Fuel Grades, Quantities and Additives

This is a diesel-cycle twin, and its approved fuels are jet fuels rather than avgas. The chapter lists the grades by national standard, sets the tank quantities, and then puts hard ceilings on the additives you may put in them.

At a glance

• Main tanks total2 x 26.0 US gal (2 x 98.4 l)
• Main tanks usable2 x 25.0 US gal (2 x 94.6 l)
• Max LH/RH main tank difference5.0 US gal (18.9 l)
• Auxiliary tanks total2 x 13.7 US gal (2 x 52.0 l)
• Auxiliary tanks usable2 x 13.2 US gal (2 x 50.0 l)
• Total with auxiliary tanks2 x 39.7 US gal (2 x 150.4 l)
• Usable with auxiliary tanks2 x 38.2 US gal (2 x 144.6 l)
• Recommended minimum cetane number36
• KATHON FP 1.5max 100 ppm
• BIOBOR JF, initial treatmentmax 270 ppm
• BIOBOR JF, permanent usemax 135 ppm
• PRIST Hi-Flashmax 1500 ppm

Approved fuel grades

The approved list

• JET A and JET A-1 — ASTM D 1655.

• TS-1 — Russia, GOST 10227-86; and Ukraine, GSTU 320.00149943.011-99.

• RT — Russia, GOST 10227-86; and Ukraine, GSTU 320.00149943.007-97.

• No. 3 Jet Fuel — China, GB 6537-2006.

• JP-8 (F34) — USA, MIL-DTL-83133G-2010.

• Blends of these grades.

A minimum cetane number of 36, determined according to EN ISO 5165 or ASTM D613, is recommended — recommended, not required. Only uncontaminated fuel from reliable sources is to be used.

Tank quantities

The main tanks hold 2 x 26.0 US gal (2 x 98.4 litres) in total, of which 2 x 25.0 US gal (2 x 94.6 litres) is usable. The maximum permissible difference between the left and right main tank is 5.0 US gal (18.9 litres).

Where auxiliary tanks are installed they hold 2 x 13.7 US gal (2 x 52.0 litres) in total, of which 2 x 13.2 US gal (2 x 50.0 litres) is usable. With them fitted the aeroplane's totals become 2 x 39.7 US gal (2 x 150.4 litres) total and 2 x 38.2 US gal (2 x 144.6 litres) usable.

Anti-microbial additives

Any mixture of different types of fuel additive is not permitted. Two anti-microbial additives are permitted individually: KATHON FP 1.5 at a maximum of 100 ppm, and BIOBOR JF at a maximum of 270 ppm for initial treatment and a maximum of 135 ppm for permanent use once that initial treatment has been done.

Where nobody knows how much went in, or too much did, purging is the answer: flush the system until the concentration is back inside the permitted band.

Anti-icing additive

For anti-icing there is one permitted additive, PRIST Hi-Flash, capped at 1500 ppm. Three grades may receive it and no others: JET A, JET A-1 to ASTM D 1655, and JP-8 (F34). The additive is therefore tied to the grade, and the national-standard grades fall outside it.

Check yourself

• What is the usable fuel in the main tanks, and what is the maximum permitted difference between them?

• Is the cetane number a requirement or a recommendation, and what is the figure?

• What are the two BIOBOR JF limits, and what distinguishes them?

• Which fuel grades may PRIST Hi-Flash be used with?

• What must be done if the additive dosage is unknown?

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