Propeller

Question 1

What is a propeller?

Answer 1

A rotating propeller converts power from a piston engine into thrust. The propeller comprises 2 or more blades. On single-engine aircraft, equipped with Western-made engines, the propeller almost always rotates clockwise when viewed from the cockpit.

Question 2

Blade angle

Answer 2

Angle between blade chord line and plane of rotation

Question 3

Fine Pitch

Answer 3

propeller pitch with a lower blade angle

Question 4

Coarse pitch

Answer 4

propeller pitch with a high blade angle

Question 5

Blade Angle of Attack

Answer 5

angle between the blade chord line and the relative wind

Question 6

GEOMETRIC PITCH

Answer 6

distance to advance at one revolution without the slippage

Geometric pitch = Effective pitch + Slip

Question 7

Effective pitch

Answer 7

the actual distance at one revolution with slippage

Effective pitch = Geometric pitch - Slip

Question 8

Propeller Efficiency

Answer 8

is the ratio of thrust horsepower to brake
horsepower. - varies from 50 to 87 percent, depending
on propeller “slippage.

Question 9

PITCH DISTRIBUTION or propeller twis

Answer 9

A propeller tapers towards the
tip and appears to twist. In effect the airfoil
section alters from the hub of the propeller to
the tip and the blade angle decreases.

Question 10

Propeller Tip Speed

Answer 10

Flutter or vibration may be caused by the tip of
the propeller blade travelling at a rate of speed of
sound and approaching the speed of sound , thus
causing excessive stresses to develop

Question 11

Types of Propellers

Answer 11

-Fixed pitch propeller
-Ground adjustable propeller
- Constant speed propeller

Question 12

FIXED PITCH propellers

Answer 12

Efficient at only one RPM and speed setting. At a constant RPM, a fixed pitch prop with increasing forward speed would result in a decrease of propeller angle of attack.

At fast true airspeeds, a fixed pitch prop is very inefficient

Question 13

Cruise Propeller (Fixed pitch)

Answer 13

fixed pitch prop with high pitch, therefore more drag. This results in lower rpm. Increased efficiency during cruising flight

Question 14

Climb Propeller (Fixed pitch)

Answer 14

fixed pitch prop that has a lower pitch, therefore less drag. Results in the higher rpm by the engine. This increases performance during takeoffs and climbs

Question 15

Standard propeller

Answer 15

Compromise of both Climb and Cruise Propeller

Question 16

Disadvantage of cruise propeller

Answer 16

It is most efficient only at a condition of cruise, but until reaching cruise speed, the AOA of the propeller blade is comparatively larger, therefore the propeller is less efficient.

Question 17

GROUND ADJUSTABLE PITCH PROPELLER

Answer 17

Mechanic can change the Pitch setting only on the ground
when the aircraft is not flying, or engine is not running.

Question 18

CONTROLLABLE PITCH PROPELLER

Answer 18

Pilot can change the Pitch even when the propeller is rotating, or the aircraft is flying

Question 19

Constant speed propeller

Answer 19

often called automatic propeller, which automatically adjusts the propeller pitch to maintain a selected propeller rpm. It utilizes a hydraulically, mechanically or electrically pitch- changing mechanism called a “GOVERNOR”.

Question 20

PROPELLER CONTROL

Answer 20

the blue knob which controls the RPM a pilot sets
in flight.

-As the blade angle is reduced, the torque required to
spin the propeller is reduced and RPM of the engine will tend to increase for any given power setting

• Pulling the propeller control back forces prop blade to the coarse pitch taking a bigger bite of air. Drag increases and RPM slows down

Question 21

Manifold Pressure

Answer 21

-Power output is controlled by the throttle and
indicated by a manifold pressure gauge (MAP Gauge)

-The gauge measures the absolute pressure of the
fuel/air mixture inside the intake manifold and is more
correctly a measure of manifold absolute pressure
(MAP)

-Increasing the throttle setting, more fuel and air is
flows to the engine at any given time; therefore, MAP
increases

Question 22

Feathered

Answer 22

The chord line of the blade is parallel to the airflow, therefore preventing wind milling

• On single-engine aircraft, whether a powered glider or turbine powered aircraft, the effect is to increase the gliding distance
• On a multi-engine aircraft, feathering the propeller on a failed engine allows the aircraft to maintain altitude with the reduced power from the remaining engines

Question 23

GROUND FINE PITCH

Answer 23

The minimum torque position for ground operation and sometimes referred us “Superfine Pitch”.

Question 24

REVERSE PITCH

Answer 24

An aerodynamic brake position used for braking

Question 25

Alpha Range

Answer 25

The flight operating range, from Flight Fine Pitch to Coarse Pitch

Question 26

Beta Range

Answer 26

From Flight Fine Pitch to Reverse Pitch which is the ground operating range and is hydro mechanically controlled by a flight deck power lever

Question 27

Critical engine

Answer 27

The CRITICAL ENGINE of a multi-engine with both propellers rotating clockwise (viewed from the pilot’s point of view) , fixed wing aircraft is the one whose failure would result in the most adverse effects on the aircraft's handling and performance

Question 28

Factors Affecting Critical Engine

Answer 28

1. P-FACTOR / ASYMMETRICAL DISK LOADING 2. ACCELERATED SLIPSTREAM 3. SPIRALING SLIPSTREAM 4. TORQUE

Question 29

Critical engine solution

Answer 29

Most aircraft which have COUNTER-ROTATING PROPELLERS do not have a critical engine defined by the above mechanism, because the two propellers are made to rotate inward from the top of the arc; both engines are equally critical