Narrative:

[Flying] northbound to eik; which is only 1.5nm outside of the bjc airport traffic area/class D airspace. While flying on an approved northerly heading; I was given frequency change by bjc tower. As I approached eik I realized that I was already too far north to enter the downwind leg of the eik right traffic pattern for runway 15 on the recommended 45-degree angle; and decided to make a 270-degree left turn to put me in a better position for a 45-degree entry. During this maneuver my flight path took me back into the edge of the class D airspace by approximately 1/2 mile for a short time without being in communication with bjc tower. I realized my error just after I entered into the class D airspace by looking at the GPS display for my aircraft on my ipad; which was displaying the VFR sectional chart for the area using the foreflight app. I continued my approach to eik; entered the downwind leg on a 45-degree angle; and landed safely.there are two factors that caused the error. (1) primarily; I had previously flown into eik numerous times; I had never before approached eik from the south. I was therefore unfamiliar with the area in the context of how close to the bjc class D airspace I was maneuvering; and where the actual edge of the class D airspace is located in relation to recognizable landmarks. (2) I had enlarged (zoomed in) the image of the VFR sectional chart displayed on my ipad to such a high magnification that the screen only showed the very northernmost portion of the blue segmented circle designating the bjc airport traffic area. Without seeing more of the blue segmented circle along with the airport inside it; it did not register in my mind as being what it was; the edge of the airport traffic area; until after I had crossed it. In other words; when I zoomed the screen to a point where the blue segmented line appeared out of context; it temporarily suppressed the bjc airport traffic area from my consideration as an important navigation factor that I was in close proximity to and which I must avoid. It is important to note that I was not flying by constant reference to my ipad. I was flying by visual reference to the ground and checking my position on the ipad from time to time. Nonetheless; by altering the display such that the airport traffic area as such was not visible; it had an effect on my mental picture and contributed to my error. Out of sight; out of mind. After landing; I called the bjc tower and spoke with the controller who I had worked with; notifying him of and apologizing for my encroachment into his class D airspace without communication and discussing what had happened. His reaction was positive; and he commended me both for apologizing and for being aware of what had happened. He said that he had been unaware of the encroachment.to my knowledge this is the first time that I have ever unintentionally encroached on any airspace that has requirements for entry; and it shocked me as soon as I realized that I had done so. I have reviewed my actions; and closely examined the area of the event to determine precisely where the edge of the class D airspace is located and how to recognize it from the air using landmarks. I have also resolved to be more careful in planning my flight path when approaching an airport from an unfamiliar direction; and to be more careful when maneuvering in congested airspace. Finally; I am now aware that; when using an electronic flight bag; I should avoid enlarging the image of my VFR sectional chart (or any other chart) to a point where chart designations can lose their context and significance.

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Original NASA ASRS Text

Title: A general aviation pilot reported briefly entering Class D airspace while conducting a VFR approach to another field.

Narrative: [Flying] northbound to EIK; which is only 1.5nm outside of the BJC Airport Traffic Area/Class D airspace. While flying on an approved northerly heading; I was given frequency change by BJC tower. As I approached EIK I realized that I was already too far north to enter the downwind leg of the EIK right traffic pattern for runway 15 on the recommended 45-degree angle; and decided to make a 270-degree left turn to put me in a better position for a 45-degree entry. During this maneuver my flight path took me back into the edge of the Class D airspace by approximately 1/2 mile for a short time without being in communication with BJC tower. I realized my error just after I entered into the Class D airspace by looking at the GPS display for my aircraft on my iPad; which was displaying the VFR sectional chart for the area using the Foreflight app. I continued my approach to EIK; entered the downwind leg on a 45-degree angle; and landed safely.There are two factors that caused the error. (1) Primarily; I had previously flown into EIK numerous times; I had never before approached EIK from the south. I was therefore unfamiliar with the area in the context of how close to the BJC Class D airspace I was maneuvering; and where the actual edge of the Class D airspace is located in relation to recognizable landmarks. (2) I had enlarged (zoomed in) the image of the VFR sectional chart displayed on my iPad to such a high magnification that the screen only showed the very northernmost portion of the blue segmented circle designating the BJC Airport Traffic Area. Without seeing more of the blue segmented circle along with the airport inside it; it did not register in my mind as being what it was; the edge of the Airport Traffic Area; until after I had crossed it. In other words; when I zoomed the screen to a point where the blue segmented line appeared out of context; it temporarily suppressed the BJC Airport Traffic Area from my consideration as an important navigation factor that I was in close proximity to and which I must avoid. It is important to note that I was not flying by constant reference to my iPad. I was flying by visual reference to the ground and checking my position on the iPad from time to time. Nonetheless; by altering the display such that the Airport Traffic Area as such was not visible; it had an effect on my mental picture and contributed to my error. Out of sight; out of mind. After landing; I called the BJC tower and spoke with the controller who I had worked with; notifying him of and apologizing for my encroachment into his Class D airspace without communication and discussing what had happened. His reaction was positive; and he commended me both for apologizing and for being aware of what had happened. He said that he had been unaware of the encroachment.To my knowledge this is the first time that I have ever unintentionally encroached on any airspace that has requirements for entry; and it shocked me as soon as I realized that I had done so. I have reviewed my actions; and closely examined the area of the event to determine precisely where the edge of the Class D airspace is located and how to recognize it from the air using landmarks. I have also resolved to be more careful in planning my flight path when approaching an airport from an unfamiliar direction; and to be more careful when maneuvering in congested airspace. Finally; I am now aware that; when using an Electronic Flight Bag; I should avoid enlarging the image of my VFR sectional chart (or any other chart) to a point where chart designations can lose their context and significance.

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.