We did a really interesting program over the weekend, and it started as so many of the best things do, with a conversation over lunch.
Chris Higbee, Jenn and I were eating and talking about cool wooden airplanes with franklin engines, and it was observed that the Flybaby has an uncoventional static port. The airplane is equipped with a typical twin boom pitot static probe. One boom is total pressure with the hole in the center and the other is the static with the hole drilled in the side. The weird thing is the probe's static holes are only on one side of the probe. This led to the obvious question, does beta effect the airplanes natural position error. The result is the video, shot in flight, that is so textbook it makes it hard to believe it didn't happen in a lab.
What you see in the video is the airplane is flying straight and level at 60 MIAS and 4,000 feet. The pilot applies left rudder displacing the ball to the right and showing the asymmetrical static probe to more of the ram pressure that the total pressure side of the probe is seeing. The result is less delta P for the airspeed indicator to compare and therefore an artificially low airspeed by ten MPH. You also can see the altitude indicate low by about 50 feet. Then the pilot applies right rudder displacing the ball to the left, blocking the static probe which makes the airspeed read artificially high by ten MPH and the altimeter read artificially high by about 50 feet.
There are pictures of the probe and the test report below.
Go work on your airplane!!
Elliot and Jenn
