Hi folks I came across a neat article by Tony Bingelis on the net last night. Do a google search on pitot static error. Tony described a really simple method for adjusting any airspeed error provided you have an external static tube (as distinct to a fuselage or interior source). He suggested an o-ring be slided along the tube. Locating it in front of the little static holes in the tube results in a drop in static pressure and an increase in indicated airspeed. Behind the holes leads to the opposite. Distance from the hole determines amount of change. Once the correct position is ascertained, the o-ring is replaced by a more permanent fixture, eg. a small band of metal or filler. I guess something similar could be obtained on a fuselage side static vent using a small mound of something either in front or behind the hole that can be sanded down accordingly to suit.
I reckon my airspeed is under-reading by about 12 knots in the cruise because the static is affected by high pressure under the wing. The above is so simple and apparently accurate that I can't wait to try it out and compare with a three leg GPS readout at different speeds. Certainly heaps easier than relocating tubes etc. It will also hopefully resolve a minor altitude error picked up by my annual transponder check whereby, for example, altitude readout on the ground by slight evacuation of the static to give 1000 feet was not obtained until 1100 feet or so in the air. Thanks to all who have provided me with assistance on this. The Martindale Family 29 Jane Circuit TOORMINA NSW 2452 AUSTRALIA phone: 61 2 66584767 email: johnj...@chc.net.au
