Individually Owned: 150,657
Corporate Owned: 137,281
N/A Airport
Aircraft Accident/Incident Report
Piney Flats, Tennessee 37686
Thursday, May 24, 2012 18:30 EDT
NTSB Narrative Summary Released at Completion of Accident
The pilot reported that, while on short final for landing, he heard a “high pitched whine” and that the helicopter’s tail rotor authority subsequently degraded. He immediately initiated a full autorotation to landing. During the landing in a field with uneven terrain, the helicopter was substantially damaged. Postaccident examination revealed that, during the flight, the tail rotor driveshaft (TRDS) had become uncoupled from the drive assembly and main rotor belt transmission. The forward TRDS retention nut was found safety wired; however, it was less than hand tight. The main rotor transmission input aft pinion nut was found backed off the pinion; the nut and pieces of its fractured cotter pin were found captured in grease contained in the TRDS fitting grease cavity. The nut was intact, but it exhibited thread wear. The cotter pin was shorter and thinner than the cotter pin specified in the helicopter manufacturer’s illustrated parts catalog. The grease in the aft pinion splines was discolored, caked, and dry, indicating that it had not been serviced in a long time.
The main rotor transmission input pinion exhibited significant wear on the forward spline set and the aft spline set that engaged the driving spline, which was normally retained by the aft pinion nut. The aft upper H-frame bearing was displaced on the driving spline. The driving splines’ interior spline teeth exhibited severe wear matching the wear on the pinion, and rotation damage was found on the spline ends. Other areas of the pinion exhibited fretting corrosion.
According to the helicopter manufacturer’s Handbook of Maintenance Instructions, during the 1,200-hour inspection, the mechanic was required to remove the upper pulley, inspect the pinion, and torque and safety wire the aft pinion nut during reassembly. The mechanic who performed the 1,200-hour inspection (and others) stated that, during the inspection, he had “never gotten into” the drive assembly, had not checked the torque on the aft pinion nut, and had not inspected the cotter pin.
NTSB Probable Cause Narrative
The mechanic’s improper maintenance of the main transmission aft pinion nut and belt drive system, which resulted in the uncoupling of the tail rotor driveshaft and the subsequent loss of helicopter control.
Event Information
| Type of Event | Accident |
| Event Date | 5/24/2012 |
| Event Day of the Week | Thursday |
| Time of Event | 1830 |
| Event Time Zone | Eastern Daylight Time |
| Event City | Piney Flats |
| Event State | TENNESSEE |
| Event Country | -- |
| Zipcode of the event site | 37686 |
| Event Date Year | 2012 |
| Event Date Month | 5 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 362439N |
| Event Location Longitude | 0822104W |
| Event Location Airport | N/A |
| 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 | 1543 |
| Weather Briefing Completeness | -- |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1853 Eastern Daylight Time |
| Direction of event from weather observation facility (degrees) | 315 |
| Weather Observation Facility ID | TRI |
| Elevation of weather observation facility | 1519 |
| Distance of event from weather observation facility (units?) | 5 |
| Time Zone of the weather observation | EDT |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | 6500 |
| Sky/Lowest/Cloud Conditions | Few |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 27 |
| Dew Point at event time (in degress fahrenheit) | 13 |
| Wind Direction (degrees magnetic) | -- |
| Variable Wind Indicator | Variable |
| Wind Speed (knots) | -- |
| Wind Velocity Indicator | Light and Variable |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 29.96 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | -- |
| Event Highest Injury | None |
| On Ground, Fatal Injuries | -- |
| On Ground, Minor Injuries | -- |
| On Ground, Serious Injuries | -- |
| Injury Total Fatal | -- |
| Injury Total Minor | -- |
| Injury Total None | 2 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 33347 |
| NTSB Notification Source | Pilot/Owner |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Oct 22 2014 5:05PM |
| User who most recently changed record | kenj |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N760DA |
| NTSB Number | ERA12LA368 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | None |
| Flight plan Was Activated? | No |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | SCHWEIZER |
| Aircraft Model | 269C |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | S1326 |
| Certified Max Gross Weight | 2050 |
| Aircraft Category | Helicopter |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | -- |
| Cabin Crew Seats | -- |
| Passenger Seats | -- |
| Total number of seats on the aircraft | 3 |
| Number of Engines | 1 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | Annual |
| Date of Last Inspection | Dec 9 2011 12:00AM |
| Airframe hours since last inspection | -- |
| Airframe Hours | 6489 |
| ELT Installed | No |
| ELT Activated | Unknown |
| ELT Aided Location of Event Site | Unknown |
| ELT Type | -- |
| Aircraft Owner Name | TURBINATOR AVIATION LLC |
| Aircraft Owner Street Address | -- |
| Aircraft Owner City | JOHNSON CITY |
| Aircraft Owner State | TN |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 37601-1560 |
| Operator is an individual? | No |
| Operator Name | TURBINATOR AVIATION LLC |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | -- |
| Operator City | JOHNSON CITY |
| Operator State | TN |
| Operator Country | USA |
| Operator Zip code | 37601-1560 |
| Operator Code | -- |
| Owner has at least one certificate | None |
| Other Operator of large aircraft? | -- |
| Certified for Part 133 or 137 Operation | -- |
| 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) | Personal |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | 0A9 |
| Departure City | Elizabethton |
| Departure State | TN |
| Departure Country | USA |
| Departure Time | 1815 |
| Departure Time Zone | EDT |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | -- |
| Destination City | Piney Flats |
| Destination State | TN |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Oct 22 2014 5:05PM |
| User who most recently changed record | kenj |
| Since inspection or accident | Last Inspection |
| Event Location Runway Number and Location | N/A |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |