![]() If there are two airports near one another with runways at the same angle, sometimes one of the airports will add or subtract one from the runway number to help planes differentiate between the airports. Even though these are the same strip of concrete, they are treated as separate runways by pilots and controllers. A runway with 35 for landings to the north will have runway 17 for landings to the south. Opposite ends of the same runway have different numbers, 18 (which represents 180 degrees) apart. For example, if the magnetic heading is 345° then 345/10=34,5, so the runway number will be 35 which will be a runway used for landings (and takeoffs) to the north. Divide its magnetic heading by 10, round it to the nearest whole number and you'll usually get the runway number. However, most of the transpositions occurred at SFO.Runways are usually numbered according to their direction, more precisely called runway magnetic bearing or QFU ( see Q codes).Ĭonsider a plane flying toward the runway on final approach in a day without any wind. The analysis also identified several other airports with the potential for a runway number transposition error involving runways of different lengths, the SAFO said. The analysis could not identify causes of the events, but “it was determined that some events were likely associated with a number transposition,” the SAFO said. A subsequent analysis of the ASIAS database found an additional 25 takeoffs at SFO with less than 1,000 ft remaining on the runway. The air carrier’s data was shared with the Commercial Aviation Safety Team and the Aviation Safety Information Analysis and Sharing (ASIAS) program as “a potential systemic issue in the National Airspace System,” the SAFO said. Its actions included prioritizing Runways 01L/R as primary takeoff runways, adding a caution note to the TPS data for SFO and locking out 10L/R data. “The flight crew realized the safety implication and associated risks and promptly submitted a voluntary safety report describing the event under the aviation safety action program (ASAP),” the SAFO added, noting that the air carrier reviewed their report and evaluated the event under its safety management systems process “to identify the underlying factors that contributed to the event and implemented mitigation procedures to avoid a reoccurrence.”Īfter examining data from its ASAP and flight operational quality assurance (FOQA) program, the carrier found that similar, less serious errors had occurred before the 2017 event and implemented strategies designed to prevent other problems in the future. 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.
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