Aviation Safety Letter 3/2003

From the Investigator's Desk: Undue risk at uncontrolled aerodromes?

by Glen Friesen, Transportation Safety Board of Canada (TSB), Pacific Region


On January 8, 2002, two airplanes were on scheduled passenger-carrying flights from Vancouver to Campbell River, British Columbia. One of the airplanes, a Shorts SD-3-60, was operating in accordance with VFR, intending to land on Runway 29, while the other, a Beech 1900D, was operating in accordance with IFR, and had been cleared by ATC for a straight-in LOC(BC)/DME approach to Runway 29. The crews of both aircraft were in contact with the Campbell River Flight Service Station (FSS) on the mandatory frequency (MF). The VFR aircraft first reported on a non-standard right base leg to arrive first but, at the shoreline, the flight encountered weather conditions below VFR limits. The crew aborted the visual approach by turning left nearly 230° and climbing to the east. The aircraft under IFR rules, which was established on the back course and behind the Shorts, then received a resolution advisory from the traffic alert and collision avoidance system (TCAS) on board; the crew of the Beech executed a missed approach with an avoidance manoeuvre to the left of track (see diagram). Both aircraft were in each other's proximity as they climbed in opposite directions. Both crews later asked for radar vectors to IFR approaches and landed without further event.

This risk-of-collision incident, as described in TSB Final Report A02P0007, involved two commercial aircraft, both flown by professional two-pilot crews, and the airport was served by an operating FSS. The Canadian Aviation Regulations (CARs) do not limit air carriers to flight solely in accordance with IFR rules, so when weather conditions along selected routes meet the minima specified in the operator's operations manual, many realize time and cost savings by conducting flights in accordance with VFR rules, which allow for more direct routing. In this case, an IFR routing from Vancouver to Campbell River may take the aircraft on a longer, southbound and westbound routing before proceeding north. Such a routing ensures terrain clearance but increases flight distance. VFR flights can result in more direct flights, but the practice bypasses several safety defences built into the IFR environment.

Once again, the contributing issues identified in the TSB investigation included non-standard or ineffective communication and non-standard circuit procedures at an uncontrolled airport within a MF area.

In 1999, there were three midair collisions in British Columbia involving a total of six aircraft. Nine of the 12 people involved died in the accidents. Two of these accidents occurred at uncontrolled airports - one within an aerodrome traffic frequency (ATF) area and one within a MF area served by an operating FSS. In both of these accidents, the TSB Investigation Findings as to Causes and Contributing Factors included non-standard or ineffective communications and non-standard circuit procedures. With the increasing concerns brought on by these accidents, agencies such as NAV CANADA, Transport Canada and the TSB have participated in pilot-education briefings to emphasize the issues associated with midair collisions. In issue 5/2000 of the Aviation Safety Vortex, a fictitious accident scenario was described. The author concluded the story by writing, "This accident didn't take place, but it is just a matter of time before it does." It would appear that the author was unaware that an amazingly similar accident had already occurred in Penticton, British Columbia the previous year (TSB file # A99P0108) between two privately operated fixed wing aircraft.

The non-standard procedures used included things like late and incomplete inbound position reports, conducting circuits on the non-circuit side of the aerodrome, joining the circuit at points which are not authorized or not recommended, using frequencies other than the published MF or ATF. Other elements have included flight service specialists not obtaining, or not passing on all available and pertinent information and not clarifying ambiguous information. Is all of this the result of sloppiness, laziness, poor airmanship, lack of recurrent training, difficult or confusing procedures, or shortage of enforcement resources? Perhaps that extra two or three minutes of air time required to join the circuit in a recognized manner is too expensive?

Safety in aviation is based primarily on the concept of defences built into the system. Recommended procedures, technical equipment, and communication provide forms of defences. Procedures are published to encourage commonality of operations and to ensure that poor performers at least meet a minimum acceptable standard. By disregarding standard procedures, especially within uncontrolled airspace, all pilots are deprived of a primary defence for conflict detection and resolution. When the defences are compromised, the risk of conflict increases.

Pilots are required to make a number of standard radio calls directed to the FSS, and to monitor the MF frequency when operating within a MF area. The responsibility dissemination of traffic information pertinent to the existing conditions.1 Research conducted by the Lincoln Laboratory showed a 50 percent improvement in the visual target acquisition rate by pilots alerted to the presence of other aircraft, and the median range of visual acquisition improved by 40 percent.2

Why don't we follow the basics? Users of the system are probably the best source of that information. Is the Aeronautical Information Publication (A.I.P.) Canada section RAC 4.5 easy to understand? Does training cover these procedures adequately? Are you prepared to operate confidently and safely at an uncontrolled aerodrome? If readers have specific examples regarding this area of operation, the TSB would like to hear of constructive, workable suggestions or comments. Please fax hard copy to (604) 666-7230 or forward electronically to glen.friesen@tsb.gc.ca.

1 NAV CANADA, FSS MANOPS, parts 810 and 811.

2 J.W. Andrews, "Modeling of Air-to-Air Visual Acquisition", The Lincoln Laboratory Journal, Volume 2, Number 3 (1989) p. 478.

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