In July 2024, a LATAM Airlines Boeing 777-300ER scheduled for a flight from Milan to São Paulo suffered a severe tail strike during takeoff, an event recently reclassified as an accident by Italian investigators (ANSV). The root cause was a staggering 100-ton weight miscalculation made by the crew during pre-flight performance planning.
The error originated when the line-training captain mistakenly subtracted the expected taxi fuel from the aircraft’s zero-fuel weight. This mental arithmetic error resulted in a reported take-off weight of 228.8 tonnes, whereas the actual weight was 328.4 tonnes. Because this incorrect figure was announced verbally, both pilots entered the same erroneous data into their respective Electronic Flight Bags (EFBs). This created a "single point of failure," as the standard cross-check appeared to confirm the data since both devices yielded identical (but wrong) performance speeds.
As a result, the aircraft attempted to rotate at 149 knots—roughly 30 knots slower than required for its actual mass. Despite a "V-speeds unavailable" warning from the flight management computer, the crew proceeded with the takeoff. The aircraft struggled to lift off, dragging its tail along the runway for over 700 meters before the cruise captain intervened by commanding full thrust.
The jet eventually became airborne and returned to Milan safely after dumping 72 tonnes of fuel. While no injuries occurred, the aircraft sustained significant structural damage and remained grounded for seven months. The investigation highlights how high cognitive load and procedural lapses can cause even advanced automated systems to fail if fed incorrect human data.
https://simpleflying.com/100-ton-weight-miscalculation-pilots-latam-777-accident-milan/
img: ID 109491297 | Latam Airlines © Mohamed Ahmed Soliman | Dreamstime.com
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