Stall Speed vs. Weight and Altitude

[PA32]

Can someone explain how and why stall speed (TAS?) varies with aircraft weight and altitude? If you need equations to explain this, I can still handle algebra, but I have forgotten all of my college calculus! Thanks.

 

[RandomGuy88]

If your weight increases, then the amount of lift you must produce increases. But your maximum obtainable CL does not change. So for the same CLmax the heavier aircraft would have to fly faster, so the stall speed would increase.

The stall speed varies with altitude because the density of the air varies with altitude. At a higher altitude the density decreases so again, for the same CLmax you must fly at a faster speed to achieve the same lift at a higher altitude.

 

[NatSusan]

Stall speed, also known as the minimum airspeed at which an aircraft can maintain lift, is affected by a variety of factors, including weight and altitude. This is because the amount of lift generated by an aircraft is directly related to its weight and the density of the air it is flying through.

As an aircraft increases in weight, it requires a greater amount of lift to remain airborne. This means that the airspeed at which the aircraft reaches its maximum lift capacity, or its stall speed, will also increase. This is because the aircraft needs to move faster through the air to generate enough lift to support its increased weight.

Similarly, as an aircraft flies at higher altitudes, the air becomes less dense. This means that there are fewer air molecules for the aircraft's wings to interact with, resulting in a decrease in lift. As a result, the stall speed of the aircraft will also increase at higher altitudes.

To understand the relationship between stall speed, weight, and altitude, we can use the following equation:

Stall speed = √(2 * weight / (density * wing area * lift coefficient))

In this equation, weight and wing area are directly proportional to stall speed, meaning that an increase in either of these variables will result in an increase in stall speed. Density, on the other hand, is inversely proportional to stall speed, meaning that as density decreases (at higher altitudes), stall speed will increase.

To summarize, as an aircraft's weight or altitude increases, its stall speed will also increase. This is due to the relationship between weight, density, and lift, as described by the equation above. I hope this explanation helps to clarify the concept of stall speed for you.