FAA Powerplant Written Practice Test

How is the majority of heat from combustion dissipated in a typical aircraft reciprocating engine?

1. Through the radiator

2. By cooling fins

3. With the exhaust gases

4. Through oil circulation

The correct answer is: With the exhaust gases

The majority of heat from combustion in a typical aircraft reciprocating engine is dissipated with the exhaust gases. When fuel combusts within the engine cylinders, a significant amount of heat is produced. This heat is transferred to the combustion chamber walls and engine components. As the gases expand and are expelled from the engine through the exhaust system, they carry away a large portion of this heat. The design of the exhaust system plays a crucial role in ensuring effective heat dissipation, helping to maintain optimal engine temperature. While other methods, such as oil circulation and cooling fins, do assist in managing engine temperature, they are secondary to the principle of heat removal through the exhaust gases. The cooling fins may help with heat loss to the surrounding air, and oil circulation does aid in cooling the engine, but the most efficient transfer of combustion heat is achieved by expulsion of hot gases. This process not only removes heat but also contributes to the mechanical work necessary for propulsion.