Hughes 369HS accident near Pacific Ocean, PO, June 7, 1999
On June 7, 1999 at about 9:00 am local time, a Hughes 369HS (helicopter), registered N4278M, was destroyed in an accident near Pacific Ocean, PO. It was an aerial observation flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The removal of the tail rotor blade abrasion strips by the use of an unapproved method by the maintenance personnel which resulted in the imbalance of the tail rotor blade assembly and subsequent separation of the 90-degree gear box; the pilot/mechanic's unapproved repair to the tail rotor blade tip caps; and, his continued operation of the helicopter with known deficiencies.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 7, 1999 · about 9:00 am local time
- Place
- Pacific Ocean, PO
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Hughes 369HS · all 369HSs on the register
- Registration
- N4278M · registry record · serial 230450S
- Damage
- Destroyed
- Flight
- Aerial observation flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
About 10 minutes into a fish spotting mission from a fishing vessel, the pilot felt an intense vibration through the tail rotor pedals and helicopter control became increasingly difficult. About 250 feet above the water, the 90-degree gear box and tail rotor assembly separated. The helicopter spiraled down toward the water, spinning to the right with an estimated 55- to 60-degree nose-down attitude. The pilot reported the last moments before contacting the water were 'uncontrollable.' The helicopter was recovered, except for the tail rotor system rotating components and gearbox. The operator reported that he had removed the tail rotor abrasion strips from the blades during an annual inspection about 73 hours before the accident. He reported that he applied 'direct and intense heat' to the blades to remove the strips. According to the manufacturer, the abrasion strips can be removed; however, it must be done by an approved blade overhaul facility and cannot be accomplished in the field. The manufacturer stated that the use of heat is unauthorized and likely induced a bond separation within the tip cap area. A review of the McDonnell Douglas maintenance manual revealed that tail rotor blade repairs are not specifically addressed. A McDonnell Douglas representative reported that if a repair is not addressed in the manual, it is not authorized. He stated that certified blade repair stations are authorized expanded repairs. The pilot/mechanic reported that he was aware that the operator had removed the tail rotor abrasion strips and had observed a small gap between one of the tail rotor blade tip caps and the blade during a routine inspection before the accident. He contacted the operator and requested a new blade. He then applied clear epoxy resin at the joining surfaces then test-flew the helicopter and noticed 'no change in the flight characteristics of the aircraft.' He stated that he felt the 'blade [was] airworthy and was as originally constructed.' McDonnell Douglas Service Bulletin HN-195 directs mechanics to visually inspect the tip cap-to-blade bonding for failure and states that 'if any evidence of debonding is noted, replace blade.'
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: 3,046 hours in all; 1,825 in this make and model
- Medical certificate: Class 2 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 8,168 hours
- Last inspection: annual inspection, April 16, 1999; 73 hours since
- Maximum gross weight: 2,550 lb
- Seats: 2
- Landing gear: fixed
- Engine: Allison 250-C20B (turboshaft); 0 hours total
The flight
- Departed from: Fishing Vessel at 8:45 am
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 120° at 18 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 81°F (27°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 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.