N8170M

On August 24, 2017, about 1400 mountain daylight time, a Cessna 310I airplane, N8170M, was substantially damaged when it was involved in an accident near Salt Lake City, Utah. The airline transport pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 aerial photography flight.

The pilot reported that, after starting both engines, neither engine ran smoothly at idle power, and the left engine shut down when the throttle was brought to the idle position, but easily restarted. The pilot stated that both engines ran smoothly slightly above an idle power setting. The fuel mixture was leaned for taxi and runup, and exhaust gas temperatures (EGTs) were higher than usual.

During the engine runup, the left engine again lost power when the throttle was reduced to idle power, and the pilot again restarted the engine. The propellers produced normal rpm loss when cycled, but the engines ran rougher than expected during the magneto checks, with a loss of about 200 rpm. The pilot advanced the throttles and leaned the mixtures to both engines to clear “suspected carbon buildup on the sparkplugs.” Upon completion of this procedure, both engines ran smoothly at idle power, and a subsequent magneto check produced normal rpm loss.

During the initial climb after takeoff, the pilot retracted the landing gear and noticed that the airplane did not accelerate as normal. The pilot reduced the angle of attack to aid in acceleration and noticed that both engines indicated fluctuations in power, fuel flow, and rpm. He confirmed that the propeller and throttle levers were full forward, and he placed the auxiliary fuel pump to “high.” The airplane continued to decelerate and began to yaw to the left. The pilot banked right and feathered the left propeller, but the airplane continued to descend, and the pilot reduced the mixture controls to idle-cutoff. The airplane impacted two power poles and the ground before skidding to a stop adjacent to a building. A postaccident fire ensued.

The wreckage was relocated to a secure facility for further examination. The propellers separated from the engines during the accident sequence. The upper engine cowlings were removed and the interior surfaces of both the upper and lower cowling halves were dirty. The engines exterior surfaces were clean and undamaged. The spark plugs were removed from both engines; some of the electrodes displayed sooty deposits and the others were dark in color. The left engine’s tachometer generator was undamaged, and the cannon plug was not attached to the tachometer drive on the engine. The cannon plug and attachment fitting were undamaged. Both engine-driven fuel pumps were removed, and their drive couplings were undamaged. The fuel pumps were undamaged, and their drive shafts rotated freely by hand. Examination of the engines revealed no evidence of preexisting malfunctions or failures that would have precluded normal operation.

Each engine fuel system was equipped with an electric fuel boost pump controlled by switches in the cockpit. Integrated into each pump electrical circuit was a pressure switch. The cockpit switches had three positions, LOW, OFF, and ON. With the switch in the LOW position, the pump operated at a reduced speed. With the cockpit switch in the ON position, the pump operated at low speed unless the pressure switch sensed a loss of fuel pressure, upon which the electric pump operated at full speed. In 1988, the aircraft manufacturer released Service Bulletin MEB88-3, "Auxiliary Fuel Pump Wiring Modification." The compliance requirement was listed as "Mandatory: Shall be accomplished within the next 100 hours of operation, or no later than the next annual inspection, or during an equivalent inspection for airplanes utilizing the Cessna Progressive Care Inspection Program, whichever occurs first." The Service Bulletin called for the removal of the pressure switches and reconfiguring the cockpit switches and wiring so that the cockpit switches directly controlled the operation of the electric fuel pumps in both LOW and HIGH modes. The cockpit switches were to be relabeled, LOW, OFF, and HIGH.

The fuel pump switches in the accident airplane indicated that the middle position was labeled OFF and the upper position was labeled ON. Both switches were found in the OFF position. Additionally, the pressure switches were still installed and connected to the fuel pump wiring. Testing determined that the left engine's pressure switch was stuck in the "pressure" position.

The right fuel selector valve handle was found between the "Right" and "Off" positions. The right fuel selector valve was found in the "Off" position. The left fuel selector valve handle was found in the "Left" position. The alternate air door connection on the right engine was excessively worn.

Maintenance documentation revealed that both engines were installed in August 2017. The engines had about 16 hours of operation since their overhaul and installation.

According to the airplane's Owner’s Manual, the “Before Take-off” procedure included placing the auxiliary fuel pump switches in the “ON” position.

The manual stated that twin-engine climb performance at 5,000 ft mean sea level (msl), at 41°F and at maximum gross weight (5,100 lbs), was 1,220 ft per minute (fpm), and 1,650 fpm at 4,300 lbs. Single-engine climb performance at 5,000 ft msl, 41°F, and maximum gross weight was 155 fpm. The rate of climb at that altitude and temperature and a gross weight of 4,300 lbs was 325 fpm.