Aircraft Accident/Incident Report

Stites, Idaho 83552
Tuesady, November 2, 1999 11:18 PST

NTSB Narrative Summary Released at Completion of Accident

During a low-altitude fish survey, the helicopter experienced a separation of a control rotor while leveling off from a climb to about 400 feet above ground level (AGL). The pilot initiated an emergency descent but, due to severely reduced cyclic controllability resulting from the separation, was unable to avoid power lines in the aircraft's emergency descent flight path. The helicopter struck the power lines about 50 feet AGL and fell to the ground, landing hard but upright. Post-accident examination disclosed a fatigue failure in the cuff which retains the control rotor blade. The fatigue originated on two opposite sides of a retaining bolt hole that appeared to have been unevenly hand chamfered or deburred during original manufacture of the cuff, with gouging and sharp-bottomed dents visible at the origins. However, while a company mechanic had signed off an Airworthiness Directive (AD) requiring recurring inspection of the cuff about two months/56 flight hours before the accident, post-accident examination disclosed evidence indicative of inadequate inspection and maintenance of the assembly, including: old dried grease between the cuff and control rotor blade spar, large areas of the spar missing required paint with associated corrosion areas, and zinc chromate primer in corrosion pits. The FAA-approved Hiller service bulletin referenced by the AD contains procedures for inspection of spar tube retention bolt holes for 'elongation, corrosion, burrs, pitting or fretting' and associated repair procedures, but does not contain any instructions to inspect or repair bolt holes in the control rotor cuff for those same conditions.

NTSB Probable Cause Narrative

Inadequate inspection of the control rotor cuff by a company mechanic and subsequent fatigue fracture of the cuff, resulting in an inflight separation of the control rotor blade. Factors contributing to the accident were: inadequate quality control during manufacture; insufficiently defined manufacturer's inspection and repair procedures; inadequate FAA approval of the manufacturer's inspection and repair procedures; power lines in the helicopter's emergency descent flight path; and reduced aircraft controllability following the control rotor separation.

Event Information

Type of Event Accident
Event Date 11/2/1999
Event Day of the Week Tuesday
Time of Event 1118
Event Time Zone Pacific Standard Time
Event City STITES
Event State IDAHO
Event Country --
Zipcode of the event site 83552
Event Date Year 1999
Event Date Month 11
MidAir Collision Indicator No
On Ground Collision occurred ? No
Event Location Latitude --
Event Location Longitude --
Event Location Airport
Event Location Nearest Airport ID
Indicates whether the acc/inc occurred off or on an airport Off Airport/Airstrip
Distance from airport in statute miles --
Degrees magnetic from airport --
Airport Elevation --
Weather Briefing Completeness Unknown
Investigator's weather source Pilot
Time of the weather observation 0
Direction of event from weather observation facility (degrees) 0
Weather Observation Facility ID
Elevation of weather observation facility 0
Distance of event from weather observation facility (units?) 0
Time Zone of the weather observation
Lighting Conditions Day
Lowest Ceiling Height 0
Lowest Non-Ceiling Height 0
Sky/Lowest/Cloud Conditions Clear
Sky Condition for Lowest Ceiling None
Visibility Runway Visual Range (Feet) 0
Visibility Runway Visual Value (Statute Miles) 0
Visibility (Statute Miles) 50
Air Temperature at event time (in degrees celsius) 18
Dew Point at event time (in degress fahrenheit) --
Wind Direction (degrees magnetic) 0
Variable Wind Indicator Unknown
Wind Speed (knots) 0
Wind Velocity Indicator Calm
Wind Gust Indicator Not Gusting
Wind Gust (knots) 0
Altimeter Setting at event time (in. Hg) --
Density Altitude (feet) --
Intensity of Precipitation Unknown
METAR weather report --
Event Highest Injury Serious
On Ground, Fatal Injuries 0
On Ground, Minor Injuries 0
On Ground, Serious Injuries 0
Injury Total Fatal --
Injury Total Minor --
Injury Total None 1
Injury Total Serious 2
Injury Total All 2
Investigating Agency NTSB
NTSB Docket Number (internal use) 1943
NTSB Notification Source --
NTSB Notification Date Nov 2 1999 12:00AM
NTSB Notification Time 1306
Fiche Number and/or location -used to find docket information IMAGE
Date of most recent change to record May 25 2001 4:45AM
User who most recently changed record dbo
Basic weather conditions Unknown
FAA District Office --

Aircraft Involved

Aircraft #1

Aircraft Registration Number N5388V
NTSB Number SEA00TA013
Missing Aircraft Indicator N
Federal Aviation Reg. Part Public Use
Type of Flight Plan filed Company VFR
Flight plan Was Activated? --
Damage Substantial
Aircraft Fire None
Aircraft Explosion None
Aircraft Manufacturer's Full Name Hiller
Aircraft Model UH-12E
Aircraft Series Identifier UH-12E
Aircraft Serial Number 2099
Certified Max Gross Weight --
Aircraft Category Helicopter
Aircraft Registration Class U.S. Registered/U.S. Soil
Aircraft is a homebuilt? No
Flight Crew Seats --
Cabin Crew Seats --
Passenger Seats --
Total number of seats on the aircraft --
Number of Engines 1
Fixed gear or retractable gear Fixed
Aircraft, Type of Last Inspection 100 Hour
Date of Last Inspection Oct 29 1999 12:00AM
Airframe hours since last inspection 57
Airframe Hours 22137
ELT Installed Yes
ELT Activated Yes
ELT Aided Location of Event Site No
ELT Type --
Aircraft Owner Name JAMES R. POPE
Aircraft Owner Street Address P.O. BOX 54
Aircraft Owner City CLARKSTON
Aircraft Owner State WA
Aircraft Owner Country
Aircraft Owner Zipcode 99403
Operator is an individual? --
Operator Name
Operator Same as Owner? Yes
Operator Is Doing Business As --
Operator Address Same as Owner? Yes
Operator Street Address
Operator City
Operator State
Operator Country
Operator Zip code
Operator Code GGVA
Owner has at least one certificate Yes - certificate holder
Other Operator of large aircraft? No
Certified for Part 133 or 137 Operation External Load
Operator Certificate Number --
Indicates whether an air carrier operation was scheduled or not Unknown
Indicates Domestic or International Flight Unknown
Operator carrying Pax/Cargo/Mail Unknown
Type of Flying (Per_Bus / Primary) Public Use
Second Pilot on Board No
Departure Point Same as Event No
Departure Airport Code
Departure City CLARKSTON
Departure State WA
Departure Country
Departure Time 930
Departure Time Zone PST
Destination Same as Local Flt --
Destination Airport Code
Destination City GRANGEVILLE
Destination State ID
Destination Country
Specific Phase of Flight Climb
Report sent to ICAO? --
Evacuation occurred --
Date of most recent change to record Oct 22 2001 3:26PM
User who most recently changed record dbo
Since inspection or accident --
Event Location Runway Number and Location 0
Runway Length --
Runway Width --
Sight Seeing flight No
Air Medical Flight No
Medical Flight --