WPR18LA002 · Cessna 172S S
Cessna 172S S · Accident: loss of engine power (partial) en route
From Winnemucca Municipal Airport (KWMC) to St George Regional Airport (KSGU)
Narrative check · The NTSB narrative appears to contradict this record's location. Values are shown as recorded, not corrected; compare with the narrative.
Event
- NTSB case
- WPR18LA002
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Cessna 172S S
- Aircraft type
- Cessna 172
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N5311H
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Winnemucca Municipal Airport (KWMC), Winnemucca, NVTo St George Regional Airport (KSGU), St. George, UT
- Aircraft age
- About 15 years (built 2002)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of engine power (partial)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft power plant
- Personnel issues › Action/decision
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The private pilot departed for a long cross-country flight with the mixture leaned to the high field elevation. He then further leaned the mixture for lean-of-peak exhaust gas temperature as he climbed the airplane to 10,500 ft mean sea level (msl) for improved fuel efficiency. Thirty minutes into the flight, he descended the airplane to about 8,000 ft msl. The pilot did not enrich the mixture during the approximate 2,500-ft descent. Shortly after, the engine sputtered, followed by a loss of about 700 rpm. He verified the position of the throttle and enriched the fuel/air mixture with one full rotation of the control knob, but he never advanced the knob to the "full rich" position. The pilot then decided to perform a precautionary landing because he was concerned the airplane would not have the power to cross an approaching mountain range. He chose a dry river bed despite the availability of two nearby airports with dirt runways. During the landing, the airplane nosed over and came to rest inverted, which resulted in substantial damage to the rudder.
Postaccident examination of the airframe and engine did not reveal any evidence of preimpact mechanical anomalies that would have precluded normal operation, and the engine achieved full and continuous power during a test run.
The Pilot's Operating Handbook (POH) required a mixture adjustment during the descent for smooth operation, which the pilot did not do during the 2,500-ft descent. An engine manufacturer representative reported that the engine may suffer leaning misfires if the fuel/air mixture is not enriched during a descent. Therefore, it is likely that the engine sputtered and lost partial power due to the pilot's failure to properly enrich the fuel/air mixture during the descent in accordance with the POH. The pilot could have remediated this condition if he had advanced the mixture to the "full rich" position in accordance with the POH emergency procedures; however, instead the pilot made a minor mixture adjustment, which did not restore engine power.
Probable cause
The pilot's failure to enrich the mixture during the descent, as required by the Pilot's Operating Handbook (POH), and his subsequent failure to follow the POH emergency procedures, which resulted in an excessively lean fuel/air mixture and subsequent loss of rpm. Contributing to the accident was the pilot's improper decision to land on unsuitable terrain despite the availability of two nearby airports.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR18LA002
- Event ID
- 20171002X04059
- Case number
- WPR18LA002
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (5)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 182e76256f3773832b0243a8c647ba4b8b67f798f8a0e6cf7009bff116654d0d; retrieved 2026-09-16T05:54:15.722Z.
- Corrected after a review of the NTSB narrative, which states these values explicitly: destination. KSGU is St. George Regional Airport in St. George, Utah; there is no St. George, Nevada airport with that identifier, so the state code NV is wrong.