The Aviation Fuel Club has released initial results from a study that shows between 80% and 83% of the current fleet of piston engine aircraft could safely operate on autogas.
First approved by the FAA as an aviation fuel in 1982, autogas (also known as mogas) is ethanol-free, lead-free automotive fuel. Either 87 or 91 AKI may be used, depending on the engine’s STC or TC. About 59,000 autogas STCs have been sold since the FAA approved the first one in 1982, club officials report. Autogas currently sells on average for about $1.40 a gallon less than leaded avgas at airports where it is offered.
Todd L. Petersen, a founding director of the Aviation Fuel Club and owner of many autogas STCs, described the motivation behind this study: “We looked at the FAA’s registry of aircraft last in 1992, two decades ago. We determined then that approximately 115,000 aircraft were capable of burning autogas using STCs from the EAA and my company, Petersen Aviation. This represented about 78% of all piston aircraft in 1992, and we did not include homebuilts, ultralights or piston rotorcraft, most of which may operate on autogas. Much has changed since 1992, with many owners of heavy twin aircraft that needed avgas having switched to turbine aircraft, and with continued growth in the homebuilt and more recently the LSA sectors. We felt it was time to look at the latest data and see to what extent autogas could be used to lower the cost of flying and reduce lead emissions from our aircraft.”
To make sense out of the FAA’s massive online registry of aircraft, the club employed the services of Dilip Jumani, a database expert and member of EAA Chapter 1114 of Apex, N.C.
“We asked Dilip to extract from the registry the number of all active aircraft that are currently covered under the autogas STCs from the EAA or Petersen Aviation, being careful not to double count,” explained club director Kent Misegades. “We were not interested in the number of aircraft which actually have the STC, only the number which could legally operate on the fuel today. Unfortunately, there are many textual errors in the registry, requiring Dilip untold hours of tedious work to assure accuracy in his work.”
The study revealed that 127,168 fixed-wing and rotary piston aircraft can operate with autogas today under the EAA or Petersen STCs. This represents 80% of the 159,007 active aircraft in the latest General Aviation Statistical Database from the General Aviation Manufacturers Association (GAMA).
Autogas-burning aircraft are found in every class — from light aircraft (Piper J-3), popular two-and four-seat single-engine pistons (Cessna 152/172/182, Piper Cherokee), some high-performance singles (early Bonanzas), crop dusters (Ayres Thrush, Grumman Ag Cat, Piper Pawnee), and radial-engine aircraft including many models of the Stearman, T-6, DeHavilland Beaver, Beech 18, and even the mighty DC-3. This also includes piston-engine helicopters, 74% of which may operate today on autogas.
Two other categories of aircraft were considered in this study: Experimental- Amateur Built (E-AB or homebuilts) and Light Sport Aircraft (LSA). In its 2012 Report to Homebuilders, the EAA claims that 33,000 E-ABs are registered and a net of 500 are added annually. By definition, 100% of these homebuilt aircraft may use autogas (or any other fuel), although some have high-performance powerplants that will require the use of 100LL avgas, Misegades noted.
According to the most recent listing of the LSA market by LSA expert and Light Aircraft Manufacturers Association (LAMA) Chairman Dan Johnson, there are 2,235 S-LSA aircraft currently registered. Approximately 1,600 of these use engines (Rotax, Jabiru, VW conversions, etc.) that are factory-certified to operate with autogas. The remainder of the LSAs use Continental’s O-200-D engine, which is not currently certified for autogas. With Continental now offering its autogas-burning O-200-AF, we expect these LSA manufacturers to offer this engine in the future, Misegades noted.
Including E-ABs and LSA aircraft to those covered under STCs brings the total to 83% of all piston engine aircraft that could be operated today on autogas. Not counted here are several thousand ultralight aircraft, typically powered by two-stroke engines or the same powerplants found in modern LSAs (Rotax, Jabiru, etc.) that are generally run best on autogas.
The bottom line: Somewhere between 80% to 83% of all active piston engine airplanes and helicopters registered in the U.S. could operate on autogas today, dramatically reducing the cost of flying and lead emissions from general aviation, according to the report.
The authors of the study are now analyzing the data to determine these percentages in several different categories of aircraft (light single, high-performance singles, twins, etc.) and to estimate the relative fuel consumed. Details will be presented during a forum “Autogas at 30 Years” on Thursday, July 26 at EAA AirVenture Oshkosh. Speaking at this forum will be a number of experts on aviation fuel. Topics addressed will include a recent development allowing the remaining 20% of high-performance aircraft to use autogas.
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