F li g h t Te s t in g Te c hn i q u e s
Airspeed Calibration
Ground course data reduction
By Ed Kolano
You've finished flying your airspeed calibration ground
course flight tests and collected the necessary data.
Now we'll turn that raw data into a plot of calibrated
airspeed (VC) versus observed airspeed (VO) for your
airplane's operator's manual.
During each of your test runs, you recorded your VO,
pressure altitude (PA), outside air temperature (OAT),
and the elapsed time (ET) required to fly between your
start and end checkpoints. You also made a note of your
airplane's external configuration for the test series. A
stickler for documentation, knowing you will spot-check
on another flight, you calculated your airplane's weight
before and after the test flight and made an estimate of
its average weight during the test.
Photography by BW Brock
Get out your calculator, pencil, and paper; fun with
numbers awaits. Figure 1 is a suggested data grid
with flight test and postflight data filled in, which we'll
use to work through the data reduction process. The
entries in the left six columns come directly from the
test flight. The right six columns contain the results of
postflight calculations. We'll use the 120-knot VO data
(first two data rows on the grid) during our data reduction explanation.
Ground Speed
Calculate your ground speed for each run the same
way you probably do it during cross-country flying. By
knowing the course length, 7,890 feet in our example,
EAA Experimenter
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