FlightAware reported track log altitude consistently incorrect


#1

When flying at 5,500 feet, the FlightAware track log reports a consistent 5,400 along the way (autopilot engaged showing 5,500). Today, the track log was reporting 6,200 the entire flight while I was at 6,500. I know there might be some variance due to difference in pressures along the way, but not 100 to 300 feet for 50 or so nautical mile trips. Is FlightAware incorrect or per chance could it be something wrong with my plane?


#2

I see that a lot while flying. We have TCAS and go past aircraft that are reporting 100 feet higher or lower than they should be, it is a difference betweenin the mode C reporting and their altimeter. An avionics guru told me that you are dealing in microvolts and adjusting it to the nearest 100 feet is often as close as they can get especially in older light aircraft systems.


#3

You’re probably looking at a position from a source that reported pressure altitude uncorrected.


#4

Note that Mode S / ADS-B transponders (and TCAS) always report uncorrected pressure altitude. If you’re comparing those to an altimeter that’s corrected for local pressure then that’s where the difference comes from.


#5

Thank you. However, it’s a 2015 Cirrus with the G1000.


#6

Thank you, but it’s a 2015 Cirrus with the G1000.


#7

Even up to 300 feet difference?


#8

Sweet airplane but could still have very minor pitot-static errors that are putting the reporting off by 100 or 200 feet. Don’t forget your mode C puts out a flight level that is then corrected by ATC radar depending on whether you are above or below 18,000 feet. rounding and microvolt differences could be the difference.

frostfam5
September 10 |

Thank you, but it’s a 2015 Cirrus with the G1000. Visit Topic or reply to this email to respond.
In Reply To

porterjet
September 10 |

I see that a lot while flying. We have TCAS and go past aircraft that are reporting 100 feet higher or lower than they should be, it is a difference betweenin the mode C reporting and their altimeter. An avionics guru told me that you are dealing in microvolts and adjusting it to the nearest 100 fee… Visit Topic or reply to this email to respond. To unsubscribe from these emails, click here.


#9

Sure, 300ft is around 10hPa so an altimeter setting of <1003hPa or >1023hPa would cause that much difference.