CEN12LA524 · Cessna 177B
Hawkeye Helicopter Cessna 177B · Accident: loss of engine power (partial) while maneuvering
From Shreveport Regional Airport (SHV) to Shreveport Regional Airport (SHV)
Event
- NTSB case
- CEN12LA524
- 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 177B
- Aircraft type
- Cessna 177
- 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
- N17201
- Operator
- Hawkeye Helicopter
- Onboard fatalities
- Unknown
- Route
- From Shreveport Regional Airport (SHV), Shreveport, LATo Shreveport Regional Airport (SHV), Shreveport, LA
- Aircraft age
- Not recorded
- 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
- Maneuvering · low-altitude flying
- 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
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The engine lost partial power without warning during a pipeline patrol flight at 500 feet above ground level. The airplane impacted logs during a forced landing on a logging site. A postaccident examination revealed that the No. 1 cylinder intake valve was not present under its rocker arm tip and that its retainers were worn, deformed, and segmented in the bottom of its rocker box. The tip of the rocker arm was worn consistent with the rocker arm contacting the upper valve stem and its retainer. Inboard of the tip, the rocker arm exhibited a wear mark consistent with contact with the valve spring retainer. Further, the piston exhibited impact marks consistent with valve contact, and the No. 1 intake port exhibited a hole consistent with a liberated valve stem impacting the side of the intake port. It is likely that, when sufficient rocker arm wear occurred, the intake valve was released. The liberated valve was found in pieces in the Nos. 3 and 4 intake tubes. The No. 1 intake valve examination revealed no indications of fatigue in any of the fractures, and the valve face did not exhibit erosion or wear. The intake valve and its guide exhibited no evidence indicating that the valve was stuck. The Nos. 2 through 4 intake valve rocker arms were sectioned, and they met the minimum overhaul hardness specifications, but the depth of the carburized case layer was somewhat shallow consistent with its having been resurfaced during overhaul, which the engine had undergone 878.5 hours before the accident. The wear damage to the failed rocker arm tip precluded the determination of the depth of its carburized layer. However, it is likely that the rocker arm tip's wear occurred because of the thin carburized case layer.
Probable cause
The loss of engine power during a low-level aerial observation flight as the result of the wearing of the rocker arm tip due to a thin carburized case layer, which resulted in a forced landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN12LA524
- Event ID
- 20120807X31724
- Case number
- CEN12LA524
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- 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: 108be4cfd2b370c500a4744e0f4d4c9e73241d8a2d153ff6dd269441f0d36163; retrieved 2026-09-15T19:15:36.717Z.