History of Flight
On November 15, 2017, at 1515 mountain standard time, a Cessna T207A, registration N9825M, experienced a total loss of engine power and impacted terrain during a forced landing about two miles west of Rock Springs-Sweetwater County Airport (RKS), Rock Springs, Wyoming. The airplane sustained substantial damage. The commercial pilot and one survey crewmember received minor injuries, and two survey crewmembers received serious injuries. The airplane was registered to Slickrock Air Guides Inc and operated by Aerowest Aviation, dba Redtail Air Inc, under Title 14 Code of Federal Regulations Part 91 as a public-use aerial wild horse and burro survey flight for the Bureau of Land Management (BLM). Visual meteorological conditions prevailed. The flight originated from Miley Memorial Field Airport (BPI), Big Piney, Wyoming, at 1320 and was returning to RKS after completing the aerial survey.
The pilot stated he planned to fly the three crewmembers on a survey estimated at 1:45 hours total flight duration, comprising 1:15 hours for the survey and 30 minutes for the return. The survey altitude was 1,000 feet above ground level (AGL). The flight departed with full fuel in both tanks, totaling 80 gallons, with 36.5 gallons useable per tank. The pilot calculated fuel consumption for start, taxi, takeoff, climb, and cruise as 27 gallons for 1:30 hours. He planned to use fuel from the left tank for the first 1:30 hours. The survey was completed about 1:20 hours, and the GPS indicated a 20-minute return. After 1:30 hours of flight and 10 minutes from the airport, the left fuel gauge was "rapidly shifting from full to ¼." The pilot had previously observed the left gauge behaving similarly—often stuck at full then flickering—when fuel level was low. He believed ¼ tank remained and planned to switch to the right tank upon entering the traffic pattern. On base leg about 3.5 miles from runway 9, at about 900–1,000 feet AGL, just before switching tanks, the engine sputtered. The pilot selected the right tank, pushed the throttle full forward, and turned the auxiliary fuel pump to HI then LOW, but the engine continued sputtering. He turned toward State Highway 370 for a forced landing. During the approach, the stall warning horn sounded; the airspeed indicator showed 65 knots. The pilot lowered the nose to increase airspeed, and the airplane descended rapidly. He could not restart the windmilling engine with periodic use of the auxiliary pump HI setting or the starter. The stall warning horn sounded periodically, prompting nose-lowering each time. Over the road, he extended flaps to full. Realizing a hard landing was imminent, he veered right to land on dirt next to the road to soften impact.
A USGS employee seated behind the pilot in the aft left seat stated the engine sputtered and quit at about 700 feet AGL, and he heard the stall warning horn at about 200 feet AGL. He noted that another of the operator's pilots who flew the accident airplane earlier in the survey would use fuel from the right tank for an hour then switch to the left, whereas the accident pilot used the left tank until empty then switched to the right. A BLM employee in the right front seat corroborated that fuel management procedure and stated he did not hear the stall warning during the flight.
Personnel Information
According to the operator's training records, the pilot began employment on April 9, 2013 as pilot-in-command (PIC) on Cessna 172 airplanes under Part 135. On April 7, 2014, he began flying as PIC on Cessna 207 airplanes and subsequently as PIC on Quest Kodiak 100 airplanes under Part 135. His last proficiency check was a Part 135 check using a Cessna 207, lasting 0.8 hours. The check airman was the operator's director of operations, also an FAASTeam Representative. The records indicated that the operator provided all the pilot's ground and flight training before the accident.
Aircraft Information
The airplane was a 1981 Cessna T207A operated and maintained by Aerowest Aviation, dba Redtail Air Inc. It was also operated and maintained under a Part 135 air carrier and operator certificate. The last annual inspections of the airframe and engine were performed on October 27, 2017, by Red Tail Aircraft Services, Moab, Utah, with a tachometer time of 4,007.2 hours, airframe total time 12,990.9 hours, and engine time since major overhaul 1,024.3 hours. A 50-hour inspection was performed on November 13, 2017, at a tachometer time of 4,047.3 hours. At the accident, the Hobbs meter read 9,395.9 hours and the tachometer read 4,057.3 hours.
The USGS employee stated he witnessed the left fuel gauge inoperative on previous survey flights in April 2017, and the BLM employee also noted the same discrepancy. On September 23, 2003, the FAA issued a Revised Special Airworthiness Information Bulletin (SAIB) CE-03-43R1 regarding resistance and capacitance-type fuel quantity gauging systems on Cessna models. The non-mandatory SAIB recommended a detailed calibration procedure within the next 100 hours or at the next annual, repeated at 5-year intervals or when components are disturbed. The Cessna 207 and T207 Series Service Manual required inspection of fuel quantity indicators and transmitters after 50-hour and 100-hour/annual inspections. Section 16-50 listed troubleshooting for fuel quantity transmitters. Part 91.205 required an operable fuel gauge for each tank under visual flight rules. According to the FAA principal maintenance inspector assigned to the operator, maintenance personnel were never notified of the left fuel gauge issue, and no write-ups appeared in the flight logs as required by Part 135.
The Pilot Operating Handbook (POH) Section 2 listed Vso (white arc lower limit) as 58 KIAS and Vs (green arc lower limit) as 63 KIAS. Section 3 prescribed engine failure restart procedures. The forced landing checklist specified airspeed 85 KIAS with flaps up and 80 KIAS with flaps down. Section 4 noted that stall characteristics are conventional and the stall warning horn sounds 5 to 10 knots above the stall. Section 7 described fuel quantity indicators as electrically operated, calibrated in gallons and pounds, with an empty indication leaving about 3.5 gallons useable per tank. The auxiliary fuel pump system had a yellow/red split-rocker switch. The yellow side (START/ON) operated at flow rates dependent on throttle setting. The red side (EMERG/HI) was for high power failure or extreme vapor purging; it was spring-loaded and automatically turned the yellow side to ON. The POH recommended verifying auxiliary fuel pump operation before running a tank dry and switching tanks at first power loss with the pump ON momentarily. It cautioned against excessive ON use at high altitude and full rich mixture to avoid flooding.
Wreckage and Impact Information
The airplane came to rest about 1.63 nautical miles and 279 degrees from the approach end of runway 9, at an elevation of 6,390 feet mean sea level, on the southern edge of State Highway 370, a two-lane east/west asphalt road. Ground scarring from the road toward the airplane had an approximate heading of 095 degrees, and the tail-to-nose heading was 350 degrees. The terrain was flat, dirt, and brush covered without aerial obstructions. The wing flaps were fully extended. The nose landing gear was buckled and crushed upward and aft into the engine firewall; main landing gear struts displayed upward buckling. The fuselage was buckled near the aft edge. The left fuel tank contained no useable fuel; the right tank contained full fuel but had impact damage and leaked the following day. The throttle and propeller controls were at the forward stop; the mixture control was about ½ inch from its forward stop. The left fuel gauge indicated about 1/3 fuel remaining. A placard above the three-position fuel selector (OFF, LEFT ON, RIGHT ON) read: "WHEN SWITCHING FROM DRY TANK TURN AUX FUEL PUMP 'ON' MOMENTARILY." The wings were removed for recovery.
Fuel transmitter testing of the left and right units (part number C668050-0201) showed both within allowable specification on the lower stop and 5° above. Both were slightly high on the upper stop. The right transmitter moved smoothly; the left transmitter stuck repeatedly when allowed to free-fall from mid-travel to the lower stop. The auxiliary fuel pump could not be tested in the aircraft due to wiring damage but operated normally when removed and powered. The fuel selector showed no mechanical anomalies.
An engine test run was performed with a replacement propeller and auxiliary fuel pump, using an external fuel tank. The engine started and ran at 1,100 rpm, then at full throttle produced manifold pressure 37-38 inHg and 2,600 rpm. After a brief idle, full power was reapplied without anomaly. The trailer and forklift securing the airframe began to move at high power, so power was reduced, idle held for turbocharger cool-down, then shut down. The engine restarted easily with a hot start procedure and ran at low to medium power.
Additional Information
The pilot suggested that the accident could have been avoided if the fuel gauge had been functioning properly, as he would have been alerted to the actual fuel level sooner and switched to the fuller tank earlier. He stated the airplane had never exhibited problems with resuming fuel flow after switching to a fuller tank and believed a fuel line blockage or mechanical issue inhibited flow after the switch. The Airplane Flying Handbook, FAA-H-8083-3B, Chapter 3, notes that best glide airspeed maximizes distance flown during an engine failure, occurring at the highest lift-to-drag ratio.