Military Helicopter Bearings

Situation:
• Combat helicopter are vulnerable to sudden loss if transmission lubrication due to enemy fire.
• Increasing the transmission life after sudden lubrication loss increases the probability of finding a suitable emergency landing site, thus savings lives.

Testing:
• The performance of standard bearings and Dicronite dry lubricated standard bearings was compared under sudden lubrication loss conditions.
• Bearings: M-50 steel roller bearings
• Load: 11Kgf (250lbf) radical load
• Speed: 10,000 rpm, inner race
• Lubricant: MIL-PRF-7808 lubricant as 65°C (175°F)

Results:
• Under normal lubricated conditions, the outer race temperature measured 107°C (250°F)
• Under lubricated loss conditions, standard bearings failed at a maximum time of 6 minutes, minimum time of 3 minutes. An outer race temperature of 154°C (335°F) was measured at failure time.
• A Dicronite dry lubricated bearing ran for the duration of the test (38 minutes), under lubrication loss conditions, a sic fold increase. An outer race temperature of 204°C (425°F) was measured.

Conclusion:
• Dicronite dry lubrication increased bearing life sufficiently to enable an emergency landing per the military’s test conditions.