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When more is lessWhen more is less

The old joke holds that the reason light twins have two engines is that they need them. It’s a lot less funny when a student is hot and high on a single-engine approach and you have to hope engine No. 2 will catch in time to pull off the go-around. The accident record confirms the conventional wisdom: While accidents in twins are not a great deal more likely to kill the occupants than accidents in complex singles, almost all the fatalities seem to be the product of single-engine work.

We realize that this won’t come as a surprise to anyone who’s operated a multiengine training program. Still, the record was starker than we’d expected. More than five-sixths of the fatal multiengine training accidents over the past 10 years were either known to have been caused by engine-out drills gone wrong, or involved spins from altitude that are hard to explain in any other way. Half of the handful that remains involved engines that shut down inadvertently, most often due to errors in fuel management. The fatal accidents that seemed unrelated to a twin’s single-engine performance and handling characteristics were pretty much limited to a bird strike at night that destroyed the horizontal stabilizer of a Seminole and a previously undiagnosed brain disease that led a CFI to suffer a seizure on short final.

Single-engine work also figures heavily into nonfatal accidents, too. Go-arounds account for twice as large a share of the multiengine accident record as for singles. Twenty percent of them are fatal, but almost all are the outcomes of single-engine approaches that don’t go quite as planned. Many are the result of configuration errors—the CFI forgets having turned off the fuel selector for the dead engine, or the student forgets to richen the mixture—but in others, the engine just won’t start in time. There’s an argument to be made for teaching students from Day One that single-engine go-arounds aren’t likely to be an option in most piston twins, and having the instructor time any interventions accordingly.

Stalls and spins figured heavily into the fatal accident count. Some were self-inflicted wounds, like the school that tasked low-time instructors to prepare for a designated pilot examiner who liked to “simulate engine failure during slow flight or stall recoveries.” A CFI conducting an instrument proficiency check in a Beech Duke pulled one throttle back to idle at 200 feet above the ground and refused to let the airplane’s owner, whom he was training, restore power. The owner suffered serious burns when the airplane rolled over into the trees, but at least he survived. It’s not clear whether the instructor knew what VMC is in that model, but if he wasn’t below it, he was awfully close. Others are downright mysterious, like the flight review of a 3,400-hour commercial pilot that ended less than an hour later in a fatal flat spin. No one saw the accident, and both he and his CFI had considerable experience in the airplane, leaving little clue as to what went wrong.

Gear-ups, premature gear retractions, and fuel-management accidents are also more common in twins, even though most show no obvious relation to single-engine practice. In most cases, it seems more as though the process of flying a twin took the student (and instructor) too close to the saturation point to deal with one more variable. At least relatively few of these killed anyone, or left the aircraft past the point of being cost-effective to repair.

Admittedly, twin trainers do spend a lot of their working lives with one propeller either windmilling or feathered. Still, the near-absence of all other operations from the fatal-accident record should open an eye or two. That same record suggests a couple of commonsense precautions: Have instructors introduce students to single-engine operations gradually, from a safe altitude, before moving on to approaches or engine failures after takeoff. Make sure your MEIs are thoroughly versed in every aspect of the subject, from aerodynamics to the specific operational details of that make and model, before letting them train new students. And here, too, it’s well worth your while to find out what they’re really doing when they’re out where you can’t see them. It helps if your students understand that face time with the chief instructor is a gift, particularly if they get it at no extra charge. Genuine interest in what they’re learning and how they’re processing it goes a long way to foster forthright discussion of their training experiences.

ASI Staff

David Jack Kenny

Manager, Safety Analysis
David Jack Kenny analyzes GA accident data to target ASI’s safety education programs while also supporting AOPA’s ongoing initiatives and assisting other departments in responding to breaking developments. David maintains ASI’s accident database and regularly writes articles for ePilot, Flight School Business, Flight Training, CFI-to-CFI, and other publications.

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