Page 703 - PPL-engelsk 2025

Aircraft general knowledge

8.5.1.2 Aviation gasoline vs. auto gasoline

Many of our aircraft can be approved for Mogas (unleaded auto gasoline).

However, this requires an STC (Supplemental Type Certificate) from the

authority.

The octane number of auto gasoline and aviation gasoline cannot be directly

compared, as they are measured using different methods.

If you take a super 98 auto gasoline, you can subtract 10-15, and you then have

approximately the value that corresponds to aviation gasoline. This means that
aircraft that can use 80 (80/87) gasoline in terms of octane can use super 98.

However, there are many problems with flying with auto gasoline. Vapor pockets
can form in the gasoline supply, the gasoline can dissolve gaskets, etc. in the fuel

system, the exhaust gas can be corrosive, and the oil in the engine can be

damaged by the various additives in the gasoline.

8.5.1.3 Non-usable vs. non-drainable fuel

A sign must be placed close to the tank so that

you can see which type of gasoline is to be filled.

You must also be able to read the total tank
content and usable content in the tank.

Usable content is that which can be supplied to the engine for consumption in

normal flight positions.

Note the difference between unusable and non-drainable gasoline.

Our workshop removes the non-drainable stock at regular intervals.

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 703