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Windows Program for Calculation of Circular Flight Parameters

Illus 1: The program CircularFlight in action. Parameters entered are (V0=50 kt) and the bank angle (40°).

Depending on a given velocity named V0 (see illus 1 above) and a bank angle the program CircularFlight calculates parameters such as

  • the circular velocity V (labeled Velocity V in the dialog)
  • the diameter of the flown circle (labeled Diameter in the dialog)
  • the time for flying the full circle (labeled Time for a full circle in the dialog)
  • the horizontal acceleration impacting the aircraft and the crew due to centrifugal forces (labeled Centrifugal Acceleration in the dialog
Illus 2: Straight level flight. Lift force = weight force

What is V0?

Here, V0 denotes the speed at which the lift force of the aircraft is equal to the force of its weight. If you don’t know the V0 value for your aircraft, you can assume that this is approximately the speed at which your airplane takes off (provided ground effects don’t need to be taken into account). Therefore, V0 is the minimum velocity required for a straight, level flight. V0 is not normally the stall speed velocity vS0 of an aircraft. V0 will usually be somewhat greater than vS0. But if you enter the value of vS0 in the field labeled V0 of the CircularFlight dialog (see illus 1), you will get the stall speed calculated required to fly a circle at a given angle or diameter.

Bank Angle

Illus 3: Bank angle (40°) when flying a right turn. The brown section denotes the earth, the blue section denotes the sky.

If an aircraft is flying a horizontal curve or circle, it will be exposed to a centrifugal force which needs to be compensated by a horizontal component of the lift force: the centripetal force (see forces in illus 1). This is achieved by turning the aircraft around its longitudinal axis by a bank angle. The bank angle is measured from the horizontal.


The minimum speed for our aircraft for a straight and level flight is 50 knots. If the airspeed (velocity V) is tied to VO, V is calculated depending on V0 and the bank angle for which we enter 40. The remaining fields are filled automatically with values, which all are dependent on V0 and the bank angle. CircularFlight calculates:

  • Velocity V (57.1 kt)
  • Diameter (209.90 m)
  • Time for a full circle (22.4 s)
  • Centrifugal Acceleration (8.2 m/s², 0.84 g)

We see: for a bank angle of 40° the airspeed must be raised to 57.1 kt.
Alternatively, you can also input a diameter to see which bank angle and speed (V) is required to fly a circle with a given diameter.
The graphics is changed according to the value of the bank angle. You can select either „Pilots View“ (see illus 3) or „Analytical View“ (see illus 1). The latter, if you prefer to see the balance of forces.
If you want the results being displayed textually, press the [Log Results] Button.

Illus 4: The „Log Results“ field displaying the current input and the results of the calculations
Units – Set Your Preferences

When CircularFlight is run for the first time the following units are set:

  • Velocity unit: kt (knots)
  • Diameter unit: m (meter)

You can change these settings via a dialog window titled „Units“  (see illus 5).

Illus 5: The „Units“ dialog. Select the unit you prefer to be used in the main dialog.

When you close CircularFlight, your preferred unit settings are saved so you find them set when you start the program next time.

Download, Evaluation, Installation and Licensing

CircularFlight is licensed per PC or user (so-called single-user license). After downloading and unpacking the file (size less than 2 MB) in a directory of your choice, it can be used immediately for 7 days in evaluation mode. An actual installation is not necessary. After unpacking, there are 2 files in the installation directory. One is the program (CircularFlight.exe) and the other is the user manual (CircularFlight.chm). Both can be started by double-clicking on the file names or symbols, as is usual in Windows. In evaluation mode, a message appears at the start of the program run indicating when the evaluation period will end.
For further use, a license file is required, which we send by email when you purchase a license. The license file must be copied to the CircularFlight installation directory. The program can then be used without any time restrictions. The message that appears at the beginning is also no longer displayed. An internet connection is not necessary to use CircularFlight.
To unpack the file you need a password, which we will send to you by email upon request (please include your name).

Zusätzliche Informationen

single user license

without support, with support service for 1 year (incl. updates and technical support)