747 goes supersonic*

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801mph is over the supersonic speed of 768mph. That plane would beat sound from New York to London = "supersonic". Works for me. [Linked Image]
 
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JHZR2

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I was going to post on this too. Are commercial jetliners "designed" (at least built with sufficient margin and safety factors) to go over 800mph? I thought special considerations had to be made even for surface paint temperatures? I'm not calling it supersonic because it's awful high and awful cold up there, and those conditions change the speed of sound IIRC....
 
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Originally Posted by JHZR2
I'm not calling it supersonic because it's awful high and awful cold up there, and those conditions change the speed of sound IIRC....
Also, is it really supersonic with a tailwind of 260? Relative to ground i guess its over 800. Relativity wise, is the air-frame really seeing 800mph? Calling Astro!
 
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Originally Posted by PimTac
I guess the meaning of supersonic has changed since I went to school.
Agreed, I think that supersonic speed is literally that at which the speed of sound is exceeded, and is thus relative to the surrounding air. The jet stream wind speed would have to be subtracted from the ground speed to give the actual air speed of the aircraft. As well, the speed of sound (Mach 1) is c. 760 mph @ STP (standard temperature and pressure, 20 C @ sea level) but decreases with altitude, as atmospheric pressure drops. As atmospheric pressure drops, the air becomes less dense, and sound travels more slowly. This chart helps: https://www.fighter-planes.com/jetmach1.htm Per the chart, the speed of sound is about 660 mph at typical airliner altitudes. The aircraft under consideration is said to have hit a maximum ground speed of 825 mph, but if we subtract the 260 mph tailwinds, we're left with a maximum airspeed of 565 mph, well below supersonic (660 mph) at that altitude. To put it another way, if you could somehow have projected a loud sound from the aircraft, its waves would have traveled in front of (that is, faster than) the aircraft, not behind the aircraft.
 
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Did anyone read the article ?
Originally Posted by article
...it wouldn't have broken the sound barrier as the differential between the speed of the plane and the air moving around it was to low.
 

JHZR2

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Originally Posted by hallstevenson
Did anyone read the article ?
Originally Posted by article
...it wouldn't have broken the sound barrier as the differential between the speed of the plane and the air moving around it was to low.
I saw a different article. But that's why I didn't claim it to be supersonic. Still, the ground speed, tailwind or not, seems to me to be impressive. Not that I know much about flying... but I know if I go much over 30 on a bicycle, down a hill and in a tailwind, it's not the most comforting feeling... regardless of the reason the speed is achieved... thus my curiosity on what the design speed is.
 
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Right time,right route,right conditions,even a four engine freighter/transport can do concorde like cross-Atlantic travel times. The relative wind kept the loads to subsonic levels.
 

DeepFriar

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Gentlemen this item was firmly tongue in cheek hence the asterisk. Supersonic in this case is just numerical. The 747 was no more supersonic than when there is no tailwind. Sub five hour flight from New York to London is still remarkable even for the extreme swept wing wonder from Everett and is the real *story* here.
 
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Saw this elsewhere. Nice that the old girl set a record in her declining years. An aircraft from the days when "Boeing" really meant something.
 
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