Individually Owned: 150,657
Corporate Owned: 137,281
South Lafourche Airport
Aircraft Accident/Incident Report
Galliano, Louisiana 70354
Wednesday, January 19, 2011 11:34 CST
NTSB Narrative Summary Released at Completion of Accident
During the initial approach, as the airspeed decreased through about 70 knots, the helicopter began an uncommanded right yaw of more than 100 degrees, and the yaw could not be stopped by the application of left pedal. The crew diverted to a nearby airport and performed a successful roll-on landing, touching down at 72 knots using differential braking to maintain the runway heading. An after-landing inspection showed that the tail rotor pitch change beam retaining nut, pitch beam retaining washer, and associated screws and washers were missing. The remainder of the tail rotor assembly remained attached and did not depart the helicopter.
Recent maintenance had been performed to replace the pitch change beam retaining nut and pitch beam retaining washer. According to maintenance personnel, the maintenance had been performed per the existing maintenance procedures, and the mechanics did not notice anything odd or out of place. Evidence of witness marks along with plastic deformation on the end faces of the pitch change shaft splines is consistent with the retaining washer installed with its indexing spline slightly off, resulting in a cocking condition and incomplete engagement of the spline teeth. Accordingly, there was likely an improper alignment of the components during reassembly, which would have prevented the nut from locking in place. Subsequent tests on an exemplar assembly showed that it was possible for the pitch beam retaining washer to be misaligned with the teeth on the shaft splines, which then showed barely visible evidence of the misalignment.
NTSB Probable Cause Narrative
The misalignment of the retaining washer during routine maintenance, resulting in the subsequent separation of the washer and nut.
Event Information
| Type of Event | Incident |
| Event Date | 1/19/2011 |
| Event Day of the Week | Wednesday |
| Time of Event | 1134 |
| Event Time Zone | Central Standard Time |
| Event City | Galliano |
| Event State | LOUISIANA |
| Event Country | -- |
| Zipcode of the event site | 70354 |
| Event Date Year | 2011 |
| Event Date Month | 1 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 292616N |
| Event Location Longitude | 0901524W |
| Event Location Airport | South Lafourche Airport |
| Event Location Nearest Airport ID | GAO |
| 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 | 1 |
| Weather Briefing Completeness | -- |
| Investigator's weather source | Weather Observation Facility |
| Time of the weather observation | 1140 Central Standard Time |
| Direction of event from weather observation facility (degrees) | 360 |
| Weather Observation Facility ID | KGAO |
| Elevation of weather observation facility | 1 |
| Distance of event from weather observation facility (units?) | 0 |
| Time Zone of the weather observation | CST |
| Lighting Conditions | Day |
| Lowest Ceiling Height | -- |
| Lowest Non-Ceiling Height | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | -- |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 15 |
| Dew Point at event time (in degress fahrenheit) | 8 |
| Wind Direction (degrees magnetic) | 10 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 11 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Gusting |
| Wind Gust (knots) | 15 |
| Altimeter Setting at event time (in. Hg) | 30.08 |
| Density Altitude (feet) | -- |
| Intensity of Precipitation | -- |
| METAR weather report | KGAO 191740Z AUTO 01011G15KT 10SM CLR 15/08 A3008 |
| 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 | 18 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 30849 |
| NTSB Notification Source | Bristow U.S. LLC |
| NTSB Notification Date | -- |
| NTSB Notification Time | -- |
| Fiche Number and/or location -used to find docket information | -- |
| Date of most recent change to record | Nov 29 2012 1:01PM |
| User who most recently changed record | latt |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | -- |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N920AL |
| NTSB Number | CEN11IA156 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 135: Air Taxi & Commuter |
| Type of Flight Plan filed | Company VFR |
| Flight plan Was Activated? | Yes |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | SIKORSKY |
| Aircraft Model | 92 |
| Aircraft Series Identifier | A |
| Aircraft Serial Number | 920088 |
| Certified Max Gross Weight | 26500 |
| Aircraft Category | Helicopter |
| Aircraft Registration Class | -- |
| Aircraft is a homebuilt? | No |
| Flight Crew Seats | 2 |
| Cabin Crew Seats | 1 |
| Passenger Seats | 15 |
| Total number of seats on the aircraft | 21 |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Retractable |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Jan 17 2011 12:00AM |
| Airframe hours since last inspection | 4 |
| Airframe Hours | 1248 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | C126 |
| Aircraft Owner Name | BRISTOW US LLC |
| Aircraft Owner Street Address | 4605 INDUSTRIAL DR |
| Aircraft Owner City | NEW IBERIA |
| Aircraft Owner State | LA |
| Aircraft Owner Country | USA |
| Aircraft Owner Zipcode | 70560-9124 |
| Operator is an individual? | No |
| Operator Name | BRISTOW US LLC |
| Operator Same as Owner? | Yes |
| Operator Is Doing Business As | -- |
| Operator Address Same as Owner? | Yes |
| Operator Street Address | 4605 INDUSTRIAL DR |
| Operator City | NEW IBERIA |
| Operator State | LA |
| Operator Country | USA |
| Operator Zip code | 70560-9124 |
| Operator Code | ALGA |
| 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 | ALGA151C |
| Indicates whether an air carrier operation was scheduled or not | Non-scheduled |
| Indicates Domestic or International Flight | Domestic |
| Operator carrying Pax/Cargo/Mail | Passenger Only |
| Type of Flying (Per_Bus / Primary) | -- |
| Second Pilot on Board | Yes |
| Departure Point Same as Event | No |
| Departure Airport Code | -- |
| Departure City | Gulf of Mexico |
| Departure State | LA |
| Departure Country | USA |
| Departure Time | 1030 |
| Departure Time Zone | CST |
| Destination Same as Local Flt | -- |
| Destination Airport Code | 2LS0 |
| Destination City | Galliano |
| Destination State | LA |
| Destination Country | USA |
| Specific Phase of Flight | -- |
| Report sent to ICAO? | -- |
| Evacuation occurred | -- |
| Date of most recent change to record | Nov 27 2012 9:04PM |
| User who most recently changed record | latt |
| Since inspection or accident | Time of Accident |
| Event Location Runway Number and Location | 36 |
| Runway Length | 6502 |
| Runway Width | 100 |
| Sight Seeing flight | No |
| Air Medical Flight | No |
| Medical Flight | -- |