# Accident 19990824013459A: Bell UH1B, Lost Hills, CA, August 24, 1999 - Type: FAA accident report (Accident/Incident Data System), as reported - Date: August 24, 1999, 23:00 local time - Place: Lost Hills, CA - Damage: Substantial damage - Phase of flight: To Init Climb(1st Pwr Reduct) - Operating rules: Agricultural (Part 137) - Operator: CUFG - Location: 35.6094° N, 119.8995° W: From the FAA, an estimate near the named town, within about 3 miles - Nearby events: https://openairdocs.org/map.md?lat=35.6094&lon=-119.8995&mi=10 - Aircraft: N999SJ, a cancelled registration (https://openairdocs.org/deregistered/N999SJ-2020-05-29) (OpenAirDocs) - Registry model: Bell UH-1B (registry code 1181410, https://openairdocs.org/model/bell-uh-1b) (OpenAirDocs) - Registry engine: Lycoming T-53 series (registry code 41552, https://openairdocs.org/engine/lycoming-t-53-series) (OpenAirDocs) - Reported make and model: BELL UH1B - Reported engine: LYC T53L11B - People aboard: 1 - Fatal injuries: 0 - Pilot flight hours: 11,500 total, 6,500 in this make and model, 90 in the last 90 days - NTSB investigation: [NTSB LAX99LA283](https://openairdocs.org/ntsb/LAX99LA283) (OpenAirDocs) - FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/) - Page: https://openairdocs.org/incident/19990824013459A ## Narrative As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^. 1963 BELL UH-1B HELICOPTER CRASHED ON TAKE-OFF AND SUSTAINED SUBSTANTIAL DAMAGE, OTHER CIRCUMSTANCES ARE UNKNOWN.(-23) A BHT-UH1B HELI, N99SJ, SERIAL #1025, CRASHED ON DEPARTURE DURING AGRICULTURAL SPRAYING OPERATIONS,IN A FIELD LOCATED APPROX. 13.5 MILES WEST NORTH WEST FROM LOST HILLS, CA. 93249. AFTER TAKE-OFF, WHILE MAINTAINING FOUR TO FIVE FEET SKID HEIGHT, THE HELI WENT THROUGH EFFECTIVE TRANSITIONAL LIFT, AND CONTINUED TO GAIN AIRSPEED. BETEEN 20 TO 30 MPH GROUND SPEED THE PIC HEARD A LOUD BANG, THE HELI LOST DIRECTIONAL CONTROL. THE HELI MADE APPROX. THREE 360 DEGREE RIGHT TURNS BEFORE CONTACTING THE GROUND. AFTER THE HELI CONTACTED THE GROUND THE FORWARD SECTION OF THE COMPLETELY CRACKED 90 DEGREE GEARBOX FELL TO THE GROUND. (.4)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 NTSB's investigation of this event (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB LAX99LA283](https://openairdocs.org/ntsb/LAX99LA283), Aug 25, 1999: Bell UH-1B (N999SJ), Lost Hills, CA, substantial damage. Probable cause: 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. From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.