National Transportation Safety Board
Aviation Accident Final Report

 

 

Location:

Canon City, CO

Accident Number:

CEN17LA192

Date & Time:

05/20/2017, 1340 MDT

Registration:

N778TL

Aircraft:

ROBINSON HELICOPTER CO R66

Aircraft Damage:

Substantial

Defining Event:

Settling with power/vortex ring state

Injuries:

5 None

Flight Conducted Under:

Part 91: General Aviation - Other Work Use - Sightseeing

Analysis

 

The commercial pilot reported that, after completing the local air tour flight in the helicopter, he approached the private helipad location from the south. On approach and about 50-60 kts, the pilot began to arrest the helicopter's descent to view the windsock and determine the proper approach to the helipad. The pilot reported that the wind was from the south, so he decided to make the final approach from the north. About 200 ft above ground level and west of the helipad, the pilot initiated a left turn, and the helicopter started an uncommanded descent. The pilot applied power to stop the descent, but the helicopter continued sinking toward terrain. Due to the low altitude, the pilot committed to land and leveled the helicopter. During the landing, the back of the landing gear skids struck the terrain, which resulted in the main rotor blades contacting and severing the tail boom. Postaccident examination did not reveal any anomalies with the airframe or engine that would have precluded normal operation, and both the pilot and the operator reported that there were no mechanical malfunctions or failures. The pilot's calculated weight and balance was within limits at the time of the accident. A video of the accident sequence was consistent with the pilot's statement. It is likely that, during the descent to land, the helicopter encountered a vortex ring state (settling with power) condition, which resulted in a rapid descent and hard landing.

 

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
 

The pilot's loss of helicopter control on approach to land due to a vortex ring state (settling with power) condition, which resulted in a hard landing.

 

Findings

Aircraft

Descent rate - Not attained/maintained (Cause)

Personnel issues

Aircraft control - Pilot (Cause)

Factual Information

 

On May 20, 2017, about 1340 mountain daylight time, a Robinson Helicopter Company R66 helicopter, N778TL, impacted terrain following a loss of control on approach to landing near Canon City, Colorado. The commercial pilot and four passengers were not injured, and the helicopter sustained substantial damage. The helicopter was registered to Hynes Aviation Industries, Inc, and operated by Colorado Vertical under provisions of Title 14 Code of Federal Regulations Part 91 as a local air tour flight. Day visual meteorological conditions prevailed and a company visual flight rules flight plan was filed for the local flight. The flight originated from a private helipad near Canon City about 1335.

The pilot reported to the National Transportation Safety Board (NTSB) investigator-in-charge that after completing the local air tour flight, the helicopter approached the private helipad location from the south near highway route 50. After crossing over route 50 on approach about 50-60 kts, the pilot began to arrest the descent to view the wind sock and determine the proper approach to the helipad. The pilot reported the winds were from the south, so he decided to make the final approach from the north. About 200 ft above ground level and west of the helipad, the pilot initiated a left turn, and the helicopter started an uncommanded descent. The pilot applied power to stop the descent, but the helicopter continued sinking towards the terrain. Due to the low altitude, the pilot then committed to land and leveled the helicopter. During the landing, the back of the landing gear skids struck the terrain, which resulted in the main rotor blades contacting and severing in the tail boom. The helicopter came to rest upright and the occupants exited the helicopter.

Postaccident examination of the helicopter airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

The pilot reported that the helicopter weight was 2,580 lbs at the time of the accident, and the pilot's calculated center of gravity was 92.92 inches.

A GoPro HERO3 Silver Edition camera was mounted on the helicopter windshield facing inward into the cabin. The camera was installed on the helicopter to provide passengers a video of their air tour flight. A copy of the accident flight video was recovered by the operator and provided to the NTSB. The video was reviewed by the NTSB's Office of Research and Engineering and a video study was completed. The study goal was to estimate the forward and vertical speeds of the helicopter before the hard landing.

The analysis of the video was based on a mathematical model of the camera. Four parameters, yaw, pitch, roll, and horizontal field of view angle, were estimated from video frames recorded before takeoff, when the helicopter was on the departure helipad. Parameter estimation was based on several reference points, which were visible through the helicopter windows and aerial images of the accident area.

According to the study calculations, the forward speed was estimated at 34+3 knots, and the highest estimated vertical descent speed was 570+60 ft/min. In addition, the helicopter experienced an elevated level of vibrations during a time interval of approximately seven seconds that ended just before ground impact.

 

 

History of Flight

Approach

Settling with power/vortex ring state (Defining event)

Landing-flare/touchdown

Hard landing

 

 

Pilot Information

Certificate:

Flight Instructor; Commercial

Age:

44, 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):

Helicopter

Toxicology Performed:

No

Medical Certification:

Class 2 Without Waivers/Limitations

Last FAA Medical Exam:

04/21/2017

Occupational Pilot:

No

Last Flight Review or Equivalent:

10/31/2015

Flight Time:

520 hours (Total, all aircraft), 95 hours (Total, this make and model), 412 hours (Pilot In Command, all aircraft), 31 hours (Last 90 days, all aircraft), 7 hours (Last 30 days, all aircraft), 2 hours (Last 24 hours, all aircraft)

 

 

Aircraft and Owner/Operator Information

Aircraft Make:

ROBINSON HELICOPTER CO

Registration:

N778TL

Model/Series:

R66 NO SERIES

Aircraft Category:

Helicopter

Year of Manufacture:

 

Amateur Built:

No

Airworthiness Certificate:

Normal

Serial Number:

0469

Landing Gear Type:

Skid

Seats:

5

Date/Type of Last Inspection:

03/15/2017, 100 Hour

Certified Max Gross Wt.:

2700 lbs

Time Since Last Inspection:

 

Engines:

1 Turbo Shaft

Airframe Total Time:

197 Hours as of last inspection

Engine Manufacturer:

Rolls-Royce

ELT:

Installed, not activated

Engine Model/Series:

250-C300/A1

Registered Owner:

Hynes Aviation Industries, Inc

Rated Power:

300 hp

Operator:

Colorado Vertical

Operating Certificate(s) Held:

None

 

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual Conditions

Condition of Light:

Day

Observation Facility, Elevation:

1V6

Distance from Accident Site:

10 Nautical Miles

Observation Time:

1300 MDT

Direction from Accident Site:

101°

Lowest Cloud Condition:

Few / 16500 ft agl

Visibility

10 Miles

Lowest Ceiling:

None

Visibility (RVR):

 

Wind Speed/Gusts:

10 knots /

Turbulence Type Forecast/Actual:

/ None

Wind Direction:

180°

Turbulence Severity Forecast/Actual:

/

Altimeter Setting:

30.1 inches Hg

Temperature/Dew Point:

16°C / 5°C

Precipitation and Obscuration:

No Precipitation

Departure Point:

Canon City, CO

Type of Flight Plan Filed:

Company VFR

Destination:

Canon City, CO

Type of Clearance:

None

Departure Time:

1335 MDT

Type of Airspace:

Class G

 

 

Wreckage and Impact Information

Crew Injuries:

1 None

Aircraft Damage:

Substantial

Passenger Injuries:

4 None

Aircraft Fire:

None

Ground Injuries:

N/A

Aircraft Explosion:

None

Total Injuries:

5 None

Latitude, Longitude:

38.290000, -105.190000 (est)

 


 


Administrative Information

Investigator In Charge (IIC):

Aaron M Sauer

Report Date:

07/05/2018

Additional Participating Persons:

Keith Burke; Federal Aviation Administration; Denver, CO

Ken Martin; Robinson Helicopter; Torrance, CA

Publish Date:

04/17/2020

Note:

The NTSB did not travel to the scene of this accident.

Investigation Docket:

http://dms.ntsb.gov/pubdms/search/dockList.cfm?mKey=95202