Definition
A piston engine designed to run on diesel fuel or jet fuel (Jet A) using compression ignition, in which fuel is injected into hot, highly compressed air in the cylinder and ignites without a spark plug. In aviation, these engines are sometimes called 'jet-fuel piston engines' or compression-ignition aircraft engines.
Plain English
A piston engine that burns diesel or jet fuel and lights the fuel by squeezing the air until it gets hot enough to ignite the fuel on its own — no spark plugs needed.
Context Anchor
Seen in discussions of aircraft engine types, fuel requirements, and how reciprocating engines produce power.
Derivation
Diesel' comes from Rudolf Diesel, the German engineer who developed the compression-ignition engine in the 1890s. 'Reciprocating' comes from the Latin reciprocare, meaning to move back and forth — describing the up-and-down motion of the pistons.
Why Pilots Care
Diesel-fueled reciprocating engines provide improved fuel efficiency and the ability to use widely available jet fuel or diesel, reducing operating costs on long flights.
Analogy
A hand pump gets warm when you squeeze air in it. A diesel-type engine uses that same basic idea: compressed air becomes hot enough to help ignite the fuel.
Intuition Check
Do not assume this means a car diesel engine installed in an airplane. In aviation, it means an approved aircraft piston engine designed to burn approved diesel-type fuel, often Jet-A.
Example Sentence 1
The flight school's newest trainer has a diesel-fueled reciprocating engine, so it fuels up at the Jet A pump instead of the avgas pump.
Example Sentence 2
During preflight the mechanic inspected the fuel injectors on the diesel-fueled reciprocating engine before the training flight.