Why is the exhaust turbine bearing considered the most critical lubricating point in a gas turbine engine?

The exhaust turbine bearing is considered the most critical lubricating point in a gas turbine engine primarily because it operates at the highest temperature normally present. In gas turbine engines, as exhaust gases pass through the turbine section, they can reach extremely high temperatures. This condition places substantial thermal stress on the bearing, necessitating effective lubrication to prevent overheating and potential failure.

Proper lubrication at this point is essential to ensure that the bearing can withstand not only the high temperatures but also the centrifugal forces and loads acting on it during operation. If adequate lubrication is not maintained, it can lead to rapid wear, reduced performance, or catastrophic failure of the engine.

Although other points in the engine may exhibit significant mechanical stresses or require maintenance, the combination of temperature and operational demands makes the exhaust turbine bearing particularly critical for the overall health and efficiency of the gas turbine engine.