DGCA & EASA Module 15 : Part-8 Engine's Bearings and Seals Question

DGCA & EASA Module 15 : Part-8 Engine's Bearings and Seals Question-Answer


1. Main bearing oil seals used with turbine engines are usually what type(s)?.
A. Teflon and synthetic rubber.
B. Labyrinth and/or carbon rubbing.
C. Labyrinth and/or silicone rubber.
Ans : Labyrinth and/or carbon rubbing.
Explanation: Jeppesen A&P Powerplant Textbook 3-5.



2. If, during inspection at engine overhaul, ball or roller bearings are found to have magnetism but otherwise have no defects, they.
A. are in an acceptable service condition.
B. cannot be used again.
C. must be degaussed before use.
Ans : must be degaussed before use.
Explanation: Jeppesen A&P Powerplant Textbook 4-26.

3. A carbon seal has which type of sealing arrangement?.
A. Full contact with race.
B. Full contact with casing.
C. Full contact with labyrinth.
Ans : Full contact with race.
Explanation: Rolls Royce The Jet engine page 92 refers.

4. The highest turbine bearing temperature takes place.
A. all the time.
B. at start-up.
C. at shut-down.
Ans : at shut-down.
Explanation: On shut down the bearing loses its cooling so for short periods it may actually heat up.

5. Indentations on bearing races caused by high static loads are known as.
A. fretting.
B. galling.
C. brinelling.
Ans : brinelling.
Explanation: NIL.

6. The function of a labyrinth seal is to create.
A. a restricted leakage of air between fixed and rotating components.
B. an airtight seal between fixed and rotation components.
C. an airtight seal between fixed adjacent casing surfaces.
Ans : a restricted leakage of air between fixed and rotating components.
Explanation: Jeppesen Gas Turbine Powerplants Page 5-36 Refers.

7. The bearings of a compressor rotor are usually.
A. ball and roller.
B. plain.
C. sintered.
Ans : ball and roller.
Explanation: Jeppesen Gas Turbine Powerplant Page 4-49/50 refers.

8. Bearing seal failure would most probably cause.
A. high oil temperature.
B. high oil consumption.
C. low oil pressure.
Ans : high oil consumption.
Explanation: Jeppesen Gas Turbine Powerplants Page 5-36 refers.

9. Why are oil seals pressurised?.
A. To ensure minimum oil loss.
B. To ensure oil is forced into the bearings.
C. To ensure that the oil is prevented from leaving the bearing housing.
Ans : To ensure minimum oil loss.
Explanation: Pressurised labyrinth seals stop oil leaking out of the bearing housing between rotating shafts and stationary casing. Note that oil is always scavenged out of theses housings therefore answer c must be wrong.

10. What bearing is used to take axial loads on a main rotation shaft of a gas turbine engine?
A. Plain bearing.
B. Roller bearing.
C. Ball bearing.
Ans : Ball bearing.
Explanation: Ball bearings absorb force in all directions. The others only do so radially.

11. Seals on a gas turbine engine restrict leakage of oil by.
A. spring pressure.
B. closely tolerated contacting components.
C. air pressure.
Ans : air pressure.
Explanation: NIL.

12. An abradable lining in the fan case.
A. prevents fan blade tip rub.
B. produces less leakage at tips for anti-ice.
C. provides acoustic medium.
Ans : provides acoustic medium.
Explanation: The prime purpose is to optimise fan performance, but it is also an acoustic lining.

Click Here For : DGCA & EASA Module 15 : Part-9 Lubricants and Fuels Of GTE Question

13. Squeeze film bearings are usually found on.
A. H.P compressor section.
B. the turbine section.
C. LP compressor section.
Ans : LP compressor section.
Explanation: Squeeze film bearings utilise the oil film to dampen radial out of balance. The largest rotor is normally going to have the largest out of balance. hence L.P compressor section is our best guess. No reference can be found.

14. Taper roller bearings accept loads in which direction?.
A. Axial loads only.
B. Radial and axial in both directions.
C. Radial and axial in one direction only.
Ans : Radial and axial in one direction only.
Explanation: Taper rollers are only used when the axial load is low. I.E thrust bearings are not taper rollers, but ball bearings.

15. Some labyrinth seals.
A. control the outflow of air at the turbine.
B. are self lubricating.
C. are spring loaded.
Ans : control the outflow of air at the turbine.
Explanation: Labyrinth seals can be air seals as well as oil seals.

16. The purpose of 'squeeze film' type bearing is to.
A. increase the flow of oil to the rolling element.
B. minimise the effect of vibration.
C. improve outer race cooling.
Ans : minimise the effect of vibration.
Explanation: The film of oil acts as a buffer between the outer race and the casing.

17. In a jet engine the rotating assembly oil seals are maintained oil tight by means of.
A. a garter seal.
B. an annular expander ring.
C. air pressure.
Ans : air pressure.
Explanation: Air pressure acts across a labyrinth seal to hold the oil in the bearing chamber.


Click Here For : DGCA & EASA Module 15 : Part-9 Lubricants and Fuels Of GTE Question

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