----- Original Message ----- From: "Thomas Holmstr=F6m" To: Sent: Thursday, June 20, 2002 7:14 AM Subject: Re: [OT] Autopilot landing system for model aircraft (air speed) (snip) > Regarding the current discussion, isn't the nose cone, pointing forward > the optial place to have the pitot at providing you don't have a > propeller disturbing the measurement? Where do an aircraft with a pushe= r > prop have its pitot tube? > My model is a ducted fan, ie similar construction as a jet. > > --Thomas I would think, in the absence of a propeller, that the nose cone would be the best choice, unless it gets in the way of your radar system. ;-) Of course, in subsonic flight, the flow ahead of the aircraft is affected. The impact of the fuselage on the measured values is less than that of th= e wing, and depends on things like the shape of the nose and how far out in front the pressure port is. From http://naca.larc.nasa.gov/reports/1947/naca-tn-1496/ "The results of the test showed that, at 1 fuselage diameter from the nos= e, the error in static pressure was only about 1.5% of the impact pressure f= or the pointed-nose body, about 5% of the impact pressure for the elliptical-nose body, and about 10% of the impact pressure for the circular-nose body for zero angle of attack of the bodies." (In this context, it seems that "impact pressure" refers to the dynamic pressure.) There is also some calibration data for some older military aircraft: http://naca.larc.nasa.gov/reports/1957/naca-rm-h57a02/ Jeremy Furtek mailto:jfurtek@agames.com -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu