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On May 27, 2012, about 0810 Pacific daylight time (PDT), a Beech B36TC, N8234M, experienced a total loss of engine power and landed gear-up in a field near Santa Ynez, California. The pilot/owner was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot was not injured, and the airplane sustained substantial damage to the lower fuselage structure during the landing. The cross-country personal flight departed Santa Barbara Municipal Airport, Santa Barbara, California, about 0750, with a planned destination of Mammoth Yosemite Airport, Mammoth Lakes, California. Visual meteorological conditions prevailed, and a visual flight rules flight plan had been filed.
The pilot reported taking off from Santa Barbara, and initiating a climb to the northwest. He was subsequently cleared by air traffic control personnel to climb to an altitude of 8,500 feet mean sea level (msl). During the initial climb, he began his cruise-climb checklist, completing it as the airplane reached an altitude of 4,500 feet. As he continued the climb, he noted that the ground was obscured by clouds in the Santa Ynez area. About the time the airplane reached 8,500 feet, the engine lost all power. He immediately configured the airplane for best glide airspeed, and began a turn to the west. He began to follow the emergency checklist from memory, however the engine did not restart, and he then began to refer to the emergency checklist in the airplane’s flight manual.
He switched the fuel selector valve to the left tank, and stated that he followed the checklist twice without success. During the checks, he cycled the auxiliary fuel pump from LOW to HI on multiple occasions, however, on the third attempt, he surmised that he may have flooded the engine with excessive fuel. As such, he turned off the auxiliary pump, and adjusted the mixture. He then became concerned that the engine may have experienced a “hot start situation”, so he cycled the throttle control. He then switched the fuel selector valve back to the right tank position and went through the checklist again. With no engine response, he again turned on the auxiliary fuel pump, and applied forward throttle control and rich mixture; the engine restarted for a few seconds, and then lost all power. About that time, the airplane descended below the broken cloud layer, and rather than attempting another restart, he performed a forced landing into a ploughed field.
A review of Federal Aviation Administration (FAA) airman records revealed that the pilot held a private pilot certificate with ratings for airplane single-engine land, issued 19 days before the accident. He reported a total flight experience of 131.7 hours, with 36.7 in the accident make and model. His total flight time as pilot-in-command was 24.8 hours, 14.4 of which were in the accident airplane. He was issued his high performance, and complex airplane endorsements on May 21.
The single engine airplane was manufactured in 1991, and powered by a Teledyne Continental Motors Inc. model TSIO-520-UB turbocharged, fuel-injected engine.
The airplane’s fuel system consisted of two interconnected bladder-type fuel cells per wing, each located in the leading edge. Each wing contained a total of 54 gallons, with a usable supply of 51 gallons. The tanks were filled utilizing a single filler neck located on the outboard wing fuel cell. The thickness of the tanks, and their interconnected design, meant that ascertaining fuel quantity through the “dipping” method was not possible.
Each wing contained a fuel quantity sight gauge. According to the airplane’s flight manual, the gauge is for partial filling or off-loading of fuel, and is to be used only when it reads within the calibrated area of 25 to 35 gallons. The sight gauge was of the radial type, with a float-operated needle. The upper segment of the gauge face displayed markings for 25, 30, and 35 gallons, with its lower (uncalibrated) segment painted black.
Total fuel quantity for each wing was measured by two float-operated fuel sensors located in each fuel cell. The sensors were of the electrical type, and connected in series to a fuel quantity indicator gauge within the cabin.
TESTS AND RESEARCH
The airplane was recovered from the accident site and examined by the NTSB investigator-in-charge at a repair facility in Chino, California.
Fuel Supply System
None of the airplane’s fuel cells had been breached during the accident, and recovery personnel reported that during removal of the wings from the airframe, about 42 gallons of fuel was recovered from the left tank, and about 1/4 of a gallon from the right tank.
The external surfaces of the airplane were free of fuel stains or indication of a fuel leak. Examination of the fuel system revealed about 2 teaspoons of fuel in the fuselage drain, and about 6 drops of fuel in the line connecting the drain to the auxiliary fuel pump. No fuel was present in the line from the fuel pump to the fuel injection servo. All fuel lines from both wing tanks through to the auxiliary fuel pump were examined for blockage, and were clear. The fuel selector valve handle was rotated by hand, and all detents were well defined. The fuselage drain screen was removed, and was free of debris. The right wing fuel cap was intact, and remained locked within the filler neck.
The pilot reported that on May 23, he asked personnel at the local FBO (Fixed Base Operator) to service the airplane with 15 gallons of fuel in each tank. Fueling records revealed that on that day, the left tank was serviced with 18.8 gallons, and no fuel was added to the right tank. A note on the fuel receipt stated, “Right wing was already past (30) only fueled left wing”.
Having completed a flight with his wife on May 24, the pilot asked her to check the fuel quantity with the wing-mounted sight gauges. She reported that the right tank gauge indicated 32 gallons, with the left 25. She then proceeded to the FBO (Fixed Base Operator) and made a request that the airplane be serviced with 12.5 gallons in each tank. The pilot subsequently confirmed the order request with the FBO. Examination of fueling receipts revealed that after the request, the left tank was actually serviced with 25 gallons of fuel, and no fuel was added to the right tank. The pilot reported that he was not aware of this discrepancy until he reviewed the fuel receipts after the accident.
The airplane was not flown again until the accident flight. On that day, the pilot performed a preflight inspection, and observed that when viewed through the sight gauges, the right tank contained about 32 gallons of fuel, and the left contained 45 gallons. He stated that he was aware that the gauge was not calibrated to read 45 gallons, and that he estimated this value by reading the needle location in the uncalibrated range of the gauge. He stopped his preflight inspection short, in order to move his airplane for another aircraft on the ramp. He then continued the preflight inspection from inside the airplane, and asked an FBO ramp agent to double check the wing tank sight gauges. The agent confirmed the same values, and the pilot cross checked this with the cabin gauges. He stated that the gauges indicated that the left tank was filled to 3/4 of its capacity, with the right to just over 1/4. He surmised that this disparity should have been a red flag, but that he estimated that this indication was equivalent to about 27 gallons, and close to the sight gauge value.
Fuel Quantity System Calibration
A calibration test was performed on the fuel indication system for the right wing in accordance with the Beech maintenance manual, “Fuel Indicating Maintenance Practices” section. The tank was filled with fuel, and then incrementally emptied, while measuring the sensor resistance. Additionally, the cabin indicators were cross referenced against the sight gauges. The sensor resistance was within the required tolerance, and the gauges indicated the correct quantity of fuel throughout the test.
The right tank quantity sensors were then sent to the manufacturer, Rochester Gauges, for examination in the presence of an NTSB investigator. The gauges were tested, and were within specifications. Subsequent disassembly did not reveal any malfunctions or failures which would have precluded normal operation.
A calibration test was also performed on the sight gauge for the right wing; the gauge indicated the appropriate values when filled within its calibrated range. When the tank was filled to 1/4 of its capacity or less, the needle pointed towards the lower uncalibrated segment, however the tail of the needle pointed to about the 32 gallons position.
The engine appeared undamaged, and contained about 11 quarts of dark-colored oil when checked via the dipstick. The throttle and mixture control cables were continuous from the cabin controls through to their respective engine controls. The top spark plugs were removed, and exhibited light grey coloring, and worn out-normal wear signatures, consistent with normal service life when compared to the Champion AV-27 aviation check-a-plug chart. The engine cylinder chambers were examined through the top spark plug bores utilizing a borescope. All valve heads and piston crowns appeared intact, with grey deposits, and no indication of catastrophic internal damage.
A new propeller was mounted to the engine, and a fuel canister containing 100 octane low-lead aviation gasoline was connected to the right wing tank supply line at the wing root. The engine was subsequently primed in accordance with engine operating procedures, the starter was engaged, and the engine started immediately. The engine was subsequently operated at idle power for about 1 minute, and then an uneventful magneto check was performed with an appropriate rpm drop observed. The throttle and propeller controls were then advanced, and the engine was operated at 2,600 rpm with 36 inches of manifold pressure for about 30 seconds. The engine responded to throttle commands, and operated smoothly throughout the test. The auxiliary fuel pump was in the OFF position during the engine run.
The Beech B36TC emergency procedures checklist stated the following regarding the use of the auxiliary fuel pump:
The only purpose for the Aux Fuel Pump HI position are:
1) To prime the engine prior to starting.
2) To provide an alternate source of fuel pressure if the engine-driven fuel pump fails.
DO NOT USE THIS POSITION FOR ANY OTHER REASON. If HI position is selected when the engine-driven pump is operating, the engine will run rich and may quit depending on the throttle setting, temperature and altitude.”
The emergency procedures checklist stated the following regarding loss of engine power caused by fuel depletion:
Characterized by an empty indication on the Fuel Quantity Gauge and zero fuel flow:
1. Fuel Selector Valve.......SELECT OTHER TANK
2. Aux Fuel Pump...........................LOW”
The limitations section of the Pilots Operating Handbook stated that takeoff is not permitted when the fuel quantity gauges indicate a quantity in the yellow arc (1/4 tank or less) or with less than 13 gallons in each tank.