Saturday, March 16, 2019

System / Components Malfunction / Failure (Non-Power): Eurocopter-Kawasaki BK-117B-2, N1174U, accident occurred March 04, 2018 at Sheboygan County Memorial Airport (KSBM), Wisconsin

The National Transportation Safety Board traveled to the scene of this accident.

Additional Participating Entities:

Federal Aviation Administration / Flight Standards District Office; Milwaukee, Wisconsin
Air Methods Corporation; Denver, Colorado

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


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


http://registry.faa.gov/N1174U


Location: Sheboygan, WI
Accident Number: CEN18LA115
Date & Time: 03/04/2018, 2324 CST
Registration: N1174U
Aircraft: MESSERSCHMITT-BOLKOW-BLOHM BK 117 B-2
Aircraft Damage: Substantial
Defining Event: Flight control sys malf/fail
Injuries: 3 None
Flight Conducted Under: Part 135: Air Taxi & Commuter - Non-scheduled - Air Medical (Medical Emergency) 

Analysis 

Before departure on the air ambulance flight, standard flight control and hydraulic transfer checks were performed with no anomalies noted with the flight controls. The helicopter’s hover, departure, and cruise were normal. During his approach to the hospital, the pilot started a slow descent using the collective and performed the before landing checks; all systems were normal. However, when attempting to decelerate from cruise speed, the pilot noticed restricted cyclic control movement, about 1 inch in any direction, with normal collective and yaw control movement. He then chose to abort the descent and execute a precautionary landing at a nearby airport.

During the short flight to the airport, the pilot cycled the hydraulic test switch twice with no change noted to his flight controls. During the approach to land, the pilot held the cyclic trim switch aft in an attempt to gain additional aft cyclic authority. With continuous cyclic pressure against the aft stop, the pilot was able to slow the helicopter to 80 knots on final approach. The helicopter touched down near the runway centerline, skidded about 500 ft, exited the runway surface, and came to rest upright. The helicopter sustained substantial damage to the main rotor blades and fuselage structure.

Postaccident examination of the helicopter’s flight control system, including the trim system, did not reveal any evidence of malfunctions or failures that would have precluded normal operations. The cyclic trim was found in the full forward and left position. The flight control dual hydraulic pack was functionally tested on the helicopter and at a repair facility with no anomalies noted. Thus, the reason for the restricted cyclic control movement could not be determined. 

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The restricted cyclic control movement for reasons that could not be determined because postaccident examination and testing of the cyclic control system did not reveal any evidence of mechanical malfunctions or failures that would have precluded normal operation.

Findings

Not determined
Not determined - Unknown/Not determined (Cause)


Factual Information 

On March 4, 2018, about 2324 central standard time, a Messerschmitt-Bolkow-Blohm BK 117 B-2 helicopter, N1174U, operated by Air Methods Corporation, Englewood, Colorado, sustained substantial damage during a hard landing at Sheboygan County Memorial Airport (SBM), Sheboygan, Wisconsin. The commercial pilot, flight nurse, and flight paramedic were not injured. The flight was operated under the provisions of Title 14 Code of Federal Regulations Part 135 as a helicopter air ambulance flight. Night visual meteorological conditions prevailed at the time of the accident, and a flight plan was not filed for the flight that departed about 2257, from Fond du Lac, Wisconsin. The flight was destined for the HSHS St. Nicholas Hospital, Sheboygan, Wisconsin.

According to the pilot, prior to departure from Fond du Lac, standard flight control and hydraulic transfer checks were performed, and no anomalies noted with the flight controls; the hover and departure were normal. The pilot, who was wearing night vision goggles, climbed the helicopter to 2,500 ft above ground level (agl) and accelerated to 125 knots indicated airspeed. Approaching the hospital, the pilot started a slow descent utilizing the collective and performed the before landing checks; all systems were normal. When attempting to decelerate from cruise speed, the pilot noticed restricted cyclic control movement, about 1 inch in any direction, with normal collective and yaw control. He then elected to abort the descent and execute a precautionary landing at SBM, located about 6 miles west of the hospital.

During the short flight to SBM, the pilot cycled the hydraulic test switch twice, which was located on the cockpit overhead panel, with no change noted to his flight controls. In addition, he asked the flight paramedic, who was seated in the left seat, to check if any circuit breakers were popped, verify systems were in normal operational ranges, and no cautions or advisory lights were illuminated. All circuit breakers and systems were normal with no anomalies noted.

The pilot initially flew an approach to runway 22; however, due to being too high and fast, he elected to circle to land on runway 13, which provided a more favorable quartering headwind. During the runway 22 approach and circle to land to on runway 13, the pilot held the cyclic trim switch aft in an attempt to gain additional aft cyclic authority. With continuous cyclic pressure against the aft stop, the pilot was able to slow the helicopter to 80 kts on final approach. The helicopter touched down near runway centerline, skidded about 500 ft, exited the runway surface, and came to rest upright.

During the landing, the helicopter's top wire strike protection system was separated due to contact by the main rotor blades, and the landing gear skids were partially collapsed. One main rotor blade had a portion of the blade skin and core separated, and all the blades sustained leading edge damage.

Postaccident examination of the helicopter's showed the cyclic trim position was found in the full forward and left position. Examination of the flight control system, to include the trim system, revealed no anomalies that would have precluded normal operations. The flight control dual hydraulic pack was functionally tested on the helicopter with no anomalies noted. The pack was removed from the helicopter for further examination and testing.

On April 5, 2018, under the supervision of a Federal Aviation Administration (FAA) inspector, the helicopter cyclic control trim system switch and motors were tested about 50 times in each direction of full travel and from the neutral positions. No anomalies were noted during the tests.

On April 16, 2018, under the supervision of FAA inspectors at Air Methods Corporation, which was an approved component overhaul facility, the dual hydraulic pack was tested in accordance with repair manual REM 401-04-22 Dual Hyd-Pack Final Work/Test procedure. No anomalies were noted during the examination or test procedures.

A review of the aircraft maintenance logbook revealed no reports of control problems or recent maintenance to the flight control system.

According to the helicopter flight manual should a hydraulic system caution light illuminate, the hydraulic test switch should not be operated in-flight, but remain in the [normal] position.

Pilot Information

Certificate: Commercial
Age: 57, Male
Airplane Rating(s): Single-engine Land
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 2 With Waivers/Limitations
Last FAA Medical Exam: 03/27/2017
Occupational Pilot: Yes
Last Flight Review or Equivalent: 06/05/2017
Flight Time:  5684 hours (Total, all aircraft), 84 hours (Total, this make and model), 3746 hours (Pilot In Command, all aircraft), 18 hours (Last 90 days, all aircraft), 8 hours (Last 30 days, all aircraft), 1 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Make: MESSERSCHMITT-BOLKOW-BLOHM
Registration: N1174U
Model/Series: BK 117 B-2
Aircraft Category: Helicopter
Year of Manufacture: 1988
Amateur Built: No
Airworthiness Certificate: Transport
Serial Number: 7146
Landing Gear Type: Skid
Seats: 7
Date/Type of Last Inspection: 02/15/2018, AAIP
Certified Max Gross Wt.: 7385 lbs
Time Since Last Inspection:
Engines: 2 Turbo Shaft
Airframe Total Time: 8613 Hours as of last inspection
Engine Manufacturer: Honeywell
ELT: C126 installed, not activated
Engine Model/Series: LTS-101
Registered Owner: MILWAUKEE REGIONAL MEDICAL CENTER INC
Rated Power: 675 hp
Operator: Air Methods Corporation
Operating Certificate(s) Held:  On-demand Air Taxi (135)

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Night
Observation Facility, Elevation: SBM, 755 ft msl
Distance from Accident Site: 0 Nautical Miles
Observation Time: 2353 CST
Direction from Accident Site:
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 9 knots / 18 knots
Turbulence Type Forecast/Actual: / None
Wind Direction: 110°
Turbulence Severity Forecast/Actual: /
Altimeter Setting: 30.34 inches Hg
Temperature/Dew Point: 2°C / -4°C
Precipitation and Obscuration: No Precipitation
Departure Point: Fond du Lac, WI (FLD)
Type of Flight Plan Filed: None
Destination: Sheboygan, WI (SBM)
Type of Clearance: VFR
Departure Time: 2257 CST
Type of Airspace: 

Airport Information

Airport: Sheboygan County Memorial (SBM)
Runway Surface Type: Asphalt
Airport Elevation: 755 ft
Runway Surface Condition: Dry
Runway Used: 13
IFR Approach: None
Runway Length/Width: 5002 ft / 75 ft
VFR Approach/Landing: Precautionary Landing; Straight-in

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: 2 None
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 3 None
Latitude, Longitude:  43.764444, -87.851389 (est)

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