So why is stall speed so significant?

Firstly the obvious one is that planes with lower stall speeds have smaller turn radius and if they have good power to weight ratio they can do a sustainable low radius turns such as the A6M Zeros.

If you ever seen any of my performance posts for planes, i usually state their stall speed, this is how i was able to get those figures for different planes.

Guide to using this calculator:

Airplane Aircraft Wing Lift Design Equations Formulas Calculator - Velocity

Let’s do BF-109E as an example.

Kurfürst - R.A.E. - Messerschmitt Me.109 Handling and Manoeuvrability Tests

• It says that BF-109E has CL_Max of 1.4 without its flaps deployed and that its stall speed is 95.5mph (154km/h) at 5580lb (2530kg) loaded weight.

- First the calculator requires Lift Force value. This is achieved by multiplying the weight (kg) by gravitational pull (x9.81). 2530 x 9.81 = 24819 Newtons

- Wing Lift Coefficient is already stated for us being 1.40

(Infact all BF-109A/B/C/D/E/F/G/K wings have 1.4 CL Max)

- Air Density at Sea Level is 1.225kg/m3

If you want to find the stall speed for a different altitude, you will use a value representing different altitude.

U.S. Standard Atmosphere

Here under ''U.S. Standard Atmosphere Air Properties - SI Units'' are the air density values in kg/m3 for different altitudes.

- Wing Area, well the BF-109E has 16.2m2

(If you want to find stall speed with flaps down you have to add flap area on top of wing area and set the correct CL_Max value, which in this case for BF-109E would be 1.9 as stated with flaps down)

All we need to do now is press “calculate”

We got 152km/h stall speed for BF-109E whilst the British have 154km/h (probably cuz the stall was performed few hundred metres above sea level)

================================

There are few other fun things you can do with this... like 'Why cant SR-71 Blackbird reach altitude of 25,000m?' (has 24,000m service ceiling)

At 25,000m the air density is 0.04008kg/m3

SR-71 has like 250km/h Stall Speed at Sea Level. At 25,000m altitude tho the stall speed is

'The Karman line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate the altitude at which the atmosphere becomes too thin to support aeronautical flight and arrived at 83.6 km (51.9 miles) himself. The reason is that a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself. The line is approximately at the turbopause, above which atmospheric gases are not well-mixed. The mesopause atmospheric temperature minimum has been measured to vary from 85 to 100 km, which places the line at or near the bottom of the thermosphere.

The SR.71 stall speed would be

Firstly the obvious one is that planes with lower stall speeds have smaller turn radius and if they have good power to weight ratio they can do a sustainable low radius turns such as the A6M Zeros.

If you ever seen any of my performance posts for planes, i usually state their stall speed, this is how i was able to get those figures for different planes.

Guide to using this calculator:

Airplane Aircraft Wing Lift Design Equations Formulas Calculator - Velocity

Let’s do BF-109E as an example.

Kurfürst - R.A.E. - Messerschmitt Me.109 Handling and Manoeuvrability Tests

• It says that BF-109E has CL_Max of 1.4 without its flaps deployed and that its stall speed is 95.5mph (154km/h) at 5580lb (2530kg) loaded weight.

- First the calculator requires Lift Force value. This is achieved by multiplying the weight (kg) by gravitational pull (x9.81). 2530 x 9.81 = 24819 Newtons

- Wing Lift Coefficient is already stated for us being 1.40

(Infact all BF-109A/B/C/D/E/F/G/K wings have 1.4 CL Max)

- Air Density at Sea Level is 1.225kg/m3

If you want to find the stall speed for a different altitude, you will use a value representing different altitude.

U.S. Standard Atmosphere

Here under ''U.S. Standard Atmosphere Air Properties - SI Units'' are the air density values in kg/m3 for different altitudes.

- Wing Area, well the BF-109E has 16.2m2

(If you want to find stall speed with flaps down you have to add flap area on top of wing area and set the correct CL_Max value, which in this case for BF-109E would be 1.9 as stated with flaps down)

All we need to do now is press “calculate”

We got 152km/h stall speed for BF-109E whilst the British have 154km/h (probably cuz the stall was performed few hundred metres above sea level)

================================

There are few other fun things you can do with this... like 'Why cant SR-71 Blackbird reach altitude of 25,000m?' (has 24,000m service ceiling)

At 25,000m the air density is 0.04008kg/m3

SR-71 has like 250km/h Stall Speed at Sea Level. At 25,000m altitude tho the stall speed is

**1381km/h,**and 1115km/h is Mach 1.0 at 25,000m...'The Karman line is named after Theodore von Kármán (1881–1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics. He was the first person to calculate the altitude at which the atmosphere becomes too thin to support aeronautical flight and arrived at 83.6 km (51.9 miles) himself. The reason is that a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself. The line is approximately at the turbopause, above which atmospheric gases are not well-mixed. The mesopause atmospheric temperature minimum has been measured to vary from 85 to 100 km, which places the line at or near the bottom of the thermosphere.

The SR.71 stall speed would be

**64,353km/h**if it ever reached the altitude of 80,000m. It would have to fly over Mach 66.3 just to avoid stalling
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