Over the past century, General Aviation (GA), which includes all flying except for military and scheduled airline operations, has become a significant and integral part of the U.S. economy creating millions of jobs and making a positive impact on the U.S. balance of trade. The United States continues to be one of the world leaders in the design, manufacture, and use of GA airframes, engines, avionics, and supporting technologies. GA is a key catalyst for economic growth and has a profound influence on the quality of life in the United States. GA today touches nearly every aspect of our daily lives, and its continued success will shape American society and the American economy over the next century. Often, GA is thought of as recreational aviation, but there are many commercial and governmental operations that fall within this category of flying.
Consequently, aviation gasoline (AVGAS), which is a vital element in the operation of aircraft, which are powered by piston-driven engine, is vital within GA. There are approximately 167,000 aircraft in the United States GA fleet, the vast majority of which rely upon, and are currently fueled with 100 low lead (100LL) AVGAS, which is the only readily available gasoline for these aircraft.
Unfortunately, the 100LL AVGAS of today contains the additive tetraethyl lead (TEL), which has been used as an aviation gasoline additive for decades in order to meet the very high octane levels required to prevent detonation (engine knock) in high compression and high performance aircraft engines, and to satisfy the valve train lubricity needs of these engines.
It must be understood however, that of all the aircraft in the US and world-wide fleet of GA, as many as 80 percent are not powered by high compression or high performance engines; rather, they are powered by lower compression and lower performance engines, and which consequently could be fueled with lower performance aviation gasoline, if such a fuel was made readily available. That is, if a suitable lesser performance aviation gasoline was introduced into the marketplace, 80 percent of the GA fleet could operate on it; whereas, the balance of the fleet (20 percent of the aircraft) would continue to operate on the 100LL AVGAS (or an Unleaded replacement for 100LL AVGAS). Complicating matters, there are serious problems with 100LL AVGAS. Petitions and potential litigation from environmental organizations regarding lead-containing 100LL AVGAS, citing the adverse health impacts to humans and the environment from exposure to lead, have called for the US Environmental Protection Agency (EPA) to consider regulatory actions to eliminate or reduce lead emissions from aircraft. Similar regulatory actions are under consideration globally.
These activities raise concerns about the continued availability and use of leaded 100LL AVGAS. With the current number of aircraft that are powered by piston-driven engines in the US alone, which is more than 200 times larger than annual new aircraft production, the turnover rate of the existing fleet is very low. This low turnover rate leaves existing aircraft owners particularly vulnerable to devaluation of their aircraft should an unleaded replacement AVGAS be incompatible with the existing fleet. This vulnerability has created a sense of urgency regarding the development and deployment of an unleaded replacement for 100LL AVGAS. However, while efforts are under way towards developing an unleaded 100LL AVGAS replacement, these efforts are focusing on a replacement AVGAS that meets the performance demands of the entire GA fleet, not simply the 20 percent that actually needs it. As mentioned above, 80 percent of the GA fleet does not need 100LL AVGAS or an unleaded replacement for 100LL AVGAS to operate safely and efficiently.
Regardless, in response to the rapidly increasing concerns expressed by the GA community, the Unleaded AVGAS Transition Aviation Rulemaking Committee (UAT ARC) was chartered on January 31, 2011, by the Federal Aviation Administration (FAA) Administrator to investigate, prioritize, and summarize the current issues relating to the transition to an unleaded replacement for 100LL AVGAS; and to recommend the tasks necessary to investigate and resolve these issues. The UAT ARC confirmed that an unleaded replacement fuel that meets the needs of the entire fleet does not currently exist. As such, there remains a need for less expensive, suitable, and unleaded aviation fuel to relieve the pressures involved with transitioning GA towards the elimination of lead in aviation fuel………………………………