Date: 201303
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Aircoupe A2
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Initial Approach
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: GPS & Other Satellite Navigation
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Private
Human factors: Confusion; Training / Qualification
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented
Contributing factors: Equipment / Tooling; Procedure
Primary problem: Equipment / Tooling

Narrative: On the final leg of a pleasure flight I established radio contact with the Tower at my Class D home base airport. I reported my location and distance from the airport (using my notebook computer's GPS indicator; Fore-flight program); as well as the ATIS information I received from the Tower's automated system; along with my intentions to enter the airspace and land. The Tower responded with the anticipated assignment of approach and runway; instructing me to report two (2) miles out from the airport. I acknowledged the directions from the Tower; repeating back their directions; and proceeded toward the airport. I again looked at the notebook [and] began to realize that I was just outside of the Class D airspace dashed lines by approximately one mile and that the GPS distance from the airport I had initially reported could not have been accurate (I reported about a 10 mile distance). I quickly pushed a 'direct to' button and found that I was in fact a little over five (5) miles out at that moment. Within a minute of this discovery the Tower contacted me and requested my position and I gave my position as now indicated. The Tower never commented further and cleared me for landing as previously instructed. Nothing happened as a result of the inaccurate distance reporting. Frankly; I assume that the Tower saw my transponder signal after my first report and simply followed with verification. I am choosing to report this because it seems that we pilots are relying more and more on the electronic/GPS technologies as 'gospel.' If [there are] major issues starting to be reported because of errors occurring with reliance on this technology; perhaps my experience can additionally show that no matter how minor; errors do occur using this technology. The message I take from this is that I need to use other resources that are readily available to insure I do not isolate myself; and safety; to a single resource; in this case; a notebook computer.... I must have made an error in reference to the screen. Perhaps some awareness training in some of the WINGS/FAA safety training could go a long way in alerting pilots to use several resources and not fall into the 'electronic trap.'




Synopsis: Aircoupe pilot; using a notebook computer GPS 'indicator;' attributed an error in the reported distance the airport to a GPS malfunction.