How to Save on Avgas

One of the most logical ways we’ve heard of saving that extra little bit of fuel is in a weight-and-balance exercise.

The trick is in loading your aircraft so it flies with a slightly aft c of g. A retrospective study of your “early days” aerodynamics and Theory of Flight will reveal the fact that an aircraft’s tail surfaces have to generate negative lift to balance the aeroplane around its centre of lift.

The tail has to generate more negative lift at forward c of g loadings than at aft loadings. The book says that for each pound of negative lift the tail has to develop, the wing has in turn perforce to generate an additional pound of positive lift – over and above the normal amount of lift required.

To generate that extra lift, the wing must be flown either faster or at a higher angle of attack – which means more drag. To offset increased drag, more thrust is needed – in turn needing greater power and increased fuel consumption. The obvious thing to watch when arranging for a rearward c of g is not to go outside the stated limits at any stage, remembering the fuel consumed during the flight will give you a rear-tending c of g.

Obvious aids to fuel conservation include doing as many vital actions as possible on the taxi out to the runway, ‘trying to gauge your holding time and picking a time when most of the other aircraft have queued up and eventually departed, not spending too much time on checks after engine start – all within the limits of safety and accepted regulation of course.

Some pilots recommend taking off at normal climb power when flying a lightly loaded high-performance machine. We would not endorse this method but mention it for those who really have the expertise and confidence to do this.

Cleaning up your aircraft after lift-off – again within recognised safety limitations – is another way to get those extra drops in your tank.

So is reducing power to climb settings at 1000ft, after take-off, and not leaving the engine at full bore until you can’t think of anything else to do.

In flight, careful study of met conditions and your manual performance figures pay off in terms of fuel saved. So does a cold-blooded look at your ETAs, comparing the 75 per cent power settings arrival with a 50 per cent power setting time at destination.

The time difference isn’t all that enormous …

This is where an EGT comes into its own, in cruise. Using the exhaust gas temperature gauge sensibly can save you up to a gallon an hour at 75 per cent settings, on some engines.

In the circuit on arrival, it’s up to your own cockpit drill and/or memory when you drop the undercarriage. The wheels, together with flaps, constitute more drag, don’t forget.

You will of course have made a precise let-down using as little fuel as possible – but not glided down from a dizzy height listening to expensive cracking sounds coming from a supercooled cylinder block.

That standard 500fpm descent rate makes for comfortable, precise power and rpm adjustments which usually result in a fuel-saver for most pilots.

In brief, this fuel-saving business is something most pilots who attach pride to the label of “Pilot”. will be practising already. But some of those facts bear repeating …