N9825MCessna T207A · 1981

On November 15, 2017, at 1515 mountain standard time, a Cessna T207A, 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 at the time of the accident. The flight originated from Miley Memorial Field Airport (BPI), Big Piney, Wyoming at 1320 and was returning to RKS after having completed the aerial survey.

The pilot stated he was to fly the three crewmembers on the survey, which he estimated to have a flight duration of 1:45 hours. The fight duration consisted of 1:15 hours for the survey and 30 minutes for the return to RKS. The altitude of the survey portion of the flight was 1,000 feet above ground level (AGL). He stated the flight departed with full fuel in the left and right fuel tanks for a total of 80 gallons, of which 36.5 gallons were useable in each tank. His fuel consumption calculations for start, taxi, takeoff, climb, and cruise yielded a total of 27 gallons for 1:30 hour of operation. He planned to use fuel from the left fuel tank for 1:30 hours. He stated that the survey was completed about 1:20 hours, and the GPS indicated the return to RKS was 20 minutes. After 1:30 hours of flight time and 10 minutes from the airport, he looked at the left fuel gauge and "it was rapidly shifting from full to ¼." He stated that he had seen this behavior with the left gauge before as it was "often stuck at a full reading then flicked back and forth between full and the actual fuel level," when the fuel level in the tank was lower. He thought there was ¼ tank of fuel remaining and planned to switch to the right fuel tank upon entry into the airport traffic pattern. The airplane was on a base leg about 3.5 miles from runway 9, about 900-1,000 feet AGL (700 feet above airport elevation) when the pilot was going to select the right fuel tank. Just before he switched to the right fuel tank, the engine sputtered. The pilot then selected the right fuel tank, pushed the throttle control full forward, and selected the auxiliary fuel pump to HI and then LOW, but the engine continued to sputter. He looked for a place to land and turned toward State Highway 370 for a forced landing. During the approach to the road, the stall warning horn sounded; the pilot looked at the airspeed indicator and saw it indicated 65 knots. He lowered the airplane nose to increase airspeed, and the airplane was "descending rapidly." He was unable to restart the wind-milling engine with periodic selection of the auxiliary pump HI setting and by using the engine starter. The pilot stated that the stall warning horn would sound periodically, which prompted him to lower the airplane nose each time. When the airplane was over the road, he extended the flaps to full. He realized it was going to be a hard landing when the airplane was close to the road surface. He veered the airplane right to land in the dirt next to the road to soften the landing.

A United States Geological Service (USGS) employee, who was seated behind the pilot in the aft left seat, stated the engine sputtered and quit while the airplane was about 700 feet AGL, and he heard the stall warning horn when the airplane was about 200 feetAGL. He said that another one of the operator's pilots that flew the accident airplane the first week of the survey would use fuel from the right fuel tank for an hour then use fuel from the left fuel tank. The employee stated that the accident pilot would use fuel from the left fuel tank until it was empty and then use fuel from the right fuel tank.

A BLM employee, who was seated in the right front seat, stated that he did not hear the stall warning during the accident flight. He witnessed the same procedure used by the accident pilot in fuel management as reported by the USGS employee.

According to the operator's training records for the pilot, the pilot began employment for the operator 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. The pilot passed his last proficiency check, which was a Part 135 proficiency check that was 0.8 hours in duration, using a Cessna 207 airplane. The check airman for the proficiency check was the operator's director of operations, who was also a FAASTeam Representative. The records showed that the operator provided all the pilot's ground and flight training prior to the accident.

The airplane was a 1981 Cessna T207A operated and maintained by Aerowest Aviation, dba Redtail Air Inc. In addition to its Part 91 operations, the airplane was also operated and maintained under a Part 135 air carrier and operator certificate.

Aircraft Maintenance Information

The airplane and engine underwent their last annual inspections, dated October 27, 2017 and were performed by Red Tail Aircraft Services, Moab, Utah. The tachometer time of the inspections was 4,007.2 hours, the airframe total time was 12,990.9 hours, and the engine time since major overhaul was 1,024.3 hours. A 50-hour inspection of the airplane, dated November 13, 2017, was performed by the Red Tail Aircraft Services at a tachometer time of 4,047.3 hours.

The Hobbs and tachometer indications at the time of the accident were 9,395.9 hours and 4,057.3 hours, respectively.

The USGS employee stated he witnessed the same discrepancy of an inoperative fuel gauge on previous survey flights flown in April 2017. The BLM employee stated that he witnessed the left fuel gauge as inoperative on previous flights flown in April 2017.

On September 23, 2003, the FAA issued a Revised Special Airworthiness Information Bulletin (SAIB) CE-03-43R1, which updated information issued in SAIB CE-03-43, dated June 27, 2003. The SAIB, which was not mandatory, informed owners or operators of Cessna model 100, 200, 300, and 400 series airplanes, that a safety concern exists regarding resistance and capacitance-type fuel quantity gauging systems. The SAIB recommended an FAA-certificated mechanic or repair station accomplish the detailed calibration procedure within the next 100 hours of operation or at the next annual. Further, the calibration procedure should be repeated by a properly FAA-certificated mechanic or repair station at 5-year intervals or any time the fuel gauging system components are disturbed or accuracy is suspect.

According to the Cessna 207 and T207 Series Service Manual, the fuel quantity indicators and transmitters were to be inspected after a 50-hour and 100-hour/annual inspection. Section 16-50 of the manual, Troubleshooting – Fuel Quantity Transmitters, lists in part:

Part 91.205, Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements, stated in part, that no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation under visual flight rules unless that aircraft had a fuel gauge indicating the quantity of fuel in each tank that was in an operable condition.

According to the FAA principle maintenance inspector assigned to the operator, the operator's maintenance personnel were never notified nor were there any write ups prior to the accident regarding the left fuel gauge in the flight logs, as required by Part 135 maintenance regulations.

Pilot Operating Handbook Information

Section 2, Limitations, stated that the lower limit of the airspeed indicator white arc, Vso, in a landing configuration at maximum weight was 58 knots indicated airspeed (KIAS). The lower limit of the green arc, Vs, at most forward CG at maximum weight was 63 KIAS.

Section 3, Emergency Procedures, listed the engine failure restart procedures during flight as:

The Emergency Procedure checklist for Forced Landings stated the airspeed for flaps UP as 85 KIAS and flaps DOWN as 80 KIAS.

Section 4, Normal Procedures, Stalls, stated:

"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."

Section 7, Airplane Systems and Systems Descriptions, pertaining to the fuel quantity indicators, stated in part:

"Fuel quantity is measured by two float-type fuel quantity transmitters (one in each tank) and indicated by two electrically operated fuel quantity indicators on the right side of the instrument panel. The fuel quantity indicators are calibrated in gallons (lower scale) and pounds (upper scale). An empty tank is indicated by a red line and the letter E. When an indicator shows an empty tank, approximately 3.5 gallons remain in each standard or long-range tank as useable fuel. …"

The systems description of the auxiliary fuel pump system stated the auxiliary fuel pump switch is a yellow and red split-rocker switch. The yellow (right) half of the switch is labeled "START," and its upper "ON" position is used for normal starting, minor vapor purging, and continued engine operation in the event of an engine-driven fuel pump failure. With the yellow half of the switch in the "ON" position, the pump operates at one of two flow rates that are dependent on the setting of the throttle. With the throttle open to a cruise setting, the pump operates at high enough capacity to supply sufficient fuel flow to maintain flight with an inoperative engine-driven fuel pump.

The red (left) half of the switch is labeled "EMERG," and its upper "HI" position is used in the event of an engine-driven fuel pump failure during takeoff or high power operation. The "HI" position may also be used for extreme vapor purging. Maximum fuel flow is produced when the left half of the switch is held in the spring-loaded "HI" position. In this position, an interlock within the switch automatically trips the right half of the switch to the "ON" position. When the spring-loaded left half of the switch is released, the right half will remain in the ON position until manually returned to the off position.

"If it is desired to completely exhaust a fuel tank quantity in flight, the auxiliary fuel pump will be needed to assist in restarting the engine when fuel exhaustion occurs. Therefore, it is recommended that proper operation of the auxiliary fuel pump be verified prior to running a fuel tank dry by turning the auxiliary fuel pump "ON" momentarily and checking for a slight rise in fuel flow indication.

To ensure a prompt engine restart in flight after running a fuel tank dry, immediately switch to the tank containing fuel at the first indication of fuel pressure fluctuation and/or power loss. Place the right half of the fuel pump switch in the "ON" position momentarily (3 to 5 seconds) with the throttle at least ½ open. Excessive use of the "ON" position at high altitude and full rich mixture can cause flooding of the engine as indicated by a short (1 to 2 second period) period of power followed by a loss of power. If flooding does occur, turn off the auxiliary fuel pump switch, and normal propeller wind-milling should start the engine in 1 to 2 seconds."

The airplane was located 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, which was a two-lane east/west asphalt road. Ground scarring from the southern edge of the road toward the airplane had an approximate heading of 095 degrees, and the approximate tail-to-nose heading of the airplane was 350 degrees. The area around the road was devoid of aerial obstructions and its terrain features were flat, dirt, and brush covered.

The wing flaps were fully extended. The nose landing gear was buckled and crushed upward and aft into the engine firewall, and the main landing gear struts displayed upward buckling. The fuselage was buckled near the aft edge of the fuselage. The left fuel tank contained no useable fuel, and the right tank contained full fuel. The right fuel tank had impact damage and was broken open, and the fuel leaked out 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. There was a placard above the three-position fuel selector (OFF, LEFT ON, RIGHT ON) that stated:

"WHEN SWITCHING FROM DRY TANK TURN AUX FUEL PUMP 'ON' MOMENTARILY"

The wings were removed to facilitate the recovery of the airplane to a salvage facility where an additional examination of the airplane and an engine run were performed.

Fuel Transmitter Testing

The left and right fuel transmitters were of the resistive type and were both stamped with part number C668050-0201. The following numbers were also stamped on the left and right transmitters respectively, 7740 167 G81 and 7740 167 D90. The left and right fuel quantity transmitters were removed from the wings and tested with an ohmmeter. The test results were as follows:

Both transmitters were within the allowable specification on the lower stop and 5° above the lower stop. Both transmitters were slightly higher than the specification on the upper stop. The right fuel quantity transmitter moved smoothly from stop to stop. The left fuel quantity transmitter did not move smoothly from the upper stop to the lower stop; when it was positioned near mid-travel and allowed to free-fall to the lower stop; it repeatedly stuck in place.

The auxiliary fuel pump in the aircraft could not be used for the engine test run due to wiring damage in the lower forward fuselage area. The auxiliary fuel pump operated without anomaly after it was removed and connected to an electrical source of power.

Examination of the fuel selector revealed no mechanical anomalies that would have precluded normal operation.

Engine Test Run

Exterior examination of the engine (Continental TSIO-520-PcRcM, serial number 513025) revealed that all its accessories/components were attached and secure. The fuel system was intact, secure and displayed no evidence of leakage. Engine control continuity from the cockpit to the engine was confirmed. Borescope examination of the engine through the top spark plug holes revealed no mechanical anomalies. The top spark plugs displayed features of normal wear and operation.

In preparation for the engine test run, the airframe and attached engine were secured to a trailer and forklift. The propeller and the auxiliary fuel pump were replaced. A portable fuel tank containing 100 low-lead aviation fuel was connected to the fuel system. The engine was started and operated at 1,100 rpm to warm the engine to operating temperatures. At full throttle, the manifold pressure was about 37-38 inches of mercury, and the engine speed was about 2,600 rpm. Engine power was reduced to idle and after about one minute was returned to full power and operated without anomaly. The trailer and forklift began to move, and engine power was reduced to idle. Engine power was kept at idle power for about one minute to allow the turbocharger to cool and was then shut down. The engine was restarted without hesitation using a hot start procedure. The engine was operated at low to medium power due to the previous movement of the trailer and forklift at higher power settings.

In the pilot's recommendation of how the accident could have been avoided, he stated, due to his fuel calculations and the lack of any substantial headwinds, he felt he had enough fuel left in the left tank to reach the traffic pattern. If the fuel gauge had been functioning properly, he would have been alerted to the actual fuel level sooner and would have changed to the fuller tank sooner. This airplane has never exhibited any problems with resuming full fuel flow immediately after switching to a fuller tank. He believed there was either a fuel line blockage or a mechanical problem that inhibited fuel flow once switched to the fuller tank.

The Airplane Flying Handbook, FAA-H-8083-3B, Chapter 3, Basic Flight Maneuvers, stated in part:

"The best glide airspeed is used to maximize the distance flown. This airspeed is important when a pilot is attempting to fly during an engine failure. The best airspeed for gliding is one at which the airplane travels the greatest forward distance for a given loss of altitude in still air. This best glide airspeed occurs at the highest lift-to-drag ratio (L/D). When gliding at airspeed above or below the best glide airspeed, drag increases."

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