What are the two sources for heating turbine fuel?

• A. Bleed air and engine oil
• B. Electric heater and coolant
• C. Ambient air and fuel
• D. Exhaust gas and water

Answer: (A)

Heating turbine fuel relies on heat exchangers that use heat already available in the engine. The two sources used are bleed air from the compressor and the engine’s lubricating oil. Bleed air provides hot, high‑temperature air that passes through a fuel heat exchanger to warm the fuel before it reaches the pump and injectors. The engine oil, circulating and absorbing heat from the engine, can also be routed through an exchanger to heat the fuel, especially when bleed air alone isn’t enough or during warmup. This keeps the fuel at the right viscosity and helps prevent icing or waxing in cold conditions, ensuring smooth fuel flow and reliable starting. Other options like ambient air, electric heaters, coolant, exhaust gas, or water aren’t the standard pair used for heating turbine fuel in most designs.