Fuel Types - Fuel Systems - Airframes & Aircraft Systems #64

Summary

This lesson delves into the properties and production of aircraft fuels, including gasoline for piston engines and kerosene for gas turbines, both derived from crude oil. It discusses the distillation process, fuel specifications, and the importance of factors like calorific value, ease of combustion, and safety. The video also covers aviation gasoline grades, octane ratings, and the challenges of fuel storage and transfer, such as water and fungus contamination. It addresses fuel waxing, vapor lock issues, and the role of additives in enhancing fuel performance. The lesson concludes with insights on specific gravity's impact on fuel weight and volume, emphasizing the importance of fuel quality control for safe and efficient aircraft operation.

Takeaways

• ✈️ Aircraft engines use different types of fuels: piston engines use gasoline, while gas turbine engines use kerosene.
• 🌡 Both gasoline and kerosene are derived from crude oil through a distillation process that separates hydrocarbons based on their boiling points.
• 🔍 The ideal aircraft fuel should have high calorific value, low corrosiveness, and ease of combustion, but achieving all these properties is costly, so compromises are made.
• 🏁 Aviation gasoline is graded by octane rating, which measures the fuel's resistance to detonation under high temperature and pressure.
• 🌐 The UK aviation fuels Committee sets standards for aviation gasoline, which is color-coded and has specific performance numbers.
• 🚫 Gas turbine engines use kerosene-based fuels like Jet A1 and Jet A, which have different specifications depending on the region.
• 🌀 Water and fungus can cause problems in fuel systems, leading to the use of additives like fuel system icing inhibitors and corrosion inhibitors.
• 🌀 Fuel waxing, where heavy hydrocarbons in kerosene-based fuels solidify at low temperatures, can be mitigated by keeping these hydrocarbons to a minimum.
• 📉 The boiling point of fuel decreases with reduced pressure, which is a concern as aircraft climb, potentially leading to vapor lock in fuel systems.
• 📏 Specific gravity (SG) of fuel is crucial as it affects the weight of fuel for a given volume, with implications for aircraft fuel loading and performance.

Q & A

What are the two main types of fuels used in aircraft engines?

Aircraft piston engines primarily use gasoline, while gas turbine engines use kerosene.

How is the required fuel extracted from crude oil?

The required fuel is extracted from crude oil through a distillation process where the oil is heated and vaporized, then cooled in a distillation column, allowing different hydrocarbons to condense and be collected at various points based on their boiling points.

What are the main requirements for an ideal fuel used in aircraft engines?

An ideal fuel should flow easily under all operating conditions, combust efficiently, have a high calorific value, be non-corrosive, pose a low fire hazard, facilitate easy engine starting, and be able to lubricate moving parts in the fuel system.

What is the significance of the octane rating in aviation gasoline?

The octane rating of a fuel indicates its resistance to detonation under high temperature and pressure. It is measured with a weak and rich fuel-air mixture, and the ratings are used together as the fuel's performance number or index.

What is the difference between AVGAS 100 and AVGAS 100LL?

AVGAS 100LL has the same performance number as AVGAS 100 but contains less lead, making it more environmentally friendly. AVGAS 100 is colored green, while AVGAS 100LL is colored blue.

Why is the specific gravity of fuel important for pilots?

Specific gravity is important because fuel is delivered by volume, but pilots need to know its mass or weight. The energy available from the fuel depends on its mass, not its volume.

What are the two main types of gas turbine fuels used in civilian aircraft?

The two main types of gas turbine fuels used are Aviation Turbine Fuel (ATF) and Aviation Turbine Gasoline (ATAQ).

What is the purpose of a fuel system icing inhibitor?

A fuel system icing inhibitor helps to prevent water in the fuel from freezing and also acts as a pesticide to inhibit the growth of fungus in the fuel, which can block fuel system components.

How can water contamination in fuel be minimized in aircraft tanks?

Water contamination can be minimized by allowing the fuel to settle after replenishment, so that water droplets, being heavier, fall to the bottom of the tank and can be drained off. Additionally, topping up the tanks to full can exclude atmospheric moisture.

What is fuel waxing and how can it affect aircraft operation?

Fuel waxing occurs when heavy hydrocarbons in the fuel freeze and form wax crystals at low temperatures. This can clog fuel filters and interfere with engine operation, particularly in cold climates or at high altitudes.

How does specific gravity affect the amount of fuel that can be carried on an aircraft?

The specific gravity of fuel affects the amount of fuel that can be carried because it determines the weight of a given volume of fuel. A higher specific gravity means more mass for the same volume, which can be critical for long flights where the required fuel mass is high.