Individually Owned: 150,657
Corporate Owned: 137,281
Bear Dip Landing Zone Airport
Aircraft Accident/Incident Report
Fredonia, Arizona 86022
Thursday, October 16, 2003 16:50 MST
NTSB Narrative Summary Released at Completion of Accident
As the NOTAR (No Tail Rotor) helicopter entered a normal descent for landing, the pilot experienced a loss of control following the failure of the anti-torque system. The helicopter entered an uncommanded and uncontrollable right spin as it descended to ground impact. During the approach, and after passing over a group of trees, while the helicopter was about 15 to 30 feet above ground level (agl) and 60 feet from the intended touchdown location, the helicopter began a rapid, uncommanded right yaw. The pilot input full left pedal pressure in an effort to stop the rotation. Despite his attempts, the pilot's control inputs had no effect on the spin rate. The pilot retarded the left engine throttle, and maneuvered the helicopter away from the trees as it continued to descend. Upon touchdown, the helicopter rolled on its left side, and the main rotor blades impacted terrain. The helicopter's NOTAR anti-torque yaw control system utilizes a transmission driven fan with variable pitch blades to supply air to circulation control slots on the tail boom and a pilot-controlled directional jet thruster nozzle. Movement of the anti-torque control pedals changes the fan blade pitch to produce more airflow to the circulation control slots and the anti-torque thruster nozzle. As the pedals are displaced from center toward either extreme of travel, the airflow increases proportionally. During post-accident examination of the NOTAR control system, a fracture and separation was found in the force limiting control rod. With the rod assembly disconnected, the NOTAR fan blades assume a neutral pitch, preventing a sufficient volume of air in the tail boom to provide anti-torque control and maintain a heading. The helicopter had previous mechanical problems with the rod assembly and it was replaced about 779 hours prior to the accident. Using a scanning electron microscope, an examination of the fracture surface revealed that the rod separated due to a fatigue crack originating from the base of the thread roots, and final tension overload. There was no evidence of damage sites, foreign material inclusions, or other potential fracture initiating conditions.
NTSB Probable Cause Narrative
the pilot's in-flight loss of control due to the fatigue fracture and separation of the force limiting control rod (an integral part of the anti-torque system), which resulted in the helicopter's uncommanded yaw/spin and subsequent collision with terrain.
Event Information
| Type of Event | Accident |
| Event Date | 10/16/2003 |
| Event Day of the Week | Thursday |
| Time of Event | 1650 |
| Event Time Zone | Mountain Standard Time |
| Event City | FREDONIA |
| Event State | ARIZONA |
| Event Country | -- |
| Zipcode of the event site | 86022 |
| Event Date Year | 2003 |
| Event Date Month | 10 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 383323N |
| Event Location Longitude | 121170 W |
| Event Location Airport | Bear Dip Landing Zone |
| Event Location Nearest Airport ID | -- |
| Indicates whether the acc/inc occurred off or on an airport | On Airport |
| Distance from airport in statute miles | 0 |
| Degrees magnetic from airport | -- |
| Airport Elevation | 8970 |
| Weather Briefing Completeness | -- |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1653 Mountain Standard Time |
| Direction of event from weather observation facility (degrees) | 180 |
| Weather Observation Facility ID | GCN |
| Elevation of weather observation facility | 6609 |
| Distance of event from weather observation facility (units?) | 25 |
| Time Zone of the weather observation | MST |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| 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) | 22 |
| Dew Point at event time (in degress fahrenheit) | -8 |
| Wind Direction (degrees magnetic) | 220 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 6 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | 30.36 |
| 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 | 5 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 19201 |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Oct 16 2003 12:00AM |
| NTSB Notification Time | 1700 |
| Fiche Number and/or location -used to find docket information | DMS |
| Date of most recent change to record | Feb 28 2006 12:35PM |
| User who most recently changed record | NTSB\JOHB |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | WP-LAS-FSDO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N179PA |
| NTSB Number | LAX04TA017 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Public Use |
| Type of Flight Plan filed | VFR |
| Flight plan Was Activated? | Yes |
| Damage | Substantial |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | MD Helicopter |
| Aircraft Model | 900 |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 900-00021 |
| Certified Max Gross Weight | 6250 |
| 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 | 10 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | 100 Hour |
| Date of Last Inspection | Sep 29 2003 12:00AM |
| Airframe hours since last inspection | 41.5 |
| Airframe Hours | 2761 |
| ELT Installed | Yes |
| ELT Activated | Yes |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | Gulf Inc. |
| Aircraft Owner Street Address | 12515 Willows Rd. NE Ste. 200 |
| Aircraft Owner City | Kirkland |
| Aircraft Owner State | WA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 98034 |
| Operator is an individual? | No |
| Operator Name | National Park Service |
| Operator Same as Owner? | No |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | No |
| Operator Street Address | P.O. Box 129 |
| Operator City | Grand Canyon |
| Operator State | AZ |
| Operator Country | USA |
| Operator Zip code | 86023 |
| 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) | Public Use |
| Second Pilot on Board | No |
| Departure Point Same as Event | No |
| Departure Airport Code | -- |
| Departure City | North Rim |
| Departure State | AZ |
| Departure Country | USA |
| Departure Time | 1610 |
| Departure Time Zone | MST |
| Destination Same as Local Flt | crash at destination city |
| Destination Airport Code | -- |
| Destination City | FREDONIA |
| Destination State | AZ |
| Destination Country | USA |
| Specific Phase of Flight | Approach - VFR pattern - final approach |
| Report sent to ICAO? | Yes |
| Evacuation occurred | No |
| Date of most recent change to record | Nov 9 2005 11:20AM |
| User who most recently changed record | COOS |
| Since inspection or accident | Time of Accident |
| Event Location Runway Number and Location | -- |
| Runway Length | -- |
| Runway Width | -- |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |