Eurocopter MBB-BK117-B2 N909CP

Summary

On 15 April 1997 at about 21:37 local time, a Eurocopter MBB-BK117-B2 registered N909CP was involved in an accident near New York, New York, United States. 4 people were on board and one died, 2 were seriously injured, one had minor injuries. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

15 April 1997 at 21:37

Classification

Accident

Location

New York, New York, United States

Nearest airport

60TH Street Heliport (6N4)

Coordinates

40.7590, -73.9695

Aircraft

Eurocopter MBB-BK117-B2

Registration

N909CP

Category

Helicopter

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Executive/Corporate

Phase of flight

Not recorded

Route

Unknown → White Plains

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

NYC97FA076

1 person died.

Fatigue failure of the vertical fin, accelerated by the installation of blind rivets in lieu of solid rivets in the replacement of the yaw SAS mount support, which resulted in the loss of helicopter directional control and collision with the terrain (water). Factors contributing to the accident were: a lack of information regarding repair of the yaw SAS mount support in the manufacturer's maintenance manuals, and the design of the vertical fin which was susceptible to fatigue cracking. An additional factor was the lack of an adequate passenger briefing.

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

Read the full NTSB narrative

After taking off, the helicopter climbed to approximately 30 feet, and produced a loud bang. The helicopter rotated nose right several times, descended, struck the heliport pier and continued into the East River where it submerged. The pilots were evacuated underwater; the passengers were found in the cabin unconscious and recovered by divers. The throttles were found in the flight position. The investigation revealed that the upper 3 feet of the vertical fin had failed due to fatigue fractures and had separated, along with the tail rotor assembly. About 4 1/2 years prior, the left-hand yaw SAS actuator mounting plate attached to the vertical fin developed a crack and was replaced using blind rivets in lieu of the solid rivets specified in the manufacturer's design drawings. Neither the repair nor the substitution of rivets was addressed in the manufacturer's maintenance manual. Literature from the rivet manufacturer indicated that blind rivets may be substituted for solid rivets in most applications. No specific reference by the FAA was found to allow for this rivet substitution. The investigation revealed 11 other helicopters with fatigue cracking in the vertical fin spar similar to the accident helicopter. Testing revealed that materials fastened with blind rivets are more susceptible to fatigue cracking than materials fastened with solid rivets. Passenger interviews disclosed that many were not aware of emergency exit locations, or how to operate them; life vests were available, but were not used.

Quoted verbatim from the NTSB record.