Strong high-altitude winds over the Mid-Atlantic sped up sky traffic on Saturday night, getting passengers on at least two commercial planes to their destinations early, after both aircraft hit supersonic speeds topping 800 mph.
Winds at cruising altitude peaked at about 265 mph, according to the Washington, D.C., area National Weather Service office — the second-highest wind speed logged in the region since recordings began in 1948. The highest-ever wind speed recorded in the area at a similar altitude was 267 mph on Dec. 6, 2002.
“For those flying eastbound in this jet, there will be quite a tail wind,” the NWS warned in a tweet.
Sure enough, that tailwind helped cut down the flight time for passengers on a Virgin Atlantic flight from D.C. to London by 45 minutes, according to the tracker FlightAware.
There’s no reason at all for it to slow down. If you’ve ever been on one of those moving walkways think about it like that, yes by walking on it you’re moving faster than the people around you, but to you you’re not walking any faster than normal even though you’ll arrive at your destination earlier.
That’s actually a really good analogy. Mind if I throw some numbers on it to flesh things out?
Let’s set that moving walkway going at 5mph, and we’ll put ourselves on that walkway, on a turned-off rascal scooter. The scooter is stationary on the belt, but it’s still moving at 5mph - that’s your tailwind pushing the air around the plane forward.
Now, let’s turn that scooter on and throttle it up to 5mph. The scooter is plugging along comfortably at 5mph, but it’s actually moving at 10mph. This is your plane flying with a tailwind, performing normally for its indicated air speed, while having a much higher ground speed.
Curiously, this does make the phrase “supersonic speeds” somewhat debatable. While they were traveling over the ground faster than sound would, they weren’t moving faster than sound would in the air around them.
Ooh, there’s another fun one…
“Indicated” airspeed isn’t actually how fast you are going relative to the air. “Indicated” airspeed is how hard the air is pushing into the front of the pitot tube. But, at high altitude, the air is thinner, and doesn’t push as hard. To get the same indicated airspeed at altitude, you have to be flying much, much faster.
Indicated airspeed is how fast the wings “think” they are moving. If the stall speed is 80kts, and the true airspeed is 200kts, but you’re so high that the wings “think” they are only moving at 75kts, the aircraft is in a stall.
Next up, “critical mach number” and “coffin corner”