Bell 222U N225LL

Summary

On 14 April 2000 at about 21:12 local time, a Bell 222U registered N225LL was involved in an accident near St. Paul, Minnesota, United States. 2 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

14 April 2000 at 21:12

Classification

Accident

Location

St. Paul, Minnesota, United States

Coordinates

44.9707, -93.2003

Aircraft

Bell 222U

Registration

N225LL

Category

Helicopter

Engines

2

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Positioning

Phase of flight

Not recorded

Route

St. Paul → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CHI00FA111

Nobody was injured.

The loss of clamp-up force between the transmission case and the pylon mounted actuator support assembly which resulted in fatigue failure of the threaded studs and dowel pins, the failure of the flight control system, helicopter control not being possible after the flight control failure, and the inadequate maintenance procedures by the company maintenance personnel.

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

Read the full NTSB narrative

During cruise flight the pilot lost control of the helicopter and an uncontrolled forced landing was made onto the top of a two-story industrial warehouse. The pylon mounted actuator support assembly had separated from the transmission case. The support assembly, attachment hardware, and portions of the transmission case were sent to the NTSB Materials Laboratory for analysis. According to the NTSB Materials Laboratory Factual Report, "... all of the studs showed progressive fatigue cracking from multiple origins." The report stated, "All but one stud fracture ... showed progression from diametrically opposed sides, typical of reversed bending fatigue loads." The report stated that all of the stud and dowel holes in the actuator support were, "... elongated on opposite sides from contact with the respective dowel or stud." The report further stated, "In addition to the elongation of the holes, the faying surfaces of the support and the transmission case were severely worn from relative movement. The directions of indicated movements and wear correspond to the axis of elongation of the respective support holes." The lead mechanic for the helicopter reported that one of the dowel pins was found during routine maintenance approximately one year prior to the accident date and the maintenance staff did not determine the identify the source of the dowel pin.

Quoted verbatim from the NTSB record.