# NTSB SEA00FA021: Bell 206L-3, N206AC, Seattle, WA, November 17, 1999 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Field investigation · Final report - Date: November 17, 1999, 12:10 local (20:10 UTC) - Place: Seattle, WA - Coordinates: 47.620906, -122.349075 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.6209&lon=-122.3491&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor, 2 uninjured - Status: Completed, report May 17, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 47773 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA00FA021 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/47773/pdf - Page: https://openairdocs.org/ntsb/SEA00FA021 ## Probable cause (aircraft 2) Adequate separation and lookout not maintained by the pilots of both aircraft. ## Probable cause (aircraft 1) Adequate separation and lookout not maintained by the pilots of both aircraft. ## Analysis (aircraft 2) The pilot of N5735A reported that he was transitioning the area of Lake Union (on a local electronic news gathering flight) in a south-southwesterly direction when the two aircraft collided. He stated that he simultaneously saw the other aircraft and felt the impact. After the collision, the pilot initiated a descent and landed on a nearby helipad. The pilot reported that prior to the collision he was monitoring the common traffic advisory frequency (CTAF) for Lake Union (122.90). He stated that just before transitioning the area he reported his position, altitude and heading on 122.90. The pilot of N206AC reported that he departed Boeing Field and was proceeding northbound. He stated that he had just cleared Boeing's Delta airspace and switched to Seattle Radio (122.50) when he '...experienced a loud bang and vibration in the main rotor system'. The pilot initiated a descent to a nearby helipad, and was able to land without further incident. The pilot stated he did not see the other aircraft before, or after the collision. There were no reported mechanical failures or malfunctions that may of contributed to the accident. A calculated convergence angle between the two aircraft indicated that there were no visual restrictions that would have prevented the pilot from seeing the other aircraft. ## Analysis (aircraft 1) The pilot of N5735A reported that he was transitioning the area of Lake Union (on a local electronic news gathering flight) in a south-southwesterly direction when the two aircraft collided. He stated that he simultaneously saw the other aircraft and felt the impact. After the collision, the pilot initiated a descent and landed on a nearby helipad. The pilot reported that prior to the collision he was monitoring the common traffic advisory frequency (CTAF) for Lake Union (122.90). He stated that just before transitioning the area he reported his position, altitude and heading on 122.90. The pilot of N206AC reported that he departed Boeing Field and was proceeding northbound. He stated that he had just cleared Boeing's Delta airspace and switched to Seattle Radio (122.50) when he '...experienced a loud bang and vibration in the main rotor system'. The pilot initiated a descent to a nearby helipad, and was able to land without further incident. The pilot stated he did not see the other aircraft before, or after the collision. There were no reported mechanical failures or malfunctions that may of contributed to the accident. A calculated convergence angle between the two aircraft indicated that there were no visual restrictions that would have prevented the pilot from seeing the other aircraft. ## Factual narrative (aircraft 2) HISTORY OF FLIGHT On November 17, 1999 about 1210 Pacific standard time, a Bell 206L-3, N206AC, registered to and operated by Aero-Copters, Inc., as a 14CFR91 commercial flight, and a Bell 206B, N5735A, registered to WPXI, Inc. and operated by KIRO Television as a 14CFR91 commercial flight, collided in mid-air about seven miles north of Boeing Field Airport, Seattle, Washington. Visual meteorological conditions prevailed and no flight plan was filed for N5735A; however, there was a flight plan on file for N206AC. Both aircraft received substantial damage. The commercial pilot of N5735A sustained minor injuries, and his passenger was uninjured. The commercial pilot, the sole occupant of N206AC, was not injured. N206AC departed Boeing Field approximately five minutes prior to the accident with a planned destination of Vancouver, British Columbia, Canada. N5735A departed Boeing Field approximately 36 minutes prior to the accident for a local electronic news gathering flight. In a written statement, the pilot of N5735A reported that he was transitioning the area of Lake Union in a south-southwesterly direction when the two aircraft collided. He stated that "...I simultaneously saw the other aircraft and felt the impact". The passenger of N5735A, a news photographer, stated that he "...heard a loud bang and felt the helicopter shake". After the collision the pilot determined the aircraft was still controllable and initiated a descent to a rooftop helipad located approximately a 1/2 mile from where the helicopters collided. The pilot landed the aircraft on the helipad without further incident. After landing at the helipad, the pilot and photographer determined that the other aircraft involved in the collision was operated by Aero-Copters. They contacted Aero-Copters and learned that the other helicopter involved in the collision landed at a nearby helipad. The pilot of N5735A reported that prior to the collision he was monitoring the common traffic advisory frequency (CTAF) for Lake Union (122.90). He also stated that just before transitioning the area he reported his position, altitude and heading on 122.90. During a telephone interview and subsequent written statement, the pilot of N206AC reported that he departed Boeing Field, Seattle, Washington, and was proceeding northbound. He stated that he had just cleared Boeing's Delta airspace and switched to Seattle Radio (122.50) when he "...experienced a loud bang and vibration in the main rotor system". The pilot initiated a descent to a nearby helipad at the University of Washington and was able to land without further incident. The pilot reported that after landing he discovered damage to the main rotor blades and suspected that he had collided with a weather balloon. Neither pilot reported experiencing any mechanical failures or malfunctions prior to the collision. DAMAGE TO AIRCRAFT Both aircraft sustained substantial damage. The leading edge of the main rotor blade of N206AC had a large gouge, with paint transfer, approximately twelve inches inboard from the rotor tip. The gouge was approximately 5 inches in length with scratch marks radiating aft on both the top and bottom surfaces of the rotor blade. Just above the leading edge damage, a five-inch slash in the honeycomb material was noted. The slash was approximately 1/4 inch deep and ran perpendicular to the leading edge. A small puncture type hole was also noted to the fuselage aft of the rear door (refer to photograph #2). The helicopter operated by WPXI, Inc., N5735A, sustained substantial damage to the to main rotor blades and fuselage. A large slash was noted to the forward engine/transmission cowling, measuring approximately 18 inches in length. The helicopter's wire cutter and support brackets, located just forward of the engine cowling, were fractured. Both the right and left windshields were broken, and numerous fragments of Plexiglas were found in the cockpit area. Approximately 6 inches outboard of the main rotor blade trim tab, a gouge in the lower surface of the rotor blade was noted. The gouge paralleled the chord line and was approximately 6 inches in length (refer to attached photos). METEOROLOGICAL INFORMATION At 1153 Pacific Standard Time, the hourly observation (METAR) for Boeing Field, seven miles south of the accident site, reported winds from 360 degrees at 4 knots; visibility 10 miles; broken clouds at 1,700 feet AGL; temperature 51 degrees F; dew point temperature 44 degrees F; altimeter 29.97 inches hg. ADDITIONAL DATA Preliminary Radar data provided by Seattle-Tacoma Air Traffic Control Tower, Seattle, Washington, indicated that N5735A was tracking a heading of 227 degrees magnetic, with an airspeed of 70 knots and an altitude of 1,000 feet above mean sea level prior to the collision; N206AC was tracking a heading of 342 degrees magnetic with an airspeed of 118 knots and an altitude of 1,000 feet above mean sea level. Hard copies of the radar data from Seattle-Tacoma Air Traffic Control Tower were not available to the National Transportation Board. Both aircraft were released to the operators on November 17, 1999. ## Factual narrative (aircraft 1) HISTORY OF FLIGHT On November 17, 1999 about 1210 Pacific standard time, a Bell 206L-3, N206AC, registered to and operated by Aero-Copters, Inc., as a 14CFR91 commercial flight, and a Bell 206B, N5735A, registered to WPXI, Inc. and operated by KIRO Television as a 14CFR91 commercial flight, collided in mid-air about seven miles north of Boeing Field Airport, Seattle, Washington. Visual meteorological conditions prevailed and no flight plan was filed for N5735A; however, there was a flight plan on file for N206AC. Both aircraft received substantial damage. The commercial pilot of N5735A sustained minor injuries, and his passenger was uninjured. The commercial pilot, the sole occupant of N206AC, was not injured. N206AC departed Boeing Field approximately five minutes prior to the accident with a planned destination of Vancouver, British Columbia, Canada. N5735A departed Boeing Field approximately 36 minutes prior to the accident for a local electronic news gathering flight. In a written statement, the pilot of N5735A reported that he was transitioning the area of Lake Union in a south-southwesterly direction when the two aircraft collided. He stated that "...I simultaneously saw the other aircraft and felt the impact". The passenger of N5735A, a news photographer, stated that he "...heard a loud bang and felt the helicopter shake". After the collision the pilot determined the aircraft was still controllable and initiated a descent to a rooftop helipad located approximately a 1/2 mile from where the helicopters collided. The pilot landed the aircraft on the helipad without further incident. After landing at the helipad, the pilot and photographer determined that the other aircraft involved in the collision was operated by Aero-Copters. They contacted Aero-Copters and learned that the other helicopter involved in the collision landed at a nearby helipad. The pilot of N5735A reported that prior to the collision he was monitoring the common traffic advisory frequency (CTAF) for Lake Union (122.90). He also stated that just before transitioning the area he reported his position, altitude and heading on 122.90. During a telephone interview and subsequent written statement, the pilot of N206AC reported that he departed Boeing Field, Seattle, Washington, and was proceeding northbound. He stated that he had just cleared Boeing's Delta airspace and switched to Seattle Radio (122.50) when he "...experienced a loud bang and vibration in the main rotor system". The pilot initiated a descent to a nearby helipad at the University of Washington and was able to land without further incident. The pilot reported that after landing he discovered damage to the main rotor blades and suspected that he had collided with a weather balloon. Neither pilot reported experiencing any mechanical failures or malfunctions prior to the collision. DAMAGE TO AIRCRAFT Both aircraft sustained substantial damage. The leading edge of the main rotor blade of N206AC had a large gouge, with paint transfer, approximately twelve inches inboard from the rotor tip. The gouge was approximately 5 inches in length with scratch marks radiating aft on both the top and bottom surfaces of the rotor blade. Just above the leading edge damage, a five-inch slash in the honeycomb material was noted. The slash was approximately 1/4 inch deep and ran perpendicular to the leading edge. A small puncture type hole was also noted to the fuselage aft of the rear door (refer to photograph #2). The helicopter operated by WPXI, Inc., N5735A, sustained substantial damage to the main rotor blades and fuselage. A large slash was noted to the forward engine/transmission cowling, measuring approximately 18 inches in length. The helicopter's wire cutter and support brackets, located just forward of the engine cowling, were fractured. Both the right and left windshields were broken, and numerous fragments of Plexiglas were found in the cockpit area. Approximately 6 inches outboard of the main rotor blade trim tab, a gouge in the lower surface of the rotor blade was noted. The gouge paralleled the chord line and was approximately 6 inches in length (refer to attached photos). METEOROLOGICAL INFORMATION At 1153 Pacific Standard Time, the hourly observation (METAR) for Boeing Field, seven miles south of the accident site, reported winds from 360 degrees at 4 knots; visibility 10 miles; broken clouds at 1,700 feet AGL; temperature 51 degrees F; dew point temperature 44 degrees F; altimeter 29.97 inches hg. ADDITIONAL DATA Preliminary radar data provided by Seattle-Tacoma Air Traffic Control Tower, Seattle, Washington, indicated that N5735A was tracking a heading of 227 degrees magnetic, with an airspeed of 70 knots and an altitude of 1,000 feet above mean sea level prior to the collision; N206AC was tracking a heading of 342 degrees magnetic with an airspeed of 118 knots and an altitude of 1,000 feet above mean sea level. Hard copies of the radar data from Seattle-Tacoma Air Traffic Control Tower were not available to the National Transportation Safety Board. Both aircraft were released to the operators on November 17, 1999. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Midair collision, cruise - visual lookout - inadequate, pilot in command (cause) - visual lookout - inadequate, pilot of other aircraft (cause) - Midair collision, cruise - visual lookout - inaccurate, pilot in command (cause) - visual lookout - inadequate, pilot of other aircraft (cause) ## Aircraft 1 - Registration: [N206AC](https://openairdocs.org/aircraft/N206AC), registered now, S/N 3521, built 1981 (OpenAirDocs) - Reported make and model: Bell 206L-3 - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Registry engine: [Allison 250-C20 series](https://openairdocs.org/engine/allison-250-c20-series) (registry code 03020, turbo-prop) (OpenAirDocs) - Category: Helicopter - Serial number: 51545 - Airframe hours: 1698 - Engines: Allison 250-C30P 650 horsepower turbo shaft - Damage: Substantial damage - Flight: Business, Part 91 - Registered owner: Aero-Copters, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 17, 1999, 1 hours before - Departed: BFI, SEATTLE, WA - Destination: YVR, VANCOUVER - Flight plan: VFR ## Aircraft 2 - Registration: [N5735A](https://openairdocs.org/deregistered/N5735A-2013-03-28), registration cancelled 2013-03-28, S/N 3002 (OpenAirDocs) - Reported make and model: Bell 206B - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Category: Helicopter - Serial number: 3002 - Airframe hours: 10969 - Engines: Allison 250-C20B 320 horsepower turbo shaft - Damage: Substantial damage - Flight: Business, Part 91 - Operator: Kiro Inc. - Registered owner: Wpxi Inc - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, October 16, 1999, 76 hours before - Departed: BFI, SEATTLE, WA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot, aircraft N206AC; age 57; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--w/ waivers/lim; seat: right; flight hours: 19,000 total, 14,000 in this make and model, 18,750 as pilot in command, 200 in the last 90 days, 85 in the last 30 days - Pilot, aircraft N5735A; age 52; commercial; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 12,500 total, 10,000 in this make and model, 12,300 as pilot in command ## Weather - Conditions: Visual (VMC), Day - Wind: 360° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: 1,700 ft broken - Temperature: 52 °F, dew point 45 °F - Altimeter: 29.00 inHg - Observed at: BFI, 7 nm away ## FAA reports on this event (2) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19991117040881A](https://openairdocs.org/incident/19991117040881A), Nov 17, 1999: Bell 206L3, Seattle, WA, No damage. (-23) Aircaft departed bfi at 1205 headed north to vancouver, Canada. The pilot had climbed to approx. 1000 ft MSL and had an indicated airspeed of 10 KTS.… - [Accident 19991117043239A](https://openairdocs.org/incident/19991117043239A), Nov 17, 1999: Bell 206B, Seattle, WA, No damage. (-23) A/c traveling sw bound from webster point on east side of lake union toward downtown Seattle at approx. 1000 fet at 90 KTS indicated. Pilot… From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.