# How does pitot tube shape affect indicated airspeed? [closed]

Air flow over wings and engine inlets greatly changes due to a number of factors, such as atmospheric conditions, speed, and the design of the surfaces. On some engines you can see mist behind the leading edge of the nacelle in front of the fan, indicative of various pressures resulting from the shape of the edge. In the same way I would guess that the shape of the pitot tube would affect the indicated airspeed- possibly at higher speeds or with a wider edge less air would enter the tube, giving an incorrect reading to the pilot. So how do various shapes affect the indicated airspeed? How about fast aircraft such as the blackbird VS common commercial aircraft VS slower aircraft like a small Cessna?

1:

• I don't understand your question. Wouldn't this just be corrected for by the device that actually displays the airspeed to the pilot? Dreaded car analogy follows. Car speedometers measure how fast the wheel is rotating and translate that into how fast the car is moving. Obviously, the translation on your car is different from, say, the translation on a farm tractor with huge wheels. But that doesn't mean that either speedometer is wrong: you have to look at the whole system and not just the rotation-measuring-thingy/pitot tube. Aug 10, 2018 at 14:17
• @DavidRicherby aircraft don't have speedometers that depend on something so easy to redirect as air, and they don't have a range of speeds from 0 to Mach 2 Aug 10, 2018 at 14:28
• Sure. But the pitot tube is just a sensor. It gives a signal, which is processed to give the indicated airspeed. If you used a pitot tube with a different response, it would have to be processed differently. The indicated airspeed is an output of the system as a whole, not just the pitot tube. You seem to be comparing different aircraft, seeing that they have different shaped pitot tubes and concluding that they must give different IAS. Aug 10, 2018 at 14:43
• @DavidRicherby so you're saying shape isn't important to the reading because no matter what it can just be re calibrated? Aug 10, 2018 at 15:31
• Perhaps you should edit your question to ask: Does pitot tube shape affect indicated airspeed? Aug 10, 2018 at 15:34