ASN Wikibase Occurrence # 173057
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| Date: | Friday 16 January 2015 |
| Time: | 12:30 |
| Type: | Safari 400 |
| Owner/operator: | Private |
| Registration: | N416JB |
| MSN: | CH2181 |
| Year of manufacture: | 2010 |
| Engine model: | AEROSPORT O-360 |
| Fatalities: | Fatalities: 1 / Occupants: 1 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | The Woodlands, TX -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Conroe, TX |
| Conroe, TX | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On January 16, 2015, about 1230 central standard time, an experimental, amateur-built Safari 400 helicopter, N416JB, impacted terrain following a loss of control in The Woodlands, Texas. The commercial pilot was fatally injured, and the helicopter was destroyed. The helicopter was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, and no flight plan was filed.
The commercial pilot was conducting a personal flight in the experimental, amateur-built helicopter. Several witnesses reported seeing the helicopter flying overhead. They reported that it appeared to by flying normally but that it then turned sideways, banked left, and descended to the ground. One witness reported hearing a breaking sound and then seeing the “back rotor” hanging from the helicopter.
The horizontal stabilizer was found separated from the tailboom. Postaccident examination revealed that the horizontal stabilizer spar tube had fractured at the weld area just outboard of the mounting flange. Examinations of the fracture surfaces revealed features consistent with fatigue cracking that had initiated at multiple origins along the weld toe. Although no weld defects or corrosion were noted at the fatigue origins, large areas of both fracture faces were covered by red and brown corrosion products, indicating that the cracks were present and exposed for a considerable amount of time (at least many days but more likely many weeks).
The fatigue origins were located on the aft surface of the spar and propagated generally forward. The origin location and direction of propagation were indicative of cyclic bending loads in the spar as if the tip of the stabilizer repetitively moved forward relative to the mount. The source of the cyclic bending loads was not clear but could have been the result of many different helicopter factors. These factors could have been unique to the accident helicopter or could be present on all similar helicopters. It is likely that the horizontal stabilizer separated in flight due to undetected fatigue cracking in the stabilizer spar, which resulted in the uncontrolled descent.
As assembled, the fracture location and weld were partially hidden by the horizontal stabilizer’s airfoil skin and not directly visible, which would have made any cracking difficult to see. Following the accident, the kit manufacturer issued a mandatory inspection and modification bulletin for the horizontal stabilizer, which detailed inspection criteria and spar replacement guidance if cracking was found.
Probable Cause: An in-flight separation of the helicopter’s horizontal stabilizer due to undetected fatigue cracking of the stabilizer spar, which resulted in a loss of control.
Accident investigation:
 |
|
Sources:
NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N416JB
Location
Images:
Photograph of fractured spar tube from horizontal stabilizer (NTSB)
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 17-Jan-2015 03:49 | Geno | Added |
| 17-Jan-2015 04:01 | Geno | Updated [Aircraft type, Location, Source] |
| 21-Jan-2015 02:07 | Geno | Updated [Aircraft type, Registration, Cn, Operator, Source, Narrative] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 11-Oct-2017 07:36 | ASN Update Bot | Updated [Cn, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 11-Sep-2022 16:59 | Captain Adam | Updated [Aircraft type, Location, Phase, Source, Damage, Narrative, Photo] |
| 11-Sep-2022 16:59 | Captain Adam | Updated [Other fatalities] |
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