Sunday, April 22, 2018

Bell 407, N4999, operated by PHI Air Medical: Accident occurred June 03, 2016 in Mountain City, Johnson County, Tennessee


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

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Nashville, Tennessee
PHI Air Medical; Phoenix, Arizona
Rolls Royce; Indianapolis, Indiana
Aero Propulsion Support; Harrison, Ohio

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

http://registry.faa.gov/N4999



Aviation Accident Factual Report - National Transportation Safety Board


Location: Mountain City, TN
Accident Number: ERA16LA202
Date & Time: 06/03/2016, 1345 EDT
Registration: N4999
Aircraft: BELL 407
Aircraft Damage: Substantial
Defining Event: Loss of engine power (partial)
Injuries: 1 Minor, 3 None
Flight Conducted Under:  Part 135: Air Taxi & Commuter - Non-scheduled - Air Medical (Medical Emergency)

On June 3, 2016, about 1345 eastern daylight time, a Bell 407, N4999, operated by PHI Air Medical, was substantially damaged during a forced landing to a parking lot, following a partial loss of engine power during initial climb near Mountain City, Tennessee. The commercial pilot incurred minor injuries. The two crewmembers and one patient were not injured. The on-demand air medical flight was conducted under the provisions of 14 Code of Federal Regulations Part 135. Visual meteorological conditions prevailed and a company flight plan was filed for the flight that originated from the parking lot; destined to Johnson City Medical Center Heliport (TN91), Johnson City, Tennessee.

The pilot stated that during initial climb, about 125 feet above ground level, he heard a loud "bang" that was accompanied by a left yaw and rapidly increasing measured gas temperature (MGT). The pilot advised the crewmembers that he was rejecting the climb and landing immediately. The pilot further stated that he had to maneuver the helicopter right to avoid ground personnel, level the helicopter with cyclic control, and used all available collective to cushion the landing.

The helicopter was equipped with a Rolls Royce (Allison) 250-C47B, 650 horsepower turboshaft engine. Examination of the helicopter by a Federal Aviation Administration (FAA) inspector revealed that it landed hard, which spread the skids and resulted in substantial damage to the fuselage.

Review of data downloaded from an engine monitor revealed that during the accident takeoff, the MGT increased beyond maximum for takeoff while the power turbine rpm decreased. Examination of the engine at the operator's facility revealed a partial separation of the compressor diffusor, which allowed intake air to leak prior to combustion. The compressor diffusor was forwarded to the engine manufacturer's facility for teardown examination under the supervision of an FAA inspector.

Examination of the compressor diffuser revealed that a portion of the aft plate had separated near a braze joint. Review of engine manufacturer specifications revealed that the aft plate should have been a single component and not two components joined together by a brazing process. Maintenance records revealed that the compressor diffusor had been overhauled by a repair facility and installed on the accident helicopter about 98 hours of operation prior to the accident.

According to the FAA principle maintenance inspector (PMI) of the repair facility, a machinist had joined a second ring to the compressor diffuser aft plate using a brazing process. There was no approval (neither through the engine manufacturer nor the FAA) for that process and it is possible that the machinist performed the procedure to correct a mistake he had made during a dimensional shim repair, which was approved through the FAA designated engineering representative (DER) program. The machinist no longer worked for the repair facility and had left the company prior to the accident.

Further review of the repair facility by the FAA PMI revealed that they had authorization through the FAA DER program for approximately 4 years to repair compressor diffusers. During those 4 years, the repair facility had performed repairs on 52 other compressor diffusers. Most of those were common repairs to vanes, with 17 being dimensional shims to the aft plates. Review of the other 17 similar repairs revealed that the machinist in question had not worked on any of those.

According to the Quality and Engineering Manager at the repair facility, ultrasonic testing also failed to identify the unapproved repair. An immediate corrective action for the repair facility was to suspend dimensional shim repairs indefinitely. The repair facility also ensured that their three-tier approval process (engineering, quality and management) was required for any fixture, tooling, drawing, or process before it was performed and that all necessary personnel were trained in that method. 

Pilot Information

Certificate: Commercial
Age: 53, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used: 4-point
Instrument Rating(s): Airplane; Helicopter
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 1 With Waivers/Limitations
Last FAA Medical Exam: 07/13/2015
Occupational Pilot: Yes
Last Flight Review or Equivalent: 08/16/2015
Flight Time:  8550 hours (Total, all aircraft), 680 hours (Total, this make and model), 6900 hours (Pilot In Command, all aircraft), 52 hours (Last 90 days, all aircraft), 17 hours (Last 30 days, all aircraft), 1 hours (Last 24 hours, all aircraft)



Aircraft and Owner/Operator Information

Aircraft Manufacturer: BELL
Registration: N4999
Model/Series: 407 NO SERIES
Aircraft Category: Helicopter
Year of Manufacture: 1998
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 53323
Landing Gear Type: High Skid;
Seats: 4
Date/Type of Last Inspection: 06/01/2016, AAIP
Certified Max Gross Wt.: 5250 lbs
Time Since Last Inspection: 99 Hours
Engines: 1 Turbo Shaft
Airframe Total Time: 8449 Hours as of last inspection
Engine Manufacturer: ALLISON
ELT: C126 installed, activated, did not aid in locating accident
Engine Model/Series: 250-C47B
Registered Owner: PHI INC
Rated Power: 650 hp
Operator: PHI AIR MEDICAL
Operating Certificate(s) Held: On-demand Air Taxi (135)
Operator Does Business As: 
Operator Designator Code: VE7A 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: TNB
Observation Time: 1355 EDT
Distance from Accident Site: 15 Nautical Miles
Direction from Accident Site: 180°
Lowest Cloud Condition: Scattered / 3600 ft agl
Temperature/Dew Point: 25°C / 14°C
Lowest Ceiling: None
Visibility:  10 Miles
Wind Speed/Gusts, Direction: 11 knots, 310°
Visibility (RVR):
Altimeter Setting: 30.17 inches Hg
Visibility (RVV):
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Mountain City, TN
Type of Flight Plan Filed: Company VFR
Destination: Johnson City, TN (TN91)
Type of Clearance: None
Departure Time: 1345 EDT
Type of Airspace:

Wreckage and Impact Information

Crew Injuries: 1 Minor, 2 None
Aircraft Damage: Substantial
Passenger Injuries: 1 None
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Minor, 3 None
Latitude, Longitude: 36.474722, -81.804722 (est)



NTSB Identification: ERA16LA202
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Friday, June 03, 2016 in Mountain City, TN
Aircraft: BELL 407, registration: N4999
Injuries: 1 Minor, 3 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 June 3, 2016, about 1345 eastern daylight time, a Bell 407, N4999, operated by PHI Air Medical, was substantially damaged during a forced landing to a parking lot, following a partial loss of engine power during initial climb near Mountain City, Tennessee. The commercial pilot incurred minor injuries. The two crewmembers and one patient were not injured. The on-demand air medical flight was conducted under the provisions of 14 Code of Federal Regulations Part 135. Visual meteorological conditions prevailed and a company flight plan was filed for the flight that originated from the parking lot; destined to Johnson City Medical Center Heliport (TN91), Johnson City, Tennessee.

The pilot stated that during initial climb, about 125 feet above ground level, he heard a loud "bang" that was accompanied by a left yaw and rapidly increasing measured gas temperature. The pilot advised the crewmembers that he was rejecting the climb and landing immediately. The pilot further stated that he had to maneuver the helicopter right to avoid ground personnel, level the helicopter with cyclic control, and used all available collective to cushion the landing.

The helicopter was equipped with a Rolls Royce (Allison) 250-C47B, 650 horsepower turboshaft engine. Examination of the helicopter by a Federal Aviation Administration inspector revealed that it landed hard, which spread the skids and resulted in substantial damage to the fuselage. Initial examination of the airframe and engine did not reveal any preimpact mechanical malfunctions; however, the engine was retained for further examination.

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