Bell UH 1B accident near Maxwell, California, May 7, 2016
On May 7, 2016, a 1962 Bell UH 1B (helicopter), registered N486SA, was substantially damaged in an accident during takeoff near Maxwell, California. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 7, 2016
- Place
- Maxwell, California · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell UH 1B NO SERIES, built 1962 · all UH 1Bs on the register
- Registration
- N486SA · registry record · serial 62-4583
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Loss of engine power (partial) during takeoff defining event
- Autorotation Hard landing
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine bleed air system › Engine anti › icing system › Malfunction
- cause Aircraft › Aircraft power plant › Engine bleed air system › (general) › Fatigue/wear/corrosion
- cause Aircraft › Aircraft power plant › (general) › (general) › Damaged/degraded
- factor Aircraft › Fluids/misc hardware › Fluids › (general) › Not serviced/maintained
Pilot
- Certificate: commercial pilot
- Ratings: instructor: helicopter; instrument: helicopter; rotorcraft: helicopter
- Flight time: 1,906 hours in all; 213 in this make and model; 203 in the last 90 days; 44.2 in the last 30 days; 1,829.3 as pilot in command
- Medical certificate: Class 2 (without waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 9,132 hours
- Last inspection: annual inspection, July 15, 2015; 106 hours since
- Maximum gross weight: 9,500 lb
- Landing gear: fixed
- Engine: Lycoming T-53-11B (turboshaft); 2,294 hours total
The flight
- Departed from: Maxwell CA
- Destination: Maxwell CA
- Flight plan: none
Weather at the time
- Light: daylight
- Wind: from 170° at 6 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 5,000 ft; a few clouds at 3,000 ft
- Temperature: 68°F (20°C), dew point 54°F (12°C)
- Altimeter: 29.85 inHg
- Observation at 11:53 pm from KMYV, 34 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.