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Can you help us laypersons understand why leaded gas is still needed in GA engines? Is this as simple as using better valve seats or something? I mean cars ha
by cellularmitosis 5y ago
Can you help us laypersons understand why leaded gas is still needed in GA engines? Is this as simple as using better valve seats or something? I mean cars haven’t needed leaded gas for a long time, why can’t GA aircraft just use modern parts / engines?
- throwaway0a5e 5y agoBecause they were designed for leaded gas and you can't just modify certified aviation stuff without spending millions on the process of getting your modification approved.
- MaxBarraclough 5y agoI think it's more that most aviation piston engines were originally approved for use with leaded fuel, and things have been slow to change. At least some of them apparently run fine on the right unleaded fuel. https://en.wikipedia.org/wiki/Avgas#UL94_(formerly_94UL) https://en.wikipedia.org/wiki/Avgas#UL94_(formerly_94UL)
- DebtDeflation 5y agoNot an aviation guy, but a car guy. Lead has historically been used to raise the octane rating of gasoline. Octane rating expresses the resistance of the fuel to "knock" which is the sudden explosion of the air-fuel mixture inside the cylinder versus a controlled burn and which can damage the engine. The main factor that raises the octane requirement of an engine is the compression ratio (max cylinder volume to min cylinder volume). High compression ratios generate more horsepower but require higher octane fuel. The other thing is that lead lubricates the valve seats preventing excess wear, but that's a solved problem with hardened valve seats.