Cx251 From Hong Kong, joined Sep 2003, 52 posts, RR: 0
Reply 2, posted (11 years 6 months 4 days 6 hours ago) and read 4175 times:
You're right. I've forgotten the tailwind speed at that point (something close to 200km/h) and that piece of info was indeed from the PTV. Believe it or not, the usual 11.5 hours flight from LHR took us just 11 hours. The speed over ground was over 1000km/h for most of the journey anyway.
QF747 From Australia, joined Nov 1999, 164 posts, RR: 0
Reply 8, posted (11 years 6 months 4 days 3 hours ago) and read 4005 times:
Mine was on Air New Zealand 744 LAX-SYD, it 1250 km/h. There were problems with seat assignments, so everyone had to be deplaned and reassigned seats. Delayed about two hours and made it all up inflight.
Broke From United States of America, joined Apr 2002, 1322 posts, RR: 3
Reply 10, posted (11 years 6 months 4 days ago) and read 3870 times:
Jet powered airliners fly using a Mach Number as their targeted cruising speed.
Since the speed of sound varies according to air temperature, the air speed for a certain Mach Number will also vary according to air temperature. The higher the air temperature, the faster the speed of sound.
On a standard day, the speed of sound at sea level is about 761 mph or 661 kts.
At 35,000' or about 10,700 m, the speed of sound is about 650 mph or 576 kts.
So when you are trying to determine your true air speed for a certain Mach Number, it's nice to have an air data computer to help you out.
Ground speed, of course, is dependent on the winds aloft in addition to you cruising Mach Number. One of the funnier things I have ever seen is a Piper Cub going backwards over the ground on a very windy day while trying to land.
La Carlota From United States of America, joined Jun 2001, 358 posts, RR: 0
Reply 12, posted (11 years 6 months 4 days ago) and read 3820 times:
Sorry for the question, but does that means that if your subsonic flight reaches, let's say, around 1,000 km/h, (and of course depending on the air temperature someone mentioned above, and the altitude)... you are technically flying supersonic???
I've always asked myself that...
B2707SST From United States of America, joined Apr 2003, 1374 posts, RR: 59
Reply 14, posted (11 years 6 months 3 days 22 hours ago) and read 3721 times:
1,000 km/h works out to about 620 miles per hour, or a Mach number of .94 at standard stratospheric temperatures, so you'd still be subsonic. But using 1,500 km/h an an example, unless you reach 1,500 km/h groundspeed without a substantial tailwind, thus breaking the sounds barrier "on your own," you're still subsonic. Mach number is calculated relative to the airstream, so headwinds/tailwinds have no effect (leaving temperature changes aside).
Airplanetire From United States of America, joined May 2001, 1809 posts, RR: 2
Reply 19, posted (11 years 6 months 3 days 16 hours ago) and read 3460 times:
My fastest was on a Delta 777 in the beginning of July flying from ATL to FCO. The fastest I remember seeing on the PTV was 688 mph (1107 km/hr). It wasn't that fast the whole time though because if it had been, we'd have been there at least an hour faster. The flight took 8 hours 39 minutes.