History of Flight
On October 2, 2017, at about 1230 Pacific daylight time, a Cessna 172S airplane, registration N5311H, sustained substantial damage when it impacted a dry river bed near Tonopah, Nevada. The private pilot was not injured. The airplane was registered to L-Bird, LLC and operated by Tactical Aeronautics (TacAero) under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed Winnemucca Municipal Airport (WMC), Winnemucca, Nevada, at 0900, destined for St. George, Utah.
The pilot had refueled the airplane to capacity with 100 low-lead aviation gasoline. The flight was uneventful until the engine began to sputter as the flight neared a large dry river bed in eastern Nevada. Engine rpm decreased from 2,200 to 1,500. The pilot had both fuel tanks selected on the fuel selector, and both magnetos were engaged. He enrichened the fuel/air mixture by one full rotation but did not move the mixture control to the full rich setting. The throttle was in the full open position. The pilot configured the airplane for a precautionary landing, turned 180° to approach a landing zone with a headwind. After touchdown, the pilot applied back pressure to delay nose gear contact. When the nose gear settled, the airplane stopped abruptly, nosed over, and came to rest inverted. The rudder sustained substantial damage. The debris field included about 200 ft of main landing gear marks and a nose gear impact mark.
The pilot stated that he normally flies with the mixture leaned, and on the day of the accident, he leaned the mixture before departing from Winnemucca (field elevation 4,308 ft msl) and further leaned in flight. The partial power loss occurred shortly after descending from 10,500 ft msl to about 8,000 ft msl.
Pilot Information
The pilot, age 54, held a private pilot certificate with a single-engine land rating. His most recent second-class medical certificate was issued on August 15, 2016, with the limitation that he must have glasses available for near vision. He reported 145 total flight hours, of which 9 were in the accident airplane make and model. He was the Director of Maintenance for the operator.
Aircraft Information
The 2002-model Cessna 172S was powered by a Lycoming IO-360-L2A fuel-injected engine (180 hp). The most recent 100-hour inspection was completed on August 1, 2017, at a total time of 1,770.4 flight hours. At the time of the accident, the engine had 1,810 hours of total time in service.
Engine Examination
A postaccident examination on January 9, 2018, by Textron Aviation under NTSB supervision found the engine mounts unremarkable and the case intact. Loose sand and debris were on the battery and engine cases. Continuity of mixture and throttle controls was confirmed. The air filter was clean. The top spark plugs were gray with some carbon deposits, consistent with normal wear. The ignition harness leads showed normal wear except the cylinder no. 1 lead, which had foreign debris. Continuity from the magneto switch to the harness leads was verified, and spark was observed when the propeller was turned.
Fuel system: A trace amount of 100LL fuel was drained from the strainer. The fuel selector moved normally through its detents. Flight control continuity was confirmed. The wing flap actuator was not extended, consistent with flaps retracted.
An engine test was conducted: the original propeller had aft bending and was replaced with a test propeller. The engine started after priming and ran rough at idle before a run-up at 1,800 rpm. Both magnetos showed a drop of about 100 rpm. Idle performance was smooth at about 500 rpm. Full power produced 2,300 rpm without roughness. Fuel flow, amperage, oil temperature, and oil pressure were normal. After the test, bottom spark plugs exhibited normal wear; cylinder no. 2 had lead deposits on the cone, and cylinder no. 3 had bridging between the cone and ground electrode, but no bridging between electrode and post. Fuel injectors were unobstructed. The fuel strainer had trace debris but was not blocked. Fuel lines from the wing roots to the engine-driven pump were clear.
Meteorological Information
The 1253 weather observation at Yelland Field, about 60 nm northeast of the accident site, included wind from 250° at 5 knots, visibility 10 miles, few clouds at 8,000 feet, temperature 8°C, dew point -11°C, and altimeter setting 29.91 inHg.
Additional Information
The Pilot's Operating Handbook emergency procedures for engine failure in flight include setting airspeed to 68 kts, fuel shutoff valve on, fuel selector to both, auxiliary fuel pump on, mixture rich, and ignition switch to both. The POH normal procedures for descent state to adjust mixture for smooth operation and set fuel selector to both. An engine manufacturer representative reported that the engine may suffer leaning misfires if the mixture is not enrichened during a descent.