Those who’ve watched from the ground won’t be too surprised to learn that by far the largest share of helicopter training accidents happen during autorotation practice. While the maneuver is not inherently dangerous, the speed of descent and the need to flare within a narrow band of altitude don’t leave much margin for error—and helicopter pilots practice them a lot. With all those opportunities, it’s no wonder that things go wrong often enough to lead to more than 40 percent of all accidents at every level of dual instruction.
For all the damage done to the machinery, though, the aircraft do a remarkably good job of protecting their occupants. In 10 years, only three of 147 autorotation accidents during flight instruction were fatal. That’s just 2 percent, comparable to the lethality rate of fixed-gear landing accidents. The rotorcraft community seems to have learned how to practice emergency procedures without undue risk to life and limb.
The same can’t really be said of flight instruction in airplanes. Inadvertent stalls during emergency drills, almost all of them simulated engine failures, were the most common type of maneuvering accident during fixed-wing training, accounting for more than one-third—and nearly half of them were fatal. In advanced instruction, where the student is already a certificated pilot, the lethality of these accidents was 60 percent.
Why such a difference? As the judo coach likes to put it, part of it is “just physics.” Autorotations are done at a relatively low airspeed, most of which is bled off in a properly executed flare; carried through to touchdown, the aircraft should land with relatively little forward momentum, vastly reducing impact forces. This also multiplies the number of potentially suitable landing sites, since there’s no need to dissipate speed over a couple of hundred yards of ground roll. Airplanes, on the other hand, have nothing but airspeed to keep the wings flying, and the typical engine-failure drill calls for maintaining best-glide speed—which in many models is significantly higher than normal touchdown speed—until the pilot is certain of reaching the intended field.
Part of it, though, may be judgment. The accident narratives suggest that an unfortunate number of fixed-wing CFIs seem to have gotten comfortable putting a great deal of trust in themselves and their equipment. These include the instructors who believe the best time to teach the response to an engine failure after takeoff is just after takeoff, a mistake that’s destroyed such high-end aircraft as Beechcraft Bonanzas, Cirrus SR22s, and even a Pilatus PC-12. Then there are those who pull the throttle in locations that offer no place to set the airplane down without significant damage—over a reservoir, say, or an expanse of corn fields where the stalks are six feet high and growing. It’s worth remembering that any emergency landing that damages the aircraft is more likely to hurt those inside than one that doesn’t. (And, yes, there’s no guarantee a real engine failure will happen within gliding distance of a suitable landing field, but that’s no reason to tempt fate by offering the engine additional chances to quit when there’s no good place to go if it does.)
Judging from the NTSB reports, helicopter instructors don’t seem quite as prone to putting all their eggs in the power-recovery basket. The rare ones who do are sometimes among the most experienced, perhaps to the point of having grown a bit complacent. One of the three fatal autorotation accidents happened during a CFI checkride. The FAA inspector had thousands of hours in large turbine helicopters but only two in the piston model used for the test. Simulating an engine failure, he chopped the throttle—contrary to both the flight school’s policy and explicit warnings in the rotorcraft flight manual—accidentally shutting the engine down for real. The candidate set up a straight-line autorotation to an unobstructed stretch of road, but though the winds were only six knots, the inspector took the controls and turned toward the trees in order to land into the headwind.
This was the first helicopter checkride he had given, and it turned out to be his last. The collision with the trees killed him. The candidate at least survived, though with significant injuries. Had the inspector trusted the pilot who had time in type to make the emergency landing, odds are both would have walked away.