7.11 Bearings Flashcards
What must all aircraft bearings be inspected in accordance with?
All aircraft bearings must be inspected in accordance with the appropriate maintenance manuals.
What problems can visual examinations detect in aircraft bearings?
Visual examinations can detect surface flaws, over-heating, lack of lubricant, and other defects.
What types of bearings are predominantly used on aircraft?
The majority of bearings used on aircraft are either sealed or shielded.
What is the purpose of sealed or shielded bearings?
These bearings are designed to prevent the ingress of foreign particles, which could cause Foreign Object Damage (FOD) or contaminate the bearing contact surfaces.
What is usually tested in a bearing?
Testing a bearing is usually restricted to rotational checks for excessive backlash or free play.
What indicates roughness in a bearing during testing?
Slow rotation of the rolling elements and raceway will highlight roughness due to damage, corrosion, or wear.
What must a serviceable bearing exhibit?
A serviceable bearing must have a smooth actuation and movement.
How should free play be tested in a bearing?
Free play must be tested in both a radial and axial direction.
What is the consequence of excessive backlash in a bearing?
Any wear that leaves excessive backlash in the system is unsatisfactory.
How does the speed of rotation affect bearing wear?
The rate of wear depends on the speed the bearing is rotated at, with high-speed bearings failing quicker than those that rotate slowly.
What must be done if a bearing shows any indication of a fault?
A bearing that shows any indication of a fault or defect must be removed and replaced.
What is the minimum cleaning procedure for bearings?
The bearing must be cleaned of any preservative oil in a solvent bath approved for bearing cleaning purposes.
What is used to remove heavy grease, carbon, or oil from bearings?
Heavy grease, carbon, or oil is removed in a soak bath with chemicals to suit the requirements.
What is an ultrasonic bath used for in bearing cleaning?
Ultrasonic baths are used as a final cleaning method to shake off any stubborn particles or contaminants.
What should be done after cleaning a bearing?
When the bearing has completed its cleaning process, it is rinsed and then coated in light preservative oil if it is not to be immediately inspected.
How should cleaned bearings that are not installed immediately be stored?
Cleaned bearings must be coated in a rust-preventing oil, wrapped in greaseproof paper, boxed, and labelled, and stored horizontally in a clean and dry atmosphere.
What happens after a bearing has been cleaned?
Once the bearing has been cleaned, it can be inspected for unacceptable conditions.
What grounds for rejection or replacement exist for bearings?
Nearly any flaw or defect detected in a bearing assembly is likely to be grounds for replacement.
Why is the correct maintenance of bearings important?
The correct maintenance of bearings is important to prevent defects and shorten service life caused by foreign object contamination, moisture, and vibration.
What is required on a scheduled basis for bearing maintenance?
The application of a lubricant is required on a scheduled basis, as recommended by the manufacturer.
What should be done before lubricating bearings?
Thoroughly clean the lubrication equipment and fittings before lubricating to prevent dirt from causing bearing failures.
What can happen if too much grease is used in bearings?
Too much grease can overpack the bearing, causing it to run hot and shortening its service life.
What is a lubricant?
A lubricant is a fluid or grease introduced between two moving surfaces to reduce friction, improving efficiency and reducing wear.
What do lubricants typically consist of?
Lubricants contain 90% base oil and less than 10% additives.
