MIDTERMS L:1&2Propeller

Propeller Performance Metrics

are measurements used to evaluate how efficiently and effectively a propeller converts engine power into thrust

Time between overhaul

5-7 years or 1,500 to 2,000 flight hours

TBO

Air resistance

acts against the rotation of the propeller blades

• profile drag

• Induced drag

2 types or drag

Friction

It is the force that resists motion when two surfaces touch each other

Noise

It is the sound produced when a propeller rotates and disturbs the air

Propeller Slip

Air is compressible and not solid

Propeller Thrust

is the forward force produced by a spinning propeller that pulls (or pushes) the aircraft through the air

Power Output

It is the power produced by the engine to turn the propeller and create thrust

Brake horse power (BHP)

Power measured at the engine crankshaft

Shaft horsepower (SHP)

Power delivered to the propeller shaft

Thrust horsepower (THP)

Useful power that actually moves the aircraft forward

Propulsive Efficiency

Measures how effectively a propeller converts engine shaft power into useful thrust power that moves the aircraft forward

Fuel consumption

refers to how much fuel the engine burns to produce power that turns the propeller and generates thrust.

Although the engine burns the fuel, it greatly affects how much fuel is needed to maintain flight.

Advance Ratio

It is a dimensionless parameter that represents the ratio of aircraft forward velocity to the product of propeller rotational speed and diameter.

It measures how far the propeller "advances" in one revolution.

Propeller Efficiency

is the ability of the propeller to convert engine shaft power into thrust power

Blade Pitch

is the theoretical distance a propeller would move forward in one complete revolution if it were moving through a solid material

Low pitch & high pitch

Types of blade pitch

Low pitch

has a smaller pitch angle and is commonly used during takeoff to produce maximum thrust

High pitch

has a larger pitch angle and is commonly used during cruising to improve efficiency.

Angle pitch

is the angle between the propeller blade chord line and the plane of rotation

Pitch angle is small

▪Blade cuts the air easily

▪Propeller spins faster

▪Used for takeoff

pitch angle is large

Blade pushes more air backward

Propeller spins slower

Used for cruise

Slip

It is the difference between the theoretical distance a propeller should move forward in one revolution and the actual distance the aircraft moves forward

Torque

is the twisting force produced by the engine that rotates the propeller about its axis.

In an aircraft engine, ____ is produced by the engine crankshaft and transmitted to the propeller, causing it to spin and generate thrust

Tip speed

It is the linear velocity of the propeller blade tip as it rotates around the propeller hub

• Propeller diameter

• Propeller rotational speed (RPM)

Tip depends on?

▪Shock waves form

▪Drag increases

▪Propeller efficiency decreases

▪Noise increases

Problems that occur when tip speed becomes too high

Flanged shaft installation

a common method used to attach a propeller to the engine crankshaft in many light aircraft

The crankshaft has a flat circular flange, and the propeller hub is bolted directly to this flange using high-strength bolts and nuts

Tapered Shaft Installation

uses a cone-shaped shaft where the propeller hub slides onto the taper and is tightened with a large nut.

When the nut is tightened, the hub grips the shaft very tightly due to the tapered friction fit.

Splined Shaft Installation

It has longitudinal grooves (splines) along its surface

Splines

propeller rotates with the shaft without slipping

a method where the engine shaft and the propeller hub have matching grooves called?