VAN NUYS, CA, USA
N1801B
Beech C90
N162JC
Gulfstream G-1159A
The Gulfstream descended from above and behind the Beech C90 and collided with it while both aircraft were on 2.5-mile final approach to the same runway. Visual meteorological conditions prevailed. The Gulfstream was on an ILS instrument approach and the Beech was on a VFR approach. Both airplanes subsequently landed without additional damage or injury to the occupants. Upon initial contact with the air traffic control tower, the Beech C90 was instructed to make a straight-in approach to the runway and was given a transponder code. The pilot miss-set the assigned code, which, due to an air traffic control computer software anomaly, caused the Beech's identifying data block to be suppressed and not available to the radar approach controller. The approach controller attempted to provide traffic advisories to the overtaking Gulfstream pilot but could not determine the Beech's type, destination, or altitude. (Altitude data became available to the controller 1 minute 14 seconds before the collision via a conflict alert message.) The controller did not issue a traffic alert to the Gulfstream crew when the Beech's altitude became known. Additionally, for unrelated reasons, the approach controller experienced frequent failures of his communication radio transmitter and was required to repeat transmissions to the Gulfstream and other aircraft. Despite the traffic point-out, in front of them 1 mile, altitude unknown, and later at short distance at a known altitude near theirs, the Gulfstream flight crew did not visually identify and avoid the Beech nor did they request radar separation services. On initial contact with the tower, the Gulfstream crew was cleared to land on the same runway the tower had previously cleared the Beech to make a straight-in approach to. When asked by the Gulfstream if there was any traffic in their vicinity, the tower replied, "nothing reported." The tower controller realized his mistake approximately 16 seconds later, however, the collision had already occurred. The Gulfstream pilot reported there were no TCAS 2 traffic advisories within 3 miles and there were no resolution advisories. The Gulfstream first officer recalled a TCAS "traffic" advisory close by at near their altitude, but no annunciation in the minute or two before the collision. With the model TCAS aboard the Gulfstream, when the aircraft's landing gear is extended, the lower TCAS antenna goes into an omni-directional mode wherein targets detected on the lower antenna only are displayed to the flight crew on the cockpit TCAS display with a text message of range and delta altitude but no bearing information. The Beech's transponder antenna was on the lower fuselage and airframe structure shielded it from interrogation by the Gulfstream's TCAS.
HISTORY OF FLIGHT On October 17, 2000, at 1551 Pacific daylight time, a Beech C90, N1801B, collided in midair with a Gulfstream Aerospace G-1159A, N162JC, while both aircraft were on 4-mile final approach to runway 16R at the Van Nuys, California, airport. Both aircraft subsequently landed safely at Van Nuys airport, and there were no injuries to the airline transport certificated pilot and two passengers aboard the Beech C90, or to the airline transport certificated pilot and two crewmembers aboard the Gulfstream G-1159A. The Beech C90 was substantially damaged and the Gulfstream G-1159A received minor damage. The Beech C90 was operated on a visual flight rules flight plan under 14 CFR Part 135 as a nonscheduled, domestic air taxi flight by Sun Quest Executive Air Charter, and had departed from Bakersfield, California, at 1520. The Gulfstream G-1159A was operated under instrument flight rules by Trans-Exec Air Service, Inc., under 14 CFR Part 91 as a positioning flight, and had departed from Reno, Nevada, about 1500. A flight instructor, who was employed by the flight school division of Sun Quest Executive Air Charter, witnessed the midair collision from his car while driving westbound on the 118 freeway just past the 405 freeway interchange. The instructor said he just happened to look upward and his attention was attracted to two aircraft flying in close proximity, one behind the other, nearly co-speed but with the rear aircraft overtaking the aircraft in front of it. The swept wing aircraft that he later learned was a Gulfstream G3 was overtaking a smaller airplane. He couldn't judge altitude precisely; however, as he watched the two aircraft came together and the smaller airplane shuddered and then dropped down out of view behind some trees. It appeared the larger, swept-wing aircraft initiated a go-around maneuver. Another witness observed the collision from his home in the 10,000 block of Odessa Avenue (2 miles north of the Van Nuys airport). He reported looking up after hearing a jet aircraft and seeing a corporate jet aircraft (which he identified as a "G-3", i.e. Gulfstream) making what he considered a normal approach to the airport but with a smaller, twin-engine propeller aircraft (which he identified as a "King Air") behind and to the left of the corporate jet. The King Air was about one plane length behind the Gulfstream, one fuselage diameter below the jet, and was offset to the left so that the fuselage centerline of the King Air was even with the Gulfstream's left wingtip. As he watched for the next 5 - 7 seconds, the King Air overtook the Gulfstream until the King Air was under the left wing of the Gulfstream. About the time the King Air was under the wing of the Gulfstream, the vertical gap also closed and he observed the King Air to "make some slight maneuvering motions. The wings and fuselage moved around some. The King Air then fluttered like a falling leaf. The nose pointed down and the King Air dove toward the ground with its wings rocking back and forth." The King Air then recovered and continued flying toward the airport. He heard the engines of the Gulfstream increase in power and the aircraft pulled up and banked right before continuing toward the airport. He lost sight of both airplanes about 5 - 7 seconds after the collision. PERSONNEL INFORMATION In an interview the day following the accident, the pilot of the Beech C90 told the Safety Board investigator that the accident flight was conducted under 14 CFR Part 135, he was the sole pilot, and there were two passengers aboard. His flying day started at 0845, and the accident flight was his fifth flight of the day. The accident flight originated from Bakersfield. He said that the flight was conducted under visual flight rules with flight following from Los Angeles Air Route Traffic Control Center (Los Angeles Center). While descending toward Newhall Pass, as the aircraft reached about 4,000 feet (msl), he was advised that radar contact was lost and to squawk 1200 and contact the Van Nuys Air Traffic Control Tower (Van Nuys Tower). He contacted the tower at Newhall Pass with (ATIS) information Papa and was issued a discrete transponder code and was told to make a straight in approach to runway 16R. He saw the airport and aligned the aircraft with runway 16R. The weather was clear, the visibility was unrestricted, and the sun angle was not a factor. The approach was made by visual reference alone. He stated he never heard anything on the radio about another aircraft that was a factor for him. When he was 3 - 4 miles out on final for 16R with airspeed of 120 - 125 knots, with landing gear down and flaps at the approach position, suddenly and unexpectedly, there was a shadow over his aircraft and the nose of the Gulfstream became visible in the top of his windshield. Immediately there was a loud "bang," his aircraft rocked violently, and he thinks it turned to the right. He looked outside and saw the damage to the left wing and asked his passengers if they were okay. They were very frightened and he said, "We are okay" to reassure them. He heard the Gulfstream transmit that they (the Gulfstream) had either encountered wake turbulence or had hit someone. He transmitted that the Gulfstream had hit them; they were going to land and to "bring out the trucks." Unbeknownst to the King Air pilot, his aircraft's radio antenna had been broken off and he could neither transmit nor could he hear the tower. He slowed the aircraft and proceeded to land. While on short final approach he received a green light from the control tower. After landing, without radio contact, he taxied with care to parking. In an interview the day following the accident, the pilot-in-command of the Gulfstream G-1159A reported that on the morning of the accident he and the first officer had flown from Van Nuys to Reno, Nevada, as a 14 CFR Part 135 air taxi flight and dropped passengers in Reno. The accident occurred on the return flight, which was a 14 CFR Part 91 repositioning flight. His first officer was the pilot flying for the return trip. They departed Reno on an instrument flight rules (IFR) flight plan and remained IFR throughout the approach (where the accident occurred) and landing. Their arrival route was via the Fillmore VORTAC (navigational aide) and then radar vectors to the Van Nuys ILS (navigational aide) runway 16R final approach course. The Gulfstream pilot said that as they were established on the ILS final near Magic Mountain [amusement park, 10 miles north of Van Nuys] at 5,000 - 6,000 feet msl and north of the Newhall Pass, they received a traffic advisory from Southern California Terminal Radar Approach Control (SOCAL Approach) advising them of traffic. He wasn't certain of the bearing but recalled that the traffic was generally in front of them at 2,900 feet msl. As the pilot-not-flying, he spent most of his time looking outside the aircraft for traffic. He recalled looking at the TCAS display, which was on the 5-mile scale, and noting a single target about 5 miles ahead of them. His practice in the terminal area is to keep the TCAS on short range settings to avoid clutter, so he reset the scale to 3 miles and there was no traffic displayed. As they continued the approach, with landing gear and landing flaps extended, they received a second traffic advisory from SOCAL Approach regarding the traffic ahead, and at one point, the first officer flattened the approach until they were about a dot high on the glideslope. He did not recall any TCAS annunciation. He reported that at no time did SOCAL Approach say what the traffic ahead was doing (i.e. preceding them to the airport) nor instruct them to follow anyone or offer or issue vectors for separation from the traffic. When they were about 4 miles north of the runway threshold, on the ILS at 140 - 145 knots, he felt the aircraft roll. He didn't know what had happened but knew it was not normal. He thought it might have been wake turbulence but he then saw a King Air aircraft below them, on his left and very close. He took control of the aircraft from the first officer and initiated a go-around. The first officer took over communications and reported to Van Nuys Tower that they had possibly had a midair collision and they were going to do a flyby to have the tower check the position of the landing gear and flaps. Following the flyby, the tower said that the landing gear and flaps appeared normal. They turned into right-hand traffic for runway 16R and made two more low passes to confirm the landing gear was undamaged and then made a normal landing. The Gulfstream pilot also said that the TCAS pretakeoff self-test had been satisfactory prior to both takeoffs that day and that it was his observation, in this and other aircraft, that not all traffic is displayed on TCAS so he still emphasizes visual scanning. He has flown 10 - 15 trips with this first officer previously, and reported they had good cockpit coordination and practiced crew resource management as taught in their training at Flight Safety International. He also stressed that they had no awareness there had been an aircraft inbound to Van Nuys ahead of them. In his written statement to the Safety Board, the Gulfstream pilot added that he and his copilot were wearing noise-canceling headsets and communicated via a "hot mic" intercom in which both pilots heard both intercom and radio communications. He elaborated that when they were over Newhall Pass, SOCAL Approach Control "issued a traffic advisory to the effect that traffic was ahead unverified at 2,900 feet (as I recall) and ATC was not talking to them." Following resetting of the TCAS to the 3-mile scale, "both pilots agreed that we had none of the following: 1) Visual contact with any aircraft; 2) TCAS target; 3) ATC vector for traffic or suggested altitude; [or] 4) ATC issuance of instructions to follow another aircraft inbound to Van Nuys. A mutual decision was made by both pilots that we had no traffic within three miles." Following the collision, which he stated was "a soft roll," he "caught sight of a King Air that was 90 degrees left and very close (within 50 feet). I could see the entire airplane including its tail ahead of our left wing." In a telephone interview with the Safety Board investigator on the evening of the accident, the first officer (copilot) aboard the Gulfstream said the flight was a Part 135 drop-off in Reno, Nevada and a Part 91 deadhead home. The first officer was the pilot flying on the return trip. He said that the return flight from Reno was unremarkable until the approach to Van Nuys commenced. The flight was on an instrument flight plan and cruised at flight level 330 (approximately 33,000 feet). He said that approaching Van Nuys they could have cancelled IFR because the visibility was very good, however, they remained on the instrument flight plan and executed the "Fernando 5" arrival. About the time they intercepted the glideslope (from above), SOCAL Approach advised they had traffic at 12 o'clock, he did not recall the range, at 2,900 feet, and the controller said, "I'm not talking to him." They replied "we're looking." The captain looked outside full-time to locate the traffic and the first officer divided his time between looking for the traffic and flying the aircraft. There were additional calls about the traffic at 2,900 feet in front of them from SOCAL Approach and he leveled the aircraft for a period of time at 3,000 feet; however, when it appeared the approach was becoming destabilized and they thought the traffic was past, they continued their descent. The aircraft was equipped with TCAS 1 that has a display on both the pilot's and copilot's panels which was set to less than the 10-mile scale. The TCAS announced "traffic, traffic" and he thinks there was traffic displayed close by at near their altitude but he said this version of TCAS does not provide resolution advisories. They never saw the traffic. About the time they were changing radio frequencies to the Van Nuys tower they felt a shudder in the aircraft that they at first thought was wake turbulence but the captain was suspicious they might have hit another aircraft. The captain took control of the aircraft from the first officer and started a go-around. The first officer notified the tower that they had either encountered severe wake turbulence or had hit someone, and that they were going to do a flyby and ask the tower to look the aircraft over. The landing gear had been extended at the time of the collision and they had three green lights on the landing gear. They did a flyby and the tower personnel and the pilot of a Hawker HS-125 (on the ground awaiting takeoff clearance) radioed that the gear looked down and normal. Following the flyby, the captain called their company on the radio and the Director of Maintenance (DOM) came out to observe the aircraft as they performed a second flyby. The DOM said the gear looked OK and so the crew returned and made a normal landing with flaps at 20 degrees. The flaps had been at 20 degrees at the time of the collision and they did not want to move them. The first officer said that SOCAL approach was moderately busy but never mentioned the type of aircraft they were looking for or the fact that it was on approach to Van Nuys. He thought, for some reason, that the traffic was crossing in front of them. SOCAL Approach never issued instructions to stop descent and never issued a radar vector for separation. In his written statement to the Safety Board, the Gulfstream first officer reported that, following the initial traffic advisory from SOCAL Approach Control, "About this time, our TCAS system displayed a traffic advisory in front of us inside three miles. As I recall, SOCAL issued a second traffic advisory and again mentioned the altitude as 2,900 ft, unverified. At this time, to the best of my recollection, we were descending at approximately 800 fpm, on glide slope, landing gear down at approximately 140-145 KIAS, when I decided to reduce the rate of descent until we were clear of the reported traffic. We were then handed off to VNY tower, and about this time I recall the TCAS contact disappearing, indicating a non-threat condition. After a minute or two with no traffic conflict announced by VNY tower, displayed on the TCAS, or in sight, [the captain] and I continued our normal descent from a position now approximately one dot above the glide slope. [The captain] suggested full flaps, I concurred, and he lowered the flaps to the full down position. As I gradually increased our rate of descent to recapture the glide slope, we felt the aircraft shudder slightly." AIRCRAFT INFORMATION The Gulfstream G3 was equipped with an Allied Signal Aerospace TPU-67A Traffic Collision Avoidance System (TCAS-2) with version 6 software. On October 18, 2000, the TCAS system was ramp tested in accordance with the Allied Signal Aerospace Field Diagnostics Program and satisfied the test for return to service. According to the technician who performed the ramp test, with this model TCAS, when the aircraft's landing gear is extended, the lower TCAS antenna goes into an omni-directional mode wherein targets detected on the lower antenna only are displayed to the flight crew on the cockpit TCAS display with a text message of range and delta altitude but no bearing information. Also, when the aircraft descends below 900 feet radar altitude on approach, resolution advisories are inhibited and only "traffic" advisories are announced. Below 400 feet on approach all audio warnings are inhibited. Version 6 software does not record the history of resolution advisories that have been issued by the TCAS system. A Federal Aviation Administration (FAA) inspector from the Van Nuys Flight Standards District Office examined the Beech C90 aircraft on the afternoon following the accident and determined that the transponder was set to code 0226. The transponder in the Beech, a King (Honeywell) KT-76 model, was ramp tested in accordance with FAR Part 91.411 and passed the test for return to service on October 18, 2000, including mode C interrogation/reply at airport elevation. The transponder anten
The failure of the pilot to correctly set a new transponder code and an anomaly in ATC software that precluded the controller from manually overriding the resulting inhibition of displayed data. Factors in the accident were impaired function of the collision avoidance system in the other airplane due to structural masking of the airplane's transponder antenna, an intermittent failure of the approach controller's communication radio transmitter which interfered with his ability to communicate traffic information to the flight crew of other airplane, the failure of both the approach controller and the tower controller to issue safety alerts when the traffic conflict became apparent, and the failure of the flight crew of the other airplane to maintain an adequate visual lookout to see and avoid the airplane.
Source: NTSB Aviation Accident Database
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