Individually Owned: 150,657
Corporate Owned: 137,281
Aircraft Accident/Incident Report
Franklin, Wisconsin 53132
Monday, April 27, 1998 15:00 CDT
NTSB Narrative Summary Released at Completion of Accident
The pilot said he felt an abnormal vibration in his helicopter during cruise flight. He said he reduced power and made a partial power auto-rotation to a normal landing in an open field. The on-scene investigation revealed that the tail rotor's hub bolt had fractured completely. The hub bolt attaches the tail rotor assembly to its drive shaft. Examination of the bolt revealed it had failed due to fatigue. Maintenance records showed the bolt had 168.3-hours on it since had been examined. It had been removed from the hub assembly so that new teeter bearings could be installed in the hub. The mechanic said he visually examined the bolt and believed it could be returned to service. The mechanic said he did not use the required teeter bearing alignment tool to reinstall the new bearings because the fit was not tight. He said he did not re-balance the tail rotor assembly afer the work had been done. Re-balancing is a required process according to the manufacturer's maintenance procedures. The mechanic said he told the customer to have it checked if he felt any vibration.
NTSB Probable Cause Narrative
The mechanic's failure to follow the manufacturer's maintenance rebuilding instructions.
Event Information
| Type of Event | Incident |
| Event Date | 4/27/1998 |
| Event Day of the Week | Monday |
| Time of Event | 1500 |
| Event Time Zone | Central Daylight Time |
| Event City | FRANKLIN |
| Event State | WISCONSIN |
| Event Country | -- |
| Zipcode of the event site | 53132 |
| Event Date Year | 1998 |
| Event Date Month | 4 |
| 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 | Not pertinent |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1456 Central Daylight Time |
| Direction of event from weather observation facility (degrees) | 90 |
| Weather Observation Facility ID | MKE |
| Elevation of weather observation facility | 720 |
| Distance of event from weather observation facility (units?) | 10 |
| Time Zone of the weather observation | CDT |
| Lighting Conditions | Dawn |
| Lowest Ceiling Height | 25000 |
| Lowest Non-Ceiling Height | 0 |
| Sky/Lowest/Cloud Conditions | Unknown |
| Sky Condition for Lowest Ceiling | Broken |
| Visibility Runway Visual Range (Feet) | 0 |
| Visibility Runway Visual Value (Statute Miles) | 0 |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 7 |
| Dew Point at event time (in degress fahrenheit) | 2 |
| Wind Direction (degrees magnetic) | 30 |
| Variable Wind Indicator | Unknown |
| Wind Speed (knots) | 12 |
| Wind Velocity Indicator | Unknown |
| 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 | None |
| On Ground, Fatal Injuries | 0 |
| On Ground, Minor Injuries | 0 |
| On Ground, Serious Injuries | 0 |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 2 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 5017 |
| NTSB Notification Source | -- |
| NTSB Notification Date | Apr 27 1998 12:00AM |
| NTSB Notification Time | 1917 |
| Fiche Number and/or location -used to find docket information | IMAGE |
| Date of most recent change to record | Dec 18 2002 11:28AM |
| User who most recently changed record | NTSB\GIUV |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N8331F |
| NTSB Number | CHI98IA136 |
| Missing Aircraft Indicator | N |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | Unknown |
| Flight plan Was Activated? | -- |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Robinson |
| Aircraft Model | R22 BETA |
| Aircraft Series Identifier | R22 BETA |
| Aircraft Serial Number | 2578 |
| Certified Max Gross Weight | 2400 |
| 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 | 2 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | 100 Hour |
| Date of Last Inspection | Apr 19 1998 12:00AM |
| Airframe hours since last inspection | 34 |
| Airframe Hours | 889 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | W.W. HELICOPTER |
| Aircraft Owner Street Address | 2985 HWY L. HANGAR I-1 |
| Aircraft Owner City | EAST TROY |
| Aircraft Owner State | WI |
| Aircraft Owner Country | |
| Aircraft Owner Zipcode | 53120 |
| 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 | |
| Owner has at least one certificate | None |
| Other Operator of large aircraft? | No |
| Certified for Part 133 or 137 Operation | Unknown |
| Operator Certificate Number | -- |
| Indicates whether an air carrier operation was scheduled or not | -- |
| Indicates Domestic or International Flight | -- |
| Operator carrying Pax/Cargo/Mail | -- |
| Type of Flying (Per_Bus / Primary) | Unknown |
| Second Pilot on Board | Unknown |
| Departure Point Same as Event | No |
| Departure Airport Code | MKE |
| Departure City | MILWAUKEE |
| Departure State | WI |
| Departure Country | |
| Departure Time | 0 |
| Departure Time Zone | |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | |
| Destination City | |
| Destination State | |
| Destination Country | |
| Specific Phase of Flight | Cruise |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Feb 26 2001 8:05AM |
| 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 | -- |