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Plane Talk MAXIMIZING YOUR INVESTMENT
Alternative Fuel: Your Next Engine Upgrade
AIt’s bad enough that the price of AVGAS has swollen to more than $5 a gallon at some airports.
Now comes word that the nation’s supply of AVGAS may be drastically reduced or eliminated entirely because it is so costly for refineries to produce.
Experts say AVGAS isn’t likely to go away in the next five or 10 years, but if you fly in Europe or South America, you may find AVGAS hard to come by at your local airport. And if you own a piston engine aircraft, the future of AVGAS is something that will directly affect the value of your aircraft investment.
Aside from the current oil crisis that has pushed the price of all petroleum products through the roof, AVGAS faces additional cost pressures because it is produced in relatively small quantities. Several aviation experts estimate a single refinery can produce a year’s supply of AVGAS in just three days, so clearly, it’s not a big part of any company's growth strategy.
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The SMA SR305-230 Engine provides a safe,
clean, reliable alternative to AVGAS.
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AVGAS comes in a few varieties, but the most common is 100-octane low-led, which requires a special additive called TET that is only manufactured by one company. TET was outlawed in the United States for every other use except use in AVGAS, so refineries that produce AVGAS have to undergo an extensive cleaning process of the refinery when switching from AVGAS to other forms of fuel. This makes the whole production process somewhat of a nuisance. With aircraft engines lasting 20 years or more, any owner who is coming up on TBO should consider the long-term ramifications of simply installing a factory replacement engine burning AVGAS.
There are currently three options for aviation engines to run on alternative fuels-automobile gas, diesel or Jet-A fuel, and a relatively little-known fuel called Aviation
Grade Ethanol, or AGE85. AGE85 is a higher grade cousin to E85, an ethanol-based fuel that has been slowly gaining popularity as an automotive fuel in the US. During last summer’s fuel crunch, WalMart said it will begin selling E85 at its gas stations across the country as a less expensive alternative to petroleum-based fuels.
Jack Johnson, founder of aircraft engine manufacturer Texas Skyways says AGE85 offers the best long-term alternative to AVGAS shortages. AGE85 is distilled from corn, a process that eliminates any dependence on foreign oil supplies. It’s also cleaner and produces more engine power than AVGAS, meaning engines will be able to have longer TBOs.
High-octane automotive gas in and of itself is an alternative and is currently used (both with and without FAA approval) in areas where AVGAS is difficult to come by. But Johnson notes that automotive gas is not of uniformly high quality, and so it's difficult for owners to know exactly what is running in their engines or what kind of damage might be done from poor quality fuel.
Converting AVGAS burning airplanes into diesel-driven airplanes is an area that has been gaining significant attention. This conversion involves replacing the entire AVGAS engine with a heavier diesel engine, requiring a number of modifications including installation of a lighter, composite propeller. Thielert has FAA approval to install a diesel engine in 172 Skyhawks and Piper PA28 aircraft, while SMA was recently given approval to install diesel engines in 182s.
The diesel conversions have a fuel burn that is as much as 40 percent less than the AVGAS engines they replace, which gives the SMA’s 182 conversion a full-power cruise consumption of about 9 gallons per hour.
But the conversions are not cheap. SMA estimates that because of the number of components that need to be upgraded or replaced, a complete, firewall forward engine conversion for a 182 will cost about $80,000, including a new composite propeller to compensate for the weight of the bigger engine and a complete FADEC system. Compare that with a factory new engine for a 182 that runs about $30,000, and you see why owners aren’t exactly standing in line to convert to diesel.
Johnson says AGE85 could be the best deal going. He said his STC for a 182 conversion from AVGAS to AGE85 costs about $100 to install; it basically involves installing a bigger jet on the engine’s carburetor. For a fuel-injected engine, the conversion is much simpler, simply re-calibrate the injector for a higher fuel flow.
If AGE85 is such a great deal, why isn’t it everywhere? For one thing, the FAA hasn't established a standard for AGE85. According to David Quale, Aircraft Mechanic for the South Dakota State University project spear-heading AGE85 research, previous aviation fuels were developed by the military, so AGE85 presents the first time the FAA has had to develop a standard for an aircraft fuel.
The process, being undertaken by the American Society for Testing and Materials, would determine the precise standards by which AGE85 could be manufactured. No one seems to have any idea when the standardization process will be completed, although Quale says the process has been going on for at least two years.
Besides standardizing the fuel, the FAA will need to develop standards for aircraft flying with AGE85. Because AGE85 has a higher flow rate than AVGAS, fuel burn will be about 20 percent higher than the aircraft were certificated for. This essentially means that a 50-gallon tank becomes a 40-gallon tank, and you do the math in terms of what that means for your endurance.
On the good side, Quale said AGE85 typically produces 9 percent more horsepower and runs about 30 percent cooler than AVGAS, meaning less wear and tear on engines and potentially an extra 50 percent on the TBO.
Best of all, Quale says that engines that have been modified to run AGE85 will still run on AVGAS. The only difference is that the engine running on AVGAS will need to be leaned, since it has been tuned to accommodate the higher fuel flow of AGE85.
For his part, Johnson is frustrated with the FAA's approach toward AGE85. Texas Skyways was originally awarded an STC to modify engines for Cessna 180 and 182 aircraft to run on AGE85 before the FAA ordered the ASTM standards
developed.
Now, the company continues to sell its line if bigger, more efficient power plants for the entire Cessna line, and Johnson notes that every one of the engines he sells can be retro-fitted for AGE85 when the time comes. A firewall-forward engine replacement for a Cessna 182, upgrading the 470 engine to a 550 produces 155 knots airspeed and costs between $50,000 and $60,000.
But Johnson says you can save about 3 gallons per hour by pulling the power back to the 182’s standard cruise of 135 knots.
Until the FAA approves more of his $100 engine modifications, that’s about the only way you’ll be able to reduce your AVGAS consumption without replacing your engine.
—Sean Fulton
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