Each year a number of aircraft accidents are related to fuel starvation, exhaustion or contamination. There were numerous reasons for these avoidable accidents: ranging from inadequate fuel systems knowledge by the crew, preflight planning issues, takeoff and landing checks and failing to monitor fuel consumption during flight. Or even failing to refuel the correct quantity before the flight.

On this page we will discuss basic procedures to follow when gaining insight in the fuel system and managing it during the flight.

Aircraft Fuel Systems Knowledge

Unfamiliarity with the fuel system can (and has) lead to accidents. It is very important that the pilot receives thorough training on the fuel systems of the aircraft they fly. Some countries conduct a type rating which is added to the license of the pilot showing the types of aircraft they may fly. During training for the type rating the aircraft manual must be studied with close attention to:

• Fuel grade, system capacity and the usable and unusable quantities
• The number of fuel tank/system drain points and fuel quantity measuring procedures
• Fuel selector operation and markings, cross-feeding
• Fuel pump operation, normal fuel pressure and fuel flow indications
• Leaning procedures and fuel flow at different manifold/RPM combinations and altitudes
• Manifold pressure (turbo) and RPM for maximum range and endurance
• Fuel consumption of cabin heaters
• Engine emergency checklists and drills

Make sure that the person giving this instruction is qualified and has the experience on the type of aircraft.

If you are not current in a particular type of aircraft reread the aircraft flight manual and re-familiarise yourself with special attention to the fuel system.

Planning for Fuel

Calculating fuel requirements for a flight includes a number of variables, often beyond the control of the pilot (think ATC delays or more wind than anticipated). Taking off with just the bare minimum legal fuel is foolish. It is much better to either remove some weight and add fuel or to plan for a fuel stop along the flight. The amount of fuel onboard never become a concern.

Warm-up, Taxi and Climb fuel
After calculating the required fuel for the trip an allowance should be made for fuel required for warm-up and taxi. In cold weather warm-up can be much longer than expected as can the taxi times at large and busy airports. Add 15 minutes of cruise fuel for this. For climb out fuel, you will have to work out how long the climb will be to the planned altitude and multiply that with the fuel consumption found in the manual, averaging between maximum power and cruise power to obtain climb out fuel consumption.

Legal Fuel Reserves
The fuel reserves as required by law are basically as follows (they may differ per country somewhat). VFR operations: 30 minutes by day and 45 minutes by night for fixed wing and 20 minutes for rotary wing. For IFR operations: sufficient fuel to divert to a suitable airport and hold for 45 minutes at 1500 feet for non turbine aircraft and 30 minutes for fixed and rotary wing turbine powered aircraft.
Remember that a 30 minute VFR reserve fuel isn't that much at all. It would be wise to have at least an hour of fuel onboard when you land at your destination. Just in case.

Contingencies
To allow for the unexpected like stronger headwinds, leaning method not so efficient, diversion due to weather, climbing more than necessary and ATC delays, do have some extra fuel onboard. Normally 10 to 15% (of the fuel required) should be enough. Take a good look at the weather forecast and note the winds aloft at different altitudes so that a favorable altitude can be chosen (to your alternate airport too).

Fuel Consumption
The rate of fuel consumed can vary greatly between different aircraft of the same type due to their age, maintenance condition, hours on the engine and such. With fixed pitch propellers the increase of 100 RPM could increase fuel flow by 10% or more. Not using the mixture knob (even at low altitudes) increases fuel burn too. It is therefore wise to determine the fuel flow rate for different altitude/RPM/manifold settings in the preflight planning phase. Round off to the next higher number and make an allowance for the age of the engine (fuel flow tends to increase with age).

Weight and Balance
You will find often that the amount of fuel in the aircraft is limited by weight and balance. Flying solo in a C-150, for example, usually means that you can carry full fuel. But having a passenger with you equates to leaving fuel out and planning for an extra fuel stop.
Some aircraft also have a maximum zero fuel weight, all weight above that figure must be fuel, or else you risk damaging the wing structure. See the table for more weight definitions.