CEN16FA224

The pilot's loss of airplane control during descent following a loss of engine power for reasons that could not be determined because postaccident examinations and engine test-runs of both engines revealed no evidence of any mechanical malfunctions or failures that would have precluded normal operation.

The commercial pilot and crew were conducting aerial photography work under contract with the U.S. Department of Agriculture. Shortly after departure, the pilot noticed an engine vibration coming from the airplane's right side and returned to the departure airport to have a mechanic inspect the engine. The pilot called the company operator to notify the company's owner of the engine anomaly; the operator and the crew agreed that they would stop aerial photography work and return to the operator's base in Longmont, Colorado but that they would call the operator's base to provide an update on the mechanics' findings before departing; however, the operator received no further communications from the crew. GPS data showed the airplane departing AEJ and then heading south in the opposite direction of the operator's base and overflying one aerial survey point near C24. The airplane maintained an altitude of between 11,300 and 13,000 ft mean sea level (msl) with a ground speed between 120 to 169 knots for most of the flight. The last two minutes of flight showed the airplane circling around C24 while decreasing in altitude and fluctuating in airspeed between 140kts and 98kts. During the last 3 minutes of the flight, the airplane was descending, and the groundspeed decreased from 141 knots to 98 knots, before increasing to 128 knots and then rapidly decreasing to 99 knots during a sharp, 90º left turn to the north.  The last recorded parameter showed the airplane at 8,665 ft msl with a groundspeed of 99 knots. Witnesses stated that the airplane was on a left base for the runway but did not appear to be correctly positioned or high enough for the pattern into the airport. One witness stated that the airplane appeared to yaw and then return to wings level while descending to the ground. One witness stated he saw the propellers turning; however, two witnesses reported that they did not hear engine sounds.   Flight control continuity was established from all control surfaces to the cockpit input controls. Left and right engine test-runs and examinations revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. However, examination of the left and right propellers indicated that the engines were likely operating with low to no power at the time of impact. Additionally, both propellers had several indications consistent with operating near their low-pitch position and they were not in the feathered position, consistent with the engines not being shut down by the pilot. The flaps were set to the 10º position and the gear was up, consistent with an approach configuration. The pilot's autopsy findings revealed that he had an enlarged heart and moderate coronary artery disease, which slightly increased his risk of impairment from a cardiovascular event. However, there was no evidence of recent or old ischemic damage to the heart muscle or evidence of pilot impairment or incapacitation. Therefore, it is unlikely the pilot's cardiovascular disease contributed to the accident. Given the evidence, it is likely the engines experienced a loss of power and that the pilot subsequently lost airplane control during the descent to the airport for landing, which resulted in impact with terrain. The reason for the dual loss of engine power could not be determined based on available evidence.

HISTORY OF FLIGHT On June 15, 2016, about 1409 mountain daylight time, a Cessna 320E airplane, N777GY, was destroyed when it impacted terrain near Mineral County Memorial Airport (C24), Creede, Colorado. The commercial pilot and two passengers were fatally injured. The airplane was registered to Left Hand Financial, Inc., and was being operated by Rocky Mountain Aerial Surveys (RMAS) under contract with the U.S. Department of Agriculture (USDA) as a Title 14 Code of Federal Regulations Part 91 aerial photography flight. Day visual meteorological conditions prevailed, and no flight plan had been filed for the flight, which departed Central Colorado Regional Airport (AEJ), Buena Vista, Colorado, about 1307. According to an RMAS employee, about 1240, the pilot called the RMAS base in Longmont, Colorado, to provide a mid-day briefing. The pilot reported that the airplane had performed "fine" for the first 2.5 hours of surveying. However, he added that, after they had lunch at AEJ and departed about 1307, the airplane experienced an engine vibration that felt like it was coming from the right side and that the airplane seemed slow. According to the AEJ manager, about 15 minutes after takeoff, the pilot called AEJ to report that he had an issue and would be returning to the airport. After the pilot landed the airplane at AEJ, he and a local mechanic inspected it to determine what was causing the vibration. The pilot called the RMAS base, and the RMAS employee and the pilot agreed that he would fly to Rocky Mountain Metropolitan Airport (BJC), Longmont, Colorado, for maintenance but that he would call the RMAS base to provide an update on the mechanics' findings before departing AEJ. The RMAS base received no further communications from the pilot. A Garmin GPSMAP 396 was found near the wreckage and was submitted for examination by the NTSB Vehicle Recorders Division for pertinent data for the accident flight. The data started at 1307:41 and ended at 14:09:27. The data showed that the airplane departed AEJ about 1307 and followed highways, first traveling south away from the operator's base (93 miles northeast), then turning west over Del Norte, Colorado, and then turning northwest toward Creede. Approaching C24, the airplane overflew one aerial survey point just north of the airport. The airplane was between 11,300 to 13,000 ft above mean sea level (msl) and at a groundspeed of between 120 to 169 knots for much of the approximate 1-hour flight. However, during the last 2 minutes of the flight, the airplane passed north of C24, then circled around to the south side of the airport. During this time, the airplane was descending, and the groundspeed decreased from 141 knots to 119 knots to 98 knots, before increasing to 128 knots and then rapidly decreasing to 99 knots during a sharp, 90º left turn to the north. The last recorded data were at 1409:27, at which time the airplane was at a GPS altitude of 8,665 ft with a ground speed of 99 knots. Due to data buffering on the GPS unit, the data recording may have ended before the accident event. Figures 1 and 2 are graphical overlays showing about the first hour and the last 3 minutes of the airplane's flightpath, respectively. Figure 1. A graphical overlay showing the accident flightpath. (GPS Time recorded in UTC (MDT +6 hours)) Figure 2. A graphical overlay showing the last 3 minutes of the airplane's flightpath. (GPS Time recorded in UTC (MDT +6 hours)) One witness reported seeing the airplane making a left base turn for approach to runway 25 at C24. Another witness stated that the airplane was at a "very low altitude for his position in the pattern," that the propellers were turning, and that the airplane then yawed, returned to a wings-level position, and continued to descend until impacting the ground. Another witness stated that the airplane did not appear to be "far enough out to line up appropriately with the runway." Two witnesses stated that the landing gear were up. One witness, who lived near the accident location, reported that the airplane flew about 10 ft above her house, that it then veered left, and that it was making "loud revving noises." However, two other witnesses located about 1/4 mile west of the accident site reported that they did not hear engine noise. The accident site was located 0.7 miles from east of runway 25 at C24; which was southwest of AEJ, while BJC was located northeast of AEJ. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with airplane single- and multiengine land and instrument ratings. The pilot's most recent Federal Aviation Administration (FAA) second-class medical certificate was issued on June 22, 2015, with the limitation that he "must have available glasses for near vision." On his medical certificate application, the pilot reported that he had about 1,591 total hours of flight experience, with 230 hours in the previous 6 months. The pilot reported no significant medical conditions and no use of medications to the FAA. According to the pilot's logbook, his first flight in a Cessna 320 was in the accident airplane on August 20, 2015. The pilot accumulated 28.9 hours of experience in the airplane between August 20 and September 16, 2015. He accumulated an additional 71.5 hours in the airplane between April 12 and May 5, 2016, for a total of 100.4 hours of experience in the Cessna 320. The pilot had 1,985.1 hours total flight experience, with 295.1 hours in multi-engine airplanes. His last flight review was completed on July 7, 2014, in a Cessna 182. AIRCRAFT INFORMATION According to FAA records, the low-wing, turbocharged, twin-engine airplane, serial number 320E0027, was issued its original airworthiness certificate on September 3, 1966, and was registered to the operator on September 6, 2011. The airplane had been reconfigured from its original six-seat configuration to a three-seat configuration to allow space for the use of an aerial camera and survey equipment. According to the airplane's maintenance records, Western Plains Aviation, LLC (WPA), completed the last annual inspection on March 23, 2016, at a recorded Hobbs time of 572.7 hours. The last maintenance entry for the airframe was on June 6, 2016, at a Hobbs time of 789.6, after the operator reported a vibration in the airplane during flight. WPA found the left and right main gear doors were loose and repaired the gear doors and engine nacelle lower skins. Also completed during this maintenance was installation of a Heli-Coil in the left engine oil drain pan, as described below, and replacement of an inoperative left-hand gear indicator switch. On March 21, 2016, at a time since major overhaul (TSMOH) of 1,059.3 hours and a Hobbs time of 572.7 hours, Aircraft Cylinders & Engines, Inc. (ACE), disassembled and repaired the right engine after the mechanic found spalled lifters during a top overhaul. The engine was reinstalled on the airplane using the existing engine mounts, hoses, and turbocharger components. The last maintenance entry for the right engine was dated April 1, 2016, at a Hobbs time of 573.5 hours and indicated that the right engine cowl flaps had been adjusted. On June 19, 2013, at a Hobbs time of 2,698.1 hours and a TSMOH of 1,703.7 hours, ACE removed, repaired, and then reinstalled the left engine's Nos. 2 and 4 cylinders. According to the records, a new Hobbs meter was installed sometime in 2014; an entry dated December 12, 2014, listed the Hobbs time as 0, the engine total time as 6,698.5 hours, and the TSMOH as 2,051.5 hours. On March 15, 2016, at a Hobbs time of 572.7 hours, ACE overhauled the left engine and installed overhauled turbocharger components. The engine was installed in the left nacelle with new hoses and new engine mounts on March 23, 2016. The last maintenance entry was dated June 6, 2016, at a Hobbs time of 789.6, and it reported WPA installed a Heli-Coil in the left engine oil drain pan.