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The speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed ("IAS"), calibrated airspeed ("CAS"), true airspeed ("TAS"), equivalent airspeed ("EAS") and density airspeed.

43 votes
Accepted

What happens if you exceed the maximum speed on a C172?

You can, but you have to live with the consequences. There are several things that can happen: Depending on the vertical gusts ahead, you might not even get close to v$_{NE}$. There is another speed …
Peter Kämpf's user avatar
37 votes
Accepted

Is there any equation to bind velocity, thrust and power?

In reality, there is no neat boundary between the air flowing through the propeller and that surrounding it, but for computing thrust this simplification works well if the airspeed is identical across … flow times speed change: $$T = \pi \cdot\frac{d_P^2}{4}\cdot \rho \cdot \left( v_{\infty} + \frac{\Delta v}{2} \right) \cdot \Delta v$$ If the engine has the power P, the thrust is net power divided by airspeed
Peter Kämpf's user avatar
29 votes
Accepted

Why did the Solar Impulse flight take so long?

At sea level, the optimum range speed is only 9.96 m/s or 35.86 km/h, just about its take-off airspeed. …
Peter Kämpf's user avatar
20 votes
Accepted

Is trimming for constant speed equal to trimming for constant angle of attack?

Now the reduced density will require more angle of attack and will reduce engine output so in the end the same angle of attack is maintained at a higher altitude but a slightly lower indicated airspeed
Peter Kämpf's user avatar
18 votes

What is the fastest possible transatlantic flight today?

If you prefer something more realistic and readily available, go with the fastest business jet, the Cessna Citation X, or if you need a little more range, the Gulfstream 650. The Cessna can cruise at …
Peter Kämpf's user avatar
14 votes
Accepted

How (and why) does engine thrust change with airspeed?

The first diagram you link to shows three lines but does not indicate what they represent. I guess the bold line is thrust over speed. Then this diagram is correct for a turbojet. Thrust $T$ is the …
Peter Kämpf's user avatar
13 votes

Why do some military aircraft use variable-sweep wings?

Swing wings combine the high sweep angle helpful for Mach 2+ flight with tolerable low-speed handling characteristics. They were needed to fulfil the demands on military aircraft called for in tenders …
Peter Kämpf's user avatar
12 votes
Accepted

What would be the stall speed of Solar Impulse?

Solar Impulse has no flaps and a high aspect ratio wing. Therefore, the c$_{l_{max}}$ of the wing should be no higher than 1.8, most likely 1.6. While a rigid airfoil can be designed with a higher c$_ …
Peter Kämpf's user avatar
12 votes

How does the IAS stall speed vary with increasing altitude?

Airplanes do not stall at the same indicated speed or even at the same angle of attack - it all depends on circumstances. The angle of attack dependency is discussed here. An increased pitch rate can …
Peter Kämpf's user avatar
11 votes
Accepted

How close is the air resistance or drag force to being proportional to the airspeed squared?

Subsonic aircraft drag is composed of two major components: Pressure drag. Most of this is induced drag, but also some is from viscous effects which result in less pressure on the rear sections of a …
Peter Kämpf's user avatar
11 votes
Accepted

Why do aircraft have a crossover airspeed, and why does it increase at higher vertical load ...

why does an increase in vertical load factor cause the crossover airspeed to increase? Because a higher load factor needs a higher lift coefficient when flying at the same speed. …
Peter Kämpf's user avatar
10 votes

What is the commercial passenger aircraft top speed record?

If the fastest crossing of the Atlantic is your metric, the winner is the Vickers VC-10. It was very advanced for its time with airfoils close to what today would be called supercritical. In 1979, Sup …
Peter Kämpf's user avatar
9 votes
Accepted

How is V_S0 calculated for anything less than maximum weight?

All aerodynamic forces are proportional to the dynamic pressure, which is the product of air density $\rho$ and half of the square of flight speed $\frac{1}{2}v^2$. If your flight mass is reduced, red …
Peter Kämpf's user avatar
9 votes

What is the relation between airspeed and altitude at fixed throttle setting in a private jet?

The basic principles needed for an answer are: Thrust varies linearly with air density. Lift at constant angle of attack (AoA) equally varies linearly with air density. Increasing the angle of attac …
Peter Kämpf's user avatar
8 votes

Why do Vx and Vy coalesce at an airplane's absolute ceiling?

The absolute ceiling is defined as the altitude where climb speed drops to zero. This implies that there is only one speed at which the airplane does not lose altitude. Flying any faster or slower wil …
Peter Kämpf's user avatar

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