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Mach Kias?  
User currently offlineLH463 From United States of America, joined Apr 2006, 68 posts, RR: 0
Posted (8 years 4 months 2 weeks 1 day 11 hours ago) and read 1856 times:

Hey Guys,
I was just wondering if an airplane had to break the sound barrier by passing it on it's KIAS. I know the actuall speed depends on many factors such as temperature, air density etc., but is there any way the sound barrier could be broken by an aircraft (normally incapable) with a tail wind? (Assuming it can withstand the forces)

Thank's,
LH463


Turning final...
8 replies: All unread, jump to last
 
User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 1, posted (8 years 4 months 2 weeks 1 day 10 hours ago) and read 1846 times:

Winds only affect your groundspeed. Airspeed is only relative to the speed of the relative wind around the aircraft. If the aircraft is in level flight at say, mach .99 and there is a tail wind, it is at mach .99. It will not break the speed of sound because it is traveling at an airspeed that is below the speed of sound.


DMI
User currently offlineViv From Ireland, joined May 2005, 3142 posts, RR: 29
Reply 2, posted (8 years 4 months 2 weeks 1 day 1 hour ago) and read 1782 times:

Quoting LH463 (Thread starter):
there any way the sound barrier could be broken by an aircraft (normally incapable) with a tail wind

No, because airspeed does not increase in a tailwind (or decrease in a headwind).



Nikon D700, Nikkor 80-400, Fuji X Pro 1, Fujinon 35 f/1.4, Fujinon 18 f/2
User currently offlineBri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4
Reply 3, posted (8 years 4 months 2 weeks 12 hours ago) and read 1697 times:

Quoting Viv (Reply 2):
No, because airspeed does not increase in a tailwind (or decrease in a headwind).

That's right, and actually, the opposite happens. God forbid I bring out the conveyor belt loonies again, but I hope we can agree on this. If, at some place on the surface of the Earth, the wind blew as fast as the speed of sound in those particular conditions, an observer standing there would experience winds at the speed of sound (not a good idea).

Extending the concept a little, if an airplane was crusing in still air at, say, mach .75, or 75% of the speed of sound in those conditions, and a sudden current of wind came by, aimed directly at the nose of the plane, aligned with the fuselage, at least as fast as 25% of the speed of sound, it would suddenly be flying through the air faster than the speed of sound. Not being designed for it, and not having the power to sustain flight at those speeds, it would experience a violent deceleration. Most planes would probaly sustain significant structural damage. Fortunately, even in turbulent air, it's highly unlikely that winds on Earth will ever change quickly enough in a short enough time to make this happen.



Position and hold
User currently offline113312 From United States of America, joined Apr 2005, 571 posts, RR: 1
Reply 4, posted (8 years 4 months 2 weeks 6 hours ago) and read 1672 times:

Speed of sound varies with temperature only.

User currently offlineGSOShutout55 From United States of America, joined Feb 2006, 126 posts, RR: 0
Reply 5, posted (8 years 4 months 1 week 6 days 8 hours ago) and read 1607 times:

Quoting 113312 (Reply 4):
Speed of sound varies with temperature only.

god, i hope your kidding. And you claim to be an airline pilot?



B200/Ce500 Pilot
User currently onlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4195 posts, RR: 37
Reply 6, posted (8 years 4 months 1 week 6 days 8 hours ago) and read 1604 times:

]

Quoting GSOShutout55 (Reply 5):
Quoting 113312 (Reply 4):
Speed of sound varies with temperature only.

god, i hope your kidding. And you claim to be an airline pilot?

Sorry bud, my man is correct. It's a function of temperature only.



Chicks dig winglets.
User currently offlineSeanp11 From United States of America, joined Jan 2006, 290 posts, RR: 0
Reply 7, posted (8 years 4 months 1 week 6 days 8 hours ago) and read 1600 times:

Quoting XFSUgimpLB41X (Reply 6):
Quoting GSOShutout55 (Reply 5):
Quoting 113312 (Reply 4):
Speed of sound varies with temperature only.

god, i hope your kidding. And you claim to be an airline pilot?

Sorry bud, my man is correct. It's a function of temperature only.

Perhaps GSO was confused by how m.80 can be around 280 kias at altitude, and is closer to 400 kias closer to the ground.


User currently offlineWoodreau From United States of America, joined Sep 2001, 1038 posts, RR: 6
Reply 8, posted (8 years 4 months 1 week 4 days 19 hours ago) and read 1545 times:

Quoting 113312 (Reply 4):
Speed of sound varies with temperature only.

Pressure and salinity too ... oops wrong medium. I see y'all are talking about air not seawater.  Smile

But average speed of sound about ~3000kts in seawater - more useless trivia for you guys.



Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
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