Bernard, ID, USA
N922MA
CESSNA TU206F
The pilot departed on a scenic air tour flight with two passengers over an area of mountainous terrain. After surveying the desired location, the pilot chose to fly up a canyon (drainage) to return to the departure airport. The pilot stated that he could not completely recall the events of the accident flight but reported that as the airplane neared the top of the canyon, he realized that the rate of climb was insufficient to clear the terrain ahead, and he initiated a 180° turn. He stated that he remembered extending the wing flaps but did not remember when. After starting the turn, the airplane encountered a downdraft and descended into trees. Data from an onboard GPS device indicated that the airplane entered the canyon at an altitude about 6,000 ft about 4 minutes before the impact. The airplane continued to climb until the final 3 seconds of recorded data. During the last approximate 2 minutes of recorded data, the airplane climbed from an altitude about 7,000 ft to about 8,300 ft. The airplane’s pitch attitude, which had not previously exceeded about 9° nose-up during the flight, exceeded 10° nose-up for much of the final minute of the flight and increased to a maximum of 17° nose-up about 5 seconds before the end of the data. During the final minute of the flight, the speed remained below 80 knots, ultimately decreasing to below 65 knots during the final 15 seconds of recorded data. A performance analysis indicated that, given the airplane’s gross weight and the atmospheric conditions present at the time of the accident, the airplane would have required nearly 2 additional minutes to reach and clear the top of the canyon. Postaccident examination of the wreckage did not reveal any preimpact mechanical anomalies. The wing flaps were found fully extended at the accident site. Full flap extension would have adversely affected the airplane’s climb performance; however, the point at which the flaps were fully extended could not be determined. The pilot had extensive low-level flight experience in military jets; however, he had about 28 total hours and about 3 months of experience in the accident airplane, and the accident flight was his first scenic flight with passengers. Review of weather conditions indicated light wind conditions with no evidence of mountain wave activity. The density altitude in the area of the accident site was near 10,000 ft. The circumstances of the accident are consistent with the pilot’s decision to continue into a canyon that exceeded the climb performance of the airplane, which resulted in impact with terrain during an attempted course reversal.
HISTORY OF FLIGHTOn August 28, 2021, about 1316 mountain daylight time, a Cessna TU206F, N922MA, was substantially damaged when it was involved in an accident near Bernhard, Idaho. Both passengers were fatally injured, and the pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 nonscheduled charter flight. The accident flight was a scenic flight that one of the passengers had arranged for the purpose of scouting fishing locations. The airplane was equipped with an Appareo Stratus 3i GPS device. Data obtained from the unit indicated that the airplane departed McCall, Idaho, at 1232 and made a climbing left turn to the northeast toward mountainous terrain. At 1240, the airplane turned to the east and continued its climb until it reached an altitude of about 8,800 ft mean sea level (msl). The airplane then began a slow descent into the canyons of the Frank Church Wilderness. About 8 minutes later, the airplane made a left turn to the north and started a climb from about 7,200 ft msl. The airplane followed a path between canyon walls and then descended again after it reached an altitude of about 8,000 ft msl. The data showed that the airplane began a right turn to the east at 1257 and descended to about 5,300 ft msl, where it completed a 180° turn inside a canyon and then continued to fly east. The airplane overflew Soldier Bar Airport at 1309 and continued east for about 3 nautical miles (nm). Three minutes later, the airplane made a right turn to the south. The pilot was able to recount few of the final moments of the accident flight. He recalled that his passengers were ready to return home after they overflew Soldier Bar Airport, so he began to search for a drainage in the direction of their departure airport. The data showed that, once the airplane was established on its southerly heading, the pilot began a climb from an altitude of about 5,300 ft msl. At 1312, the pilot located a suitable drainage and made a right turn to the west toward McCall while he continued to climb. His goal was to overfly the mountain peaks at the end of the drainage. As the airplane started to approach the top of the drainage, near the ridge line, the pilot, who had been flying near the right side of the drainage, crossed over to the left side of the drainage. About this time, he determined that the airplane’s rate of climb was insufficient to fly over the peak at the end of the drainage and he decided to make a 180° turn to climb to a higher altitude. At this point, the data showed the airplane about 1 nm from the top of the ridgeline and the airplane slowed to a groundspeed of about 62 knots while it continued to climb, at which time the pilot began a right turn. According to the pilot, he encountered a downdraft after starting the turn and was unable to maintain altitude despite the application of full power and full propeller rpm, and his vertical speed indicator showed a rapid descent. The pilot stated that he remembered extending the wing flaps but could not recall when and stated that he would not have extended the flaps fully. He recalled “riding the edge of stall into the trees because I had nowhere to go.” He added that the stall warning horn was triggered intermittently while the airplane descended into trees. During the last approximate 2 minutes of recorded data, the airplane climbed from an altitude about 7,000 ft to about 8,300 ft. The airplane’s pitch attitude, which had not previously exceeded about 9° nose-up during the flight, exceeded 10° nose-up for much of the final minute of the flight, and increased to a maximum of 17° nose-up about 5 seconds before the end of the data. During the final minute of the flight, the speed remained below 80 knots, ultimately decreasing to below 65 knots during the final 15 seconds of recorded data. The data showed that the airplane’s groundspeed was about 55 kts at an altitude of 8,397 ft msl when the flight track data ended about 90 ft from the accident site. A signal from the airplane’s 406 MHz emergency locator transmitter was received by the Air Force Rescue Coordination Center at 1318, and a search was initiated. The wreckage was located about 1646. Figure 1: Accident airplane flight path from Soldier Bar Airstrip to Accident Site PERSONNEL INFORMATIONThe pilot was an experienced military fighter jet pilot with extensive low-level flight training. He reported that this was the first scenic flight he had flown. Before the accident flight, he had completed multiple charter flights that involved flying passengers between destinations. The pilot reported that he was not familiar with the Cessna 206 before May 2021. He completed most of his training in the accident airplane make and model with the director of operations of McCall Aviation. These flights comprised “landing pattern stuff…just basic flight characteristics. We’d go out and do approach turn stalls, regular stalls…full stall characteristics of the airplane.” During this time, they performed several local flights together to nearby airfields such as Donnelly and New Meadows, towns located about 10 nm south (at an elevation about 4,800 ft msl) and 9 nm northwest (at an elevation about 3,900 ft msl), respectively, of the operator’s base. The pilot stated that he felt the training was “pretty thorough for general aviation” and that each flight was accompanied by a “one hour long brief and debriefing afterwards.” During his training, they did not fly into any drainages; however, the director of operations would use nearby peaks to demonstrate how to properly fly within the mountain range while flying at nearby airports such as New Meadows. The pilot provided the example that he was taught to find the updraft on one side of a ridge between McCall and New Meadows for additional lift during a climb. That summer, he flew the Cessna 206 into small airfields within the Frank Church Wilderness. Having recently started flying charter in the Cessna 206, he frequently followed the other airplanes during group flights so he could observe their movements. The pilot added that, by the time of the accident, he had flown in and out of drainages multiple times by himself in the accident airplane make and model. According to the operator’s records, the pilot was signed off to fly the accident airplane on June 14, 2021. On the day of the accident, pilot departed on a charter flight to Salmon, Idaho, at 0640 and returned about 1025. METEOROLOGICAL INFORMATIONMETEOROLOGICAL INFORMATION Another charter pilot who flew to an airfield located about 43 nm east of the accident site on the morning of the accident reported that the weather conditions were “beautiful” and the wind was light. Weather observations captured by an unofficial station located about 8 miles north of the accident site at an elevation of 4,575 ft msl showed a temperature of 75°F, dewpoint 37°F, wind from 050° true, sustained wind magnitude of 2 mph and a wind gust magnitude of 7 mph. A high resolution rapid refresh (HRRR) model for the accident location at 1300 indicated the following conditions: Height (ft) Temp (C) Density Altitude Pressure Altitude (ft) (computed) 8182 13 9483 7845 8218 11.5 9349 7880 8254 10.7 9303 7914 8435 10.2 9457 8088 8690 9.2 9644 8333 9058 8 9939 8686 8504 6.5 10295 9114 Table 1: HRRR model meteorological data A review of Graphical Turbulence Guidance, which provides forecasts of information related to the expected intensity of clear-air or mountain wave turbulence, showed some light mountain wave activity in Colorado and southeastern Idaho between 7,000 and 11,000 feet at the time of the accident. The graphical forecast did not show any evidence of eddy dissipation in the Frank Church Wilderness at the time of the accident. High-resolution rapid refresh (HRRR) model sounding data was analyzed by the RAwinsone Observation Program. The table below shows the vertical wind profile from the RAOB data. Table 2: HRRR Wind profile interpolated by RAOB A pilot with about 13 years of experience flying the Idaho backcountry and who was familiar with the accident area noted that he typically worried about downdrafts when the wind reaches about 25 kts at 9,000 ft but reported that mechanical downdrafts can also occur when the wind speed is lower than 25 kts. WRECKAGE AND IMPACT INFORMATIONThe airplane was located on the east side of a mountain in the Payette National Forest at an elevation of about 8,370 ft msl, about 1,000 ft below the mountain’s peak. The initial point of impact was marked by an approximate 60-ft-tall tree that was severed at the top, located 120 ft from the main wreckage. A 50-ft-wide debris path was oriented on a northwesterly heading and identified by several broken trees between the initial impact point and the main wreckage that were consistent with an impact with terrain while in level flight. A portion of the right wing was located in the debris path a few feet from the main wreckage, which comprised the rest of the airplane. The airplane was oriented on an easterly heading. All major components of the airplane were accounted for at the accident site. Figure 2: Accident site and surrounding terrain Postaccident examination of the wreckage did not reveal any preimpact mechanical anomalies that would have precluded normal operation. Flight control continuity was traced from the cockpit controls to the aileron, elevator, and rudder control surfaces. Both the elevator control cables and the rudder cables were cut by recovery personnel. The right aileron direct cable exhibited signatures consistent with overload separation. The elevator trim tab had separated from the horizontal stabilizer; however, the actuator measured outside the normal operation range in the tab trailing end up deflection. The flap actuator position was consistent with the flaps in the near full down position, which was also consistent with the indications at the flap handle and flap position indicator. Examination of the engine established mechanical continuity throughout the rotating group, valve train, and accessory section as the crankshaft was manually rotated by hand at the propeller. The magnetos produced spark at all six plug leads and most of the spark plugs displayed signatures consistent with normal wear, except for three spark plugs that had some evidence of oil. Examination of the interior components, including the cylinders, piston, and valves using a lighted borescope revealed no indications of catastrophic engine failure. ADDITIONAL INFORMATIONADDITIONAL INFORMATION Performance Calculations The airplane's rate of climb was calculated using performance charts derived from the pilot’s operating handbook (POH). Using the operator’s reported weight at the time of the accident of about 3,200 lbs, the climb figures from 6,000 ft (the starting altitude at the drainage) to 9,000 ft (the lowest peak in the drainage where the accident occurred) were based on a nearby reported temperature of 18ºC at 6,000 ft and 8°C at 9,000 ft. The calculations indicated that, under normal operating limitations (at a maximum weight of 3,300 lbs per the POH), and an airspeed of about 95 kts, the airplane would have required about 5 minutes to climb from 6,000 ft msl to 9,000 ft msl. Factoring in an additional 15% to adjust for temperature, which was about 11° warmer than standard, the airplane would have required about 5 minutes 45 seconds to make the climb. According to the flight data, the accident occurred about 4 minutes and 5 seconds after the pilot began climbing from 6,000 ft msl. The terrain elevation at the bottom of the drainage increased from about 4,000 ft msl when the airplane turned into the drainage to about 8,000 ft msl, when the airplane began to descend over the course of about 6 nm. From the point of descent to the top of the lowest peak increased about 1,000 ft in elevation over the course of about 0.6 nm. Mountain Flying Training In addition to the practical training the pilot received, he also attended company training in May 2021, which included a presentation on mountain flying. Some of the subjects that were covered included “Clearing Mountains,” which comprised excerpts from a book on mountain flying, and an additional topic on “Course Reversal.” The “Clearing Mountains” section contained some basic guidance on having an “escape route” and selecting a canyon (drainage): ? Always remain in a position where you can turn toward lowering terrain. o This axiom also encompasses the idea that you will not enter or fly in a canyon where there is not sufficient room to turn around. Another way of stating this truth is to have an escape route in mind and be in a position to exercise this option. The pilot stated that his escape route was “simply to turn around” and that he did not remember having selected a point to abort when he was flying up the drainage. The “Clearing Mountains” section also incorporated instructions for turning around in rising terrain: ? Do not fly beyond the point of no return. o This is the position when flying upslope terrain where, if you reduce the throttle to idle and begin a normal glide, you will have sufficient altitude to turn around without impacting the terrain.” o As you near the ridge, when arriving at a position where the power can be reduced to idle and the airplane will glide to the top of the ridgeline, a commitment to cross the ridge can be made. The “Course Reversal” section comprised 1 page and included the following guidance: ? Everyone flying in the mountains will encounter situations when it becomes necessary to make a 180° turn. o To turn around, slow down. This will decrease the radius of turn. o Pull back on the control wheel to trade airspeed for altitude if you have extra speed. o Then make the steepest turn you can comfortably make, up to 60°. Airplane Stall Characteristics and Indicators According to the pilot’s operating handbook, “the stall characteristics are conventional and aural warning is provided by a stall warning horn which sounds between 5 and 10 knots above the stall in all configurations.”
The pilot’s decision to continue the flight into a canyon that exceeded the performance capabilities of the airplane, which resulted in an impact with trees an terrain.
Source: NTSB Aviation Accident Database
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