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

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 mixture Propulsive 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

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 ?

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.