![]() The transposed runway numbers “resulted in an actual takeoff runway length (for 01L) that was 4,220 feet less than what was calculated by the TPS (for 10L),” the SAFO said.ĭata provided for Runway 10L included settings intended for longer runways, and with those settings, the airplane was rotated at standard speed and took off with 400 ft of usable takeoff distance remaining, the SAFO said. The actual departure, however, was to be conducted from Runway 01L. In Safety Alert for Operators (SAFO) 18009, issued earlier this month, the FAA described the San Francisco event, in which takeoff performance system (TPS) data provided for an airliner by the air carrier included information for Runway 10L. Federal Aviation Administration (FAA), citing a 2017 event at San Francisco International Airport (SFO), is cautioning flight crews and operators about risks associated with transposing runway numbers during data entry. Notably, the FAA rechecks their numbers every five years, because periodic shifts in magnetic north can cause them to change over time.The U.S. Very short runway with a cliff in Lukla, Nepal, image by Markrosenrosen (CC BY-SA 3.0) ![]() Of course, not all airports are large enough to accommodate this. ![]() ![]() As a result, many airports feature runways running at different angles to allow airplanes to align better with the wind. One might expect airports to simply line up all their runways for simplicity, but ideal orientation is based on prevailing winds, and these can shift. This level of enunciation ensures clear communication and enhances safety.” Official runway marking font with sizes by LezFraniak (CC BY-SA 4.0) For example, Runway 4L-22R would be by air traffic control as ‘Flight 123, you are cleared to land on Runway Four Left’ or alternatively ‘…Two Two Right,’ if cleared to land the opposite direction. “During airport operations,” Dargie continues, “runway number designations are pronounced individually. Runway markings diagram: yellow angles (left) highlight the “blast pad” paved to protect the ground white arrows (next) show “displaced thresholds” sometimes used by departing aircraft parallel lines (right of numbers) reflect “touch down zone” & “fixed distance marks” ( source) In rare instances where four runways run in parallel, there is no fourth designation - instead, one number is shifted by 10 degrees (1 digit). For example, 08L-26R and 08R-26L would be used for 08-26 “left” and “right” (relative to the direction the plane is facing) while a C is added for center ones (in cases of three). When multiple runways operate in parallel, an additional designation is added to distinguish between them. Runway sign denoting 08 left and 26 right 08 in one direction and 26 in the other). The solution is to drop a digit, rounding the compass bearing by ten degrees so you end up with a range from 1 to 36. By extension, the opposite end of any given runway (180 degrees away) will be plus or minus 18 (e.g. Runway number corresponding to compass bearing (CC BY-SA 3.0) But that seems strange at first glance, since the numbers are too short to represent 360 degrees. “All runways are numbered based on the magnetic azimuth (compass bearing) in which a runway is oriented,” explains Dave Dargie, Aviation Infrastructure Sector Lead at Stantec. ![]()
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