Aircraft Incident/Accident Report


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

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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 EventAccident 
Event Date11/2/1999 
Event Day of the WeekTuesday 
Time of Event1118 
Event Time ZonePacific Standard Time 
Event CitySTITES  
Event StateIDAHO 
Event Country-- 
Zipcode of the event site83552  
Event Date Year1999 
Event Date Month11 
MidAir Collision IndicatorNo 
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 airportOff Airport/Airstrip 
Distance from airport in statute miles-- 
Degrees magnetic from airport-- 
Airport Elevation-- 
Weather Briefing CompletenessUnknown 
Investigator's weather sourcePilot 
Time of the weather observation0  
Direction of event from weather observation facility (degrees)
Weather Observation Facility ID  
Elevation of weather observation facility
Distance of event from weather observation facility (units?)
Time Zone of the weather observation  
Lighting ConditionsDay 
Lowest Ceiling Height
Lowest Non-Ceiling Height
Sky/Lowest/Cloud ConditionsClear 
Sky Condition for Lowest CeilingNone 
Visibility Runway Visual Range (Feet)
Visibility Runway Visual Value (Statute Miles)
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)
Variable Wind IndicatorUnknown 
Wind Speed (knots)
Wind Velocity Indicator Calm 
Wind Gust IndicatorNot Gusting 
Wind Gust (knots)
Altimeter Setting at event time (in. Hg) -- 
Density Altitude (feet)-- 
Intensity of PrecipitationUnknown 
METAR weather report -- 
Event Highest InjurySerious 
On Ground, Fatal Injuries
On Ground, Minor Injuries
On Ground, Serious Injuries
Injury Total Fatal-- 
Injury Total Minor-- 
Injury Total None
Injury Total Serious
Injury Total All
Investigating AgencyNTSB 
NTSB Docket Number (internal use)1943 
NTSB Notification Source-- 
NTSB Notification DateNov 2 1999 12:00AM 
NTSB Notification Time1306 
Fiche Number and/or location -used to find docket informationIMAGE 
Date of most recent change to recordMay 25 2001 4:45AM 
User who most recently changed recorddbo  
Basic weather conditionsUnknown 
FAA District Office-- 
Aircraft Involved
Aircraft #1
Aircraft Registration NumberN5388V 
NTSB NumberSEA00TA013  
Missing Aircraft Indicator
Federal Aviation Reg. PartPublic Use 
Type of Flight Plan filedCompany VFR 
Flight plan Was Activated?-- 
DamageSubstantial 
Aircraft FireNone 
Aircraft ExplosionNone 
Aircraft Manufacturer's Full NameHiller  
Aircraft ModelUH-12E  
Aircraft Series IdentifierUH-12E  
Aircraft Serial Number2099  
Certified Max Gross Weight-- 
Aircraft CategoryHelicopter 
Aircraft Registration ClassU.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
Fixed gear or retractable gearFixed 
Aircraft, Type of Last Inspection100 Hour 
Date of Last InspectionOct 29 1999 12:00AM 
Airframe hours since last inspection57 
Airframe Hours22137 
ELT InstalledYes 
ELT ActivatedYes 
ELT Aided Location of Event SiteNo 
ELT Type-- 
Aircraft Owner NameJAMES R. POPE  
Aircraft Owner Street AddressP.O. BOX 54  
Aircraft Owner CityCLARKSTON  
Aircraft Owner StateWA 
Aircraft Owner Country  
Aircraft Owner Zipcode99403  
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 CodeGGVA 
Owner has at least one certificateYes - certificate holder 
Other Operator of large aircraft?No 
Certified for Part 133 or 137 OperationExternal Load 
Operator Certificate Number-- 
Indicates whether an air carrier operation was scheduled or notUnknown 
Indicates Domestic or International FlightUnknown 
Operator carrying Pax/Cargo/MailUnknown 
Type of Flying (Per_Bus / Primary)Public Use 
Second Pilot on BoardNo 
Departure Point Same as EventNo 
Departure Airport Code  
Departure CityCLARKSTON  
Departure StateWA 
Departure Country  
Departure Time930 
Departure Time ZonePST 
Destination Same as Local Flt-- 
Destination Airport Code  
Destination CityGRANGEVILLE  
Destination StateID 
Destination Country  
Specific Phase of FlightClimb 
Report sent to ICAO?-- 
Evacuation occurred-- 
Date of most recent change to recordOct 22 2001 3:26PM 
User who most recently changed recorddbo  
Since inspection or accident-- 
Event Location Runway Number and Location0  
Runway Length-- 
Runway Width-- 
Sight Seeing flightNo 
Air Medical FlightNo 
Medical Flight--