Narrative:

I am confident based on my instrumentation that I did not violate class a airspace. However; I was in contact with center by phone who identified my aircraft via my ads-B out and mode south transponder. They informed me that they had observed on radar several gliders at or above 18;000 ft. They confirmed that it was not my aircraft that violated the airspace. I was asked to communicate with other glider pilots flying that day about the violations. I notified all of the pilots I knew of who were flying that day about my conversation with center and stressed the need to be very careful not to exceed 17;999 feet given the danger associated with gliders conflicting with arriving or departing traffic in the area. In terms of corrective action the glider community is making sure they understand the possible differences in altitude displayed in our cockpits vs. The actual altitude read by ATC. Our flight level data is sent via our transponders and it is then corrected for local altimeter settings which will be displayed on traffic control radars. Due to pressure changes occurring over our flight paths we may inadvertently be above 17;999 ft. For instance on the day of the event the local altimeter setting at one location compared to another location about 30 miles away could have resulted in an aircraft being as much as 400 ft higher than was intended by the pilot.

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Original NASA ASRS Text

Title: Sailplane pilot reported he was contacted by Center and advised some of the sailplanes flying with him violated Class A airspace.

Narrative: I am confident based on my instrumentation that I did not violate Class A airspace. However; I was in contact with Center by phone who identified my aircraft via my ADS-B out and Mode S transponder. They informed me that they had observed on radar several gliders at or above 18;000 ft. They confirmed that it was not my aircraft that violated the airspace. I was asked to communicate with other glider pilots flying that day about the violations. I notified all of the pilots I knew of who were flying that day about my conversation with Center and stressed the need to be very careful not to exceed 17;999 feet given the danger associated with gliders conflicting with arriving or departing traffic in the area. In terms of corrective action the glider community is making sure they understand the possible differences in altitude displayed in our cockpits vs. the actual altitude read by ATC. Our flight level data is sent via our transponders and it is then corrected for local altimeter settings which will be displayed on traffic control radars. Due to pressure changes occurring over our flight paths we may inadvertently be above 17;999 ft. For instance on the day of the event the local altimeter setting at one location compared to another location about 30 miles away could have resulted in an aircraft being as much as 400 ft higher than was intended by the pilot.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.