Beech 200 — Rockford, IL

What happened

The pilot departed on a positioning flight in the twin-engine airplane. Videos recorded by multiple airport-based cameras showed the airplane take off from runway 19. Shortly after liftoff, the airplane started turning left, and the airplane developed a large left bank angle as it was turning. The airplane departed the runway to the left and impacted the ground. During the impact sequence, an explosion occurred, and there was a postimpact fire.

An airplane performance study showed that during the takeoff, a nose-left sideslip, a left side force, and a left roll occurred, consistent with the loss or reduction in thrust of the left engine. The sideslip was reduced, likely due to inputting rudder to balance the side force, and the airplane briefly rolled right possibly due to an overcorrection in rudder. The airplane pitched up and was able to begin climbing again; however, it continued to lose speed. The sideslip then reversed, and the airplane rolled left again before impacting the ground. The study indicated that before rotating and lifting off, the airplane accelerated to a groundspeed of 98 knots (kts) and an airspeed of 105 kts, which was about 19 kts above the published minimum control speed for the airplane. Therefore, the airplane had achieved sufficient airspeed for the pilot to maintain control despite a loss or reduction in left engine thrust provided he made the appropriate control inputs. The sideslip force calculations indicated that there was a partially successful attempt to maneuver the airplane back to level flight when the airplane rolled back right, but it was not maintained. The right rudder input would need to be held until the thrust asymmetry was corrected.

Teardown examinations of the engines and propellers found no evidence of preimpact failure. Both engines exhibited evidence of operation at impact. Damage to the propeller blades and hubs indicated that neither propeller was feathered at impact. The predominant left propeller blade bending and twisting was aft and toward low pitch. The predominant right propeller blade bending and twisting was forward in the thrust direction and toward high pitch. Analysis of the propeller internal witness marks and the blade damage found that the right engine was producing more power than the left engine at initial impact. Based on the available evidence, it could not be determined why the left propeller was not feathered at impact, even though the autofeather system was armed.

The rudder trim knob was found 4 units to the left; the aileron trim knob was found 6 units to the right; and the rudder boost switch was found in the OFF position. The before engine starting checklist in the pilot’s operating handbook for the airplane specified that the rudder and aileron trim be set and that the rudder boost switch be on. Therefore, the postaccident positions of the rudder trim knob, aileron trim knob, and rudder boost switch likely indicate the pilot did not follow the before engine starting checklist. With the rudder boost switch not being on, it could not be determined based on the available evidence, what role that system may have had with the pilot attempting to maintain control of the airplane during the asymmetric thrust sequence.

Although the pilot’s previous history of significant coronary artery disease and the scar in his left ventricle placed him at increased risk of an acute cardiac event, whether such an event occurred at the time of the accident could not be determined from the available information.

Absent evidence of an engine malfunction, the investigation considered whether the left engine’s thrust reduction was the result of a malfunction in the throttle control system or an uncommanded throttle movement due to an insufficient friction setting of the airplane’s power lever friction locks. However, heavy fire and impact damage to the throttle control system components, including the power quadrant and cockpit control lever friction components, precluded determining the position of the throttle levers at the time of the loss of thrust or the friction setting during the accident flight. Thus, the reason for the reduction in left engine thrust could not be determined.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.