Lesson 2: Aircraft Engine Types And Construction

The Heat Engine

• Converts chemical energy (fuel) into heat energy.

• Heat energy is then converted into mechanical energy.

• The heat energy is released at a point in the cycle where the pressure is high, relative to atmospheric.

The Heat Engine

• Divided into groups or types depending upon:

• The working fluid used.

• The means of compression.

• The Propulsive working fluid.

Types Of Heat Engines

Types Of Heat Engines

• Turbojet

• Means of compression: Turbine-driven compressor• Engine working fluid: Fuel/air mixture• Propulsive working fluid: Fuel/air mixture

Types Of Heat Engines

• Turboprop

• Means of compression: Turbine-driven compressor• Engine working fluid: Fuel/air mixture• Propulsive working fluid: Ambient Air

Types Of Heat Engines

• Ramjet

Means of compression: Ram compression Engine working fluid: Fuel/air mixturePropulsive working fluid: Fuel/air mixture

Types Of Heat Engines

• Pulse-Jet

• Means of compression: Compression due to combustion

• Engine working Fluid: Fuel/air mixture• Propulsive working Fluid: Fuel/air mixture

Types Of Heat Engines

• Rocket

• Means of compression: Compression due to combustion

• Engine working fluid: Oxidizer/fuel mixture• Propulsive working fluid: Oxidizer/fuel mixture

Types Of Heat Engines

• Reciprocating

• Means of compression: Reciprocating action of pistons

• Engine working fluid: Fuel/air mixture• Propulsive working fluid: Ambient air

Engine Requirements

Engine Requirements

• Efficiency

• Power and Weight: If the specific weight of an engine is decreased, the performance of the aircraft will increase.

• Reciprocating engines produce approximately 1 HP for each pound of weight.

Engine Requirements

• Fuel Economy

• The basic parameter for describing the fuel economy of aircraft engines is specific fuel consumption.

• Specific fuel consumption for reciprocating engines is the fuel flow (lbs/hr) divided by brake horsepower.

Engine Requirements

• Durability and Reliability

• Durability is the amount of engine life obtained while maintaining the desired reliability.

• Reliability and durability are built into the engine by the manufacture.

• Continued reliability is determined by the maintenance, overhaul, and operating personnel

Engine Requirements

• Operating Flexibility

• The ability of an engine to run smoothly and give desired performance at all speeds from idling to full-power.

• The engine must also function efficiently through all variations in atmospheric conditions.

Engine Requirements

• Compactness

• To effect proper streamlining and balancing of an aircraft, the shape and size of the engine must be compact.

• In a single engine aircraft, the shape and size of the engine will affect the view of the pilot.

Engine Requirements

• Powerplant Selection

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Reciprocating Engine

• For aircraft whose cruising speeds will not exceed 250 MPH the reciprocating engine is the usual choice.

• Chosen for its excellent efficiency.

• Turbocharged or supercharged for high

altitude use.

-- Turbo-use exhaust

-- Super-use accessory drive

Turboprop Engine

• For cruising speeds from 180 to 350 MPH the turboprop engine performs better.

• Develops more power per pound then reciprocating.

• Operate most economically

at high altitudes.

Turbojet/Turbofan Engines

• Intended to cruise from high subsonic speeds up to Mach 2.0.

• Operates most efficiently at high altitudes.

• Less instrumentation and

controls required.

Types Of Reciprocating Engines

In-Line Engines

• Generally has even number of cylinders.

• Liquid or air cooled.

• Has only one crankshaft.

In-Line Engines

• Small Frontal area, better adapted to streamlining.

• When mounted inverted, it offers the added advantages of a shorter landing gear.

• High weight to horsepower ratio.

V-type Engines

• Cylinders are arranged in two in-line banks generally set 30-60° apart.

• Even number of cylinders and are liquid or air cooled.

Radial Engines

• Consists of a row, or rows, of cylinders arranged radially about a center crankcase.

• The number of cylinders composing a row may be either three, five, seven, or nine.

Radial Engines

• Proven to be very rugged and dependable.

• High horsepower.

Rotary-Radial

• Used during World War I by all of the warring nations.

• Cylinders mounted radially around a small crankcase and rotate with the propeller.

Rotary-Radial

• Torque and gyro effect made aircraft difficult to control.

• Problems with carburetion, lubrication, and exhaust.

Opposed Or O-type Engines

• Two banks of cylinders opposite each other with crankshaft in the center.

• Liquid or air cooled, air cooled version used predominantly in aviation.

Opposed Or O-type Engines

• Has low weight-to-horsepower ratio.

• Its narrow silhouette makes it ideal for installation on wings.

• Little vibration.