akafrank07
30th Nov 2012, 19:30
Wikipedia abstract on position errors
"Another class of inherent errors is that of position error (http://en.wikipedia.org/wiki/Position_error). A position error is produced by the aircraft's static pressure being different from the air pressure remote from the aircraft. This error is caused by the air flowing past the static port at a speed different from the aircraft's true airspeed (http://en.wikipedia.org/wiki/True_airspeed). Position errors may provide positive or negative errors, depending on one of several factors. These factors include airspeed, angle of attack (http://en.wikipedia.org/wiki/Angle_of_attack), aircraft weight, acceleration, aircraft configuration, and in the case of helicopters, rotor downwash (http://en.wikipedia.org/wiki/Downwash).[6] (http://en.wikipedia.org/wiki/Pitot-static_system#cite_note-allstar-pssi-6) There are two categories of position errors, which are "fixed errors" and "variable errors". Fixed errors are defined as errors which are specific to a particular make of aircraft. Variable errors are caused by external factors such as deformed panels obstructing the flow of air, or particular situations which may overstress the aircraft." (http://en.wikipedia.org/wiki/Pitot-static_system#cite_note-allstar-pssi-6)
Why is airspeed affected by position errors? is the 'airspeed' to do with bernoulli's theory, where when the dynamic pressure increases the static pressure decreases? i think i understand why angle of attack as for instance when you are climbing are making a turn, part of the wing are fuselage could be blocking the static port giving false pressure indications? I don't understand why aircraft weight affects position error? I presume with aircraft configuration, for example when you extend the flaps it would present a nose down attitude which would bring about a different flow around the static port which would then change the pressure right?
Thanks
"Another class of inherent errors is that of position error (http://en.wikipedia.org/wiki/Position_error). A position error is produced by the aircraft's static pressure being different from the air pressure remote from the aircraft. This error is caused by the air flowing past the static port at a speed different from the aircraft's true airspeed (http://en.wikipedia.org/wiki/True_airspeed). Position errors may provide positive or negative errors, depending on one of several factors. These factors include airspeed, angle of attack (http://en.wikipedia.org/wiki/Angle_of_attack), aircraft weight, acceleration, aircraft configuration, and in the case of helicopters, rotor downwash (http://en.wikipedia.org/wiki/Downwash).[6] (http://en.wikipedia.org/wiki/Pitot-static_system#cite_note-allstar-pssi-6) There are two categories of position errors, which are "fixed errors" and "variable errors". Fixed errors are defined as errors which are specific to a particular make of aircraft. Variable errors are caused by external factors such as deformed panels obstructing the flow of air, or particular situations which may overstress the aircraft." (http://en.wikipedia.org/wiki/Pitot-static_system#cite_note-allstar-pssi-6)
Why is airspeed affected by position errors? is the 'airspeed' to do with bernoulli's theory, where when the dynamic pressure increases the static pressure decreases? i think i understand why angle of attack as for instance when you are climbing are making a turn, part of the wing are fuselage could be blocking the static port giving false pressure indications? I don't understand why aircraft weight affects position error? I presume with aircraft configuration, for example when you extend the flaps it would present a nose down attitude which would bring about a different flow around the static port which would then change the pressure right?
Thanks