# Questions tagged [mach-number]

Use for the various Mach numbers, e.g. critical, cruise, etc., and the related instruments and sensors

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### wave drag: Lift coefficient in Korn's Equation

I have been using the Korn equation: $$M_c = \frac{0.95}{cos(\lambda)}-\frac{t/c}{cos(\lambda)^2}-\frac{C_L}{10cos(\lambda)^3}-\sqrt[3]{\frac{0.1}{80}}$$ to estimate the critical mach number of a ...
1 vote
198 views

### Would air having an infinite speed of sound be ideal?

Hypothetically, if aerodynamicists had the opportunity to somehow raise the speed of sound in air to an infinite level so that air was no longer compressed, how would this affect aircraft related ...
164 views

### Why do I keep getting different results to an aircraft's turn radius when I plug variables into different calculators and solve on my own?

I'm trying to solve for an aircraft's turn radius at mach 3.17 (2432 mph) and a bank angle of 19.8; however, after using various online calculators and personally solving the equation, I keep getting ...
686 views

### How do swept back wings delay shock wave

Swept back wings can delay the formation of shock wave and increase the aircraft critical mach number of the aircraft, right? But how
• 349
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### Is it possible to calculate Calibrated Airspeed from True Airspeed, Temp, and Pressure Altitude? [duplicate]

Looking at a digital E6B, there is a function for calculating CAS that I am trying to recreate and program myself. Inputs: Pressure Altitude Temp in Celcius True Airspeed Outputs: CAS Mach # ...
2k views

### How can TAS be calculated from indicated temperature and Mach number? [duplicate]

Situation I am working on programming my own E6B while I learn more about aviation, but I have run into some confusion. Two pairs of the equations are very similar except for using true or indicated ...
1 vote
590 views

### Does Indicated Stall speed increase with altitude (Coffin Corner)?

It is my understanding that Indicated Stall speed is mostly constant with altitude, the one that increases is True Stall Speed. Given that PFD show speed as IAS, how come the yellow speed range ...
1 vote
4k views

### What's the relationship between mach number and drag force on an airplane?

From what i've read drag coefficient at mach 1 is several times (up to 10x) the drag coefficient below drag divergence mach number. It drops as the mach number increases. It's easy to find plots ...
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### Who was the first person to break the sound barrier?

In this video on Wikipedia of Chuck Yeager breaking the sound barrier in the Bell X-1 in level flight, at 2:44 the narrator says "For the first time, except in dive, a man has flown an airplane ...
• 171
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### The SR-71 flew at 2193 mph. Mathematically, how can this be Mach 3.3?

Virtually every time I read about the Lockheed SR-71 Blackbird (including other threads on this forum), I see that its speed record is listed as approximately $2193$ mph. The same blurb will ...
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### Cruise Mach Number less or more than Critical Mach Number

Do commercial airplanes cruise at Mach number higher than the critical Mach number? And what is the critical Mach number of airplanes like B777 or A330?
• 461
3k views

### What prevents a Machmeter from being the standard airspeed indicator?

Airspeed is more accurate when displayed by a Machmeter than when displayed by an airspeed indicator. It isn't affected by ambient temperature / density changes. It is still affected by position error,...
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### What is the reason for changing the speed reference (IAS or Mach number) with altitude?

Inspired by that question: How is the airspeed-Mach number transition handled in modern airliners? When pressure and density decrease IAS also decreases. When temperature and pressure/density ...
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