Aviation Safety Letter 2/2004

When Things Aren't.

Artist's impression of the risk of collision
Artist's impression of the risk of collision

When things aren't running as they normally do, the level of risk is usually higher. This, in turn, means extraordinary vigilance must be applied. Case in point: in October 2000, a Boeing 747 crashed shortly after lifting off from Taipei, Taiwan, killing all onboard. The crew had been cleared for a Runway 05 left (05L) departure because Runway 05 right (05R) was closed due to construction. After reaching the end of a parallel taxiway, the crew turned the aircraft immediately to Runway 05R. After a short hold, it started its take-off roll. A few seconds after reaching decision speed (V1), the aircraft hit concrete barriers and construction equipment on the runway. The plane crashed back onto the runway, breaking up and bursting into flames.

Conditions on that day were anything but normal. A NOTAM had been issued, indicating that part of Runway 05R was closed for construction. Heavy rain and strong winds from a typhoon prevailed, affecting visibility. Moderate time pressure to take off before the inbound typhoon closed-in around the airport may have influenced the flight crew's decision-making and ability to maintain situational awareness. In the end, the flight crew lost situational awareness and took off from the wrong runway.

Airport maintenance and construction are unavoidable and necessary, which means Canadian airports are also affected. On November 20, 2002, a Shorts SD 360 was on final approach to Runway 12 at the Vancouver International Airport, British Columbia, at the same time as a Boeing 747-400 bound for Japan began its take-off roll from Runway 26R. Large aircraft rarely takeoff from Runway 26R at Vancouver, but there was a construction project going on, and two cranes were set up beyond the departure end of Runway 26L, the usual take-off runway for large aircraft at Vancouver. The "unusual" circumstances were set, the first link in the accident chain. The chain was luckily broken, as it most often is; however, there remained a serious risk of collision, when the Shorts SD 360 crossed 0.5 nautical miles (NM) in front of and 100 ft below the Boeing 747-400. The following synopsis is based on the Transportation Safety Board of Canada (TSB) Final Report A02P0299.

A NAV CANADA Operations Bulletin described the construction project and included air traffic control (ATC) operating limitations. When aircraft were too heavy to use Runway 26L for departure with the cranes operating, these aircraft would be allowed to use Runway 26R. No guidelines were issued for the coordination and use of Runway 12 when Runway 26R was being used for departures. During the incident, the Vancouver Tower was staffed with five controllers: tower south, ground south, tower advisory, clearance delivery, and the combined tower north and ground north.

At 11:29 local time, Runways 26R and 26L became the active runways. With Runway 12 already active, three runways were in use at the time of the incident. The tower south controller controlled Runway 26L (the primary runway used for departing and some arriving aircraft) and Runway 12 (used for arrivals). The tower north controller controlled Runway 26R, normally used for arriving aircraft only. However, as a result of the two cranes beyond the departure end of Runway 26L, some large aircraft were authorized to depart from Runway 26R, under specified conditions.

The tower advisory controller cleared the Shorts crew for the Point Grey arrival for Runway 12 and issued traffic information — a DHC-8 ahead, on a visual approach for Runway 12. The crew was instructed to follow the traffic. He then instructed the crew to contact the tower south controller at Point Grey. There was no coordination between the tower advisory controller and the tower north controller for Runway 12 arrivals: local procedures did not require such coordination.

At 11:52, the tower south controller cleared the Shorts to land on Runway 12 and to hold short of Runway 26L. No information was given to the crew of the Shorts about the departure of the 747 from Runway 26R. At 11:36, the tower north controller advised the 747 crew that their departure runway would be Runway 26L. On being advised of the cranes operating off the end of Runway 26L, the pilot requested and received a taxi clearance for a departure from Runway 26R.

After clearing the 747 to taxi for Runway 26R, the tower north controller walked across the tower cab to the tower south location and advised the tower south controller that there would be a departure from Runway 26R in about 5 min. The tower south controller indicated that there was traffic for Runway 12 but did not mention any specific flights. At the time, the Shorts was about a 6 mi. behind a DHC 8; the Shorts was not within the range selected on the tower south controller's radar display and was still on the tower advisory controller's frequency.

The tower north controller was aware of a DHC 8 on approach for Runway 12, because this flight was showing on his radar display as a correlated target with flight number, altitude, and speed. Behind the DHC 8, he saw another radar target with a triangular target symbol, showing only a limited data block (altitude and speed display, but no flight number). The tower south controller had not made specific reference to a second aircraft on approach, and the tower north controller concluded that this second aircraft was not on approach to Runway 12.

At 11:51, the tower north controller authorized the 747 to taxi to position and wait on Runway 26R. Thirty seconds later, he cleared the 747 for takeoff from Runway 26R. At the time, the Shorts was 3.1 NM northwest of the departure path for Runway 26R. The tower north controller did not inform the tower south controller that he had cleared the 747 for takeoff.

While the 747 was still on the take off roll, the tower north controller saw an aircraft inbound from the northwest. He queried the tower south controller, who advised that it was the Shorts aircraft, inbound for Runway 12. The tower north controller recommended instructing the inbound aircraft to keep the speed up, because it now appeared that the inbound aircraft would cross the departure path of Runway 26R ahead of the 747.

At 11:53, the tower south controller advised the crew of the Shorts to keep the speed up and that there was traffic rolling on Runway 26R. Both pilots of the Shorts observed the Boeing 747 coming toward them and just lifting off Runway 26R. They immediately banked the aircraft to the right, increased the rate of descent and increased the engine power settings. (In other words, they took EVASIVE ACTION. — Ed.)

As soon as the pilots observed that they were clear of the departing traffic, they turned toward Runway 12 again and landed the aircraft without further incident. The Shorts had crossed the Runway 26R departure path 0.5 NM in front of and about 100 ft below the take off profile of the departing 747. There was no indication that the crew of the 747 saw the other aircraft.

The NAV CANADA Air Traffic Control Manual of Operations states that controllers shall "maintain close coordination at all times between positions of operation within ATC units and between these positions and other ATC units, Flight Service Stations [FSS], and other concerned agencies." It further specifies that controllers shall "separate a departing aircraft from an aircraft using. a nonintersecting runway if flight paths intersect by ensuring that the departing aircraft does not begin its take off roll until. a preceding arriving aircraft has crossed over the departure runway." The NAV CANADA Air Traffic Services Administration and Management Manual states that managers are responsible for issuing "direction and information required for the efficient administration and operation of the unit in the form of an operations letter, for long term items related to the provision of air traffic services (e.g. control, coordination, communication.)." No specific guidance was published to guide Vancouver Tower controllers on procedures to follow when using Runway 26R for departures.

The radar display showed a small triangle for the target symbol for the Shorts and a limited data block associated with the radar target, because the target was not correlated with any flight plan information stored in the ATC computer system. The tower advisory procedures do not require the controller to manually add the aircraft's flight number to the inbound aircraft's radar target to create a full data block.

Analysis — Runway 26R was rarely used to depart aircraft. The initial coordination between the tower north and tower south controllers was deficient in the areas of specific traffic information and follow up coordination prior to the departure of the 747. Neither controller ensured that the other had the complete traffic picture. Since the arrival flight path for Runway 12 and the departure flight path for Runway 26R intersect, and operations on these runways are controlled by different controllers, the tower north and tower south controllers both had the responsibility to ensure that the complete traffic picture was relayed to the other. The coordination between the tower north and tower south controllers was not completed in a manner sufficient to prevent a risk of collision between two aircraft.

Because of equipment reconfiguration activities in the Vancouver Tower, the tower advisory controller happened to be sitting next to the tower north controller in the time leading up to the incident and knew of arriving traffic to Runway 12 that would have been of use to the tower north controller. The tower advisory controller coordinated primarily with the tower south controller for Runway 12 arrivals and overflights and did not normally bring the tower north controller into the information loop.

The two Operations Bulletins were silent on coordination requirements for an unusual situation such as a Runway 26R departure during the construction near Runway 26L. Controllers were left to rely on their own experience and judgement to ensure safe and efficient operations. Several factors resulted in both controllers having deficient situational awareness: the lack of specific guidance material for managing departures from Runway 26R; the imprecise and incomplete coordination of relevant traffic; and an assumption by both controllers that the other knew what was going on. These factors resulted in a take off clearance being given to the 747 at the same time that the Shorts had a clearance to land on Runway 12, without any form of separation being applied.

The limited data block on the radar displays in the Vancouver Tower resulted in a misinterpretation of the information relating to the Shorts. No procedures require airport controllers to add aircraft identification or intention onto the radar displayed targets of aircraft under their control. It may therefore be more difficult to distinguish arrivals to the airport from transiting traffic, reducing controllers' situational awareness about some of the aircraft operating within their airspace.

Among its findings, the TSB determined that neither the tower north controller nor the tower south controller fully coordinated the departure of the Boeing 747-400 from Runway 26R and the arrival of the Shorts SD 360 on Runway 12, and that on being informed of a pending departure from Runway 26R, the tower south controller did not advise the tower north controller of all the pertinent traffic arriving for Runway 12.

Safety Action — The day following the occurrence, an Operations Bulletin was disseminated, stipulating that: "when Runway 26R is used for departures during the Bypass Pier Construction Project. the use of Runway 12 for arrivals shall be discontinued." In addition, effective March 1, 2003, a change to Vancouver Tower Class C airspace procedures required all arriving and departing VFR aircraft to obtain discrete transponder codes. This change allows aircraft tracked by radar to be correlated with flight plan information, including flight number or aircraft registration, and, thereby, be more conspicuous on the radar display.

Readers are encouraged to obtain a copy of this Final Report from the TSB. When complex operations are further complicated by unusual circumstances, such as construction sites, realize that the risk level grows significantly. — Ed.

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