Bell 206L-1 accident near Los Angeles, California, April 21, 1998
On April 21, 1998 at about 4:30 am local time, a Bell 206L-1 (helicopter), registered N87WC, was substantially damaged in an accident near Los Angeles, California. It was a flight of an unrecorded kind under charter and air-taxi rules (Part 135). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
An overtemp of the engine during start within 10 hours of the accident, and the failure to report the event to the maintenance facility.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- April 21, 1998 · about 4:30 am local time
- Place
- Los Angeles, California · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 206L-1 · all 206L-1s on the register
- Registration
- N87WC · registry record · serial 45201
- Damage
- Substantial damage
- Flight
- Flight of an unrecorded kind · charter and air-taxi rules (Part 135)
The NTSB's narrative final · quoted from the NTSB record
The helicopter lost engine power while on approach to a rooftop helipad, approximately 50 feet high and 50 feet short of the building. The pilot landed the helicopter on the roof, severing the tail boom at the horizontal stabilizer. The Safety Board conducted a teardown examination of the engine. Disassembly of the gas producer turbine support from the power turbine support revealed a fractured first stage turbine wheel, which displayed a nine airfoil chordal segment of the rim separated from the larger portion of the wheel. According to the Allison metallurgist, both the first and second stage turbine wheel blades exhibited evidence of operation of temperatures in excess of 2,200 degrees Fahrenheit. Both primary and secondary rim crack fractures exhibited evidence of exposure to extreme temperatures during the engine start sequence. No evidence of engine oil fire was observed on the gas producer turbine components. Chemical analysis of the affected gas producer turbine components indicated conformance to the specified material types. The Allison metallurgist reported that an overtemperature event occurred as a result of a hot start when both wheels were not at operating temperature; an overtemperature event occurring when the engine was at operating temperatures would have melted the first stage turbine wheel blades. The size of the gamma prime at the altered locations indicated the event occurred approximately within the last 10 hours of engine operation. No hot start or overtemperature event was reported to the maintenance facility.
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, commercial pilot
- Ratings: single-engine land; instrument: airplane; rotorcraft: helicopter
- Flight time: 10,800 hours in all; 1,800 in this make and model; 50 in the last 90 days; 15 in the last 30 days; 10,500 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 3,738 hours
- Last inspection: 100-hour inspection, January 24, 1998; 69 hours since
- Maximum gross weight: 4,050 lb
- Seats: 5
- Landing gear: fixed
- Engine: Allison 250-C28B (turboshaft); 0 hours total
The flight
- Departed from: ONT Ontario CA at 4:10 am
- Runway 0
Weather at the time
- Light: night, dark
- Wind: from 250° at 7 knots
- Visibility: 5 statute miles
- Sky: broken clouds; not recorded
- Temperature: 57°F (14°C), dew point 55°F (13°C)
- Altimeter: 30.00 inHg
- Observation at 4:50 am from LAX, 11 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 2 |
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.