Last week’s blog generated a number of excellent comments largely to the point that we shouldn’t be paying for all the government we’re getting. Brandon responded that $50K for a Lycoming IO540 was too much and that he could get a similar car engine for about $10K installed. Reading between the lines, perhaps he’s concerned about the FAA’s certification burden on the engine manufacturers. I completely agree with the sentiment, but there are some areas where we really do need bulletproof equipment. There may be some debate whether FAA’s engine directorate is providing that function—I can’t answer that.
But let’s look at the differences between car engines and aircraft powerplants (specifically piston)—they’re not equal. There have been some great automotive conversion experiments but none, to my knowledge, have fully lived up to the promise of being commercially viable.
Car engines typically run at 20 to 30 percent of rated power and almost never hit 100 percent unless you still have teen drag-racing fantasies. Race cars are another place where engines are routinely ridden hard—hold that thought. Aircraft engines operate at 100 percent on every takeoff and then spend most of their lives at 65 to 75 percent.
In the experimental world, VW and Corvair air-cooled engines have been modified with varying degrees of success. Some large block V-8s have also been tinkered with, and I flew an experimental Cessna 172 on a really hot Kansas afternoon with a Ford Escort 4-banger. It had a belt-driven gearbox because the rpm/torque ranges of car engines just won’t work with propellers. You can’t just bolt a prop onto the front. A really stout reduction-gearing system is needed, which impacts cost (significantly) and weight and balance (significantly). Let’s just say that the Escort-powered Cessna’s performance was lackluster, and let it go at that.
Mooney and Porsche conducted perhaps the best commercial experiment in the mid 80′s with a 210-horsepower modified Porsche engine. The engine had a racing heritage and thus was theoretically capable of operating in those high percentage ranges. Apparently a thermodynamic barrier wasn’t factored in. If you ran the car at 100 miles per hour the fuel burn would probably be in the 5 to 6 gph range (racers help me out). The airplane needed about 11 gph and it was designed to go 2,000 hours TBO. Most race car engines might last for a couple of races and then be replaced—not the typical aviation profile.
Too many of Mooney’s Porsche engines were shelling out at 400 to 600 hours. It was a marketing disaster, and Mooney PFMs were retrofitted with big bore Continentals at the factory’s expense.
Now to Brandon’s point, the Porsche engine was certified but not especially reliable. Our experience with old technology engines is generally good. The manufacturers have some other economic realities that have nothing to do with the FAA: product liability and low volume. As I’ve said all along, the aviation cost challenges are multi-faceted, and if they were easy to address they would have been. That said—we shouldn’t stop trying. I don’t like the alternative.