What are some of the differences between piston engines used in aircraft and automobiles?
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What are some of the differences between piston engines used in aircraft and automobiles? It seems aircraft engines are much more expensive, I imagine some of that cost must be due to the more extreme environment (temperature, air density, roll angle) that an aircraft engine is expected to run in.
The engine in a typical light airplane (say a Cessna 172 or a Piper Cherokee) has a lot in common with the engine in a classic 1960s VW Beetle (Type 1): Both engines are horizontally opposed four-stroke four-cylinder spark ignition gasoline engines. Their parts even have similar metallurgy, and broadly similar failure rates. In fact if you remove the gearbox and install a magneto ignition system you basically have one of several "Volkswagen aircraft engines" that are popular in the experimental market, and have proven to be very reliable if well-maintained.
Certificated aircraft engines (the Lycoming and Continentals you would find in our hypothetical Piper or Cessna) have a few other features not found on a Volkswagen engine: They have dual ignition systems (two magnetos, two spark plugs per cylinder) for redundancy in case one fails, and an oil sump designed to hold at least twice the capacity of oil needed for safe operation. They typically also have a manual mixture control to allow the pilot to lean the fuel/air mixture as they climb (the VW Beetle generally didn't get too high above sea level, and when they did the local mechanic could adjust the mixture in the garage because those cars would probably stay at a relatively high altitude for most of their life - aircraft have an annoying habit of climbing and descending a lot, so either a manual mixture control or an altitude-compensating carburetor is necessary).
