OT: 787 jet liners approach 800 mph, break records

Norwegian Air 787 jets have been hitting speeds near 800 mph, and are setting new speed records for subsonic transatlantic crossings, thanks to help from 224 mph tailwinds.

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    - Win
Reply to
Winfield Hill
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Wow! I just had a quick look with FR24. Right now, many east-bound flights are doing well over 650 mph and one Qatar Airbus A350 is going at 610 knots (702 mph). Nowhere near the record but still impressive. Most of the poor west-bounds are struggling at well under 500 mph.

Reply to
Pimpom

And one small Dassault Falcon 7X is doing about 685 mph.

Reply to
Pimpom

Yawn. Still only about half of Concorde's top speed with no tail wind assistance.

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Reply to
Cursitor Doom

"Los Angeles Center, Aspen 20, can you give us a ground speed check?" There was no hesitation, and the replay came as if was an everyday request. "Aspen 20, I show you at one thousand eight hundred and forty-two knots, across the ground." "Ah, Center, much thanks, we're showing closer to nineteen hundred on the money." "Roger that Aspen, Your equipment is probably more accurate than ours. You boys have a good one."

Aspen 20 was an SR-71 somewhere 13 miles above Arizona

Reply to
Lasse Langwadt Christensen

That's not a passenger aircraft!!

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Reply to
Cursitor Doom

From the horse's mouth:

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Cheers, James Arthur

Reply to
dagmargoodboat

this one is quite interesting,

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Reply to
Lasse Langwadt Christensen

Yeah, the downside is for the airlines that run 757s on transatlantic flights to and from smaller East Coast airports e.g. Newark and BWI to Paris and London. They barely have enough fuel to make it westbound at the best of times and there were probably a few stops in Labrador

Reply to
bitrex

Whadya mean! George Bush took one to Paris to meet the Iranians in

1980!
Reply to
krw

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** High speed aircraft have been using Mach Number since before WW2 to avoid such silly confusions.

.... Phil

Reply to
Phil Allison

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** Yep, Concorde really did fly above the weather - including jet streams.

Plus flying at 60,000 feet meant air density was about 1/3 of what most passenger jets experience. Made long range cruising at 1330mph possible.

.... Phil

Reply to
Phil Allison

Except it is not about supersonic craft. This is about subsonic craft record speeds.

Reply to
Long Hair

BOOM shaka laka laka!

Reply to
Long Hair

The speed of sound does not vary with density or pressure, only with temperature and average molecular mass.

For air with an average molecular mass like that at sea level, the SoS in metres/second is very close to 20*sqrt(k), where k is in Kelvin. Useful formula to remember.

As you get to the upper atmosphere, there's more lighter molecules (hydrogen, etc) so for a given temperature, the SoS is higher - since temperature is a measure of the impact energy at a surface, and that varies with the kinetic energy (1/2 m v^2). If m goes down, v must be higher to reach the same temperature. I'm not sure what altitude that starts to make a real difference.

There's also molecular geometry. Bi-atomic molecules tend to flip when they hit the surface, so instead of imparting energy they turn some of it to angular momentum. Monatomic molecules like hydrogen don't do that.

Clifford Heath.

Reply to
Clifford Heath

craft record speeds. "

Is my math off or isn't the speed of sound about 750 MPH ?

Actually sound is slower in rareified air, is that taken into account ?

Reply to
jurb6006

That's the speed of an object in still air. If the entire air mass is moving wrt ground, the adjusted speed of sound, over ground, is that much higher.

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Reply to
Winfield Hill

The cited speeds are relative to ground. Since the surrounding air is also moving at 200 mph or more in the same direction, the air speed is still subsonic. There's no claim of achieving supersonic speed for those planes.

Reply to
Pimpom

entire air mass is moving wrt ground, the adjusted speed of sound, over ground, is that much higher. "

That's not what I was asking. I was asking if it is adjusted WRT the density of the air, not its velocity or vector.

Reply to
jurb6006

That doesn't affect how Mach number is calculated, which as you can clearly see, is what I responded to.

No need to "make use of it" if your instruments calculate Mach number for you. And there's no way to calculate Mach number without using air temperature.

I suspected as much.

Indeed. Airliners fly with as little as 22% sea level pressure, but usually a little more. They make less thrust of course, but there's less drag so it tends to cancel.

Clifford Heath.

Reply to
Clifford Heath

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