Applicability: Aeroplanes powered by spark-ignited piston engines using Avgas or Motor Gasoline (Mogas).
Description: This SIB was initially published to inform all owners and operators of aeroplanes powered by spark-ignited piston engines about the use of unleaded Avgas UL 91.
Unleaded Avgas UL 91 meets the requirements of ASTM D7547-09. Unleaded Avgas UL 91 differs in parameters controlled by respective fuel standards from unleaded Hjelmco Avgas 91/96 UL, unleaded Hjelmco Avgas 91/98 UL and Avgas 100LL on certain properties, listed in Table 1.
Unleaded Avgas UL 91 may be used, if approved for the particular
engine types. No additional approval is required for the aeroplane,
provided the aeroplane is already approved for operation with
Avgas (according to ASTM D910, Def Stan 91-90, Mil-G-5572,
GOST1012-72 or equivalent) or Mogas and the engine is already
approved to use unleaded Avgas UL 91.