LAX99LA241 · Rockwell 690B
Rockwell 690B · Accident: gear collapsed during landing
From 48V · TRI-COUNTY, CO to Monterey Regional Airport (MRY)
Event
- NTSB case
- LAX99LA241
- 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
- 0
- 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
- Instrument Meteorological Cond
Rockwell 690B
- Aircraft type
- Rockwell 690
- 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
- N480K
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From 48V · TRI-COUNTY, COTo Monterey Regional Airport (MRY)
- 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
- Landing
- First occurrenceThe 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
- Gear collapsed
- 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
- Landing gear, gear locking mechanism › Overload
- Other maintenance personnel › Maintenance, adjustment, improper
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot and copilot reported that they were on approach and as they passed the outer marker, they observed three green lights indicating the landing gear was extended. They observed hydraulic pressure of about 1,000 psi during the landing checks. The pilot said he landed the airplane with a slight tailwind, observed two beta lights, and he pulled the power levers into ground idle/reverse. Shortly thereafter, he felt the left landing gear collapse and he observed one red unsafe light and two green landing gear lights, with a corresponding gear warning horn. Postaccident examination of the left main gear revealed that a piece was fractured from the inboard gear-forging boss, which houses a clevis for the attachment of the hydraulic cylinder. The clevis remained attached to the hydraulic cylinder, which in the fully extended position is consistent with gear down. Metallurgical examination of the fracture faces revealed features typical of overstress separation. No pre-existing cracks or other defects were found on the fracture. A review of the Commander maintenance manual indicates that an adjustment must be made to the cylinder over travel following gear maintenance to obtain the proper drag brace preload. The left hand hydraulic cylinder, main landing gear aft wheel well door, and hydraulic components were replaced about 34 hours before the accident.
Probable cause
The failure of maintenance personnel to properly adjust the drag brace preload during recent landing gear maintenance, which resulted in the overload failure and separation of the hydraulic cylinder attach boss.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX99LA241
- Event ID
- 20001212X19047
- Case number
- LAX99LA241
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
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. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 1999-06-17.
- API snapshot SHA-256: eece336e9b036addb44e64365343a56ae06588614782853258c32cb4593d3a02; retrieved 2026-09-22T14:48:55.907Z.