Sikorsky CH-54A accident near Yucca Valley, California, July 18, 1998
On July 18, 1998 at about 11:25 pm local time, a Sikorsky CH-54A (helicopter), registered N64KL, was destroyed in an accident near Yucca Valley, California. It was a positioning flight under general aviation rules (Part 91). 3 people were killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
An in-flight main rotor blade spar separation as a result of the pilot-in-command's decision to continue to fly the aircraft after it had failed an AD directed BIM check. Factors were the failure of the operator's chief pilot to maintain proper supervision over the operation of a company aircraft with a known grounding deficiency and the improper repair to the main rotor blade by unknown persons, which damaged the blade's spar.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 18, 1998 · about 11:25 pm local time
- Place
- Yucca Valley, California · map
- Type
- Accident
- Injuries
- 3 people were killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Sikorsky CH-54A
- Registration
- N64KL · no longer on the register · serial 68-18449
- Damage
- Destroyed
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
While in cruise flight, a main rotor blade separated. The helicopter exploded in flames and crashed. The green blade had failed an AD directed BIM check the evening prior to the accident. The crew chief recharged the blade with nitrogen and allowed the helicopter to remain parked overnight. The next morning he checked the BIM and found it had retained its charge. The crew of the accident aircraft, who were accompanied by the company's chief pilot in a second aircraft, made the decision to continue to fly the helicopter to its destination. There were several cellular calls both to and from the operator on the evening before the accident. A new exclusive-use contract for both aircraft was already in effect. The maintenance history of the green blade contained an unspecified minor repair after a reported overhaul. The operator stated that, at no time, had it performed any maintenance or repair to the blade. After the blade's mating fracture surfaces were examined, it was found that a hole had been drilled from the underside into the spar. The hole terminated at a conical point that is consistent with a drill bit. Fatigue banding could be seen in the immediate vicinity of the hole. Striations near the conical point, typical of fatigue, were seen with a SEM. The drill hole was under a blade pocket and had not been visible during previous inspections. There is no prescribed inspection/maintenance procedure short of removing the blade pockets that would have revealed the hole. Blade pockets are condition items. Stop-drilling cracks in blade pockets to prevent crack propagation is an authorized military maintenance procedure. Drilling into the spar as part of the process is not authorized.
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: single-engine land; instructor: helicopter; rotorcraft: helicopter
- Flight time: 13,000 hours in all; 10,000 in this make and model; 11,000 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 4,537 hours
- Last inspection: approved inspection programme
- Maximum gross weight: 42,000 lb
- Seats: 3
- Landing gear: fixed
- Engine: P&W JT-12-4A (turboshaft); 0 hours total
The flight
- Departed from: BLH Blythe CA at 10:43 pm
- Destination: APV Apple Valley CA
- Runway 0
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 300° at 3 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 108°F (42°C), dew point 61°F (16°C)
- Altimeter: 29.00 inHg
- Observation at 10:53 pm from PSP, 24 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 3 |
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.