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Near-record winds over the Northeast push passenger planes to speeds over 800 mph (wamu.org)

submitted 8 months ago by [email protected] to c/[email protected]

37 comments fedilink hide all child comments

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.

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[–] [email protected] 1 points 8 months ago

In case anyone is wondering, there are actually subsonic aircraft that can handle going mach.

The F-86 Sabre had a max speed of 687 mph at sea level which is about mach 0.9

But the Sabre could enter a dive from a higher altitude and safely reach past Mach 1 with help from gravity (or another additional source like rockets).

Comparatively, the MiG-15 had poor control authority reaching mach 0.9 and would subsequently break apart if it reached past mach 0.92.

Modern airliners obviously aren't fast enough to reach mach under their own power, but they also can't handle the pressure if they used something like a dive so they would also break apart like the MiG.

[–] [email protected] 60 points 8 months ago (3 children)

A) no it’s not supersonic because that depends on airspeed not ground speed

B) this is normal for west bound flights

[–] [email protected] 2 points 8 months ago

50% accuracy ain't bad I guess

[–] [email protected] 11 points 8 months ago

Not those speeds though. Usually they fly 600-700 in that direction.

[–] [email protected] 23 points 8 months ago (2 children)

Think you mean eastbound flights.

[–] [email protected] 6 points 8 months ago

Also the quote clearly said this was the second highest cruising altitude wind speed in the area since they began recording it in 1948.

[–] [email protected] 3 points 8 months ago

It depends on if you're in the northern or southern hemisphere. \s

[–] [email protected] 24 points 8 months ago* (last edited 8 months ago) (3 children)

The supersonic claim reeks of bullshit. Humans had a hell of a time engineering a plane that could withstand that speed, and I'd guess passenger jets would tear apart.

“Although its ground speed — a measure that combines the plane’s actual speed and the additional push from the wind — was greater than the speed of sound, it was still moving through the surrounding air at its ordinary cruise speed. It just so happened that the surrounding air was moving unusually fast,” the Post reported.

Oh! Never knew what "ground speed" meant. So no, those planes were not leaving a sonic boom. Not even close to supersonic at typical altitudes.

(Apologies, don't know how to format a table on here.)


Sea level	15 °C (59 °F)	761

11,000 m−20,000 m (Cruising altitude of commercial jets, and first supersonic flight )	−57 °C (−70 °F)	660

29,000 m (Flight of X-43A )	−48 °C (−53 °F)	673

[–] [email protected] 10 points 8 months ago* (last edited 8 months ago) (1 children)

So you are right they were not going supersonic speeds, not even close. Yes their ground speed exceeded the speed of sound, but ground speed is only meaningful with how fast the plane is going to get to its destination. The plane only cares about air speed.

So it is all about the frame of reference. For a plane in flight the air is in a different frame of reference than the ground. To be supersonic the plane needs to be moving supersonic speeds in relation to the air not the ground.

Also just to make life more fun supersonic is not a transition that happens at a set speed. It is actually pressure dependent. At standard pressure and temperature it is 786mph, but it will go up and down with changes to pressure and temperature.

The true definition of supersonic is when the air the plane is pushing is no longer able to flow around the plane and instead is compressed in front of it. But that definition is hard to put on an air speed indicator so they just use 786mph better known as Mach 1.0.

Thanks for coming to my TED talk.

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[–] [email protected] 1 points 8 months ago (1 children)

Yes, we know this, but can you expound upon how the penguins factor in?

[–] [email protected] 3 points 8 months ago (1 children)

The in flight entertainment system runs linux

[–] [email protected] 2 points 8 months ago* (last edited 8 months ago)

I all ready covered that 😋

https://lemmy.world/post/11881718

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[–] [email protected] 0 points 8 months ago

I’d guess passenger jets would tear apart.

Not initially. Supersonic flows disrupt the airflow around the wings, control surfaces and the fuselage in general, so the plane just gets out of control. Since gravity exists, that means the plane will begin to drop, accelerating even more. At some point, the airflow will tear the fuselage apart, but if not, the collision with the ground surely will.

Look up the coffin corner for some interesting explanations of the problems around there.

[–] [email protected] 8 points 8 months ago (1 children)

Ah so that's how aliens fly supersonic without breaking the sound barrier. Just move the air around the craft in the direction they're going! Problem solved.

[–] [email protected] 2 points 8 months ago (1 children)

The aliens just move spacetime (with the air included) next to their ships around with their warp drives around. Don't you watch any Star Trek?

[–] [email protected] 1 points 8 months ago* (last edited 8 months ago)

Fuck I'm such an idiot!

[–] [email protected] 2 points 8 months ago

Oh look, all the ocean receded. It's so cool. Let's go out and look at all the stuff that's usually underwater.

[–] [email protected] 5 points 8 months ago

Getting off a flight 45 minutes early would feel a bit like time traveling.

[–] [email protected] 7 points 8 months ago (4 children)

What about planes going the opposite direction

[–] [email protected] 1 points 8 months ago

At some point, depending on the distance to the destination and the speed of the Jetstream, it makes more sense to fly around the world with the Jetstream than directly towards your destination without it. The faster it gets, the closer that point gets.

[–] [email protected] 5 points 8 months ago

To shreds you say?

[–] [email protected] 5 points 8 months ago (1 children)

They're the new hovercraft

[–] [email protected] 4 points 8 months ago (2 children)

Alaskan bush planes need to be tied down lest a stiff breeze causes them to "liftoff". I swear I saw a video of one being landed essentially vertically as it was flying into a strong wind.

[–] [email protected] 2 points 8 months ago

Look up STOL videos on the tubes and you’ll find a ton of planes landing in less than 10ft/3m

https://youtu.be/VQq2oYAwnqY

[–] [email protected] 2 points 8 months ago (1 children)

I have a buddy that built a kit plane capable of crazy short takeoff runs, and yeah if there's a good headwind it can pretty much hover in midair.

[–] [email protected] 2 points 8 months ago

All my fixed wing friends get excited about hovering, or even flying backwards into particularly strong headwinds.

[–] [email protected] 21 points 8 months ago

if they fly a bit higher or lower, they will avoid the worst of it.

[–] [email protected] 33 points 8 months ago (3 children)

While this is an incredible travel speed, I wouldn't consider it "hitting supersonic" speeds based on ground speed. I read the article wondering about the safety of passenger aircraft at 800MPH, but it seems to not apply.

I'm not a pilot, though.

[–] [email protected] 13 points 8 months ago* (last edited 8 months ago)

Narrator: It's not.

Poorly written summary. Supersonic means exceeding the speed of sound (duh) and the indicated airspeed of the plane at cruising altitude would still be around 250kts, about 1/3rd speed of sound.

[–] [email protected] 42 points 8 months ago (1 children)

The aircraft isn't experiencing anything out of the ordinary. Its airspeed - which is the speed relative to the air it's moving through - would be the same. It's just that the air is moving relative to the ground along its direction of travel.

Think of it like a boat moving down a river. If you paddle your speed is added to the speed of the current, but the force on the boat is just from you paddling.

[–] [email protected] 3 points 8 months ago (1 children)

good analogy! If that's the case, then I can paddle a canoe 10mph (downstream, with a "tail" wind).

[–] [email protected] 0 points 8 months ago

I can fuck in a canoe.

[–] [email protected] 2 points 8 months ago (1 children)

Yeah I was curious about that too.

The plane can't really slow down to compensate in guessing as it would lose lift? Or it could extend flaps maybe.

[–] [email protected] 16 points 8 months ago (1 children)

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.

[–] [email protected] 5 points 8 months ago (1 children)

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.

[–] [email protected] 2 points 8 months ago

This is your plane flying with a tailwind, performing normally for its indicated air speed, while having a much higher ground speed.

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"

[–] [email protected] 4 points 8 months ago

That sounds very fun and exciting ngl