Mcdonnell Douglas 600N incident near Long Beach, California, October 23, 2001
On October 23, 2001, a Mcdonnell Douglas 600N (helicopter), registered N959SD, was involved in an incident near Long Beach, California (Long Beach airport). It was a public-use flight under public-use (government) rules. No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
The fatigue failure of a 5/16-inch boom attach bolt was most probably caused by the angular misalignment between the tail boom bolt hole and the fuselage mounted nutplate.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- October 23, 2001
- Place
- Long Beach, California · Long Beach · map
- Type
- Incident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Mcdonnell Douglas 600N
- Registration
- N959SD · registry record · serial RN-019
- Damage
- Not recorded
- Flight
- Public-use flight · public-use (government) rules
The NTSB's narrative final · quoted from the NTSB record
A MDHI 600N helicopter, operated by the Los Angeles County Sheriff's Department, was found to have a fractured tail boom attach bolt during a routine ground examination of the helicopter for evening ground standby duty. The pilot stated that as he pushed sideways on the tail boom it seemed loose. Subsequent examination by maintenance personnel found that the head half of the upper right 5/16-inch tail boom attach bolt was hanging loose by the safety wire. Examination of the bolt revealed that it had failed about three threads from the bolt shank. The remainder of the threaded portion of the bolt remained in the plate nut affixed to the fuselage. Fretting was observed on the fuselage and tail boom mating points in proximity to the fractured bolt. Areas of the bolt shank exhibited polishing. Subsequent examination for collateral damage revealed cracks were present at the aluminum attach fitting and associated angles. The operator examined two of their other 600N helicopters and found those with cracks at the same location. Two other local area law enforcement operators also found cracks in the same location. The tail boom is attached to the fuselage with four special OEM produced bolts. The helicopter tail boom is required to be removed every 300 flight hours for inspection, and, in addition is occasionally removed for other servicing procedures. Examination of the maintenance records disclosed that the bolts may have been through about 10 torque cycles. The bolts have no life limit. The failed 5/16-inch bolt, p/n HS5482-5-18, is torqued to 150-inch/pounds during installation. On November 2, 2001, MDHI issued service bulletin SB600N-036, which prescribes procedures for inspecting the upper right tail boom, attach bolt, and attach fitting assembly. "The Part 1 inspection requirements of this bulletin shall be accomplished within the next five (5) hours of helicopter operation after the receipt of this bulletin or within thirty (30) days of the issue date of this bulletin, whichever occurs first." "The Part 2 inspection and repair requirements of this bulletin shall be accomplished within the next twenty-five (25) hours of helicopter operation after the receipt of this bulletin or within ninety (90) days of the issue date of this bulletin, whichever occurs first." On November 28, 2001, the FAA issued Priority Letter Airworthiness Directive (Emergency AD) 2001-24-51, mandating compliance with the service bulletin 600N-036.
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
Crew member
No details recorded.
The aircraft
- Maximum gross weight: 4,100 lb
- Seats: 5
- Landing gear: fixed
- Engine: Allison 250-C20 (turboshaft); 0 hours total
The flight
- Departed from: LGB Long Beach CA
- Destination: LGB CA
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 63°F (17°C), dew point 0°F (-18°C)
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 LAX02IA013.