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Maximum speed in level flight, sample computation

A SIG Somethin' Extra, MDS 46, Zinger 12x5 prop

Location is Lancaster Ca, Antelope Valley Tailwinds field.

 No wind, normal temperature, Jan 20, 2001

The raw data for 3 representative video frames from the above clip are in cells B5 thru D7, in pixels

These are read from the video tape using Paint Shop Pro, Animation Shop feature. The video is read in and saved in .avi format, then the plane positions are read directly from each frame, in pixels. I have found it necessary to read each flight data pass twice, as the frame grabber tends to capture 2 frames, skip the next. The position information of both passes are then read from the computer screen, with duplicate frames data ignored. This is where a large plane image is nice to have.

To relate the reduced information to speed, the length of the plane is in cell N15, its flying weight O15, the atmospheric density in N17

These represent the input data. It is then caressed by the equations in the "reduced data, pixels" block and converted to interesting values in the "speed" block. The numbers are the averages of the input data (in this example divided by 5 to handle the 5-frame gap between the data values)

Climb rate and the average Cl are extra computations that are possible using the information from the video frames which is why the wing area is needed.

Calibrating the lens magnification permits computing the distance to the plane. Record a short tape of an object of known dimension placed in the orientation of the flight path at a known distance from the camera using the lens setting used for the flight data. Measure this dimension in pixels at the same time the flight data is read from the flight tape. Then a simple length comparison gives the distance to the plane.

..Table of flight speeds for various airplanes.

The full spreadsheet is explained and available Excel format "how to do it" file at:


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ŠPaul J. Burke .e-mail