One might think that a twin-engine aircraft is safer than a single-engine aircraft. After all, if one engine fails, you still have the other to bring you home safely. That’s the whole point of the second engine, right?
If one of the twin engines fails in cruise flight, maybe that’s true. But if it quits right after takeoff, the twin can be extremely difficult to handle. When the aircraft’s landing gear is down, its flaps set, and its airspeed just above the minimum flying speed, the asymetric thrust generated by the operating engine can flip the aircraft onto its back and out of control. A "Vmc roll", as it is called, is
almost always fatal. When an engine quits during the critical takeoff phase of flight, a pilot — even one who does everything right — may not be able to land the twin-engine aircraft safely. Fog and a short runway (such as Palo Alto’s) make matters only worse.
It’s too early to tell, but it’s possible that the Twin Cessna in which the Tesla employees were flying experienced an engine failure. First, a witness at Palo Alto Airport reported hearing the unmistakable thrumming sound of two engines as Cessna N5225J rolled down the runway. That was followed by what sounded like just one engine running, and then an impact.
Second, having flown out of Palo Alto many times, I know that Air Traffic Control instructs pilots flying on instruments to proceed straight out, then turn right to a heading of 060 degrees within one mile from the airport. (The airport was fogbound when N5225J took off, so the pilot would have been making an instrument departure.) But as depicted below, the aircraft crashed well left of the expected course. That’s consistent with a loss of control following an engine failure on takeoff.
Because it’s so hard to fly a twin-engine aircraft after one of its engines fail, many pilots feel safer taking off in a single-engine aircraft. First of all, the chances of a single-engine aircraft experiencing an engine failure on takeoff is only half that of a twin. Second, if the single engine does fail, the aircraft can still be flown like a glider. Its heading is just as easy to control as if its engine were running normally. In this case, a landing straight ahead onto the mud flats, or even a right turn toward the water, might have been accomplished successfully in a single-engine aircraft. Either path would have provided a better chance of survival than the Twin Cessna’s turn to the left.
February 20 Updates: