Max angle is correct. When we learn about speed of sound etc as pilots we are taught is is dependant on temperature alone, I believe, because this is the answer to the question in the CAA question bank!
Temperature/pressure/density are all related off course, but temperature has the greatest effect on the speed of sound for us as pilots, so for the purpose of simplification we say "speed of sound is dependant on temperature alone", when it actually isnt at simple as that.
Let us consider sonar (being ex Navy myself, but not aircrew). Now lets take a look at say a cold bit of north atlantic water at about 4 deg c. This equates to an altitude in ISA conditions of about 5000 feet. But the speed that our sonar "ping" is much faster than the speed of sound of in the air (seem to remember from my Oceanography course speed of sound in water is of the order of 790 metres per second). Why? Because the water is much more dense.
Whilst we are speed of sound etc here is an interesting thing about compressibility effect and mach cone angle. When you stand on the platform at an underground station and the train is approaching you know its coming because there is a rush of air. At the very low mach number of the train the cone angle is almost 90 degrees. Now lets suppose London Underground built a tube train that could go at mach one. Would you get an onrush of air ahead of it? You would not.
Last edited by timzsta; 4th Feb 2003 at 21:39.