Narrative:

My normal means of navigation is by reference to my ipad using the garmin app with a gdl antenna. My garmin subscription is on automatic renewal; but for some reason it inadvertently expired the day of the flight. I was able to get the app on my phone restored by renewing the subscription on the garmin website but I was not able to get the app working on my ipad. I had a GPS with a small map display in the airplane and the garmin map display on my phone so I decided to navigate with those devices. There was a presidential tfr in effect that day which required that I alter my normal routing to avoid the tfr. This route took me closer to class B and D airspace then I normally fly. I planned to fly below the class B and also to fly above the class D that was along the route. I mentally noted the airspace altitudes prior to departure. Approaching the class D airspace; I referenced my phone and noted that the top of the class D airspace was 2600ft. I elected to fly at 3000ft to be above it. I did not check the class B altitude on my phone at this time. I mistakenly assumed that it was 3500ft in this area. I may have been distracted because I was clearing airspace alerts that kept popping up on both my aircraft GPS and on my phone. When I referenced my phone a little while later for the class B altitudes. I realized that the class B altitude above the class D was actually 3000 ft. Instead of 3500ft as I had assumed. I descended but I may have skimmed the lower limit of the class B without being cleared into it. This could've been avoided if I had been more diligent in checking both airspace altitudes when I referenced my phone initially or if I had written down planned altitudes to fly along the route prior to my departure.

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Original NASA ASRS Text

Title: Citabria 7ECA pilot reported a Class B airspace incursion resulted after misreading the base of the Class B.

Narrative: My normal means of navigation is by reference to my iPad using the Garmin App with a GDL antenna. My Garmin subscription is on automatic renewal; but for some reason it inadvertently expired the day of the flight. I was able to get the app on my phone restored by renewing the subscription on the Garmin website but I was not able to get the App working on my iPad. I had a GPS with a small map display in the airplane and the Garmin map display on my phone so I decided to navigate with those devices. There was a presidential TFR in effect that day which required that I alter my normal routing to avoid the TFR. This route took me closer to Class B and D airspace then I normally fly. I planned to fly below the class B and also to fly above the class D that was along the route. I mentally noted the airspace altitudes prior to departure. Approaching the Class D airspace; I referenced my phone and noted that the top of the Class D airspace was 2600ft. I elected to fly at 3000ft to be above it. I did not check the Class B altitude on my phone at this time. I mistakenly assumed that it was 3500ft in this area. I may have been distracted because I was clearing airspace alerts that kept popping up on both my aircraft GPS and on my phone. When I referenced my phone a little while later for the Class B altitudes. I realized that the Class B altitude above the Class D was actually 3000 ft. instead of 3500ft as I had assumed. I descended but I may have skimmed the lower limit of the Class B without being cleared into it. This could've been avoided if I had been more diligent in checking both airspace altitudes when I referenced my phone initially or if I had written down planned altitudes to fly along the route prior to my departure.

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.