Aircraft bearings should not be cleaned with steam.

• A. Should not
• B. Should be cleaned with steam
• C. Should be cleaned with water
• D. No cleaning restrictions

Answer: (A)

Steam cleaning is avoided for aircraft bearings because the combination of heat and moisture can cause several problems critical to bearing life. The high temperature of steam can degrade or break down lubricants, alter grease consistency, and even affect bearing fits through uneven expansion. The moisture carried by steam can infiltrate seals and entry paths, promote corrosion of races and balls, and wash away or dilute lubricants that should remain in the bearing clearance. Residual water and contaminants can also be driven into tight spaces, increasing the risk of pitting, scoring, and premature wear.

Safer cleaning methods focus on removing oils and contaminants without introducing heat or moisture. Approved solvents or degreasers that don’t leave residues, followed by thorough drying with compressed air, are typical approaches before re-lubrication with the correct lubricant. This keeps bearings clean and dry, preserving lubrication, protecting tolerances, and reducing the chance of corrosion or damage.