Shell has announced a lead-free replacement for the 110LL that is currently used by most general aviation piston aircraft. From the AOPA website:
Shell Aviation, a subsidiary of the multinational oil giant Royal Dutch Shell, announced Dec. 3 that a 10-year effort in the laboratory has produced a fuel that may put a long-sought goal—once thought to be unattainable—within reach: a lead-free “performance drop-in” replacement for 100LL that could power any aircraft in the piston fleet.
“That’s our definite goal,” said Michael Sargeant, avgas commercial aviation manager for Shell Aviation, in a phone interview, when asked specifically about the ambition to produce a “performance drop-in” avgas replacement. “We’ve tested it and had some exciting and successful tests.”
The lead-free formulation has a motor octane number (MON) over 100, a critical factor in formulating a fleetwide fuel that could power high-compression engines. (Octane prevents premature ignition known as detonation, and is measured by more than one scale.) Shell’s new lead-free formula has passed preliminary tests in Lycoming engines on the ground, and a Piper Saratoga recently flew for about an hour on the fuel, according to a news release from Shell—the first of many tests that will be required for certification.
“It’s an exciting milestone,” Sargeant said, adding that the company looks forward to working with manufacturers across the general aviation industry, and various regulatory agencies. The company will pursue fleetwide certification rather than a model-by-model approach. Sargeant said tests done on the new formula to date “indicate that it’s a great candidate for fleetwide approval.”
The exact path that Shell must navigate to gain such approval remains to be established. The FAA has a goal of deploying a lead-free piston aviation fuel by 2018, though Sargeant said the company may be able to achieve required approvals and start distribution sooner than that.
Shell is the first major oil company to announce an unleaded avgas formulation. File photo.
Shell is the first major oil company to announce an unleaded avgas formulation. File photo.
“We believe two to three years might be possible,” Sargeant said. “That’s the timeframe that we would love to work towards. The details need to be developed.”
Sargeant said another design goal is to keep the retail price similar to avgas, though it is too early to know exactly what the new fuel would sell for. Shell has only just begun conversations with the various regulatory agencies involved. The fuel will be submitted for approval from the FAA, ASTM, and the European Aviation Safety Agency.
From Shell’s website:
Avgas is gasoline fuel for reciprocating piston engined aircraft. As with all gasolines, avgas is very volatile and is extremely flammable at normal operating temperatures. Procedures and equipment for safe handling of this product must therefore be of the highest order.
Avgas grades are defined primarily by their octane rating. Two ratings are applied to aviation gasolines (the lean mixture rating and the rich mixture rating) which results in a multiple numbering system e.g. Avgas 100/130 (in this case the lean mixture performance rating is 100 and the rich mixture rating is 130).
In the past, there were many different grades of aviation gasoline in general use e.g. 80/87, 91/96, 100/130,108/135 and 115/145. However, with decreasing demand these have been rationalised down to one principle grade, Avgas 100/130. (To avoid confusion and to minimise errors in handling aviation gasoline, it is common practice to designate the grade by just the lean mixture performance, i.e. Avgas 100/130 becomes Avgas 100).
Some years ago, an additional grade was introduced to allow one fuel to be used in engines originally designed for grades with lower lead contents: this grade is called Avgas 100LL, the LL standing for ‘low lead’.
All equipment and facilities handling avgas are colour coded and display prominently the API markings denoting the actual grade carried. Currently the two major grades in use internationally are Avgas 100LL and Avgas 100. To ease identification the fuels are dyed i.e. Avgas 100LL is coloured blue, while Avgas 100 is coloured green.
Very recently a new Avgas grade 82 UL (UL standing for unleaded) has been introduced. This is a low octane grade suitable for low compression engines. It has a higher vapour pressure and can be manufactured from motor gasoline components. It is particularly applicable to those aircraft which have STCs to use automotive gasoline.
You can read more from the AOPA entry HERE.
You can find out more about Shell’s AVGAS HERE.