Safety Spotlight: Critical moments

Crew comments from the NTSB’s preliminary report and video of the crash seem to substantiate some type of asymmetric thrust issue. The NTSB will complete a thorough investigation, which may take up to two years and could find issues different from the initial indications. In the meantime, we can use the accident to reinforce how quickly things can erode in aviation and the critical decisions that must be premeditated especially in multiengine, non-centerline-thrust aircraft.

Multiengine training centers on single-engine operations, particularly engine failures on takeoff. The critical focus is airspeed, and especially understanding minimum controllable airspeed, or V_MC. V_MC is the slowest the airplane can fly on a single engine and maintain controlled flight. Once airspeed drops below V_MC, the pilot does not have enough control authority to counteract the asymmetric thrust.

Current V_MC demonstration training in light twins is thought by many multiengine CFIs to be counter-productive. At altitude, thrust is gradually reduced on one engine so pilots can experience reduced rudder effectiveness as the aircraft slows. The problem is, it’s a docile simulation of what is in reality a rapid and violent situation. Pilots can leave the training with the mistaken notion that degraded yaw control happens gradually and controllably with plenty of time to make corrective inputs. Those who’ve experienced the full V_MC demonstration airborne at higher altitudes report being shocked and frightened by the airplane’s quick, uncontrollable reaction when the airspeed dropped below V_MC. Such full demonstrations are discouraged, since departure from controlled flight can result in a spin, which is difficult or impossible to recover from in a light twin even at high altitudes.

The concept of V_MC and required pilot action is most challenging in a takeoff with power loss near rotation speed (V_R). V₁ is the maximum speed at which a takeoff can be aborted and the airplane stopped in the remaining runway (“go speed”). In high-performance turbine twins, V₁ is often reached before V_R. Managing reactions in the gap between V₁ and V_R is critical. Accelerating an airplane on the ground with a crippled engine and a commitment to get airborne is not an intuitive reaction. It takes training and reinforcement.

In light piston twins its often possible to be beyond rotation speed, even airborne, and still have room to chop power, settle back on the runway, and stop in remaining runway distance. If an engine fails and a commitment to take off is made, multiengine pilots must maintain airspeed above V_MC at all costs and accept whatever aircraft performance results. In a light piston twin, this may mean an inability to maintain level flight—which will likely result in difficult options, such as putting the airplane back down and overrunning the runway, a quick off-airport landing, or a controlled crash. Understanding these speeds, the decision points, and prompt pilot reaction is the essence of twin-engine training. In either a light piston twin or a high-performance turbine twin, pilot performance in this window is critical and requires extensive, repeated, and recent training.

Like so much in aviation, decisions in the crucial takeoff window for multiengine flying must be premeditated and practiced. The key to being proficient at any skill is frequency and recency: Do it a lot, and do it near the timeframe when performance is needed. We should presume that honed performance dealing with engine problems on takeoff will be needed every time we fly. We can never afford to lack proficiency in this crucial skill.

The Addison accident video demonstrates just how quickly the situation can erode in critical phases of flight. There’s very little time for assessment and decision making. We must train to expect the worst problem at the worst time and know exactly how we will respond. Recurrent training is expensive, the cost of poor performance in a critical situation with lives at stake is inestimable.

Beyond recurrent training, we can stay crisp with some old-fashioned chair flying at home or in the office to think about and review the critical decision points in our airplanes and our reactions. Then, reinforce them on every takeoff prior to departure by reviewing our takeoff speeds, expecting an engine loss, and reinforcing our reaction.

Go fly.

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