Fuel Capacity and Indication Limits

This aeroplane can carry more fuel than its gauge is able to show, and the gap between the two is a limitation in its own right. Get the relationship between actual quantity and indicated quantity clear now — the tank difference limit depends on it.

At a glance

• Standard tanks, total2 × 15.0 US gal (2 × 56.8 liter)
• Standard tanks, usable2 × 14.0 US gal (2 × 53.0 liter)
• Long Range tanks, total2 × 20.5 US gal (2 × 77.6 liter)
• Long Range tanks, usable2 × 19.5 US gal (2 × 73.8 liter)
• Maximum indicated quantity14 US gal (53 liter) per tank
• Maximum difference between tanks9 US gal (about 34 liter)

Two tank configurations

In the standard configuration each tank holds 15.0 US gal (56.8 liter) in total, of which 14.0 US gal (53.0 liter) is usable. In the Long Range Tank configuration, if installed, each tank holds 20.5 US gal (77.6 liter) in total, of which 19.5 US gal (73.8 liter) is usable. In both cases one gallon per tank is unusable.

What the gauge can show

The maximum indicated fuel quantity is 14 US gal (53 liter) per tank, and the maximum permissible difference between the right and left tank is 9 US gal, about 34 liter. On a standard aeroplane the indication reaches the full usable quantity; on a Long Range aeroplane it stops 5.5 gallons short of it.

CAUTION — Take a reading of 14 US gal as 19.5 US gal when you work out how far the two tanks differ.

That caution is what makes the difference limit workable. A gauge reading 14 on one side and 5 on the other looks like a 9 gallon difference and is legal — unless the 14 is a Long Range tank that is actually full, in which case the true difference is 14.5 gallons and the limit has been exceeded.

The placard

The Long Range Tank placard beside the fuel quantity indication carries the same three numbers: maximum usable fuel 2 × 19.5 US gal, maximum indicated fuel quantity 2 × 14 US gal, and maximum difference between the left and right tank 9 US gal — with a line referring the pilot to the manual to use the entire tank capacity.

Check yourself

• What are the total and usable capacities of each standard tank?

• What are the total and usable capacities of each Long Range tank?

• What is the maximum quantity the indication can show, per tank?

• What must be assumed when an indicator reads 14 US gal, and why?

• What is the maximum permissible difference between the two tanks?

Study aid — always fly your aircraft's current AFM/POH.