History of Flight
On April 13, 2013, about 1221 mountain standard time, a Beech 35-B33, N6841Q, collided with a ditch during a forced landing near San Manuel Airport, San Manuel, Arizona. The pilot, an airline transport pilot, was operating under 14 CFR Part 91. He sustained serious injuries. The airplane sustained substantial damage to the firewall, fuselage just aft of the cabin, and both wings. The cross-country flight departed Pegasus Airpark, Queen Creek, Arizona, about 1150, with a planned destination of San Manuel. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot reported that the flight was part of a round-robin trip from Tucson International Airport to Pegasus Airpark, with a stop at San Manuel for fuel, then return to Tucson. He stated the flight was uneventful until approaching San Manuel. He overflew the airport heading north at 5,000 feet, initiated a left turn to enter the right downwind leg for runway 29, reduced power, descended to 4,100 feet, extended landing gear, and deployed full flaps. During the base turn, he increased engine power but the engine did not respond. He turned on the auxiliary fuel pump with no effect. Unable to reach the runway, he performed a forced landing in rough rising terrain short of the field.
Fuel System Observations
The pilot reported the left fuel tank quantity indicator was inoperative, and he believed the left tank contained more fuel than the right. He surmised that switching to the right tank might have restored fuel flow. Recovery crew stated the right tank contained about 12 gallons of fuel and the left about 10 gallons at the accident site. The left wing leading edge had a gouge 24 inches outboard of the root that breached the fuel tank bladder.
Engine and Airframe Examination
The engine and airframe were examined by the NTSB investigator-in-charge with assistance from Continental Motors. No anomalies were noted that would have precluded normal operation. The fuel selector valve moved through OFF, LEFT TANK, and RIGHT TANK positions with positive detents. Fuel lines from the firewall to each wing tank were free of obstruction; about 8 ounces of fuel was drained from the selector valve sump. The valve’s screen was clear. Blue-colored fuel was present from the selector valve to the engine-driven and auxiliary fuel pumps.
The engine sustained minimal damage and remained partially attached. The inlet air filter and box were crushed; the fuel injection control assembly had broken away. Fuel lines between the pump and metering unit, and from the metering unit to the manifold valve, were broken at fittings. The flow divider diaphragm was pliable and free of cracks. No fuel was observed in the divider cavity or lines forward of the engine-driven pump.
The engine-driven fuel pump was removed; its drive shaft was intact. The pump input drive was stiff to turn and made a squeaking sound. Disassembly of the pump and fuel injection control assembly at Pacific Continental Engines revealed no internal blockages or debris. Inner walls were shiny, and the pump shaft, plate end, and blades were intact with light scoring consistent with normal service. A representative stated rotational resistance was not unusual, and there were no indications of catastrophic internal failure.
GPS and Maneuvering Data
The airplane was equipped with a Garmin GPSMap handheld GPS receiver. Recorded data showed a 25-minute climb from Pegasus Airpark (1,450 feet) to 6,067 feet on a southeast heading. About 9 miles northwest of San Manuel, it descended, overflying the airport at 5,246 feet. Over the next 3 minutes, the airplane performed a series of four left turns that formed one complete circle north of the airport. It then joined the right downwind leg for runway 29 at 4,200 feet. After reaching the end of the downwind leg, it began a descending right turn through base to final, with the last recorded position at 3,192 feet, about 2,600 feet short of the runway threshold.
The most aggressive turn (left) lasted about 35 seconds, with a radius of about 2,500 feet and average ground speed of 140 knots, resulting in a bank angle of about 35 degrees.
Pilot's Operating Handbook Information
The Beechcraft Pilot's Operating Handbook for the accident airplane model defined maneuvering limits for utility category. Approved maneuvers (at 3,000 pounds) include chandelles, steep turns (entry speed 128 knots CAS), lazy eights, and stalls. Minimum fuel for these maneuvers is 10 gallons each main tank. The emergency procedure for in-flight engine power loss directs: 1) Fuel selector valve – select other main tank (check detent); 2) Auxiliary fuel pump – ON; 3) Mixture – full rich, then lean as required; 4) Magnetos – check left and right, then both.
Fuel Tanks and Engine Monitor
The airplane had two baffled wing-cell fuel tanks, each with 37 gallons usable capacity, installed in December 2011.
The airplane was equipped with an Electronics International UBG-16 engine monitor recording exhaust gas temperature (EGT) and cylinder head temperature (CHT). For the accident flight and prior 12 months, EGTs for cylinders 1 and 3 were 300–600°F lower than others, likely due to monitoring system error. Remaining cylinders showed average EGT rise to 1,600°F and CHT to 400°F initially, then 1,500°F and 350°F for most of the flight. The last 3 minutes recorded a precipitous drop in EGT to 400°F and CHT to 250°F.
Pilot Restraints
The airplane was equipped with lap-belt restraints only, without provisions for a shoulder harness. During impact, the pilot’s upper body pivoted forward, striking the instrument panel and resulting in a concussion and multiple facial lacerations and punctures. The control yoke moved forward, striking his chest and breaking his right hand.