Wednesday, January 10, 2018

Bell 407, registered to and operated by PHI Helicopters Inc: Accident occurred May 02, 2017 in Venice, Plaquemines Parish, Louisiana

***This report was modified on January 8, 2018. Please see the docket for this accident to view the original report.***

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Baton Rouge, Louisiana
PHI, Inc.; Houma, Louisiana 

Aviation Accident Factual Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

http://registry.faa.gov/N457PH

Aviation Accident Factual Report - National Transportation Safety Board:https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Location: Venice, LA
Accident Number: CEN17LA174
Date & Time: 05/02/2017, 0635 CDT
Registration: N457PH
Aircraft: BELL 407
Aircraft Damage: Substantial
Defining Event: Part(s) separation from AC
Injuries: 6 None
Flight Conducted Under: Part 135: Air Taxi & Commuter - Non-scheduled 

***This report was modified on January 8, 2018. Please see the docket for this accident to view the original report.***

On May 2, 2017, about 0635 central daylight time, a Bell 407 helicopter, N457PH, registered to and operated by PHI Helicopters, Inc., Lafayette, Louisiana, made a precautionary landing at Grand Bay Receiving Station near Venice, Louisiana, after the pilot noticed an in-flight vibration. The pilot and five passengers on board the helicopter were not injured and the helicopter sustained substantial damage. The non-scheduled domestic passenger flight was being conducted under the provisions of Title 14 Code of Federal Regulations Part 135, and a company VFR flight plan had been filed. Visual meteorological conditions prevailed at the time of the accident. The cross-country flight originated from Boothville (LS08), Louisiana, at 0629, and was en route to Main Pass 311A in the Gulf of Mexico when the accident occurred.

The pilot said he detected an in-flight vibration and made a precautionary landing on the Grand Bay oil platform. As he was shutting down the engine, the vibration increased and he initiated an emergency shutdown using the rotor brake. Post-accident inspection revealed the tip block and weights had separated from one of the tail rotor blades. Cracks were noted on the tail rotor gear box mounting hardware and the tail boom.

The tail rotor hub and blade assembly, tail rotor gear box with two fractured studs, and tail boom support casting were sent to NTSB's Materials Laboratory for examination. In addition to NTSB's staff, representatives from PHI, Inc., and Bell Helicopter were present for the laboratory examination. Visual examination of the tail rotor confirmed the tip block and blade tip weights were missing from one of the tail rotor blades. According to PHI, the blade had a total service life of 2,658.65 hours, and had a tip block replacement repair approximately 65 hours prior to the separation. The examination found that the tip block separated along the adhesive interface, leaving the majority of the adhesive attached to the blade skin. The adhesive remaining on both skins appeared as a waffle pattern, indicative of partial bonding and subsequent interfacial separation. Approximately 50% of the adhesive surface had smooth and glossy surfaces consistent with voids and lack of contact between the adhesive and the tip block.

The tail rotor gearbox was detached from the tail boom support casting, and the two outboard attach studs were fractured. The entire support casting was fractured and all but 2.7 inches of the skin and the four-inch wide cover were cracked. The fracture in the casting and crack in the skin were consistent with overstress separations. Both fractured left-hand studs displayed reversed bending fatigue fractures. Magnification of the fracture faces revealed features and topographies consistent with multiple origin reversed bending fatigue initiating in the respective root radii on opposed sides of each studs. Fretting and rub marks were observed on both the support casting and tail rotor gearbox where the attach studs were fixed. The tail rotor gearbox alignment dowel pins were missing. The tail boom support casting had cracks at the two forward stud hole locations, and stud hole elongation was noted at the two aft stud hole locations. A circumferential crack had formed from the forward left stud hole along the left sid

The pilot said he detected an in-flight vibration and made a precautionary landing on the Grand Bay oil platform. As he was shutting down the engine, the vibration increased and he initiated an emergency shutdown using the rotor brake. Post-accident inspection revealed the tip block and weights had separated from one of the tail rotor blades. Cracks were noted on the tail rotor gear box mounting hardware and the tail boom.

The tail rotor hub and blade assembly, tail rotor gear box with two fractured studs, and tail boom support casting were sent to NTSB's Materials Laboratory for examination. In addition to NTSB's staff, representatives from PHI, Inc., and Bell Helicopter were present for the laboratory examination. Visual examination of the tail rotor confirmed the tip block and blade tip weights were missing from one of the tail rotor blades. According to PHI, the blade had a total service life of 2,658.65 hours, and had a tip block replacement repair approximately 65 hours prior to the separation. The examination found that the tip block separated along the adhesive interface, leaving the majority of the adhesive attached to the blade skin. The adhesive remaining on both skins appeared as a waffle pattern, indicative of partial bonding and subsequent interfacial separation. Approximately 50% of the adhesive surface had smooth and glossy surfaces consistent with voids and lack of contact between the adhesive and the tip block.

The tail rotor gearbox was detached from the tail boom support casting, and the two outboard attach studs were fractured. The entire support casting was fractured and all but 2.7 inches of the skin and the four-inch wide cover were cracked. The fracture in the casting and crack in the skin were consistent with overstress separations. Both fractured left-hand studs displayed reversed bending fatigue fractures. Magnification of the fracture faces revealed features and topographies consistent with multiple origin reversed bending fatigue initiating in the respective root radii on opposed sides of each studs. Fretting and rub marks were observed on both the support casting and tail rotor gearbox where the attach studs were fixed. The tail rotor gearbox alignment dowel pins were missing. The tail boom support casting had cracks at the two forward stud hole locations, and stud hole elongation was noted at the two aft stud hole locations. A circumferential crack had formed from the forward left stud hole along the left side.

According to Bell Helicopters, after repairs were made to tail rotor blades, a 1,320-lb. pull test was performed on the tip block, a tap test was performed to check for voids, a peel test was performed from skin patch material, and a water leak test was performed. Bell reported that no blade had ever failed the 1,320-lb. pull test, and the facility had made approximately 25 tail rotor tip block crack repairs per year.

After the accident, the helicopter manufacturer revised its approved repair procedure, including the block replacement. The changes included, in part, a revision to the cure cycle process to use only positive pressure during the cure cycle that cures the adhesive that bonds the block on the blade tip. The manufacturer also expanded its postrepair inspection procedures. For more information, see the document titled "New Bell Helicopter Approved Tail Rotor Repair Procedures" in the public docket for this accident.

Pilot Information


Certificate: Commercial
Age: 29, Male
Airplane Rating(s): None
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used: 4-point
Instrument Rating(s): Helicopter
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 1 Without Waivers/Limitations
Last FAA Medical Exam: 07/22/2016
Occupational Pilot: Yes
Last Flight Review or Equivalent: 07/06/2016
Flight Time: (Estimated) 3272 hours (Total, all aircraft), 100 hours (Total, this make and model), 2377 hours (Pilot In Command, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Manufacturer: BELL
Registration: N457PH
Model/Series: 407
Aircraft Category: Helicopter
Year of Manufacture: 1997
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 53121
Landing Gear Type: Skid
Seats: 7
Date/Type of Last Inspection: 04/05/2017, AAIP
Certified Max Gross Wt.: 5250 lbs
Time Since Last Inspection:
Engines:  Turbo Shaft
Airframe Total Time: 5839 Hours at time of accident
Engine Manufacturer: Rolls-Royce
ELT: C126 installed, not activated
Engine Model/Series: 250 C478
Registered Owner: PHI, Inc.
Rated Power: 600 hp
Operator: PHI, Inc.
Operating Certificate(s) Held:  On-demand Air Taxi (135)

Meteorological Information and Flight Plan


Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation:
Observation Time:
Distance from Accident Site:
Direction from Accident Site:
Lowest Cloud Condition: Clear
Temperature/Dew Point:
Lowest Ceiling: None
Visibility:  10 Miles
Wind Speed/Gusts, Direction:
Visibility (RVR):
Altimeter Setting:
Visibility (RVV):
Precipitation and Obscuration:
Departure Point: Boothville, LA (LS08)
Type of Flight Plan Filed: Company VFR
Destination: Main Pass 311A, GM (NONE)
Type of Clearance: None
Departure Time: 0629 CDT
Type of Airspace: Class G

Airport Information


Airport: Grand Bay Receiving Station (NONE)
Runway Surface Type: N/A
Airport Elevation: 0 ft
Runway Surface Condition:
Runway Used: N/A
IFR Approach: None
Runway Length/Width:
VFR Approach/Landing: Precautionary Landing 

Wreckage and Impact Information


Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: 5 None
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 6 None
Latitude, Longitude: 29.310000, -89.298056

NTSB Identification: CEN17LA174 
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Tuesday, May 02, 2017 in Boothville, LA
Aircraft: BELL 407, registration: N457PH
Injuries: 6 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On May 2, 2017, about 0635 central daylight time, a Bell 407 helicopter, N457PH, registered to and operated by PHI Helicopters, Inc., Lafayette, Louisiana, made a precautionary landing at Grand Bay receiving station in the Gulf of Mexico, near Boothville, Louisiana, after the pilot noticed a vibration in-flight. Visual meteorological conditions prevailed at the time of the accident.The non-scheduled domestic passenger flight was being conducted under the provisions of Title 14 CFR Part 135, and a company VFR flight plan had been filed and activated. The pilot and four passengers on board the helicopter were not injured.The cross-country flight originated from Boothville (LS08), Louisiana, at 0629, and was en route to Main Pass 311A in the Gulf of Mexico when the accident occurred. 

The pilot had noticed a vibration in-flight and landed the helicopter on the oil platform. As he was shutting down the engine, the vibration worsened and he completed the shutdown using the rotor brake. Post-accident inspection revealed a tip cap had separated from one of the tail rotor blades, and cracks were noted on the tail rotor gear box, mounting hardware, and tail boom, all considered to be substantial damage.

1 comment:

Anonymous said...

Extremely lucky bunch of people. Smart, decisive pilot!