Twins And The Impossible Turn

The Federal Aviation Administration (FAA) calls it that — they even publish an Accident Prevention Program Bulletin by that name to warn of its dangers. What most of us are NOT taught, however, that turning back is NOT great advice, often fatal if not heeded — even in a twin-engine airplane.

SINGLE-ENGINE ADVICE — Engine failure on takeoff
Here’s what we’re generally taught about engine failures on takeoff, from the earliest days of the emergency procedures drill in single-engine airplanes.

  1. Lower the nose
  2. Aim for best glide speed (or close in to a landing spot, least-rate-of-descent speed), and
  3. Make only small turns to aim for the best landing option

Note: Below pattern altitude, don’t even think about trying to make it back to the runway. Except for very unusual circumstances, you simply won’t have the altitude to make it all the around to line up with the runway.

Back when I was teaching with a Bonanza simulator at Beech Field, I put dozens (if not hundreds) of pilots, of all experience levels, to this test:

  • First, in pre-brief I asked the pilot at what minimum altitude the he / she could make a successful return to the departure runway if the engine could quit. The average “guesstimate” was usually from 700 to 1000 feet above ground level.
  • Second, tried it in the simulator — with the pilot fully expecting the engine to quit at his/her selected altitude, we’d see if it worked. Almost all the time, it did not.
  • Next, we’d discuss ways of optimizing turn performance — “cleaning up” the airplane; immediately establishing the proper pitch attitude; turning with, versus against the wind; pulling the propeller to the low rpm (low drag) position; holding a “minimum sink” airspeed with a maximum-safe bank angle to tighten the turn — and practice the technique.
  • Finally, we’d determine the minimum altitude from which he / she could consistently make the turn back to the runway. This turned out to be about 1200 – 1300-feet AGL — after this significant, recent practice, and only then with advanced warning that the engine would quit at a known altitude.

The planned result was that pilots would realize the “impossible turn” was just that and that landing straight ahead was preferable unless obstacles prevented it. At best the pilot may be able to turn back to the airport grounds, but not likely the departure runway itself.

TWIN-ENGINE ADVICE — Engine failure on takeoff
Put a pilot in a twin-engine airplane, and take away one engine on takeoff and not only is performance dramatically reduced, but the engine that is working is doing its best to corkscrew the airplane into the ground. The pilot drills:

  1. Mixture, prop, throttle (all forward), gear up, flaps up,
  2. Identify (the failed engine), verify (that identification), and feather (the “dead” propeller).

Twin-engine pilots practice, and practice, until the pilot can do it right, consistently. But maybe we forget the lesson of the “impossible turn” along the way…

Most light twins will get, at best, a 200- 300-foot-per-minute (fpm) climb rate on one engine, at sea level and near maximum takeoff weight. Think about what that means. At 300 fpm it’ll take a little over three minutes to get to pattern altitude. At “blue line” airspeed (best airspeed for single-engine performance, a function of aerodynamic drag) you’ll get, say, a mile-and-a-half a minute ground speed during this climb, given the typical 90 to 115 knot “blue line” speed of a light twin. Of course, there’s usually a little takeoff headwind component.

Danger: To climb at all with one prop feathered, you need to go straight ahead, or very close to it. In as little as a half-standard-rate turn (less than 10 degrees bank at these speeds) and flying on a single engine, most light twins will lose about 300 to 400 fpm climb rate from what they’ll net climbing straight ahead.

1.5 miles/minute multiplied by 3 minutes (to climb to pattern altitude) = 4.5 miles covered during climb to what is really the minimum safe altitude at which to begin a turn.

Translation: Lose one of two engines on takeoff and do EVERYTHING right, and you need to climb straight ahead nearly five miles before trying to turn back to the field. If terrain, density altitude or imprecise pilot technique contribute, you may be choosing another spot to put it down. Try to turn back sooner and you’ll find yourself descending into the ground … with the temptation to pull back on the yoke as you sink, making engine-out loss of control more likely. Many have died after a propeller is feathered, while trying to return to the departure runway.

BOTTOM LINE: Just like the so-called “impossible turn” back to the runway when faced with an engine failure on takeoff in a single, so too we have an “impossible turn” scenario with an engine failure on takeoff in a twin. Train well for this most critical failure in a twin, and make sure you have the discipline to climb to a safe altitude, straight ahead, if you lose one of your engines on takeoff.