Thursday, March 25, 2010

AP paints homebuilt planes with a broad brush

As regular readers know, I generally abhor the kneejerk "the media sucks" rant that is common among pilots. But, at the same time, I need to acknowledge those news stories that clearly are ignorant.

Associated Press, step forward, son.

Here's the story. Let's take each assertion one by one, shall we?

WASHINGTON (AP) - Federal officials say high-performance homemade planes like the one that killed a beach jogger last week in South Carolina are likely to stall at higher speeds and have been involved in a disproportionately large number of fatal accidents.

Disproportionately is a pejorative term. It is also not true.

The EAA points out, "Studies by FAA and the National Transportation Safety Board (NTSB) show that Amateur-Built/Homebuilt aircraft have an accident rate less than one percentage point higher than the general aviation fleet. In fact, the accident rate for Amateur-Built/homebuilt aircraft is dropping. The total number of registered homebuilt aircraft is increasing by about 1,000 per year, while the total number of accidents has stayed virtually the same. Another good barometer of safety is insurance rates. Companies that insure both homebuilts and production aircraft charge about the same rates for owners of either type of airplane. That indicates a similar level of risk."

This question has actually been one of the most difficult to ascertain. A study earlier this decade found 1.22 fatal accidents in production aircraft per 100,000 hours flown. Homebuilts had a rate of about 1.5.

But we also know, because I wrote about it years ago, that the NTSB often resorts to guesswork on the number of hours flown by pilots of homebuilt aircraft. Many of the accident reports do not contain information about the number of hours a pilot has flown. And that's too bad because it takes the "pilot experience" equation out of the issue.

It's also worth pointing out that last year for the first time, the number of homebuilt aircraft registered exceeded the number of production aircraft.

The Federal Aviation Administration warned pilots on Thursday that the Lancair, which is built from kits, and others like it are apt to stall at speeds higher that 61 mph. The agency also cautioned that since the planes are built by amateurs, there can be differences in performance, including at what speed they might stall.

Oh for goodness sakes, where to start? First, the Lancair is a high-performance airplane. The law of physics doesn't know -- or care -- whether a high-performance airplane was built by a guy in a garage or a guy in a factory. It stalls at 65, it cruises at 225, according to the company.

Sixty-one mph is about 53 knots or the stall speed of, say, a typical trainer-type aircraft such as a Piper Warrior. The Lancair ES stalls at about 58 (dirty). But the assertion ignores the fundamental rule of physics. Speed doesn't determine when an airplane stalls. Angle of attack does. A stall speed depends on many factors including the weight of an aircraft and the wing loading. In a turn, a plane stalls at a higher speed than in level flight. The only real way to be sure a plane doesn't stall, is to keep the nose below the horizon. But suggesting that there's a magic number at which a plane will fall from the sky is simply ignorant.

Why would an "amateur-built" airplane have different stall speeds from one to another? For the same reason that production airplanes do -- weight. One builder might add 20 pounds of avionics not found in a production aircraft. Another builder might not. Two airplanes; two different flight characteristics. But the same might be true for a production airplane. One pilot might throw 20 pounds of luggage in; another might not. Two different airplanes, two different flight characteristics.

There are also many different kinds of homebuilt airplanes, most of which stall below 60 mph. Here's a chart of high-performance experimental airplanes. You'll note that the stall speed ranges from 48 to as high as 79.

Pharmaceutical salesman Robert Gary Jones was killed on a Hilton Head Island beach as the pilot of a Lancair tried to land the plane.

So that's what this is about? First of all the problem wasn't that the plane stalled, it was that an oil leak had developed. When an oil leak develops, chances are good a windshield gets covered with oil. There's no indication the plane stalled. If it had, the pilot and his passenger wouldn't have walked away. The problem likely was the pilot couldn't see the jogger who was killed.

Here, look at the picture of the plane.

When a plane stalls, one wing usually stops flying first, the plane dives one side to the other -- usually left. That obviously didn't happen here.

Finally, let's revisit the reason why the 61 mph figure is used. In the '90s, the FAA took comment on a rule that airplanes could have a higher stalling speed if they had better crash survivability equipment.

The crash cited above was a controlled emergency forced landings. Let's see what the FAA said about the relationship of stall speed in such situations:

Survivability of controlled emergency forced landings is not dependent upon landing stall speed and a clear correlation between safety and landing stall speed cannot be found.

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