Piper PA-32-260 N85CT accident near Broomfield, Colorado

Probable cause

The pilot’s failure to abort the takeoff due to degraded engine performance. Contributing to the accident was the reduced performance of the engine, the reason for which could not be determined.

NTSB analysis

The pilot and pilot-rated passenger conducted a personal flight that included troubleshooting an avionics issue. Following an extended taxi of longer than 1 hour, the airplane departed with a longer-than-normal ground roll and made a shallower-than-normal climb out. About ½ mile past the departure end of the runway, the airplane turned left and descended toward a road, which was a flight profile that was consistent with a forced landing attempt. The airplane impacted the road and then a large tree, which separated the engine and cockpit area from the fuselage, resulting in substantial damage.

Postaccident examination of the airframe and engine did not reveal any indication of a mechanical failure or malfunction that would have precluded normal operation.

Recorded data indicated engine performance during the accident takeoff was significantly lower than a previous takeoff. The engine power increased very slowly on the accident takeoff roll and fuel flow was about 45% less than the previous takeoff. The reason for the lower fuel flow during the accident takeoff could not be conclusively determined. However, one possibility was that the pilot(s) leaned the mixture during the extended ground operations of more than 1 hour and subsequently forgot to enrich the mixture before takeoff.

A second possibility for the lower fuel flow was carburetor ice. The weather conditions at the time of the accident were conducive to serious carburetor icing at glide power. Carburetor ice can affect the fuel flow by disturbing the venturi effect in the carburetor throat that draws fuel into the cylinders. The result is lower fuel flows.

Toxicology testing of the pilot did not identify any tested-for substances. The pilot-rated passenger’s toxicology indicated use of a number of substances; however, indications were limited to the urine and it is unlikely they were contributory to the accident.

The slow acceleration and extended ground roll due to the degraded engine performance necessitated an abort that was not accomplished by the pilots. Since a purpose of the flight was troubleshooting an avionics issue, it is possible that the pilots were distracted by the avionics issue during the takeoff roll. This distraction could have led to inattention to ensuring that the fuel flow/engine performance was adequate during the takeoff roll and to abort the takeoff.

Text from the NTSB. Open the NTSB docket for CEN22FA208 for the full record.