Friday, August 07, 2020

Hard Landing: Hughes OH-6A, N911EP; accident occurred August 06, 2020 at Spirit of St. Louis Airport (KSUS), Chesterfield, Missouri





Aviation Accident Factual Report - National Transportation Safety Board

Additional Participating Entity: 
Federal Aviation Administration / Flight Standards District Office; St. Louis, Missouri

Investigation Docket - National Transportation Safety Board:

St. Louis County Police Department


Location: St Louis, MO
Accident Number: CEN20CA326
Date & Time: 08/06/2020, 1515 CDT
Registration:N911EP
Aircraft: Hughes 369A
Aircraft Damage: Substantial
Defining Event: Hard landing
Injuries: 2 None
Flight Conducted Under: Public Aircraft

The flight instructor and pilot were conducting a helicopter training flight. Each pilot had performed several maneuvers, such as confined approach, slope landing, settling with power, and maximum performance takeoffs. They then flew to another airport where they conducted several practice emergency procedures; quick stops, stuck pedals, and auto rotations. They then returned to their home airfield, where they contacted the tower controller, who reported calm wind and cleared them to land. The instructor reported he was manipulating the controls and accepted the option to land on the taxiway; he decreased the throttle for a full touchdown auto rotation. About 50 ft above the ground (agl), he flared the helicopter and leveled off about 5 to 10 ft agl. The instructor reported that everything seemed "normal" at this point. He then raised the collective, but the descent was not arrested, so he raised the collective full up. The helicopter landed hard and shook violently. The instructor closed the throttle to which stopped the fuel supply.

The instructor added that he felt a slight tailwind after exiting the helicopter and that the tail wind caused a "vortex ring state" which stalled the main rotor blades.

Examination of the helicopter found that the main rotor blades had impacted the tailboom, severing the boom, just in front of the tail rotor blades.

Pilot Information

Certificate: Flight Instructor; Commercial
Age: 51
Airplane Rating(s): None
Seat Occupied: Left
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): Helicopter
Second Pilot Present: Yes
Instructor Rating(s): Helicopter
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 06/22/2020
Occupational Pilot: No
Last Flight Review or Equivalent:
Flight Time: 6814 hours (Total, all aircraft), 6814 hours (Total, this make and model), 6338 hours (Pilot In Command, all aircraft)

Pilot Information

Certificate: Commercial
Age: 39
Airplane Rating(s): None
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): None
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 Without Waivers/Limitations
Last FAA Medical Exam: 06/29/2020
Occupational Pilot: No
Last Flight Review or Equivalent: 06/18/2020
Flight Time: 635 hours (Total, all aircraft), 91 hours (Total, this make and model), 585 hours (Pilot In Command, all aircraft)

Aircraft and Owner/Operator Information

Aircraft Make: Hughes
Registration: N911EP
Model/Series: 369A No Series
Aircraft Category: Helicopter
Year of Manufacture:
Amateur Built:No
Airworthiness Certificate:
Serial Number: 591176
Landing Gear Type: Skid
Seats:
Date/Type of Last Inspection: 08/04/2020, 100 Hour
Certified Max Gross Wt.:
Time Since Last Inspection:
Engines: Turbo Shaft
Airframe Total Time: 1229.4 Hours at time of accident
Engine Manufacturer: Rolls Royce
ELT: C91 installed, activated, did not aid in locating accident
Engine Model/Series: 250-c20C
Registered Owner: St Louis County Police Department
Rated Power:
Operator: St Louis County Police Department
Operating Certificate(s) Held: None

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation:
Distance from Accident Site:
Observation Time: 1454 CDT
Direction from Accident Site:
Lowest Cloud Condition: Scattered / 25000 ft agl
Visibility: 10 Miles
Lowest Ceiling:
Visibility (RVR):
Wind Speed/Gusts: 3 knots /
Turbulence Type Forecast/Actual:
Wind Direction: Variable
Turbulence Severity Forecast/Actual:
Altimeter Setting: 30.09 inches Hg
Temperature/Dew Point: 27°C / 13°C
Precipitation and Obscuration: No Precipitation
Departure Point: St Louis, MO (KSUS)
Type of Flight Plan Filed:
Destination: St Louis, MO (KSUS)
Type of Clearance: VFR
Departure Time: CDT
Type of Airspace: Class D

Airport Information

Airport: Spirit of St Louis Airport (KSUS)
Runway Surface Type: Unknown
Airport Elevation: 463 ft
Runway Surface Condition: Dry
Runway Used: N/A
IFR Approach: None
Runway Length/Width:
VFR Approach/Landing: Simulated Forced Landing

Wreckage and Impact Information

Crew Injuries: 2 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 None
Latitude, Longitude: 38.663611, -90.644722 (est)



St. Louis County Police Department

On August 6, 2020, members of the Metro Air Support Unit were training at the Spirit of St. Louis Airport.

At around 3:15 PM, in the course of an exercise, one of the main rotor blades of the helicopter bowed and struck the tail boom. As a result, the tail rotor was cut from the rest of the helicopter.

The rotorcraft was occupied by two St. Louis County Police officers at the time of the accident. They were able to successfully land. Both are uninjured.

The helicopter was manufactured in 1968 and flew in Vietnam. Following that, it was given as a military surplus rotorcraft, free from the State of Missouri.

The Metro Air Support Unit has an additional four helicopters; therefore, their service to the region will remain unaffected.

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