A95H0008 - Mid-Air Collision - Sioux Lookout, Ontario - 01 May 1995
Safety Action Taken
(as presented in the TSB Report)
Subsequent to the accident, Bearskin Airlines developed procedures to reduce the risk of mid-air collisions in the busy Sioux Lookout area. These procedures include a requirement that all Bearskin aircraft be flown at a speed of less than 150 knots when operating within 5 nm of the Sioux Lookout airport. This reduction in airspeed should decrease the probability of mid-air collision by increasing both the likelihood of detecting conflicting traffic and the time available to take evasive action once conflicting traffic has been detected.
Transport Canada Action
Transport Canada has taken action to increase pilot awareness of procedures to reduce the likelihood of mid-air collisions. An Aviation Notice entitled "Mid-Air Collision Alert Bulletin" was issued in July 1995. The notice informs pilots of the increased potential for collision when using GPS and stresses the benefits of using arrival, departure, and position reports in order to be alerted to potential conflicting traffic. The notice also included an enhanced version of the Mid-Air Collision Avoidance Guidelines.
Two posters have been produced: the first, entitled "MF/ATF Communications Requirements," reviews applicable pilot reporting/communication requirements; the second, entitled "GPS-Traffic Separation," suggests flying one or two miles right of the centre line of the track when navigating with GPS in order to avoid conflict with opposite direction traffic.
In addition, Transport Canada has published four articles about collision avoidance in issue 2/96 of the Aviation Safety Newsletter.
Furthermore, Transport Canada (Central Region) has established a Mandatory Frequency Working Group. In July 1995, the group solicited input from the aviation community concerning the adequacy of procedures associated with mandatory frequency areas. Various procedural and structural solutions to problems related to MF areas are being evaluated in light of the responses received.
MF Area Procedures
The new Canadian Aviation Regulations, which are expected to come into force in 1996, change the reporting procedures for aircraft approaching an MF area. The pilot-in-command of a VFR aircraft will now be required, where circumstances permit, to call at least five minutes before entering the MF area. This change will give both arriving and departing aircraft more warning of conflicting traffic, and will effectively expand the radius of the MF area in accordance with an aircraft's speed; under these procedures, given the radius of the MF area and the ground speed of the Metro, the Bearskin flight would have been required to contact Sioux Lookout FSS at least 25 nm back from the airport.
FSS Traffic Awareness
Flight Service specialists are required to provide airport advisory information to aircraft operating to or from locations within an MF area. A summary of known pertinent aircraft traffic that may affect the aircraft's safety must be provided, and must be updated if the specialist becomes aware of potential conflicts. Pilots use traffic advisories to assist in seeing and avoiding conflicting traffic. The resources available to specialists to provide these advisories, however, are scant.
The quality of traffic advisories can be adversely affected by inaccurate aircraft position reports, communication errors, and frequency congestion. Further inaccuracies can be introduced when specialists rely primarily on radio to determine the position and intentions of aircraft in their area, then attempt to recognize potential conflicts by extrapolating from their mental picture of the current traffic situation. As traffic densities and aircraft speeds increase, a specialist's ability to integrate available information and provide credible and timely traffic advisories is adversely affected, thereby increasing the risk of collision.
The Board understands that relatively low cost equipment is now available which can provide a pictorial display of aircraft traffic. If used by specialists, such systems could reduce the potential for cognitive errors, reduce frequency congestion, and facilitate remote monitoring. In light of the reduced risk of collision which might accrue through the use of such systems, the TSB forwarded a Safety Advisory to Transport Canada (TC) suggesting that TC evaluate the use of systems which provide pictorial displays of aircraft position (such as ground-based TCAS systems and Personal Computer systems displaying radar data via land line) to assist Flight Service specialists in identifying potential conflicts and in providing accurate and timely traffic advisories.
Although the specialist at Sioux Lookout advised two aircraft on the MF of the approaching Bearskin 362 flight while Air Sandy 3101 was on the same frequency, it is not known if the Air Sandy pilot heard the traffic advisory concerning the Bearskin flight. The TSB is not aware of the extent to which specialists are ensuring that aircraft are aware of conflicting traffic and has suggested in a Safety Advisory that Transport Canada consider placing increased emphasis in this area during quality assurance reviews.
Safety Action Required
(as presented in the TSB Report)
Separation Procedures for Aircraft Navigating with GPS
GPS has been approved for use under VFR and as a backup aid to navigation under IFR; approval as a primary IFR navigation aid is imminent. The Canadian Air Navigation System is rapidly moving toward increased reliance on this inexpensive and accurate navigation system.
In 1995, the Board made two recommendations to TC aimed at reducing the potential for GPS-related occurrences resulting from the use of unapproved equipment, inadequate understanding of the system, or lack of approved approaches. Transport Canada agreed with the recommendations and outlined several initiatives to expedite the implementation of GPS standards and raise the aviation community's awareness of the limitations and safe use of GPS.
The correct use of GPS decreases the average displacement of an aircraft from the centre line of its desired track; consequently, if separation procedures fail, the probability of a mid-air collision will increase (see LP 95/95). This increased risk of collision applies to both IFR and VFR aircraft in all types of operations.
The probability of collision for aircraft using GPS could be reduced if pilots used the area navigation (RNAV) capabilities of GPS to avoid high traffic routes, either by flying at an off-set distance from the centre line of these routes or by creating their own routes. Although TC has taken some action in this regard (see Transport Canada Action), the action is limited in scope and short term in nature. Given the increasing use of GPS, and the increased potential for mid-air collision associated with its use, the TSB recommends that:
The Department of Transport expedite the development and implementation of safe separation procedures for the use of GPS in navigation. (A96-04)
Transport Canada's Response:
Transport Canada (TC) is very active on all GPS-related issues, including its safe usage in navigation; however, TC considers that the introduction of GPS does not require any change to current rules and procedures regarding aircraft separation. In VFR operations, there is no rule that requires pilots to follow specific tracks. Some pilots follow airways or air routes anchored by traditional ground aids while VFR, but GPS offers the chance to use any point-to-point route. This offers more routes if everyone uses GPS. When departing from an airport, a VFR pilot using GPS will generally take up a direct course to destination at some point after takeoff. This point may be different on each flight, depending on wind, runway in use, traffic, and aircraft performance. This automatically creates an offset. Since all RNAV systems allow aircraft to be flown on essentially random tracks, it is difficult to envision a separation criterion which would be more effective than that already provided for these systems. Once at cruise altitude, even when on the same track, separation is assured by flying at an altitude appropriate to direction of flight.
In IFR operations, air traffic control service ensures separation regardless of the navigation guidance being used. The key to avoiding collisions near airports like Sioux Lookout, where there is a mix of IFR and VFR aircraft, is communications. While arriving and departing, pilots have not reached opposite direction cruise altitudes, so they must be extremely vigilant. GPS makes communications more effective because it provides pilots with more accurate position, speed, and ETA information than is possible with traditional aids. Regardless of the precision of the guidance used by the pilot, it is critical, particularly when in the vicinity of an uncontrolled airport, to communicate position and intentions.
A Satellite Navigation Program Office (SNPO) has been established to work on issues specific to GPS. Current issues of concern and study include the human factors aspects of the GPS avionics, particularly during approach operations, the reliability of the avionics data base and electromagnetic interference. The SNPO regularly updates A.I.P. Canada, writes safety articles, publishes its own newsletter and has recently prepared a notice for the Canada Air Pilot, in each case advising pilots how to use GPS safely.
Transport Canada will continue to address and monitor GPS issues, and will also continue to regularly publish articles in the "Aviation Safety Letter" newsletter to sensitize the aviation community.
Procedures to separate aircraft are not always followed (as evidenced by IFR loss-of-separation incidents) and are not always effective (for example, during VFR climb/descent). There have been eight mid-air collisions in Canada since 1991, and 142 reported occurrences where aircraft safety was compromised due to a loss of separation. Where procedures to separate aircraft fail, pilots may have to rely on the see-and-avoid method to avoid a mid-air collision. This method, however, becomes less effective as aircraft airspeeds increase.
The estimated closing speed of the accident aircraft was 410 knots. At this speed, the probability of the pilots of one aircraft acquiring the other aircraft in time to take effective evasive action was only about 20 per cent (LP 086/95 and LP 001/96 refer). This probability would have been doubled if the closing speed had been reduced to about 300 knots. In light of the increased probability of acquiring conflicting traffic at reduced airspeeds, the TSB recommends that:
The Department of Transport ensure that aircraft are flown at reduced airspeeds, consistent with safe manoeuvring, in the vicinity of aerodromes where separation relies primarily on the see-and-avoid concept. (A96-05)
Transport Canada's Response:
Regulations require that all aircraft operating below 3000 feet above ground level within 10 nautical miles of a controlled aerodrome operate at 200 knots or less unless otherwise authorized by ATC. This requirement is based on the following premises: that the aerodrome has sufficient air traffic to warrant control; that the reduction in speed will enhance visual separation as well as the provision of ATC separation; and that ATC can provide authorization to those aircraft that cannot operate at slower speeds. Making the regulation universally applicable may mean that at those locations without ATC and where ATC authorization could not be obtained, all aircraft unable to reduce to the lower speeds would be in violation of the regulation.
Although in some instances a regulation would be unenforceable, the proposal will be examined further and could become a recommended practice. Good communications with users and their early participation in determining the need for speed will go a long way toward resolving this issue.
The pilots of aircraft operating in visual conditions, regardless of the type of rules under which they may be operating, are responsible for maintaining a satisfactory lookout and avoiding other aircraft and obstacles. At controlled aerodromes, ATC will provide separation between IFR aircraft and conflict resolution between IFR and VFR aircraft. However, no separation is provided between IFR and VFR aircraft and conflict resolution between VFR aircraft is only provided on pilot’s request.
Consideration will be given to amending the information in A.I.P. Canada to include a recommendation that pilots should operate at reduced speeds when in the vicinity of uncontrolled aerodromes.
Even if aircraft are flown at reduced airspeeds, pilots must be able to recognize a collision threat and take appropriate action if a collision is to be avoided. Transport Canada's Flight Instructor's Guide advocates the use of a steep turn to avoid collisions; however, this manoeuvre may actually increase the probability of impact if it is initiated when the aircraft are inside the range of approximately 10 seconds to impact (10) (evidence indicates that the Navajo was steeply banked at the time of the collision).
Since inappropriate responses to a risk of collision situation may increase the risk of a mid-air collision, the TSB recommends that:
The Department of Transport take both long- and short-term action to increase the ability of pilots to recognize in-flight collision geometry and optimize avoidance manoeuvring. (A96-06)
Transport Canada's Response:
Transport Canada will take action to increase the ability of pilots to recognize in-flight collision geometry and optimize avoidance maneuvering. Specifically, the Flight Instructor Guide will be amended and the issue will be addressed in a new Transport Canada publication, "Human Factors in Aviation".
The see-and-avoid method of traffic separation can be much more effective if pilots are alerted to the existence and relative location of conflicting traffic. TCAS I provides such proximate traffic alerts (TAs).
Although United States Federal Aviation Regulations would have required the Metro to be TCAS equipped, and many other countries are instituting TCAS requirements, no such requirements exist or are planned in Canada.
In view of the demonstrated capabilities of TCAS, and the increasing risk of collision due to improved navigational accuracy, increasing aircraft speeds, and mixed VFR/IFR traffic at uncontrolled airports such as Sioux Lookout, the Board recommends that:
The Department of Transport conduct an analysis of the benefits of requiring commercial passenger- carrying aircraft to be equipped with TCAS versus the risks associated with operating aircraft without TCAS. (A96-07)
Transport Canada's Response:
The Canadian Aviation Regulation Avdisory Council (CARAC) has formed a Working Group to study what additional equipment may be required in Canada to enhance safety and harmonize with the requirements of the U.S. regulations, in particular, GPWS, TCAS and wind shear alerts. This working group will analyze the benefits of TCAS and make recommendations with respect to future regulatory action. The first meeting of the working group is scheduled for the Fall of 1996.
(10) J.L. Harris, Sr., "Avoid", The Unanalyzed Partner of "See". ISASI Forum #2, 1983 p.16
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