WPR18LA179 · Cessna 340A A

The pilot reported that engine start, run-up, and taxi were all normal in preparation for the personal flight. The pilot began the takeoff roll using the full length of the dry, paved 6,000-ft runway, but shortly thereafter he felt a "sudden lag." The maximum speed he observed on the airspeed indicator was 43 knots, and the airspeed indicator needle "seemed to be fluttering." He confirmed that the engine controls were properly set and then decided to discontinue the takeoff about halfway down the runway by reducing power and applying the brakes and spoilers to decelerate the airplane. The airplane did not appear likely to stop before overrunning the end of the runway, so the pilot steered the airplane to the right as it ran off the runway end. The airplane impacted and stopped in a culvert about 500 ft beyond the runway and sustained substantial damage to the fuselage nose.

Postaccident examination of the airplane, airspeed indication system, and engines did not reveal any preimpact mechanical malfunctions or failures that would have precluded normal operation. Several months after the accident, the airplane was repaired, and engine test runs revealed two minor but unrelated turbocharger problems. One problem affected the left engine, and the other affected the right engine, but they did not manifest themselves concurrently. In each case, the affected engine did not develop full rpm, but the other engine did develop full rpm. The investigation was unable to determine whether these problems existed at the time of the accident takeoff. If they did exist, unless they occurred simultaneously, they would have manifested as a significant asymmetric thrust between the two engines, which would have been obvious to the pilot. The pilot did not report any shortcomings in engine rpm or such thrust asymmetry. The airplane was subsequently ferried to its destination, and both engines operated normally for that flight.

Accident site review revealed that the airplane traversed a total distance of about 6,500 ft during its takeoff roll and stop. Calculations performed postaccident indicate that, with a normal acceleration to 43 knots, had the airplane continued at that speed, it would have taken 35 seconds to reach the halfway point of the runway, at which point the pilot would have had 3,000 ft remaining to stop from 43 knots, which should have been sufficient.

The investigation was unable to determine the reason for the airplane not accelerating above 43 knots. However, the pilot's delay in aborting the takeoff when the airplane did not accelerate above 43 knots resulted in the runway overrun.

Verbatim NTSB analysis and probable cause from the NTSB dataset