When storms or floods disrupt air traffic control at a busy airport, the effects may endure long after the initial impact on operations as ATC presses temporary communications facilities into service or reassigns responsibilities for providing services.
Pilots may be called upon to follow unfamiliar procedures resulting from the constraints controllers face in separating aircraft or communicating. The uncertain nature of the scenario makes it critical for pilots to check notices to airmen frequently; they will be used to disseminate updates on service levels and availability.
After a violent weather system moved through the Austin, Texas, area recently, for example, flooding took a heavy toll on ATC facilities.
As the area’s recovery began, pilots operating to or from Austin-Bergstrom International Airport needed to know of operational constraints including this services notam (note the keyword “svc”) advising of a temporary shift of the local approach/departure control function to the Houston Air Route Traffic Control Center: “ZHU SVC AUSTIN APP OUT OF SERVICE NOW HOUSTON ARTCC 125.65 1511010019-1605010459.”
Under such circumstances, pilots calling for takeoff or landing clearances at affected airports may hear an unfamiliar form of the requested clearance as the controller adds a caveat stating that the flight operation “will be at your own risk.”
Why this phraseology?
If a temporary control tower has been pressed into service while ATC infrastructure is being restored, the small size of the mobile control tower or its location may prevent controllers from monitoring all taxiways and runways. Radio communications also may be affected.
The “at your own risk” phrasing, while rarely applicable to fixed-wing aircraft, is commonplace for controlling the movements of helicopters, as explained in the Aeronautical Information Manual 4-3-20: “If takeoff is requested from nonmovement areas, an area not authorized for helicopter use, an area not visible from the tower, an unlighted area at night, or an area off the airport, the phraseology ‘DEPARTURE FROM (requested location) WILL BE AT YOUR OWN RISK (additional instructions, as necessary). USE CAUTION (if applicable).’ The pilot is responsible for operating in a safe manner and should exercise due caution.” Similar phrasing is used for landings.
Traffic density, frequency congestion, or other factors can impose additional limitations, requiring “a high degree of pilot/controller cooperation and communication” to ensure safe, efficient operations.