Kaman K-1200 N314KA

Summary

On 26 July 2003 at about 00:03 local time, a Kaman K-1200 registered N314KA, operated by US Department of Interior (Bureau Indian Affairs), was involved in an accident near Keller, Washington, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

26 July 2003 at 00:03

Classification

Accident

Location

Keller, Washington, United States

Coordinates

48.1219, -118.7489

Aircraft

Kaman K-1200

Registration

N314KA

Category

Helicopter

Engines

1

Operator

US Department of Interior (Bureau Indian Affairs)

Operating rule

Public Use

Purpose of flight

Public Use

Phase of flight

Not recorded

Route

Keller → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

SEA03GA153

1 person died.

Corrosion fatigue within the blade retention bolt bushing(s) of the main rotor blade grip resulting in fatigue, cracking and ultimate separation of the upper grip plate. The separation of the upper blade grip plate led to a dynamic imbalance within the rotor system and the subsequent loss of all four rotor blades in flight.

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

Read the full NTSB narrative

The pilot was returning to pick up a load of water while engaged in firefighting operations. The helicopter was in cruise flight when the pilot radioed "I've got a problem" and "I'm going down." Witnesses observed rotor blades departing from the helicopter. On site examination revealed that all four main rotor blades had departed from their respective rotor hub/blade grip units coming to rest in a circumferential band within several hundred feet of the helicopter's ground impact point. Both main rotor hubs also departed the airframe and were located a short distance north and east of the ground impact site. Post crash examination revealed the presence of extensive corrosion fatigue cracking in the upper half of the blade grip plate associated with blade (s/n) 27B. The crack passed through the 7th blade retention bolt hole from the inboard section of the grip leaving the blade attached at the upper blade grip plate by one bolt inboard of the crack and 5 bolts outboard of the crack. The crack displayed corrosion fatigue striations through most of its surface. The number 7 blade retention bolt bushing was also found to have corrosion fatigue cracking in line with the grip crack. With a crack through the inboard section of the upper blade grip plate occurring, the rigidity of the associated blade (27B) would have been significantly weakened in the vertical axis and dynamic imbalance would have developed leading to successive separation of all four blades.

Quoted verbatim from the NTSB record.