WPR16LA104 · Bell UH 1B
Jones Flying Service Bell UH 1B · Accident: loss of engine power (partial) during takeoff
From Maxwell, CA to Maxwell, CA
Event
- NTSB case
- WPR16LA104
- 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
Bell UH 1B
- Aircraft type
- Bell UH-1
- Category
- Helicopter
- 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
- N486SA
- Operator
- Jones Flying Service
- Onboard fatalities
- Unknown
- Route
- From Maxwell, CATo Maxwell, CA
- Aircraft age
- About 54 years (built 1962)
- 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 137: Agricultural
- 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
- Takeoff
- 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 from the NTSB case API, not marked as estimated; no uncertainty radius is established.
NTSB narrative
The commercial pilot reported that, after loading the helicopter with chemical for the agricultural application flight, he completed a pre-takeoff checklist, noted that all instrument indications were normal, and initiated a takeoff from the loading truck platform. As the helicopter climbed over the tree canopy, the rotor and engine rpm began to rapidly decay. The pilot initiated a right turn in an attempt to gain airspeed and recover rotor rpm; however, the attempt was unsuccessful, and he initiated a forced landing within an almond orchard. The helicopter landed hard and came to rest upright.
The postaccident engine test run revealed a stuck, partially-open hot air valve used for engine inlet anti-icing. The open hot air valve allowed compressor bleed air to escape the power flow path, thereby reducing the maximum power that the engine could produce before reaching its maximum exhaust gas temperature limitations. The manufacturer of the engine reported that, with the partially-open hot air valve, the engine would only produce about 80% of its maximum power.
Further examination of the hot air valve revealed a lack of dry film lubricant on the flow surfaces in addition to corrosion buildup throughout the valve assembly. The dry film lubricant reduces friction between the sliding elements, allowing for smooth, unimpeded motion of the valve. The lack of lubricant coating in these areas would increase the sliding friction such that the closing spring would be unable to overcome the friction forces, causing the valve to remain open even when commanded closed. It is likely that the valve became stuck before the accident flight, which would have resulted in reduced power available for takeoff.
The engine overhaul manual indicated that an inspection of the hot air valve should occur with an overhaul of the engine. A review of the engine logbooks revealed that the engine was overhauled about 9 years before the accident and that the helicopter had accumulated about 598 hours since the overhaul. There were no logbook entries pertaining to the inspection of the hot air valve.
Probable cause
A reduction in available engine power during takeoff due to a stuck hot air valve, which resulted in low rotor rpm and a forced landing. Contributing to the accident was the lack of dry film lubricant and the presence of corrosion on the hot air valve assembly, which resulted in the sticking of the valve.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR16LA104
- Event ID
- 20160511X23030
- Case number
- WPR16LA104
- 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: local date, investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2016-05-07.
- API snapshot SHA-256: 4f8627987633d482bb07695e6771f2cfb2ad5f2c791c349fdb278f9e19d6c12a; retrieved 2026-09-16T03:22:46.167Z.