propeller & variable pitch propeller

Question 1

what does amount of lift depend on?

Answer 1

speed and angle of attack

Question 2

angle of attack of propeller blade is less at … than at the …

Answer 2

less at tips than at the hub

Question 3

what impact does a higher angle of attack have on forward speed and rpm?

Answer 3

low forward speed, low rpm at full throttle

Question 4

what happens to a propeller in a climb? think airspeed, rpm, angle of attack etc

Answer 4

• airspeed and engine rpm reduces
• relative airflow angle and propeller angle of attack increases (low efficiency)

Question 5

variable pitch propeller – higher angle of attack = ?

Answer 5

greater lift

Question 6

what do we call a variable pitch propeller with a high blade angle?

Answer 6

coarse pitch

Question 7

what do we call a variable pitch propeller with a low blade angle?

Answer 7

fine pitch

Question 8

coarse pitch = … forward speed

Answer 8

high

Question 9

fine pitch = … forward speed

Answer 9

low

Question 10

how does the propeller mitigate the change of propeller blade angle of attack on a variable pitch propeller? (process)

Answer 10

• propeller adjusts blade angle to reduce blade angle of attack
• propeller becomes easier to push through air
• engine rpm recovers

Question 11

what does Constant Speed Unit do?

Answer 11

detects change in rpm and adjusts propeller blade angle of attack to ensure set rpm is maintained

Question 12

what is the propeller pitch controlled by?

Answer 12

oil pressure within CSU

Question 13

how does the CSU work?

Answer 13

oil pressure acts against a spring in propeller that tries to force the pitch of propeller into coarse position

Question 14

what does ‘coarse position’ mean?

Answer 14

high pitch, low rpm