Soar Spots: A Review of Glider Conflictions in Canada

From: Transport Canada

by Nicholas van Aalst, Safety & Quality, NAV CANADA

Nicholas (Nick) van Aalst is an air traffic controller assigned to Safety & Quality at NAV CANADA and a graduate student from Embry-Riddle Aeronautical University, previously having served as faculty at Mount Royal University and holding a commercial pilot’s license, group 1 instrument rating, as well as a glider pilot’s license.

The author thanks the tremendous contributions of Dr. Jonathan Histon, Manager, Human Performance and the wider Safety & Quality Department at NAV CANADA for article development and subject matter expertise. Additional acknowledgement goes to Captain Ashley Gaudet of 2 Canadian Air Division, as well as Mr. David Donaldson of the Soaring Association of Canada.

Correspondence regarding this article can be addressed to NAV CANADA and Safety & Quality via Nicholas.vanaalst@navcanada.ca.

Soar Spots

During the late morning of August 12, 2022, a Boeing 767-375ER was conducting an instrument landing system approach to Hamilton, Ontario’s Runway 12 when a glider rapidly filled the crew’s windscreen, forcing the crew of the 767 to take evasive action, passing close enough to clearly observe the glider pilot. Fortunately, both aircraft were able to continue and make normal landings without further incident (Aviation Safety Network, 2022). This event illustrates the challenges and importance of airspace deconfliction and interactions between glider operations and other airspace users.

The Safety & Quality (S&Q) team at NAV CANADA has identified glider operations as a driver for conflicts with a heightened risk of collision within controlled airspace. Several features of glider operations contribute to this risk driver, including constraints on human performance, air traffic control operational limitations including airspace requirements, as well as the limitations on aircrew and their operational requirements. In varied and dynamic combinations of these factors, the result may render a degraded state of situational awareness and collective mental modelling leading to a mishap. Via awareness for this type of confliction, this article will provide insights into some of the pre-conditions for events, such as occurred in Hamilton, and provide readers with interest-based best practices for prevention.

Background

On August 28, 2006, a Hawker 800XP on descent near Reno, Nevada—collided with a Schleicher ASW 27 glider, as seen in Figure 1, at approximately 16 000 ft above sea level. According to the National Transportation Safety Board (NTSB) report (Charnon, 2008), “…damage sustained by the Hawker disabled one engine and other systems; however, the flight crew was able to land the airplane. The damaged glider was uncontrollable, and the glider pilot bailed out and parachuted to the ground” (p. 1). The NTSB’s findings indicated that the closure rate between the aircraft rendered collision avoidance was improbable, if not impossible once the conflict became apparent. Moreover, the lack of a transponder signal from the glider led to a degraded state of air traffic control (ATC) and aircrew situational awareness, which contributed to the mishap.

Method

The S&Q department has conducted a review of probable glider confliction areas in Canada, including transponder and ATC service provision requirements. This analysis further examined operating locations, including adjacent airspace and stakeholder interactions. Moreover, the review explored limitations of “see and be seen” and “see and avoid” principles associated with visual meteorological conditions (VMC) for both visual flight rules (VFR) and instrument flight rules (IFR) aircraft.

Figure 1: Schleicher ASW 27 glider, (Münch, n.d.)

Figure 2: Hawker 800XP following a mid-air collision with glider
(National Transportation Safety Board, 2006)

From this review, three key elements of conflicts, including their relationships, were identified as summarized below, as well as in Figure 3.

  1. human performance limitations
  2. ATC operational limitations
  3. aircrew operational limitations

Where limitations in Figure 3 overlap and interact, conflicts are more likely to occur. The following sections describe these interactions in greater detail.

Human Performance Limitations

The subject of human performance is a cross-discipline conversation requiring an understanding of situational awareness and perceptual blindness affecting mental modelling.

Figure 3: Risk driver relationships and interactions

Situational Awareness

Situational awareness (SA) is generally comprised of three levels: detection, understanding and prediction. First and foremost, detection requires aircrew and ATC to sense information regarding the environment. Second, aircrew and ATC must understand the meaning of the information, ultimately leading to the third level of situational awareness: the predicting of future needs.

Reflecting on the events of Reno, Nevada, and Hamilton, Ontario, what is apparent is that SA was not complete prior to the gliders being spotted. However, SA was rapidly restored, although with varied outcomes, with time being the critical factor in conflict resolution.

Perceptual Blindness

While levels of SA are built on our ability to sense the world around us, phenomenon such as perceptual blindness, also referred to as inattention blindness, involve failing to observe what may be considered obvious. Similarly, it is plausible that cognitive capture can promote a fixation upon a task, an object or even a thought, at the expense of SA.

What is apparent from stakeholders is that gliders are rarely forming a component of SA, largely due to low priming on the threat associated with gliders and a bias towards power-driven aircraft during traffic lookouts. Additionally, research indicates that inconspicuous coloration of objects may play a role in perceptual blindness. When applied to low-profile design gliders—predominantly white in colouration—the ability to visually identify gliders is reduced.

ATC Operational Limitations

ATC is often relied upon for traffic information to augment aircrew SA. Simultaneously, control instructions and clearances are provided based on known traffic with transponder-derived secondary surveillance radar and space-based surveillance data. However, under Canadian Aviation Regulation 605.35, gliders are permitted to operate within significant segments of Canadian domestic airspace without a transponder and altitude encoding equipment. This renders gliders as effectively invisible across vast areas of airspace, with only occasional primary radar returns being possible, which may represent any number of objects, including but not limited to birds.

Moreover, with primary radar returns not rendering altitude information and with primary radar returns being quite frequent, it may be challenging for ATC to provide relevant traffic information, particularly due to workload. To better manage workload, ATC may heavily rely upon altitudes for traffic separation, such as when aircrew adhere to standard altitudes based on flight rules and direction of flight. However, the nuance and inability of gliders to maintain constant altitudes means gliders pass through altitudes of IFR and VFR aircraft, suggesting a wide rang of altitudes where conflictions may occur.

Aircrew Operational Limitations

Having explored the concepts of human performance and limitations for ATC, operating limitations for aircrew in VMC, as well as available publications, deserves some consideration.

VMC Visual Separation

Whether operating as VFR or IFR, aircrews in VMC rely on mantras of “see and be seen,” as well as “see and avoid” for deconfliction. Of these, three elements appear:

  1. a traffic lookout
  2. being visible
  3. resolving conflicts

Glider visibility. From the vantage point of a glider pilot, traffic lookout is counter-intuitively limited, even with the visibility afforded by canopy designs. Restrictions of visibility include the wingspan and wing position, as well as the positioning of the pilot’s seat. As gliders may operate for extended periods at high bank angles and high rates of turn, glider pilots are challenged to maintain effective lookouts in rapidly changing environments. In turn, from a third-party perspective, the ability to observe a tightly orbiting glider can be difficult, particularly with low-profile designs and the absence of anti-collision lighting.

Power-driven aircraft. When discussed from the perspective of power-driven aircraft, physical obstructions limit visibility. However, a deeper challenge presents a conflict between the “heads up” monitoring of displays and effective traffic lookouts, with cockpit workload becoming increasingly predominant in modern general aviation aircraft.

Right-of-way-based deconfliction. CAR 602.19–Right of Way contains significant information regarding deconfliction. Most notable in the hierarchy is the priority of gliders, potentially rendering some measure of complacency for glider pilots, although VMC presents with shared responsibility for traffic detection and deconfliction.

Publications

A review of aeronautical publications, including applicable NOTAMs, has revealed that gliding operations are not clearly defined, nor are glider pilots required to remain confined to Class F airspace or as depicted on VFR navigation charts. This finding is not limited to VFR publications, as there is less clarity on IFR publications, including STARs and approach plates, suggesting that IFR traffic may have a degraded level of SA.

Addressing NOTAMs specifically, a published glider operations NOTAM may serve to reinforce glider pilot complacency under the assumption that NOTAMs are widely and thoroughly reviewed and understood.

A Probable Confliction Scenario

Based on the drivers in Figure 3, identifying probable confliction locations within Canada required S&Q to explore areas with a mixed requirement for ATC clearances, communication, navigation and surveillance, coupled with significant mixed flight rules and performance elements. Further review suggests that this complexity occurs more frequently within Class E airspace, where VFR aircraft operate without the element of a control service and where transponder requirements vary in accordance with the Designated Airspace Handbook. Consequently, Class E airspace is a probable driver for conflictions within controlled airspace.

As such, consider the scenario of an IFR aircrew during arrival and approach phases of flight, descending through a small area of Class E airspace on an ATC clearance, prior to transitioning into a terminal control area or control zone. During this time, this crew may face heightened cognitive workloads and competing priorities—covering distances upwards of four nautical miles per minute—transitioning between VMC and IMC through scattered or broken cumulus clouds, as depicted in Figure 4. In a multi-crew environment, workload factors for the pilot monitoring include direct controller–pilot communications and other “heads down” duties, requiring significant crew resource management skills.

Consider now the perspective of the VFR glider pilot, operating within the same segment of Class E airspace, relying upon rising air beneath a cumulus cloud through which the previously mentioned IFR aircraft, is about to pass. In this scenario, absent a requirement for communication and surveillance-related equipment, gliders are unable to contribute to the shared mental modelling of the IFR aircrew and ATC, nor are gliders fully aware of the related traffic picture. It is here that the pre-conditions for a confliction are present, and it is here that conflicts, such as previously depicted in Hamilton and Reno, potentially develop.

How You Can Stay Classy in Class E

As the prevalence of threat has presented predominantly within Class E airspace, including across airways where aircrew and ATC may not be aware of glider operations, specific locations for conflictions are vast and challenging to predict. However, during stakeholder engagement with S&Q, perhaps the most impactful moment came in the form of a philosophical quote: “…talk to the people who can kill you!”, crystalizing the core concept that awareness and collaboration drive effective flight safety initiatives.

Figure 4: Glider pilot perspective under cumulus cloud (Sosinski, 2024)

Recommended Best Practices

Recalling Figure 3, prominent best practices surfaced towards the development, maintaining and recovering of situational awareness and may largely be divided by perspective.

Glider Pilots

  1. Study airspace prior to flight operations and be aware of IFR and VFR traffic flows, including STARs and instrument approaches.

  2. Provide frequent and accurate position reporting on enroute frequencies.

  3. Develop rapports with adjacent operators and ATC units while adhering to localized agreements and best practices.

Power-driven Aircraft Pilots

  1. Study publications prior to flight operations and be familiar with adjacent aerodromes and airspace that support glider operations.

  2. Where practicable, monitor for traffic on the enroute frequency, and provide position reports.

  3. Be deliberate and critical when conducting traffic lookouts in VMC.

Air Traffic Controllers

  1. Where practicable, provide information on known and unverified traffic, including primary targets that are persistent or steady state, in areas where gliders may be present.

  2. Develop a rapport with glider operators to engage and inform on operational impacts.

  3. Where required, develop, verify and validate localized procedures for glider operations.

Conclusion

What S&Q’s review has shown is that glider conflictions are driven by three key enablers: human, ATC, and aircrew operational limitations and requirements. Further degrading situational awareness are aircraft operating without a transponder, such as the case with many gliders in Canada. As a result, best practices towards deconfliction in advance of operations, as well as during operations, including frequent and effective communications and stakeholder engagement. These practices are crucial in preventing airborne conflictions such as those having occurred in Hamilton, and mishaps such as Reno, and may serve wider benefits to the aviation ecosystem in Canada.

References

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