19 / 20
If the main oil filter of a gas turbine engine becomes clogged, oil to the main bearings is still assured:
  • A
    if breather pressure in the main compartments is increased to ensure positive lubrication of the bearings.
  • B
    because the oil filter bypass valve opens.
  • C
    because fuel upstream of the oil filter will be mixed with oil to allow easier passage through the filter.
  • D
    if a higher engine rpm is selected to increase oil pressure.

The main purpose of lubrication is to reduce the friction between the moving surfaces and dissipate heat from the moving parts. It is also used as a substance to clean the interior of the engine and accumulate the deposits gathered along the way for removal. In a gas turbine engine, the largest and some of the most important moving parts are the ball and roller main bearings of the main driveshafts, which would also crucially require an oil supply.

Right from the main oil tank, a high-pressure oil pump will draw oil and deliver it further down the line. The pump contains a pressure relief valve that will regulate the pump’s pressure and relieve the excessive pressure. Following this, the oil is fed to a fine filter consisting of a bypass system in order to ensure the engine’s bearings are always supplied with oil. Dirty/contaminated oil is always better than no oil at all. Whenever an excessive pressure is sensed at the filter by a differential pressure switch, the bypass valve will automatically open and continue delivering oil to the gearboxes and engine bearings.

Your Notes (not visible to others)

This question has appeared on the real examination, you can find the related countries below.