CPDC10-30 From United Kingdom, joined Feb 2000, 4761 posts, RR: 25 Reply 2, posted (11 years 11 months 1 week 4 days 16 hours ago) and read 16838 times:
At cruising altitudes, speed is set by Mach number, on takeoff, climb, landing and approach knots are used. A certain mach number for the same number of KIAS will increase with altitude. For example, 240 knots is a higher mach number at 31,000 ft than at 2,000 ft.
The 747 has the fastest normal cruise speed of commercial airliners (excluding the Concocrde of course) with a long-range speed of M. 0.85. Other aircraft typically fly slower such as the A340 (0.82) and the 767 (0.80).
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 1 Reply 6, posted (11 years 11 months 1 week 4 days 14 hours ago) and read 16786 times:
"knots below 18,000ft mach above"
Not necesarily I miss piedmont. It depends upon the changeover level of the particular aircraft on the day i.e the 727 changeover level is normally around the FL270 mark and the F-28 changeover level around the FL230 mark- it varies.
NZ767 From New Zealand, joined Nov 2001, 1620 posts, RR: 1 Reply 7, posted (11 years 11 months 1 week 4 days 13 hours ago) and read 16779 times:
Ahh Positive rate, I think you're confused there.
We're talking Transition levels and they don't vary from aircraft to aircraft at all; sheesh, imagine the accident rate if that were the case.
They vary from country to country, eg 18000 feet in the US, 6000 feet in the UK, 11000 feet here in New Zealand and so on.
AmericanF100, to answer you question, generally "Knots" are used below transition level and "Mach" (a percentage of the speed of sound) is used above transition level.
Also, altitude readings above transition are known as "Flight Levels".
An aircraft climbing through transition level will have to reset it's barometric pressure to the standard setting of 1013.2 millibars (29.92 inches of Mercury).
DerekF From United Kingdom, joined Feb 2001, 866 posts, RR: 0 Reply 8, posted (11 years 11 months 1 week 4 days 8 hours ago) and read 16749 times:
As far as I'm aware Positive Rate is right. You do not change to flying Mach at the transition altitude. If that were the case in the UK aircraft would changeover to flying Mach at 5000ft. That is not the case. On the Avro RJ you generally climb at 250 or 280 kts until you reach 0.66M which is say 24000ft.
Positive rate From Australia, joined Sep 2001, 2143 posts, RR: 1 Reply 10, posted (11 years 11 months 1 week 4 days 7 hours ago) and read 16734 times:
No i didn't mean different transition levels for different aircraft but i meant different changeover levels for different aircraft which is as DerekF described above. Changeover level is the altitude at which the climb IAS is equal to the corresponding climb mach no. e.g the B 727 climbs at 310 KIAS/ 0.78M
Jhooper From United States of America, joined Dec 2001, 6197 posts, RR: 13 Reply 14, posted (11 years 11 months 1 week 3 days 21 hours ago) and read 16676 times:
"Planes fly at about 12,000 Knots an hour."
Just trying to do the math here. What you're saying is that a plane flies 12,000 nautical miles per hour per hour. That would suggest a unit of acceleration, which doesn't suggest anything about cruising speed, right?
Last year 1,944 New Yorkers saw something and said something.
Tom_eddf From Germany, joined Apr 2000, 451 posts, RR: 1 Reply 15, posted (11 years 11 months 1 week 3 days 20 hours ago) and read 16663 times:
I'm not sure where the Airshow Numbers come from, but the GS shown should be very close to the real speed of the aircraft above ground. This should include the wind factors (head/tail/crosswinds, also shown in airshow).
The speed indicated on the cockpit instruments (even in MS FS) is ususally the mach number and the indicated airspeed (IAS) in knots. IAS varies with the flying altitude, i.e. 250kts IAS at 2000ft could mean around 250kts ground speed. At FL410 (41000ft) and with tailwind, 250kts IAS could also mean 550kts GS, because of the wind and the thinner air.
The mach number also does not compensate the wind components, i.e. flying an Airbus A340 at m.82 could either mean cruising above the ground at 480 knots (with little winds) or going much faster, say 550knots (with around 80kts of tailwind or so).
The mach number therefore indicates the TAS, the True Air Speed, which is constant at any altitude. It is the actual airspeed of the aircraft through the air mass. As an aircraft climbs, the indicated airspeed (IAS) will decrease as the air becomes thinner and the impact pressure is reduced, while the TAS remains stable. For a given TAS, indicated airspeed will decrease with altitude.
Sounds complicated? It sure is. Maybe I'm wrong with all this, but I'm sure someone could clarify...