Accident Overview
On January 22, 2023, about 1127 central standard time, a Beech M35 Bonanza, registration N9306Y, was substantially damaged in an accident near Tomball, Texas. The airplane was operating as a Title 14 Code of Federal Regulations Part 91 aerial survey flight. The pilot and the driver of a semi-trailer truck were not injured.
Flight Details
According to the operator, the pilot departed West Houston Airport (IWS) at 1008 with a full fuel load of 103 gallons usable. The fuel selector was initially positioned to the left main tank (22 gallons usable). About 45 minutes into the flight, the pilot switched to the auxiliary fuel tanks (19 gallons usable) and set a timer for 38 minutes. The digital engine monitor indicated a fuel flow of about 13.5 gallons per hour during cruise.
Approximately 1 hour 16 minutes into the flight, ADS-B data and the pilot's statement show the aircraft entered a left 270° turn to avoid another airplane, then headed east toward David Wayne Hooks Memorial Airport (DWH). Shortly after completing the turn, the engine lost all power while the airplane was heading east. ADS-B data placed the airplane about 11 miles west of DWH at 2,000 ft mean sea level before a sustained descent began.
Engine Failure and Forced Landing
The pilot attempted to restore engine power by switching from the auxiliary tanks to the right main tank, enriching the mixture, and checking magneto operation, but was unsuccessful. Due to low altitude, he did not continue troubleshooting or consult the emergency checklist. He declared an emergency with DWH tower and made a forced landing on the eastbound lanes of Highway 99, about one mile west of the Telge Road exit.
During the landing, the right main landing gear struck the roof of a semi-trailer, causing the airplane to roll left wing down and descend into a concrete highway median. The airplane was immediately engulfed in fire after coming to rest. The pilot unbuckled his restraints and exited the aircraft.
Wreckage Examination
FAA inspectors reported that the airplane descended onto Highway 99. The landing gear and flaps were extended. The postaccident fire destroyed most of the fuselage, cabin, and cockpit. Both wing roots showed thermal damage near the main fuel tanks. The filler caps for both main and auxiliary tanks were properly installed. The tow truck operator reportedly drained about 25 gallons of fuel before moving the aircraft, but individual tank amounts were not documented. The left and right wingtip tanks exhibited extensive damage and no residual fuel.
Engine control continuity could not be established due to thermal damage. Fuel lines within the fuselage and engine compartment showed various degrees of thermal damage. The cockpit fuel selector valve was thermally damaged but rotated freely; detents were not discernible. The airframe fuel filter contained 1/8 to 1/4 cup of fuel, and the fuel strainer was largely unobstructed with minor debris.
Fuel System Assessment
The airplane had a 110-gallon capacity fuel system (103 gallons usable), consisting of two 25-gallon main tanks, two 10-gallon auxiliary tanks, and two 20-gallon wingtip tanks. The cockpit selector offered positions for off, left main, right main, or auxiliary. When full, each main tank held 22 gallons usable; the auxiliary tanks had a combined 19 gallons usable. Wingtip fuel was transferred via electric pumps to the respective main tanks.
Engine and Propeller Inspection
The engine remained partially attached to its mounts with impact damage to forward mounts. The crankcase showed thermal damage but was intact with no cracks or holes. No evidence of oil or fuel leaks was found; the oil sump contained ample oil. The oil filter had thermal damage but no metal contamination. Intake tubes and exhaust were unobstructed.
All six cylinders exhibited minor thermal damage. Internal continuity was confirmed by rotating the crankshaft; compression and suction were noted on all cylinders. Borescope inspection revealed no anomalies. The throttle unit showed thermal damage; the fuel inlet screen was fused due to heat. The throttle plate rotated freely. The mixture arm separated from the housing with impact damage. The fuel manifold allowed free airflow. Injector lines and nozzles were clear.
Both magnetos produced spark when rotated. Spark plugs showed normal wear. The engine-driven fuel pump had extensive thermal damage; its drive coupling was sheared consistent with postaccident crankshaft rotation. Disassembly revealed thermal damage to internal components and a dark-black resolidified material in the pump chamber.
The propeller remained attached; all three blades exhibited aft bending, twisting toward low pitch, and chordwise scratching.
The semi-trailer truck sustained a minor puncture to its roof but was otherwise undamaged.