The Strategical Lateral Offset Procedure (SLOP)
Introduction The Strategical Lateral Offset Procedure (SLOP) is a byproduct of improved navigational accuracy. Stay with me we'll get to the explanation soon! Lets go back to the days before GPS navigation was widely accepted as a primary means of aeronautical navigation, the days when VORs & NDBs were used to navigate on airways. Due to the inherent inaccuracy, compared to GPS navigation, aircrafts flying on the same airway where actually scattered along the airway being slightly offset from the center of the airway. This randomness of aircraft positions flying along an airway caused by reduced accuracy was actually beneficial to safety. Getting there... The introduction of Reduced Vertical Separation Minima (RVSM), in 1982, caused aircrafts flying reciprocal tracks on the same airway to fly closer to each other than ever before. BUT thanks to the imperfection of VOR & NDB navigational accuracy aircrafts were almost always laterally separated. Inaccuracies in lateral posi...