Bell UH-1B accident near Lost Hills, California, August 25, 1999
On August 25, 1999 at about 6:00 am local time, a Bell UH-1B (helicopter), registered N999SJ, was substantially damaged in an accident near Lost Hills, 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).
Preview. This page is not yet listed for search engines.
The NTSB's probable cause their words, unchanged
Failure and separation of the 90-degree gearbox as a result of the disengagement of the pinion and gear teeth. The cause(s) of the pinion and gear disengagement were undetermined.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 25, 1999 · about 6:00 am local time
- Place
- Lost Hills, 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 · all UH-1Bs on the register
- Registration
- N999SJ · registry record · serial 1025
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
During the takeoff initial climb as the helicopter accelerated through 25 to 30 miles per hour, the 90-degree gearbox fractured through the center of the gearbox case and separated from the tailboom. The pilot was able to slow the spin rate and performed a hovering autorotation. A portion of the tail boom impacted a barbed wire fence as the helicopter settled vertically. Metallurgical examination of the gearbox case fractures disclosed overload features. Internal examination of the gearbox and gears showed that the pinion and gear teeth had disengaged. The disengagement lasted a short period of time. As a result of the disengaged gear and pinion rotating against each other, the gearbox case became overloaded and subsequently separated. The wear patterns on the pinion and gear teeth drive side did not meet the patterns specified in the maintenance manual; the patterns extended off the toe ends and the tips of the teeth. The gearbox, which is an 'on-condition' component, was last overhauled or repaired in 1984. There is no requirement for an internal inspection of the tail rotor gearbox during routine or annual maintenance inspections.
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
Pilot
- Certificate: airline transport pilot
- Ratings: instrument: helicopter; rotorcraft: helicopter
- Flight time: 11,500 hours in all; 6,500 in this make and model; 90 in the last 90 days; 38 in the last 30 days; 11,000 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 7,856 hours
- Last inspection: annual inspection, April 24, 1999; 43 hours since
- Maximum gross weight: 8,500 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming T53-L11B (turboshaft); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: night, bright
- Wind: from 210° at 4 knots
- Visibility: 10 statute miles
- Sky: not recorded; clear
- Temperature: 75°F (24°C), dew point 57°F (14°C)
- Altimeter: 29.00 inHg
- Observation at 5:56 am from BFL, 34 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| 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.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number LAX99LA283.