GPS and air data computers make en route navigation the most precise it’s been in aviation history. In some ways, too precise.
Transoceanic airliners began to suffer hours of sustained turbulence caused by dozens and dozens of wide-body aircraft flying on the same track, through each other’s wake vortices. Eventually, international airlines flying those routes figured out a solution. They developed SLOP — Strategic Lateral Offset Protocol — in other words, introducing an element of ambiguity in their navigational tracks to relieve airframes, and passengers, of the pain caused by excessive precision.
That may be the only instance I know where ambiguity is a good thing in aviation. If the reports to NASA’s Aviation Safety Reporting System I recently dissected are any indication, pilots agree that ambiguity is a bad thing. The ambiguity they are referring to is in how the FAA regulations, instrument procedures, and NOTAMS are worded. [Read more…]