The pitot-static instruments
The airspeed indicator, altimeter, and VSI all measure the same thing, air pressure, through two ports and one shared plumbing system.
15 min read · Flight instruments
After this lesson you can
- Explain why the ASI, altimeter, and VSI are all pressure instruments fed by only two sources of air.
- Convert a change in barometric pressure into an altitude error, and correct an altimeter reading for a nonstandard setting.
- Name the four kinds of airspeed and explain why the color arcs on the ASI are all expressed in indicated airspeed.
- Diagnose a blocked pitot tube versus a blocked static port from the pattern of errors it produces.
Three instruments on the panel look completely different, an airspeed dial, a set of altitude pointers, a needle that shows climb or descent, but underneath they are the same kind of instrument: a barometer. Every one of them reads air pressure, and every one of them is fed by the same two sources of air. Learn the plumbing once, and all three instruments stop being separate things to memorize.
That shared plumbing is also the weak point. A single blocked opening, wax, insects, or ice, can throw off two or three instruments at once, in a pattern that looks confusing until you know which instrument depends on which port. This lesson builds that mental map, so a pitot-static failure in flight becomes a five-second diagnosis instead of a surprise.
The rest of this lesson
- 1.One pressure, three instruments
- 2.The airspeed indicator and its four speeds
- 3.The color-coded arcs
- 4.Airspeed errors that are not failures
- 5.The altimeter and the five altitudes
- 6.The temperature error nothing corrects
- 7.The vertical speed indicator
- 8.Diagnosing a blocked pitot-static system
These 8 sections, their figures, the checks along the way and the end-of-lesson quiz come with the PPL track. Paid once, yours for good.
Key terms
Try to recall each definition before turning the card.