N70SL

On December 17, 2023, about 1414 central standard time, a Beech B36TC, N70SL, was destroyed when it was involved in an accident near Burnet, Texas. The pilot and passenger received serious injuries. The airplane was operated under Title 14 Code of Federal Regulations as a Part 91 personal flight.

The pilot stated the preflight, engine start, engine runup, and takeoff roll were normal. While climbing through 200 to 300 ft agl, the engine began to surge and lose power. The airplane was unable to climb, and the pilot was unsuccessful using emergency procedures at regaining engine power. The pilot said he could not see an area suitable to land on except for a road. During the landing, the airplane’s right wing struck a car and exploded into flames. The airplane landed in a field and was destroyed by impact forces and postcrash fire.

A witness stated that he saw the airplane intermittently emitting black smoke from the exhaust as it climbed out slowly after takeoff. A video of the takeoff showed dark smoke emitting from the airplane’s exhaust area. A second witness saw the airplane fly southbound at an estimated altitude of 100 to 150 ft agl and was having difficulty gaining altitude. The airplane’s landing gear was retracted, the wing flaps were retracted, and the propeller was turning. The airplane lost altitude and descended behind a hill.

The engine-driven fuel pump assembly was removed for testing at Continental Aerospace Technologies, Mobile, Alabama, under the supervision of the NTSB Investigator-in-Charge. The fuel pump assembly was placed on a test bench and during testing at an input speed of 2,700 rpm, the fuel flow was 38.42 gallons per hour and the maximum limit for the test was 34.9 gallons per hour. There was no test fluid leakage from the fuel pump assembly during the test. The fuel pump assembly was removed from the test bench and disassembled to determine the length of its internal aneroid. The fuel pump assembly’s aneroid adjustment screw was extended outward 0.4480 inch. The internal aneroid was not elongated and was of comparable length to the aneroid of a new production fuel pump assembly, which indicated a normal condition. According to Continental Aerospace Technologies, the greater the outward extension of the aneroid adjustment screw, the greater the output of fuel flow from the fuel pump assembly. A review of the engine maintenance logbooks showed that the fuel pump was overhauled in June 2004, and that the engine was overhauled April 14, 2022. There were no other references to work or adjustments done on the fuel pump.

The Federal Aviation Administration Aviation Maintenance Technician Handbook–Powerplant (2023), Chapter 10, Engine Maintenance & Operation, Engine Troubleshooting, Figure 10-52, lists symptoms of a rich mixture to include black exhaust smoke and sluggish engine operation.