By Ian Brown, EAA 657159
Any idea why this aircraft looks so sad? It was sent to us by Mike Davenport. What do you think happened? How did a wooden prop get bent? Was it out in the sun too long?
Actually you may have seen this yourself if you use any form of digital photography, which almost all of us do today. It’s an artifact, not dissimilar to those old black and white movies where the wheels of vehicles and stagecoaches would seem to be going backwards. In those days, frame rates of up to 24 frames per second were used, meaning each individual shot was taken in 1/24th of a second. By the time the next shot was taken, the most visible spoke in the wheel might be the one adjacent to the one your eyes were following, but slightly behind the previous position. Put a bunch of those together and your eye sees the wheels going backwards.
Now let’s look at digital scanning frame rates. Modern digital cameras scan the image one pixel at a time, in rows. One horizontal or vertical line will be “read out” from the CCD before the next one. During the time it takes to scan the next row, the propeller has moved a fraction. Depending on which direction the CCD is being read out, the section of the propeller being scanned into memory will either be earlier or later in its rotation. Hence, the bend.
Mr. Sad Airplane is probably really happy to hear that there’s nothing wrong with him.