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Truth in advertisingTruth in advertising

The news that another cash crunch has forced Diamond Aircraft to lay off most of its London, Ontario, staff brought fresh attention to both this particular manufacturer and the financial pressure that certifying a new aircraft can put on a company that was otherwise reasonably healthy. Since developing its two-seat Katana trainer from the Dimona motorglider, Diamond has built a reputation for designs that are innovative, elegant, and distinctive, if somewhat quirky. But the ongoing effort to certify a single-engine personal jet has consumed far more cash than its piston and diesel lines could generate in a slow market, and while three D-Jet prototypes have flown, the company acknowledges that certification remains at least two years away.

There are reasons beyond the natural sympathy due any aviation business to hope that Diamond gets its house in order and continues building airplanes, regardless of whether or not the D-Jet ever comes to fruition. Its advertising claims that Diamond makes the safest light aircraft in the world. An independent review of the record suggests that this boast contains a fair bit of truth.

A detailed examination of all of its designs is beyond the scope of a single article, so we’ll focus on its best-selling model in the United States, the four-seat, single-engine DA40. (By way of full disclosure, AOPA has operated one since late 2009 for short-haul business travel, glass-panel instrument instruction, and some primary training.) If you haven’t seen one, the DA40 has a 180-horsepower fuel-injected Lycoming engine with a constant-speed prop, fixed gear, a free-castering nosewheel, rudder pedals that automatically apply differential braking for taxi steering—and a wingspan that delivers a great glide ratio but makes it tough to fit into a standard T-hangar. (Contrary to rumor, it can be done without buttering the wingtips.)

Diamond’s advertising takes the interesting step of comparing the DA40 primarily to the Cirrus SR20 and SR22 and the Cessna Corvalis 350 and 400. While also four-seat fixed-gear singles with seamless composite exteriors, they’re considerably more powerful—230 hp to 310 hp—and much faster, with 40- to50-percent higher wing loadings. Their ownership and use reflects this, and so does their accident record. Some SR20s are employed as trainers, but most of these airplanes are used for transportation. This means that what accidents they do have not only involve higher speeds and greater energies, but are also more likely to happen at night or in IMC, when crashes are generally less survivable. You’d have to expect a higher share of those accidents to be fatal, so Diamond’s claim of a lower fatal-accident rate than Cirrus or the Cessna Corvalis line is somewhat beside the point.

A better, though still imperfect, comparison is with the Cessna 172 and fixed-gear Piper Cherokees. Like the DA40, they’re widely used as trainers but also popular owner-operated aircraft. Its constant-speed prop makes the DA40 a little more sophisticated and its slick fuselage makes it a bit faster, but in terms of range, speed, and mix of travel and training use, the Diamond is closer to these traditional aluminum designs than its composite cousins.

That informs the comparison, since airplanes that see significant training duty suffer relatively more accidents—disproportionately during takeoffs, landings, and go-arounds—but fewer fatalities than machines primarily flown cross-country. The accident counts are easy to get, but because there’s no hard data on either how much or why individual models are flown, putting them into a context that provides a meaningful comparison is trickier. Diamond’s answer is one we’ve also used from time to time, measuring accidents against aircraft-years of exposure (e.g., one that’s been flying for 10 years contributes 10 times as much as a year-old airplane). They also restricted both accident and exposure counts to airplanes built in the past decade, which makes some sense: Putting a two-year-old DA40 up against a 50-year-old 150-hp Cessna 172 doesn’t seem quite fair.

The results are eye-opening. There have been 15 DA40 accidents in U.S. airspace since the model entered production in 2002. Four were fatal, none of which can fairly be said to have been the airplanes’ fault. Two pilots descended below MDA during instrument approaches; one hit power lines, the other the Pacific Ocean. One pilot caught a wingtip attempting low-altitude aerobatics over a lake at dusk, and a Canadian-registered airplane was brought down by severe icing while crossing northern Maine. With an estimated 9,600 aircraft-years accumulated time in service, their accident rate works out to about 1.6 per thousand. The fatal-accident rate was just 0.4.

The Cherokees’ counts are similarly low—19 accidents, three fatal—but slow production over the past decade means they came from barely one-third the fleet exposure, about 3,300 aircraft-years. That works out to 5.8 accidents and 0.9 fatal accidents per thousand. Cessna Skyhawks have enjoyed the highest production of the three, building around 18,600 aircraft-years of service, but they’ve suffered 227 accidents, 22 of them fatal. The resulting 9.7 percent lethality is the lowest of the three, but their rates per thousand aircraft-years are the highest at 12.2 overall, 1.2 fatal.

A detailed breakdown of the causes will have to wait for the next issue, but here’s an appetizer in the meantime: Landing accidents made up about half the total in the Skyhawks and DA40s but a little less than a third in the Cherokees. Are low-wing airplanes easier to land? Does the DA40 pay for that glide performance with greater susceptibility to crosswinds? Stay tuned.

ASI Staff

David Jack Kenny

David Jack Kenny is a freelance aviation writer.

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