I have seen more than a few times having the altitude of my WAAS GPS units indicating altitude excursions of a few hundred feet positive and negative, while in a boat at SL.
Altimeter Anomaly
- Thread starter Shawn
- Start date
You never heard of GPS approaches?
Even my hand held is accurate to within 3-7 feet. I've used it for preliminary land survey work. The instruments in our airplanes are from the stone age.
My AP will fly the GPS RNAV approach to the runway. Try that with an altimeter sensitive to airpressure.
Don't the units also need an air data system for approach?
poadeleted20
Deleted
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- Apr 8, 2005
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- 31,250
No, that's only for Baro-VNAV (aka "LNAV/VNAV" operations). LPV works just fine without an air data computer, e.g., in my Tiger with a GNS530W and no ADC. But you'll note the temperature restrictions for Baro-VNAV operations in the Notes section of the approach charts of such approaches -- just because of the temperature-related errors I discussed above.
Indiana_Pilot
Line Up and Wait
I get this sometimes from ATC but the briefly say I'm at 9500 instead of 3500.. The altimeter encoder has tested fine and it's always when using a certain approach frequency.. Maybe it's their equipment.. It always displays normal to them within a few seconds... Odd and potentially dangerous!