Accident Analysis: Spreading misinformation

Shortly after that appeared in print, an attentive and courteous reader with extensive make-and-model experience reached out to correct me. In the event of an actual engine failure—an event that has so far been notable for its rarity—the DA42 pilot still has to figure out which engine has quit and double-check that identification by pulling its full-authority thrust lever back while simultaneously lowering the nose to maintain airspeed, keeping the nose straight with rudder, and banking slightly toward the operating engine. True, the feather and secure steps are simpler than in a traditional piston twin. Turning off the engine master switch signals the computer to feather the propeller; shutting off the fuel selector and alternator completes the checklist. But the difference is one of degree, not of kind as I’d believed.

Where did I go wrong? According to my correspondent, I’m not the first.Where did I go wrong? According to my correspondent, I’m not the first: The DA42’s supposed autofeathering capability is a pervasive myth that has both helped and hindered its sales. (It would be a great selling point if true.) I probably started with a preconception absorbed from that same myth, convoluting rumors of the Diamond’s ultrasophisticated electronics with reports of an emergency autoland system supposedly under development in collaboration with Garmin. I did attempt due diligence by interviewing a friend who’d recently passed his multiengine checkride in the same model. In retrospect, I realize that I overgeneralized his answers to my imprecise questions: Simulating an engine failure in flight requires shutting off the engine master, which does indeed feather the prop. Relying too heavily on my own piston experience, I didn’t think to ask how closely the practice drill mirrored the real emergency procedures.

This misunderstanding will be relatively harmless if everyone who buys a DA42 receives competent transition training that overrides the misinformation I’ve helped propagate. But other aviation myths sharing a similar veneer of plausibility have been more durable, and sometimes more destructive. The fantasy of gaining speed by climbing above your altitude, and then diving back down (objectively disproven in flight tests) doesn’t risk much more than making the perpetrator look silly, plus maybe a mild rebuke from ATC. But switching fuel tanks in the pattern does risk a low-altitude engine stoppage regardless of which checklist contains “Fuel—fullest tank,” and not everyone so afflicted makes it to the runway. And the notion that any particular airspeed provides immunity from stalls has triggered both landing overruns and fatal low-altitude spins. (To paraphrase Vince Lombardi, angle of attack isn’t everything, it’s the only thing—at least where stall avoidance is concerned.)

Yes, AOA is a difficult concept to teach. But the laws of physics are implacable, making it imperative that we get our stories straight.