GPS
Quick method: fly upwind, slowly change heading until ground speed is lowest. Note it. Turn 180. Check that ground speed is now highest. Take the average. That's your true air speed. You need to correct for density altitude, so do all this at one pressure altitude and one temperature if possible and correct on the ground.
For greater precision, set your GPS to kilometers per hour.
There are better methods available using 3 legs or four and they are all over the internet. Kevin Horton uses the NTPS 3 leg method and I like it, too.
On the ground, Kevin Horton has provided on this site the numbers you need to use a manometer (water and air pressure) to see if the instrument reads pressure correctly.
The GPS method doesn't check how the instrument reads pressure, but it does tell you the correct reading.
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H. Evan's RV-7A N17HH 240+ hours
"We can lift ourselves out of ignorance, we can find ourselves as creatures of excellence and intelligence and skill. We can be free! We can learn to fly!" -J.L. Seagull
Paid $25.00 "dues" net of PayPal cost for 2015, 2016, 2017 and 2018 (December).
This airplane is for sale: see website. my website
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Linear Mode
