The U.S. 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.
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. The actual departure, however, was to be conducted from Runway 01L.
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.
Data 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 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.”
After 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. 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 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. 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 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.
The analysis also identified several other airports with the potential for a runway number transposition error involving runways of different lengths, the SAFO said. However, most of the transpositions occurred at SFO.