Narrative:

Takeoff was from ZZZ in a single place glider; towed to 8600 feet; able to find lift (thermal and rotor) to 17;000 feet; contacted base station with request to open the wave window. Office personnel (the designated 'wave window operations manager') contacted the appropriate FAA facilities and received approval for 2 hours. This was then relayed to me and I contacted center for clearance to enter the wave window and which was received from the sector controller with limitation not to exceed 27;000 feet. I proceeded to climb in the wave system from 17;500 to 26;900 feet (or below) maintaining cloud clearance per far's and the LOA for the wave window. For navigation it is expected that ground features be used primarily to navigate; per the LOA; within the defined wave window airspace ('wave window west') but at 26;000 feet such is not easily done with accuracy and with clouds often obstructing views of the ground; electronic charting is much more feasible and accurate. Unfortunately my charting device; which I had plotted the boundaries the evening prior to the flight; malfunctioned and went into thermalling/circling mode which does not draw the window boundaries. I therefore used bearings and distances from the center of the ZZZ airport and used my sectional chart on which I had drawn the boundaries. Because the clouds did not allow me to move west I was staying along the east border and within the west window airspace. I knew I would be operating close to the edge because of the clouds. At one point as I was turning back to the west I was 132 degrees and 6.8nm from ZZZ which put me at the edge or possibly slightly within the neighboring 'central wave window' which our wwom later told me had not been requested (my fault for not clarifying; not hers). So; I might have inadvertently wandered slightly into the wave window 'central' from the west window.as I descended out of the class a airspace (18;000) I called ATC center and gave notification and the controller said I might have gone across the line. I apologized; thanked the controller and he responded it was not a problem. About that time the center supervisor contacted our base by phone requesting they call me to ask that I stay in the west window. By that time I think I had descended below 18;000 feet.probable causes:1. Failure of the charting/navigation device2. Failure on my part to appreciate only the 'west window' had been requested.3. Fall-back navigation using my sectional chart with the window boundaries drawn in and bearings/distances from ZZZ which lacks similar accuracy.4. Sector controller could have called me on the assigned center frequency; which I was monitoring continuously. Preventative actions:1. Should request all wave windows be opened that might be needed.2. Better communication between glider and center.3. Appreciate that apparently sometimes our navigation equipment might lose reliability at the low pressures and temps (I have no idea why this happened; it resolved when I descended to lower altitudes.the soaring community is dependent upon certain time honored operating privileges; such as using these wave windows for high altitude flights; and take very seriously any incursions or inconveniences; and especially safety events - which that was not; and educate everyone appropriately.

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Original NASA ASRS Text

Title: Glider pilot reported encroaching on the adjacent Wave Window airspace due to the failure of onboard navigation equipment.

Narrative: Takeoff was from ZZZ in a single place glider; towed to 8600 feet; able to find lift (thermal and rotor) to 17;000 feet; contacted base station with request to open the Wave Window. Office personnel (the designated 'Wave Window Operations Manager') contacted the appropriate FAA facilities and received approval for 2 hours. This was then relayed to me and I contacted Center for clearance to enter the wave window and which was received from the sector controller with limitation not to exceed 27;000 feet. I proceeded to climb in the wave system from 17;500 to 26;900 feet (or below) maintaining cloud clearance per FAR's and the LOA for the wave window. For navigation it is expected that ground features be used primarily to navigate; per the LOA; within the defined wave window airspace ('Wave Window West') but at 26;000 feet such is not easily done with accuracy and with clouds often obstructing views of the ground; electronic charting is much more feasible and accurate. Unfortunately my charting device; which I had plotted the boundaries the evening prior to the flight; malfunctioned and went into thermalling/circling mode which does not draw the window boundaries. I therefore used bearings and distances from the center of the ZZZ Airport and used my sectional chart on which I had drawn the boundaries. Because the clouds did not allow me to move west I was staying along the east border and within the West Window airspace. I knew I would be operating close to the edge because of the clouds. At one point as I was turning back to the west I was 132 degrees and 6.8nm from ZZZ which put me at the edge or possibly slightly within the neighboring 'Central Wave Window' which our WWOM later told me had not been requested (my fault for not clarifying; not hers). So; I might have inadvertently wandered slightly into the Wave Window 'Central' from the West Window.As I descended out of the Class A airspace (18;000) I called ATC Center and gave notification and the controller said I might have gone across the line. I apologized; thanked the controller and he responded it was not a problem. About that time the Center Supervisor contacted our base by phone requesting they call me to ask that I stay in the West Window. By that time I think I had descended below 18;000 feet.Probable Causes:1. Failure of the charting/navigation device2. Failure on my part to appreciate only the 'West Window' had been requested.3. Fall-back navigation using my sectional chart with the window boundaries drawn in and bearings/distances from ZZZ which lacks similar accuracy.4. Sector controller could have called me on the assigned center frequency; which I was monitoring continuously. Preventative Actions:1. Should request all wave windows be opened that might be needed.2. Better communication between glider and center.3. Appreciate that apparently sometimes our navigation equipment might lose reliability at the low pressures and temps (I have no idea why this happened; it resolved when I descended to lower altitudes.The soaring community is dependent upon certain time honored operating privileges; such as using these Wave Windows for high altitude flights; and take very seriously any incursions or inconveniences; and especially safety events - which that was not; and educate everyone appropriately.

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.