by Flight Training and Licensing, Civil Aviation, Transport Canada
Transport Canada promotes safe transportation. It is important to understand the purpose of displaced thresholds. Recent dialogue with the industry indicates that the motive of displaced thresholds may be misunderstood.
The mindset predominantly encouraged is that a displaced threshold published in the Canadian Flight Supplement (CFS) or as a NOTAM is caused by man-made structures such as powerlines, towers, road traffic, tall trees, degradation of the runway surface or noise abatement procedures. A temporary displaced threshold may be the result of work in progress nearby or at the aerodrome (i.e., construction cranes located on the approach path and thus necessitating a landing further down the runway). These are all reasons to abide and respect the displaced threshold, despite the legality aspect of it.
Caution must be exercised. Safe training practices advocate adhering to the displaced threshold, as it was most likely created to aid the pilot in avoiding obstacles on approach and assists the pilot in maintaining the stabilized approach criteria. You may review those criteria in one of the Flight Test Guides (i.e., TP 13723).
Guidance is available in the Transport Canada Aeronautical Information Manual (TC AIM—TP 14371). Although the guidance in the TC AIM are not regulations, it is there for a purpose. Ignoring it would most likely not stand in a tribunal.
For the avid readers, additional information is available in TP 312–Aerodrome Standards and Recommended Practices for further reading about displaced thresholds. In Chapter 5 on visual aids, white arrows or yellow chevrons markings preceding the runway threshold serve the purpose of not only alerting pilots to a displaced threshold but also indicating if the preceding surface is included or not included in the declared landing distance available in the CFS for a particular aerodrome.
Let's look at two examples.
Burlington Executive, ON (CZBA) has white arrows that can be seen in a Google image (Figure 1) and in the CFS Runway 32 has a displaced threshold of 409 ft, which is included in the reported runway length of 3 950 ft. This means that 3 541 ft is available for landing and reported as the declared landing distance available (LDA). The arrows indicate that the threshold is displaced from the beginning of the runway. It is at the pilot's discretion, with safety in mind, if the surface preceding the threshold should be used or not. Best practice recommends not to use it.
Now, if we look at Oshawa Executive, ON (CYOO), we can see chevrons (in yellow, although the Google image (Figure 2) does not make it clear), and the CFS does not picture any displaced threshold, and that the declared landing distance available for Runway 12 is the full length of the runway, at 4 250 ft. If you look closely at the airport diagram, you can see that the runway begins at the taxiway, and the preceding surface is not there. It is important to note that chevrons indicate that the surface is not certified for aircraft movement.
The runway end or displaced threshold indicates the beginning of the declared LDA depicted on the aerodrome chart of the Canada Flight Supplement (CFS) or the Canada Air Pilot (CAP). Under CAR Part VI, pilots are responsible to ensure safe aircraft operation, including landings. If a pilot elects to land prior to the declared landing distance available (indicated by the threshold markings), then it is done so at the pilot's own risk.
There have been numerous accidents related to displaced threshold, and it is worthwhile to review the following Transportation Safety Board (TSB) report.
TSB recommends:
Safety message
Runway thresholds are often displaced to ensure that the approach slope is clear of obstacles. Therefore, it is important that pilots aim to touch down beyond the displaced threshold to help maintain obstacle clearance.
There could also be temporary displaced thresholds that would be published in NOTAMs. There are different ways these could be marked, depending on how long it will be displaced for.
As pilot-in-command, and for the best outcome for you and your passengers, it is your responsibility to know your aircraft's capability and to make the best decision.
Happy and safe flying to all.
Figure 1: Google Maps image dated of September 17, 2024.
Imagery ©2024 Airbus, First Base Solutions, Maxar Technologies,
Map data ©2024.
Date: May 14, 2024. Refer to CFS for official navigation.
Figure 2: Google Maps image dated of September 17, 2024.
Imagery ©2024 Airbus, First Base Solutions, Maxar Technologies,
Map data ©2024.
Date: May 14, 2024. Refer to CFS for official navigation.