Sikorsky CH-54A N64KL

Summary

On 18 July 1998 at about 23:25 local time, a Sikorsky CH-54A registered N64KL was involved in an accident near Yucca Valley, California, United States. 3 people were on board and 3 died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

18 July 1998 at 23:25

Classification

Accident

Location

Yucca Valley, California, United States

Coordinates

34.1495, -116.2708

Aircraft

Sikorsky CH-54A

Registration

N64KL

Category

Helicopter

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

Blythe → Apple Valley

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

LAX98FA236

3 people died.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.