Fuel planning and the navigation log

Navigation · Chapter 58 · DGCA CPL and ATPL

Plan it like a road trip: enough to get there, a bit for traffic, enough for the next town, and a last few litres you never touch.

Remember

Three numbers, one rule. Fuel = flow × time. Know any two and you have the third.

Burn 2 400 kg an hour for 2 hours: 4 800 kg gone.

Fuel = flow × time Flow = fuel ÷ time Endurance = fuel ÷ flow

Turn minutes into hours first. That is where marks are lost.

Endurance is how long the fuel lasts, in hours. Wind does not touch it: a headwind makes the trip longer in miles, not the tank’s hours.

Wind changes range, never endurance. Flight-plan endurance leaves out taxi fuel.

You know the moving walkway at an airport. Your legs do the same work, but stand on the moving part and the wall slides past faster.

An aeroplane is walking on a moving walkway of air.

Air miles, NAM, are what the wings fly. Ground miles, NGM, are what the map shows. In still air they are equal.

Against a headwind, the belt runs backwards. Same air miles, fewer ground miles.

Scroll it along.

Headwind: NGM less than NAM. Tailwind: NGM more than NAM.

With a tailwind it is the other way.

The two ways to work it. Pick by what the question gives.

NGM = NAM × GS / TAS

Climb tables give air miles and minutes. Use the time form then.

NGM = NAM ± wind × minutes / 60

This lesson is part of the Navigation plan. See plans

This lesson is part of the Navigation plan. See plans

This lesson is part of the Navigation plan. See plans