MEP.1.1.2.3 The Fully Feathering Propeller

Question 1

What are the significant differences between the constant speed propeller and the fully feathering propeller?

Answer 1

Feathering propeller has a greater balde angle range beyond the full coarse position, and

Loss of oil pressure causes the blade to go to the feathered (full coarse) position (rather than the fully fine position, as is the case in a single)

Question 2

What may the propeller system include to unfeather?

Answer 2

An accumulator

Question 3

What does it do?

Answer 3

Stores pressure energy to unfeather the propeller after practice asymmetric situations

Question 4

What is the locking pin?

Answer 4

Prevents the propeller going to the feather position as the rpm decays and the oil pressure drops, when the engine is shutdown.

Pin operates at about 900 rpm, which is well below any in-flight range even when the propeller is windmilling (except engine seizure).

Question 5

How is the feathered position selected?

Answer 5

Retarding the propeller rpm levers through low rpm range to the near-most position

Note: rpm setting is independent of throttle position and it is possible to feather the live engine