MLW) as specified in the Airplane Flight Manual (AFM), it is an overweight landing. When an overweight landing occurs, an airplane examination is necessary.
 B. The Examination
 (1)  
The examination is divided into two phases (Phase I and Phase II).

 (a)  
Phase I, step A examination is applicable when conditions occur that show the landing sink rate was low to moderate.

 (b)  
Phase I, step B examination is applicable when conditions occur that show the landing sink rate was more than moderate.

 (2)  
If the examination during Phase I does not show that damage has occurred, more examination is not necessary.

 (3)  
If the Phase I, step A examination shows that damage has occurred, Phase I, step B must be done.

 (4)  
If the Phase I, step B examination shows that damage has occurred, Phase II must be done.

 TASK 05-51-74-212-001
 2. Phase I Examination
___________________
 A. Phase I, Step A (Low to Moderate Sink Rate, Overweight Landing Condition)
 S 212-002
 (1) Examine the areas of the airplane landing gear as follows:
 (a)  
Examine the main landing gear tires and wheels for signs of damage.

 (b)  
Examine the upper and lower ends of the main landing gear shock strut for signs of hydraulic fluid leakage.

 NOTE: A small quantity of hydraulic fluid on the inner
____ cylinder is satisfactory.
 (c)  
Examine the tires and wheels of the nose landing gear for signs of damage.

 (d)  
Examine the upper and lower ends of the shock strut of the nose landing gear for signs of hydraulic fluid leakage.

 NOTE: A small quantity of hydraulic fluid on the inner
____ cylinder is satisfactory.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
 B.  Phase I, Step B (More Than Moderate Sink Rate, Overweight Landing condition).
 S 212-003
　
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