A recurring question is how to calculate propeller tip speed. I have never needed to do this in all my years as a pilot, but it may be necessary if you build your own plane, or maybe it just shows up on the exam.
Let’s take an example.
- Propeller RPM = 2400 rpm
- Propeller blade length = 6 feet
If you want the answer in km / h, you have to convert 6 feet to Km, or maybe instead to meters first.
1 foot = 0.3048 meters and 6 feet = 1.8288 meters.
But you must have the radius to use the formula, so then it will be 3 feet = 0.9144 meters.
And then you probably remember that the sign π (pi) is 3.14
The formula you use is:
Vtip = 2πrRPM
Vtip = 2 x 3.14 x 0.9144 x 2400
Vtip = 13 781.8 meters / minute
Multiply by 60 to get meters per hour
Vtip = 13 781.8 x 60 = 826 910.9 meters / hour
And finally divide by 1000 to get km / h
Vtip = 826 km / h
If you do not remember how many feet there are in a meter, you can use the calculator. Set feet on the outer scale above meters on the inner scale, and then read 0.91 on the inner scale under 3 on the outer scale.
Here are some questions for ya:
Blade angle ___ from the hub to the tip of a propeller blade in order to maintain an optimal ___ from hub to tip.
- Increases, Angle of Attack.
- Decreases, Angle of Attack.
- Decreases, Geometric Pitch.
- Increases, Effective Pitch.
As an aircraft with a variable-pitch, constant-speed propeller accelerates along the runway:
- The blade pitch angle increases, maintaining a constant angle of attack and R.P.M.
- The angle of attack will remain constant and the engine R.P.M. will increase.
- The linear velocity of the propeller tip will gradually decrease.
- The angle of attack will decrease and the engine R.P.M. remain constant.
Which of the following will increase the angle of attack of a fixed pitch propeller blade?
- Decreased TAS and decreased RPM.
- Decreased TAS and increased RPM.
- Increased TAS and decreased RPM.
- Increased TAS and increased RPM.
Here is a website for those who want to go in depth. https://aerotoolbox.com/propeller/#Tip_Speed_and_Helical_Motion
And a video
have a good day