Talk:Critical Mach number

Merge this article with Critical Mach number

This article should be merged with critical Mach number for several reasons. The concepts are different, but closely related. The meaning of the term varies based on the context. One usage (currently the article entitled critical Mach number) is from aviation and refers to aircraft dynamics and controllability, while the other usage (currently the article entitled critical mach) is from pure aerodynamics. Having two separate articles allows the possibility that link will be made to the wrong article of the two. Additionally, the two concepts actually are both referred to as critical Mach number. It is somewhat nonsensical to refer to critical mach without the word number, since the Mach number is the concept to which the term refers, whereas Mach is the name of the man after whom the Mach number was named. MarcusMaximus 07:24, 19 March 2007 (UTC)

I agree with MarcusMaximus. The expression "Critical Mach" is simply shorthand for "Critical Mach Number". There is no difference so there shouldn't be two articles on the one subject. Dolphin51 (talk) 05:20, 28 November 2007 (UTC)

critical mach number verses drag divergence mach number

the article says that the critical mach number was responsible for the so called "sound barrier," I was under the impression (I'll get sources later) that the sound barrier was caused by drag divergence. That is the sound barrier was caused by what looked like an exponential increase in drag that many guessed would go to infinty as mach 1 was approached. This wasn't true.. drag levels off and eventually decreases. —The preceding unsigned comment was added by Cole.christensen (talk • contribs) 07:55, 11 December 2006 (UTC).

You may be right, however at the time the practical problem was more one of control than drag. As you probably know, as speed increases towards Mach 1.0 the centre of pressure moves rearwards causing the aircraft to become increasingly nose-heavy and requiring more and more up-elevator to maintain the angle of flight, i.e., to prevent a dive that becomes steeper and steeper causing the aircraft to bunt, however eventually the pilot runs out of up-elevator (the elevators are in the fully 'up' position) or he lacks the strength (pre powered controls) to pull harder on the control column (due to the aerodynamic load on the control surfaces) and an ever-steepening dive ensures. As speed increases further (due to gravity) the shock wave formed at the nose of the flying surfaces moves rearward until it coincides with the hinge-line of the elevators and ailerons. At this point the controls have no effect and so recovery from the dive becomes difficult if not impossible (that was the reason for the 'all flying tail'). The only saving grace for this situation was that these sort of speeds (at the time) could only be reached by diving from high altitudes where the air is rarefied/colder compared to lower heights, the speed of sound being lower, so as the dive continued the altitude decreased and the speed of sound rose relative to the actual airspeed until the aircraft was no longer affected and the pilot could then regain control. For most of the non-test pilots concerned this was more what the term 'sound barrier' meant rather than any other (more technical) meaning. Ian Dunster 20:59, 8 March 2007 (UTC)

This definition of Critical Mach Number is just plain wrong. Mcrit is that airspeed at which the aircraft first experiences localized supersonic flow. All aircraft have a critical mach number and many with high speed flight capabilities (WW2 fighters on) can experience it. Force divergent mach number is the speed at which normal shock (compression) waves are formed and coefficient of drag increases sharply (approximately 105% of critical mach). R / CrusaderF8, Sept 2 2007. —Preceding unsigned comment added by CrusaderF8 (talk • contribs) 17:14, 2 September 2007 (UTC)

WikiProject class rating

This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:46, 10 November 2007 (UTC)

Bernoulli's principle

Bernoulli's principle is described as being responsible for the wing generating lift. This conflicts with the this article. One or the other must be wrong. Would somebody who knows about this make the necessary changes, please? AJKGORDON«» 19:28, 17 January 2008 (UTC)

Introduction

As a totally uninformed person on this subject, the introduction to this article makes no sense to me. It talks about "lower critical Mach number" and "upper critical Mach number" but the rest of the article only talks about "the" critical Mach number. And as critical Mach number is defined, it seems to me there can only be one value for any given aircraft. Does the introduction actually mean "below the critical Mach number" and "above the critical Mach number" respectively? I'm just guessing, but that would seem to more nearly make sense. Or maybe the present wording is correct, but more explanation is needed? — Preceding unsigned comment added by 24.213.20.170 (talk) 00:12, 7 November 2019 (UTC)

Upper critical Mach number is only applicable to supersonic aircraft such as Concorde, Tupolev Tu-144 and modern military combat aircraft. The upper critical Mach number would be close to 1.00, perhaps between 0.95 and 1.00. I have made an adjustment to the lead paragraph of the article. Does it clarify adequately?

The range of speeds between the lower and upper Mach numbers is the range known as transonic flight. Modern jet airliners are designed to cruise just inside the transonic range and that is why they need swept wings. However, these modern jet airliners go nowhere near the upper critical Mach number. Dolphin (t) 22:05, 7 November 2019 (UTC)