Class 2 (2nd Engineer) MEKG 📅 Mar 2023

Exam Question

(a) State why fixed pitch propellers have a poor efficiency when going astern.

(b) With reference to controllable pitch propellers state:

(i) Why is it preferable that the main servomotor be housed in the propeller hub rather than in the shafting forward of the propeller shaft?

(ii) What regular maintenance and checks should be carried out to ensure maximum reliability of the gear at all times?

Reference Answer

### (a) Reasons for Poor Efficiency of Fixed Pitch Propellers (FPP) in Astern Operation
A Fixed Pitch Propeller's blade is designed as a hydrofoil, optimized for generating thrust efficiently in the forward direction. When rotation is reversed for astern movement, its hydrodynamic efficiency plummets due to several critical factors:
1. **Unfavourable Angle of Attack:**
* The blade profile has a rounded leading edge and a sharp trailing edge for smooth flow attachment in the ahead direction. When going astern, the sharp trailing edge becomes the leading edge.

Full answer on MeoMock — surveyor-grade reference answers for 7,000+ written exam questions.

View plans Browse library

← Browse more questions

Prepare on Android — MeoMock on Google Play