Passenger plane rockets to 800 mph in screaming jet stream
A flight near New York City recorded the strongest jet stream winds ever seen in the region on Monday, imbuing the plane with a scorching 801 mph (1289 km/h) ground speed.
Keep in mind this is the groundspeed; that is, the speed of an aircraft relative to the surface of the earth, or the 'true airspeed' of the plane, corrected for wind. Flying into the wind, you get a lower groundspeed, thanks to the headwind. Flying with the wind, you get a higher groundspeed, thanks to the tailwind.
And what a tailwind.
Planes are constantly recording weather conditions several kilometres above the surface, and -- with the help of with weather balloons -- the upper fringes of the part of the atmosphere we live in are sampled.
The super-powered jet stream sampled by this Los Angeles to London flight revealed a tailwind of nearly 200 knots, shortening the flight to just more than 9 hours -- about an hour and a half shorter than usual for a direct flight.
This speed measured by the instruments on-board comes very close to the record groundspeed observed by this particular type of aircraft.
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SONIC BOOM?
While 801 mph is well above the speed of sound, there wasn't a sonic boom to mark the plane's passage. Why not? It comes back to the groundspeed versus true airspeed distinction.
A sonic boom only occurs when the speed of sound is exceeded with the true airspeed of the airplane. The aircraft's true speed -- relative to the air -- was far less than the 1300 km/h ground speed that was recorded, leaving the plane well below the Mach 1 speed needed for the telltale boom.
With files from Weather Network meteorologist Tyler Hamilton.
