WPR23FA275 · Cessna T310R

Shortly after takeoff in the multi-engine airplane, the pilot reported to the tower controller that he had an engine failure. The controller cleared the pilot to land on any runway, and the pilot stated that he was going to try to gain altitude before returning for landing. There were no other transmissions from the pilot. ADS-B data indicated that the airplane lifted off from the runway and generally maintained the runway heading. The airplane climbed to a maximum altitude of about 200 ft above ground level (agl) at a ground speed about 100 knots (kts). The airplane continued south for about 2.5 miles over a sparsely populated area without climbing. The airplane then began a descending, slowly decelerating left turn toward a frontage road and an interstate highway; however, it is possible that the pilot chose not to use either location as a forced landing site due to powerlines located immediately north of the frontage road and traffic on the interstate. The pilot continued the left turn and aligned the airplane with an alley located in a neighborhood. A witness stated that the airplane’s left wing dropped just before the airplane impacted a house, consistent with a loss of control in the final moments of the flight. Examination of the left engine revealed significant internal damage. Multiple fragments of engine components were found in the oil sump, including separated crankshaft counterweight components. Further examination revealed that the aft-facing crankshaft counterweight retaining rings were installed incorrectly, with the retaining ring ears facing away from the crankshaft centerline, some of them with the sharp edge incorrectly facing inward, and with incorrect spacing of the ring ear gap. This improper installation allowed two of the counterweights to separate, and one to partially separate, from the crankshaft, which resulted in the total loss of power to the left engine. Examination of the right engine revealed the same incorrect installation of the aft-facing counterweight retaining rings; however, the crankshaft counterweights remained intact. There were no other mechanical malfunctions or failures with the right engine that would have precluded normal operations. Examination of the airframe revealed extensive thermal damage, but no anomalies that would have precluded normal operation. The landing gear were found in the retracted position, and the position of the wing flaps could not be determined. A review of maintenance records revealed that all the counterweights from both engines were removed and reinstalled about 24 years before the accident in accordance with a mandatory service bulletin which, in part, called for the removal and reinstallation of all the counterweights. The removal criteria specifically called for removing and replacing the aft-facing retaining rings as part of the counterweight removal process. Records indicated that this was the last time the rings would have been removed/replaced. Based on the airplane’s estimated weight and balance and the atmospheric conditions present at the time of the accident, performance charts in the pilot operating handbook indicated that the airplane should have been able to climb at a rate of about 300 ft per minute with one engine inoperative, but obtaining this performance would have been dependent on the pilot establishing the proper airplane configuration and single-engine best rate of climb speed (Vyse). Examination of the airplane revealed that the landing gear was retracted and that the left propeller was feathered consistent with published single-engine inoperative procedures; however, ADS-B information indicated that the airplane’s ground speed was about 100 kts; the airplane’s published Vyse was 106 kts indicated airspeed. Additionally, the procedures stated that the airplane should be banked 5° into the operating engine, and the pilot was turning the airplane left (into the inoperative engine) before the accident occurred. Based on the available information, it is likely that the pilot did not maintain adequate airspeed while maneuvering following the loss of left engine power, which resulted in the airplane’s inability to climb and a subsequent loss of control and impact with terrain.

Verbatim NTSB analysis and probable cause from the NTSB dataset