2006-11-15 23:27:32 · 5 answers · asked by fadamose1 1 in Cars & Transportation ➔ Aircraft
mach is a basic term used to describe the speed of sound... however it is not a constant. Mach changes with altitude... for example: Our base is based upon the speed of sound at sea level and we give this a coefficient of 1.00 (around 1100 feet per second), but as you increase altitude the air density reduces, thus reducing the ease sound can travel and therefore the coefficient changes... or goes down. So at 10,000 feet you could be looking at mach is .9874 of the 1100 feet/sec... in other words the sound slows down. The mach number is based upon air density, temperatures of the air, and the humidity (however this is very minor and usually omitted).
2006-11-15 23:50:32 · answer #1 · answered by Dport 3 · 1⤊ 0⤋
mach number is exactly as was stated above. Airspeed expressed as a percentage of the speed of sound.
Mach numbers are used for higher altitude and higher performance aircraft because the speed of sound becomes on of the more limiting factors on high speed jets. The speed of sound changes with air temperature, so mach number is just a quicker and easier way to express airspeed relative to some limit.
think back to private pilot days. As airflow goes over the top of the wing it accelerates and its pressure drops. In a high-speed situation, this accelerated air can begin to approach the speed of sound. Lots of bad things can happen when the shock wave caused by airflow reaching the speed of sound hits a wing. The center of pressure moves aft, pitching the nose down and accelerating the aircraft which moves the center of pressure aft which accelerates the aircraft...(and on and on) its called a high-speed stall. Or a mach tuck.
Because we don't want this to happen to us, we are much more aware of the speed that this begins to happen (known as Critical mach and usually expressed as Mmo). And because the speed of sound can vary so much it is simply easier to use mach numbers when we begin to approach high speeds.
2006-11-16 14:42:59 · answer #2 · answered by Jason 5 · 1⤊ 0⤋
Mach 1 equals the speed of sound. Mach 2 is twice the speed of sound, etc. It is used in measuring the speed of very fast aircraft.
2006-11-16 07:30:06 · answer #3 · answered by Michael 5 · 0⤊ 1⤋
Mach number is an expression of the speed of an aircraft as a ratio of the aircraft's true airspeed to the local speed of sound.
Mach number = True airspeed/ Local speed of sound
More info.
http://www.grc.nasa.gov/WWW/K-12/airplane/mach.html
2006-11-16 11:19:08 · answer #4 · answered by nov666 2 · 0⤊ 0⤋
.................. relative speed of the aircraft compared to the speed of sound at that level .................. speed of sound reduces with height .... max at sea level .............. measured in percentage 1= Mach 1 , passenger airliners fly ... Mach .81 or .84 or .74 and so on ..........
2006-11-16 08:45:05 · answer #5 · answered by spaceman 5 · 0⤊ 0⤋