National Transportation Safety Board
Aviation Incident Final Report

 

 

Location:

Los Angeles, CA

Incident Number:

DCA20IA034A

Date & Time:

12/04/2019, 1915 PST

Registration:

N71HD

Aircraft:

AIRBUS AS 350 B2

Aircraft Damage:

Minor

Defining Event:

Midair collision

Injuries:

3 None

Flight Conducted Under:

Part 91: General Aviation - Aerial Observation

Analysis

 

The helicopter was operating under the provisions of 14 CFR Part 91 as an electronic news gathering flight, under visual flight rules, within Class G airspace. The pilot heard a noise which he first thought might be a bird strike, and made a precautionary landing. Post flight examination led the pilot and operator to believe they collided with a drone.

A search by ground and electronic methods did not locate a drone.

Laboratory examinations indicated that the shape and dimensions of the damage to the horizontal stabilizer were consistent with the configuration and dimensions of many popular small drones. A small mark inside the larger round dent was consistent with the propeller shaft diameter of common small drones.

Infrared examination revealed material transfer of polycarbonate polymer, which is a commonly used construction material of small drones. Although many items which could come in contact with the helicopter as ground FOD, are manufactured of polycarbonate (e.g. safety glasses, light lenses), the shape and configuration of the indentations and scuffs were very consistent with a small drone.

The reported collision occurred in Class G airspace, but higher than the 14 CFR Part 107 regulatory maximum of 400 feet agl for small drones. A provision in Part 107 allows for operations above 400 feet if the drone is within 400 feet laterally of a tall structure. Downtown Los Angeles was approximately ¼ mile away from the collision site, therefore, although the altitude and location are not authorized for drones without a waiver, it is not inconceivable that a drone operator could have been operating near the tall buildings, and deviated or exceeded the lateral requirements.

Although no drone was located, preventing complete certainty, all the available evidence was consistent with a collision with a small UAS.

 

Probable Cause and Findings

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

an inflight collision with a hard object of polycarbonate construction, with size and features consistent with that of a small UAS (drone).

 

 

Findings

Aircraft

Horizontal stabilizer - Damaged/degraded

Environmental issues

Aircraft - Effect on equipment (Cause)

Factual Information

History of Flight

Enroute

Midair collision (Defining event)

 

On December 4, 2019, at 7:15 pm, pacific standard time (PST), the pilot of an Airbus AS-350-B2 helicopter, N71HD, reported colliding with an unknown object at 1,100 feet above mean sea level (msl) in the vicinity of Los Angeles City Hall. The pilot conducted a precautionary landing at a nearby helipad. Post-flight examination revealed minor damage to the right horizontal stabilizer and tail rotor blade. The pilot and operator reported that no visible evidence of a bird strike was apparent, and believed that the aircraft collided with a small unmanned aircraft (sUAS, or drone).There were no injuries to the pilot or two passengers. The helicopter was operated by Helinet Aviation Services as an electronic news gathering flight for ABC7 News in Los Angeles. The helicopter was operated under visual flight rules under 14 Code of Federal Regulations (CFR) Part 91. Night visual meteorological conditions prevailed at the time of the incident.

The pilot reported that it was fully night conditions, and that it was difficult to make out individual lights in the area due to high concentration of city lights. He reported that he was transitioning between story locations at 1,100 feet mean sea level (msl) cruising at 100 to 110 knots. He noted some clouds above but none in his immediate area. He said did not see anything prior to hearing the loud noise. He attributed what he might have mentioned as a flash of light as actually from his own strobes reflecting off the main rotor blades.

He described the area of the event as east of City Hall bounded by Los Angeles St, Alameda St, Cesar Chavez Ave, and East 2nd St. This location was passed on to the Los Angeles Police Department to conduct a search of the area. No drone was found.
 


Figure 1 – Reported area of collision

The operator reported that the onboard cameras were stowed and did not record video at the time of the reported collision. The operator and NTSB investigator conducted a search of social media for any possible indications of a lost drone in the area, nothing definitive was found. Two drone detection companies were operating in the area, but did not have any targets in the area at the time of the report. Both companies reported less than complete coverage of the area.

Although the reported location was in Class G airspace, the FAA was queried for any sUAS airspace authorizations active in the nearby Class B, there were none.

There was a small round dent which partially punctured the leading edge of the horizontal stabilizer. Further dents and scuff marks were approximately 6 to 8 inches outboard of the round dent on the leading edge and along the upper surface. One of the tail rotor blades exhibited a small gouge in the composite surface approximately mid-chord.
 


 



Figure 2 Damage to helicopter

The helicopter pilot held an FAA commercial pilot certificate, with rotorcraft-helicopter and helicopter instrument rating, and had logged 3,753 hours. He held an FAA first class medical certificate.

The pilot reported that he has experienced bird strikes in the past. He said he had never seen a small drone while flying the helicopter.

 

 

 

 

 

 

 

Aircraft and Owner/Operator Information

Aircraft Make:

AIRBUS

Registration:

N71HD

Model/Series:

AS 350 B2 No Series

Aircraft Category:

Helicopter

Year of Manufacture:

2004

Amateur Built:

No

Airworthiness Certificate:

Normal

Serial Number:

3849

Landing Gear Type:

Skid

Seats:

6

Date/Type of Last Inspection:

 

Certified Max Gross Wt.:

 

Time Since Last Inspection:

 

Engines:

 

Airframe Total Time:

 

Engine Manufacturer:

 

ELT:

 

Engine Model/Series:

 

Registered Owner:

Helinet Aviation Services Llc

Rated Power:

 

Operator:

Helinet Aviation Services Llc

Operating Certificate(s) Held:

On-demand Air Taxi (135)

 

The Airbus (Eurocopter) AS-350-B2 is a 6 seat single engine helicopter, powered by a Turbomeca Arriel 1D1 turboshaft engine. The main rotor blades rotate clockwise as viewed from above. It is in wide use in electronic news gathering, law enforcement, air tour, and observation roles. N71HD was delivered in May of 2005 to Helinet.

The KLAX surface observation at 6:53 pm reported wind from 270 degrees at 8 knots, visibility 10 miles, with few clouds at 1,100 feet and 3,600 feet.

The helicopter was equipped with a SpiderTrax flight following system, which indicated the helicopter passing northeasterly in the vicinity of LA City Hall at 7:15 pm at 1,104 feet msl (approximately 828 above ground level (agl)).

 

 

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual Conditions

Condition of Light:

Night

Observation Facility, Elevation:

 

Distance from Accident Site:

 

Observation Time:

 

Direction from Accident Site:

 

Lowest Cloud Condition:

 

Visibility

 

Lowest Ceiling:

 

Visibility (RVR):

 

Wind Speed/Gusts:

/

Turbulence Type Forecast/Actual:

/

Wind Direction:

 

Turbulence Severity Forecast/Actual:

/

Altimeter Setting:

 

Temperature/Dew Point:

 

Precipitation and Obscuration:

 

Departure Point:

Burbank, CA (KBUR)

Type of Flight Plan Filed:

 

Destination:

Los Angeles, CA

Type of Clearance:

None

Departure Time:

 

Type of Airspace:

Class G

 

 

 

Wreckage and Impact Information

Crew Injuries:

1 None

Aircraft Damage:

Minor

Passenger Injuries:

2 None

Aircraft Fire:

None

Ground Injuries:

N/A

Aircraft Explosion:

None

Total Injuries:

3 None

Latitude, Longitude:

33.942500, -118.408056

 

 

 


 

 

Tests And Research

NTSB Materials Laboratory

The horizontal stabilizer and tail rotor were sent to the NTSB Materials Laboratory for examination. Visual examination was consistent with an inflight hard-body impact. The dent and scuff marks were compared to the dimensions of common small drones and were consistent with the distance and orientation between the motor and center fuselage/battery compartment (Figure 3).

Figure 3 – Angled view comparing common drone to impact marks. The drone in the photo is an exemplar of a popular drone used to illustrate size comparison. Numerous manufacturers and models of drone fall into this size class. Does not necessarily depict the actual collision object.

Ultraviolet light inspection revealed no evidence of biological material. The dented region exhibiting material transfer was examined using Fourier-transform infrared spectroscopy (FTIR). The white and gray areas were probed, and the data were contrasted with an area of the painted stabilizer skin surface away from the impact zone. In subtracting out the spectrum peaks from the control area away from the impact zone, several peaks consistent with a different or foreign material were noted. These peaks were consistent with a polycarbonate polymer