Weather can determine ‘speed limits’ for landings
Question: Is there a “speed limit” for landings? We live on the edge of the landing pattern for Nashville International Airport. Some commercial airlines come in low and slow with landing gear down. Others come in hot. Private jets usually come in high and hot. Early this week, two Southwest jets came in close together using the same runway. One high and much slower.
– JRErode, Hendersonville, Tennessee
Cox: There are speed limits in parts of the airspace system. Below 10,000 feet, the speed limit is 250 knots (a knot is equivalent to 1.15 miles per hour, so that would be 288 mph). The speed limit near most airports is 200 knots (230 mph).
During an approach to landing, there are many variables that can result in different speeds.
Typically, when flying in good weather within its landing weight range, an airliner will start slowing from 200 knots when it is about 7 or 8 miles from the runway, first to 170 (196 mph) when it is 5 miles out and then 140 knots (140 mph) at 3 miles out.
If weather conditions are bad enough to fly relying on the instruments rather than visual flight rules, and the plane is configured to land, it can slow to 140 knots 5 miles out.
I have been on flights where we had a little turbulence and the “fasten seat belt sign” came on. Then things smooth out – no more turbulence – but the light stays on. Do cockpit personnel ever forget the light is on?
– AP, Utah
When the captain switches on the “fasten seat belt” light, it is due to information about potential turbulence. We try not to have it on longer than is necessary, but yes, I confess: I have, on occasion, forgotten it was on for a while.
John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.