Tuesday, January 16, 2018

Robinson R44 Raven II, N728CB, operated by Chesapeake Bay Helicopters: Accident occurred April 27, 2017 in Newton, Catawba County, North Carolina

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

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Charlotte, North Carolina
Lycoming Engines; Williamsport, Pennsylvania 
Robinson Helicopter Company; Torrance, California 

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

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms
  
Bulanov Galis LLC: http://registry.faa.gov/N728CB

Analysis 

The commercial helicopter pilot and a crewmember were conducting a pipeline patrol when they noticed a right-of-way infraction (construction work) that they wanted to photograph. The pilot then entered a left circuit at 500 ft above ground level. The pilot reported that he subsequently felt a shudder in the controls and that the helicopter began to yaw right and spin. Although the pilot reported that he maintained an airspeed of 70 knots while maneuvering, GPS data revealed that the loss of yaw control occurred at the completion of the first left circuit and the beginning of the second left circuit as the helicopter slowed to a groundspeed of about 1 mph. Weather data indicated that, at this point, the helicopter was experiencing an 8-knot tailwind. The pilot lowered the helicopter's nose but was unable to correct the spin. He entered an autorotation and maneuvered to avoid residences and utility poles, and the helicopter then impacted the ground.

Examination of the helicopter did not reveal any evidence of preimpact mechanical malfunctions that would have precluded normal operation. It is likely that the low-airspeed condition combined with a tailwind during out-of-ground-effect maneuvering resulted in a loss of helicopter control due to a loss of tail rotor effectiveness. 

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The pilot's failure to maintain an adequate airspeed during out-of-ground-effect maneuvering at a low airspeed with a tailwind, which resulted in a loss of helicopter control due to a loss of tail rotor effectiveness.

Findings

Aircraft
Airspeed - Not attained/maintained (Cause)

Personnel issues
Aircraft control - Pilot (Cause)

Environmental issues
Tailwind - Effect on operation (Cause)



Location: Newton, NC
Accident Number: ERA17LA168
Date & Time: 04/27/2017, 1330 EDT
Registration: N728CB
Aircraft: ROBINSON R44
Aircraft Damage: Substantial
Defining Event: Loss of tail rotor effectiveness
Injuries: 2 Minor
Flight Conducted Under: Part 91: General Aviation - Aerial Observation 

On April 27, 2017, about 1330 eastern daylight time, a Robinson R44 II, N728CB, operated by Chesapeake Bay Helicopters, was substantially damaged during a collision with terrain while maneuvering near Newton, North Carolina. The commercial pilot and crewmember sustained minor injuries. The local aerial observation flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and a company flight plan was filed for the flight that originated from Concord Regional Airport (JQF), Concord, North Carolina, about 1225.

The pilot reported that he was performing a pipeline patrol at 500 ft above ground level and an airspeed of 70 knots. During the patrol, the crew observed a right-of-way infraction and circled the location at the same airspeed and altitude. While extending the circling pattern, the pilot felt a shudder in the controls while at the same time, the nose of the helicopter yawed right and the helicopter began to spin. He immediately lowered the nose in an attempt to increase forward motion, but the rate of spin increased. He then attempted to set up for an autorotation and avoid residences and utility wires. The helicopter subsequently impacted the ground and the pilot was able to shut down the engine and exit the helicopter.

The crewmember reported that while on pipeline patrol, they circled to photograph construction work. While circling, the helicopter lost control and spun two or three times before impacting the ground.

Examination of the wreckage revealed substantial damage to the helicopter. Tail rotor driveshaft continuity was confirmed from the tail rotor blades to the main rotor. Continuity was also confirmed from the left anti-torque pedal to the tail rotor. A section of right anti-torque pedal control tube was found bent and separated. The separated section of control tube was retained for metallurgical examination, which revealed that the separation was consistent with overstress due to impact forces. No preimpact mechanical malfunctions were identified.

The helicopter's most recent 100-hour inspection was completed on March 10, 2017. At that time, the airframe and engine had accumulated 1,873.6 total hours of operation. The helicopter had flown an additional 43.6 hours from the time of the inspection, until the accident flight.

The recorded wind at an airport located about 10 miles northwest of the accident site, at 1253, was from 190° at 8 knots.

Review of GPS data provided by the operator revealed that after completion of the first left circuit and the beginning of the second left circuit, the helicopter's ground speed slowed to about 1 mph at a GPS altitude of 1,223 ft (about 500 ft above ground level). At that time, the GPS track was indicating a northerly course, with an approximate 8-knot tailwind. The track subsequently indicated transition from a left circuit to a right turn.

The Federal Aviation Administration issued advisory circular (AC)-90-95, Unanticipated Right Yaw in Helicopters during February 1995. The AC stated that the loss of tail rotor effectiveness (LTE) was a critical, low-speed aerodynamic flight characteristic which could result in an uncommanded right yaw rate that did not subside of its own accord and, if not corrected, could result in the loss of aircraft control. It also stated, "LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots."

Paragraph 9 of the AC covered reducing the onset of LTE. It stated:

"In order to reduce the onset of LTE, the pilot should: ... c. When maneuvering between hover and 30 knots: (1) Avoid tailwinds. If loss of translational lift occurs, it will result in an increased high power demand and an additional anti-torque requirement. (2) Avoid out of ground effect (OGE) hover and high power demand situations, such as low speed downwind turns. (3) Be especially aware of wind direction and velocity when hovering in winds of about 8 - 12 knots (especially OGE). There are no strong indicators to the pilot of a reduction of translation lift... (6) Stay vigilant to power and wind conditions."

Paragraph 10 of the AC addressed recovery techniques. It stated:

"a. If a sudden unanticipated right yaw occurs, the pilot should perform the following:
(1) Apply full left pedal. Simultaneously, move cyclic forward to increase speed. If altitude permits, reduce power. (2) As recovery is effected, adjust controls for normal forward flight. b. Collective pitch reduction will aid in arresting the yaw rate but may cause an increase in the rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor rpm. c. The amount of collective reduction should be based on the height above obstructions or surface, gross weight of the aircraft, and the existing atmospheric conditions. d. If the rotation cannot be stopped and ground contact is imminent, an autorotation may be the best course of action. The pilot should maintain full left pedal until rotation stops, then adjust to maintain heading."

Additionally, Robinson Safety Notice SN-34 addressed aerial survey and photography flights, and provided cautions about such flights below 30 knots airspeed. 



Pilot Information

Certificate: Commercial
Age: 34, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used: 3-point
Instrument Rating(s): Airplane; Helicopter
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 Without Waivers/Limitations
Last FAA Medical Exam: 08/29/2016
Occupational Pilot: Yes
Last Flight Review or Equivalent: 11/22/2016
Flight Time:  1529 hours (Total, all aircraft), 207 hours (Total, this make and model), 111 hours (Last 90 days, all aircraft), 14 hours (Last 30 days, all aircraft), 9 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Manufacturer: ROBINSON
Registration: N728CB
Model/Series: R44 II
Aircraft Category: Helicopter
Year of Manufacture: 2010
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 12899
Landing Gear Type: Skid;
Seats: 4
Date/Type of Last Inspection: 03/10/2017, 100 Hour
Certified Max Gross Wt.: 2500 lbs
Time Since Last Inspection: 43 Hours
Engines: 1 Reciprocating
Airframe Total Time: 1917 Hours at time of accident
Engine Manufacturer: LYCOMING
ELT: Not installed
Engine Model/Series: IO-540-AE1A5
Registered Owner: BULANOV GALIS LLC
Rated Power: 245 hp
Operator: Chesapeake Bay Helicopters
Operating Certificate(s) Held: Rotorcraft External Load (133)

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: HKY, 1186 ft msl
Observation Time: 1253 EDT
Distance from Accident Site: 10 Nautical Miles
Direction from Accident Site: 310°
Lowest Cloud Condition:
Temperature/Dew Point: 21°C / 13°C
Lowest Ceiling: Overcast / 4600 ft agl
Visibility:  8 Miles
Wind Speed/Gusts, Direction: 8 knots, 190°
Visibility (RVR):
Altimeter Setting: 29.88 inches Hg
Visibility (RVV):
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Concord, NC (JQF)
Type of Flight Plan Filed: Company VFR
Destination: Concord, NC (JQF)
Type of Clearance: None
Departure Time:  1225 EDT
Type of Airspace:

Wreckage and Impact Information

Crew Injuries: 2 Minor
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 Minor
Latitude, Longitude:  35.633333, -81.243889


NTSB Identification: ERA17LA168
14 CFR Part 91: General Aviation
Accident occurred Thursday, April 27, 2017 in Newton, NC
Aircraft: ROBINSON HELICOPTER COMPANY R44 II, registration: N728CB
Injuries: 2 Minor.

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 April 27, 2017, about 1330 eastern daylight time, a Robinson R44 II, N728CB, operated by Chesapeake Bay Helicopters, was substantially damaged during a collision with terrain while maneuvering near Newton, North Carolina. The commercial pilot and crewmember incurred minor injuries. The local aerial observation flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and a company flight plan was filed for the flight that originated from Concord Regional Airport (JQF), Concord, North Carolina, about 1225.

The pilot reported that he was performing a pipeline patrol at 500 feet above ground level and an airspeed of 70 knots. During the patrol, the crew observed a right-of-way infraction and circled the location at the same airspeed and altitude. While extending the circling pattern, the pilot felt a shudder in the controls while at the same time, the nose of the helicopter yawed right and the helicopter began to spin. He immediately lowered the nose in an attempt to increase forward motion, but the rate of spin increased. He then attempted to set up for an autorotation and avoid residences and utility wires. The helicopter subsequently impacted the ground and the pilot was able to shut down the engine and exit the helicopter.

The observer reported that while on pipeline patrol, they circled to photograph construction work. While circling, the helicopter lost control and spun two or three times before impacting the ground.

Examination of the wreckage revealed substantial damage to the helicopter. Tailrotor driveshaft continuity was confirmed from the tailrotor blades to the main rotor. Continuity was also confirmed from the left anti-torque pedal to the tailrotor. A section of right anti-torque pedal control tube was found bent and separated. The separated section of control tube was retained for metallurgical examination.

The helicopter's most recent 100-hour inspection was completed on March 10, 2017. At that time, the airframe and engine had accumulated 1,873.6 total hours of operation. The helicopter had flown and additional 43.6 hours from the time of the inspection, until the accident flight.

The recorded wind at an airport located about 10 miles northwest of the accident site, at 1253, was from 190° at 8 knots.

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