Foggy Issue

Runway incursions are considered to be a major threat to aviation safety worldwide. Several of these incidents have occurred in reduced visibility conditions, leading to many fatalities. Most people are familiar with the 1977 accident where two Boeing 747s collided on the runway in Tenerife, Canary Islands, causing 583 fatalities and topping the list of the deadliest aircraft collisions in aviation history.

The Transportation Safety Board of Canada (TSB) reported that from 2001 to 2009, there were 4,140 runway incursions at Canadian airports. There were a further 351 incidents in 2010, followed by another 446 in 2011. The TSB continues to investigate these occurrences in an effort to avoid future disasters, and has called upon Transport Canada to deliver more leadership when it comes to their prevention.

Since 2006, Transport Canada has issued several advisory circulars to airport operators, air traffic controllers, pilots, and commercial and corporate operators, in a multi-pronged approach designed to reduce runway incursions. The purpose of these circulars is to establish the minimum equipment and visibility requirements for taxi, takeoff and landing operations. The standard minimum visibility for an aerodrome in Canada is runway visual range (RVR) 2600 (1/2 statute mile). This means that pilots are allowed to taxi, take off and land any time the visibility is at or above this value. Airport operators may choose to support operations below this standard; however, additional equipment and/or special procedures would be required – for example, airport surface detection equipment, enhanced lighting, and special taxi routings.

Airport operators are responsible to publish the level of service their airport supports. Transport Canada has designated two levels of service below standard. These include reduced visibility operations (RVO) and low visibility operations (LVO). When RVO operations are allowed, it means that the aerodrome and the applicable runways meet the requirement for operations below RVR 2600 (1/2 sm), down to and including RVR 1200 (1/4 sm). When LVO operations are allowed, it means that the aerodrome and the applicable runways meet the requirement for operations below RVR1200 (1/4 sm), down to and including RVR 600 (1/8 sm). If no level of service is published for an airport, operations are limited to a visibility of not less than RVR2600 (1/2 sm). 

The level of service information (RVO/LVO) is published in the Canada Flight Supplement (CFS) under “Runway Data,” and in the Canada Air Pilot (CAP) on the aerodrome charts. After referencing the level of service, pilots must ascertain the aerodrome operating visibility, and ensure this visibility is at or above the level of service to permit taxi operations. 

Aerodrome operating visibility is the controlling RVR or visibility, according to a pre-set priority. The order of priority used is the RVR for the runway of intended use; ground visibility as reported in a METAR; and, finally, the visibility as determined by the pilot-in-command, but only under limited circumstances. This hierarchy is valid for most operations, except for departures from airports that do not have an active ATC tower. In that case, pilots use the lowest of the following visibilities: any reported RVR; ground visibility; and pilot visibility. It can be noted that tower visibility does not take precedence over reported ground visibility; it is considered advisory only. The exception occurs when ground visibility is missing; at this point, tower visibility is used!

If that isn’t complicated enough, a pilot must also understand that the level of service determination is different than the minimum takeoff visibility requirements and approach ban minima. There are also a number of exceptions that allow continued operation when the visibility is deemed to be below what is required. It’s conceivable that a pilot may have the required visibility to conduct an approach to landing, but is not allowed because he/she doesn’t have the required visibility to taxi. These conflicting regulations have led to much confusion within the IFR pilot ranks, at all levels. In fact, some operators have developed flow charts to help their pilots ensure they don’t break any regulations. 

In addition to the new requirements for airport operators and pilots, new direction was given to air traffic controllers on how to operate in minimum visibility conditions. Controllers are not authorized to issue clearances when traffic conditions are not known, when an airport is partially or fully closed, or when the visibility is below the aerodrome or runway operating minima. 

Since implementation, a series of occurrences prompted a review, and in August 2013, the Aeronautical Information Circular (AIC) 26/13 was issued to outline new procedures.  Controllers now use two distinct phrases when they are unable to issue clearances. “AT YOUR DISCRETION” is used to approve aircraft movement on any part of an airport that is not visible from the control tower, and “UNABLE TO ISSUE CLEARANCE” is used when a controller is not authorized to issue a clearance because the visibility is below the operating minima. So, if you hear the phrase “UNABLE TO ISSUE CLEARANCE,” it is not advisable for you to continue, as ATC is required to file an occurrence report. If you proceed, you may be subject to regulatory action from the enforcement branch of Transport Canada! 

Transport Canada is well aware of the confusion within the aviation community and is working to simplify RVR regulations.  Since the goal here is to increase safety, simplifying and harmonizing the regulations would be a benefit to all, allowing everyone involved to focus on preventing runway incursions.

For more information, please refer to the Canada Air Pilot GEN- Operating Minima, AIC 26/13, Advisory Circulars AC 602-002, AC 302-001 and AC 302-006.