Hughes 369HS accident near Pacific Ocean, PO, June 20, 1997
On June 20, 1997 at about 10:30 am local time, a Hughes 369HS (helicopter), registered N4250N, was destroyed in an accident near Pacific Ocean, PO. It was an other work-use flight under general aviation rules (Part 91). 1 person was killed and 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The unapproved field modification of the cyclic trim switch, including the use of non-standard parts, which resulted in a hard-over lateral trim failure, and the pilot's subsequent failure to maintain control of the helicopter during a landing approach. A factor in the accident was the operator's failure to comply with a factory service bulletin, which required replacement of the switch with a new version, and the pilot's continued operation with a known discrepancy.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 20, 1997 · about 10:30 am local time
- Place
- Pacific Ocean, PO
- Type
- Accident
- Injuries
- 1 person was killed and 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Hughes 369HS · all 369HSs on the register
- Registration
- N4250N · no longer on the register · serial 450734S
- Damage
- Destroyed
- Flight
- Other work-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot was spotting tuna off a ship and was approximately 10 minutes from the ship when the cyclic went full left travel. The pilot, who had not attended any factory training courses on this helicopter, said he tried to get the trim motor to reengage but to no avail. He was unable to get the cyclic to return to a neutral position. He stated that he came in to land on the boat and lost control of the helicopter because he could not hold the cyclic with one hand. The helicopter struck an antenna, rolled to the left, and landed upside down in the water. The pilot indicated to others he had problems with the trim switch on previous flights. The owner's manual states that the cyclic stick forces with a runaway cyclic would be approximately 30 pounds. It states that the helicopter will respond normally to all cyclic inputs by the pilot. The switch was returned and disassembled for detailed examination. The manufacturer could not find any identifiable markings on the switch during the examination and tool marks and other internal evidence disclosed that the switch had been disassembled and reassembled in the field. Non-standard parts were found on the inside of the switch. Boeing Helicopters sent out a mandatory service information notice dated March 10, 1994, which required all operators of the 369/500 helicopters to replace all four-way trim switches with the revision 'D' four-way trim switch. The switch is not a repairable item. No repair manual or spare parts programs exist for this switch.
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: commercial pilot
- Ratings: rotorcraft: helicopter
- Flight time: 3,132 hours in all; 248 in this make and model
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 3,908 hours
- Last inspection: annual inspection, February 2, 1997; 118 hours since
- Maximum gross weight: 2,200 lb
- Seats: 2
- Landing gear: fixed
- Engine: Allison 250-C18 (turboshaft); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 220° at 15 knots
- Visibility: 20 statute miles
- Sky: scat at 2,500 ft
- Temperature: 84°F (29°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | 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.
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.