N7070Q

HISTORY OF FLIGHTOn September 22, 2017, about 1635 mountain standard time, a Cessna 172L, N7070Q, collided with mountainous terrain near Perkinsville, Arizona. The private pilot and passenger sustained fatal injuries, and the airplane was destroyed by postimpact fire. The airplane was registered to Peach Flyers LLC and was operated by the pilot as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight. Visual meteorological conditions prevailed, and no flight plan was filed for the flight, which departed Ernest A. Love Field Airport (PRC), Prescott, Arizona, at 1621 with an unknown destination.

The pilot told family members that he was planning to fly with his friend, who was the passenger, and stay in the traffic pattern at PRC performing touch-and-go takeoffs and landings.

The Federal Aviation Administration (FAA) provided data from an airport surveillance radar sensor located in Seligman, Arizona (about 57 miles northwest of PRC), and audio recordings from the PRC air traffic control tower. The data revealed that, on the day of the accident, after contacting ground controllers, the pilot switched to the tower frequency and requested a departure to the northeast. The clearance was granted, and after taking off from runway 21R, a radar target with a transponder beacon code of 1200 entered the right downwind leg of the airport traffic pattern and departed to the northeast. Over the next 2 1/2 minutes, the target climbed to a transponder-reported altitude of 7,175 ft mean sea level (msl), about 2,100 ft above field elevation, where it leveled off 2.75 miles northeast of the airport.

For the next 8 minutes, the target began a gradual descent while maintaining the northeast track and a ground speed about 110 knots (See Figure 1). The last target was recorded at 1632:47 traveling at a ground speed of 95 knots just west of the entrance to the Verde River Canyon at an altitude of 4,550 ft msl (750 ft above the river). Beyond the canyon entrance, the Verde River followed a meandering path to the southeast, eventually reaching the town of Cottonwood, Arizona, 15 miles away.

No radar data were available to indicate that the airplane ever emerged from the end of the canyon, nor was there any evidence that the airplane reached Cottonwood.

The following morning, the pilot's family and friends became concerned when they had not heard from him since the previous night. They alerted the local sheriff's department, and at 1108, the FAA issued an Alert Notice. The sheriff's department initiated a helicopter search using radar data and network-based cell phone signal analysis, and the wreckage was discovered about 1300 within the Verde River Canyon, 1.8 miles east-southeast of the last recorded radar target and 19 miles northeast of PRC (see Figure 2).

Figure 1 - Radar track and accident site

Figure 2 – Last radar target and wreckage site AIRCRAFT INFORMATIONThe airplane was manufactured in 1972 and was originally equipped with a 150-horsepower Lycoming O-320 engine. It was upgraded to a 180-horsepower Lycoming O-360 engine in 2005 in accordance with supplemental type certificate (STC) SA4428SW. The upgrade provided for an increase in maximum gross weight from 2,300 to 2,500 lbs, along with associated changes in flight performance and fuel consumption.

The airplane's fuel capacity was 42 gallons, and its fuel consumption varied between 6.1 and 10.3 gallons per hour depending on the airplane's weight, engine power setting, and environmental conditions. The airplane's weight and balance information was not located; however, the airplane owner's manual (AOM) indicated a typical basic empty weight of 1,364 lbs.

The airplane was owned by a limited liability corporation of which the pilot had been a member for about 1 year. The pilot was the predominant operator of the airplane during that period. The airplane was kept in a hangar.

The last fueling records located indicated that the airplane was serviced to capacity with the addition of 25 gallons of 100 low-lead aviation gasoline at Cottonwood Airport (P52) on September 8, 2017. The pilot who flew the airplane and serviced it with fuel stated that the airplane flew well that day and that there were no maintenance discrepancies. He further stated that fuel was typically purchased in Cottonwood, where the fuel prices were lower, before returning to PRC.

The accident pilot was the only pilot to fly the airplane since fueling, during the 1.5-hour instrument training flight that took place on September 20. METEOROLOGICAL INFORMATIONSurface Observations

PRC (elevation 5,045 ft msl) was equipped with an Automated Surface Observation System (ASOS) augmented by the local tower controllers. The observation issued at 1653 indicated wind from 200° at 15 knots gusting to 22 knots, 10 miles visibility, clear sky below 12,000 ft, temperature 19°C, dew point -9° C, altimeter setting of 29.86 inches of mercury (Hg). Gusting wind conditions existed throughout the hottest parts of the afternoon, generally from 180° to 200°, sustained at 12 to 17 knots with gusts to 27 knots.

Similar conditions existed at Sedona Airport (SEZ), 18 miles east of the accident site at an elevation of 4,830 ft msl. The automated weather observation at 1635 indicated wind from 210° at 16 knots gusting to 24 knots, 10 miles visibility or greater, clear skies below 12,000 ft, temperature 21°C, dew point 3°C, altimeter 29.84 inches of Hg.

Sounding

A High-Resolution Rapid Refresh (HRRR) numerical model was obtained from archived data from the National Oceanic and Atmospheric Administration Air Resource Laboratory database for the approximate location of the accident at 1700.

The HRRR model depicted a surface temperature of 23.2°C, a dew point of -3.9°C, relative humidity 16%, density altitude of 6,255 ft, and a surface wind from 210° at 11 knots. The sounding supported strong thermals from the surface to 9,000 ft.

The wind profile indicated south-southwesterly winds from 10 to 20 knots through 10,000 ft. Calculated conditions at the airplane's last radar-observed altitude of 4,550 ft included wind from 210° at 14 knots, a temperature of 21°C, and density altitude near 6,343 ft.

The National Weather Service Flagstaff 1700 sounding, which was launched 28 miles northeast of the accident location, showed similar temperature structures, but with a temperature inversion at 6,240 ft above ground level (agl) and strong thermals from the surface to this level. The wind profile showed wind at the surface from 190° at 10 knots gusting to 26 knots, with wind speeds through to 1,000 ft increasing to 24 knots. The observed sounding indicated a moderate potential for low-level wind shear and a moderate and greater potential for turbulence below 1,000 ft agl.

Pilot Reports and Local Observations

There were no significant pilot reports (PIREPs) of turbulence below 8,000 ft surrounding the period of the accident.

A flight instructor operating in the immediate vicinity of the accident at the time of the accident provided a statement of the conditions that he encountered. He reported south-southwesterly winds near 25 knots, with light turbulence through 9,000 ft. He stated that he did not encounter any significant weather, and indicated that it was an ordinary windy day for the area.

Weather Research and Forecasting Model Simulation

A Weather Research and Forecasting (WRF) numerical model was run to simulate the weather conditions during the period from 1600 through 1700 with regard to wind, vertical motion, and the Richardson number (Ri) for turbulence determination surrounding the time of the accident.

The results of the model supported moderate turbulence over the area, with wind speeds of 18 to 20 knots at the accident site about 1630, with vertical velocities ranging between 300 fpm down to 500 fpm up. AIRPORT INFORMATIONThe airplane was manufactured in 1972 and was originally equipped with a 150-horsepower Lycoming O-320 engine. It was upgraded to a 180-horsepower Lycoming O-360 engine in 2005 in accordance with supplemental type certificate (STC) SA4428SW. The upgrade provided for an increase in maximum gross weight from 2,300 to 2,500 lbs, along with associated changes in flight performance and fuel consumption.

The airplane's fuel capacity was 42 gallons, and its fuel consumption varied between 6.1 and 10.3 gallons per hour depending on the airplane's weight, engine power setting, and environmental conditions. The airplane's weight and balance information was not located; however, the airplane owner's manual (AOM) indicated a typical basic empty weight of 1,364 lbs.

The airplane was owned by a limited liability corporation of which the pilot had been a member for about 1 year. The pilot was the predominant operator of the airplane during that period. The airplane was kept in a hangar.

The last fueling records located indicated that the airplane was serviced to capacity with the addition of 25 gallons of 100 low-lead aviation gasoline at Cottonwood Airport (P52) on September 8, 2017. The pilot who flew the airplane and serviced it with fuel stated that the airplane flew well that day and that there were no maintenance discrepancies. He further stated that fuel was typically purchased in Cottonwood, where the fuel prices were lower, before returning to PRC.

The accident pilot was the only pilot to fly the airplane since fueling, during the 1.5-hour instrument training flight that took place on September 20. WRECKAGE AND IMPACT INFORMATIONThe airplane came to rest at an elevation of 4,290 ft msl on 45° sloping walls at a river turn on the north cut bank of the canyon (See Figures 3, 4). The airplane was located about 200 ft below the canyon rim and 500 ft above the river. The area was strewn with sandstone slabs, rocks, and boulders up to 8 ft in size.

Figure 3 – View of the wreckage site (circled) toward the northwest

Figure 4 – Wreckage site

The airplane cabin and wings came to r...