Narrative:

I briefed the PF on the maxxo departure out of phx. I read; from the electronic charts installed on our motion computing LS800; to turn to heading 140 degrees after passing 1.9 DME off of phx VOR. The problem was discovered when the controller stopped our heading and asked why we were turning. It was discovered that I had made an error reading the departure off the computer. The SID actually stated to turn to a 140 degree heading after 9.0 DME and not 1.9 DME. After further investigation; I discovered that it read 'at 9.0 DME;' it appeared that the 'T' in 'at' moved closer to the '9' in this particular zoom setting and a speck of dirt made it appear to be 1.9 DME. Another contributing factor was our tablet pc wasn't working properly and I had lost sight of the chart on climb out after minimizing the chart program. I felt unsure of the turn during climb out when I noticed the DME on departure was many mi past 1.9 DME immediately on climb out. After rushing to get the tablet pc working again to no avail; I decided to go with our original departure brief since I had no evidence that the DME readout was wrong. This problem I feel could have been prevented had we had an additional tablet pc in the cockpit booted and available to reference. Another way to prevent this would have been to request clarification from the departure controller. This course of action wasn't taken because I felt we may have been getting close to another aircraft if we continued straight out on our original heading and not turning to a heading of 140 degrees. Callback conversation with reporter revealed the following information: the reporter stated that this computer and software package is highly usable. This type of system also saves time because a pilot can quickly transition from chart-to-chart without having to go into a paper manual and page through airport's charts. However; as in this instance some drawbacks do exist. The computer in use here had an 8 inch screen; a larger screen would have been helpful. A larger screen would have required more space in a small cockpit but would have provided better user readability. The amount of computer desktop space limits the size of charts readable area. As a result; zooming and scanning areas of a chart is required when small text or more detail is needed. This action takes time and attention.

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Original NASA ASRS Text

Title: AN LR35 PLT USING A TABLET PC AND ELECTRONIC NAV SOFTWARE MISREAD A STAR DME TURN DISTANCE BECAUSE A SPECK OF DIRT APPEARED AS A DECIMAL POINT.

Narrative: I BRIEFED THE PF ON THE MAXXO DEP OUT OF PHX. I READ; FROM THE ELECTRONIC CHARTS INSTALLED ON OUR MOTION COMPUTING LS800; TO TURN TO HDG 140 DEGS AFTER PASSING 1.9 DME OFF OF PHX VOR. THE PROB WAS DISCOVERED WHEN THE CTLR STOPPED OUR HDG AND ASKED WHY WE WERE TURNING. IT WAS DISCOVERED THAT I HAD MADE AN ERROR READING THE DEP OFF THE COMPUTER. THE SID ACTUALLY STATED TO TURN TO A 140 DEG HDG AFTER 9.0 DME AND NOT 1.9 DME. AFTER FURTHER INVESTIGATION; I DISCOVERED THAT IT READ 'AT 9.0 DME;' IT APPEARED THAT THE 'T' IN 'AT' MOVED CLOSER TO THE '9' IN THIS PARTICULAR ZOOM SETTING AND A SPECK OF DIRT MADE IT APPEAR TO BE 1.9 DME. ANOTHER CONTRIBUTING FACTOR WAS OUR TABLET PC WASN'T WORKING PROPERLY AND I HAD LOST SIGHT OF THE CHART ON CLBOUT AFTER MINIMIZING THE CHART PROGRAM. I FELT UNSURE OF THE TURN DURING CLBOUT WHEN I NOTICED THE DME ON DEP WAS MANY MI PAST 1.9 DME IMMEDIATELY ON CLBOUT. AFTER RUSHING TO GET THE TABLET PC WORKING AGAIN TO NO AVAIL; I DECIDED TO GO WITH OUR ORIGINAL DEP BRIEF SINCE I HAD NO EVIDENCE THAT THE DME READOUT WAS WRONG. THIS PROB I FEEL COULD HAVE BEEN PREVENTED HAD WE HAD AN ADDITIONAL TABLET PC IN THE COCKPIT BOOTED AND AVAILABLE TO REF. ANOTHER WAY TO PREVENT THIS WOULD HAVE BEEN TO REQUEST CLARIFICATION FROM THE DEP CTLR. THIS COURSE OF ACTION WASN'T TAKEN BECAUSE I FELT WE MAY HAVE BEEN GETTING CLOSE TO ANOTHER ACFT IF WE CONTINUED STRAIGHT OUT ON OUR ORIGINAL HDG AND NOT TURNING TO A HDG OF 140 DEGS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT THIS COMPUTER AND SOFTWARE PACKAGE IS HIGHLY USABLE. THIS TYPE OF SYS ALSO SAVES TIME BECAUSE A PLT CAN QUICKLY TRANSITION FROM CHART-TO-CHART WITHOUT HAVING TO GO INTO A PAPER MANUAL AND PAGE THROUGH ARPT'S CHARTS. HOWEVER; AS IN THIS INSTANCE SOME DRAWBACKS DO EXIST. THE COMPUTER IN USE HERE HAD AN 8 INCH SCREEN; A LARGER SCREEN WOULD HAVE BEEN HELPFUL. A LARGER SCREEN WOULD HAVE REQUIRED MORE SPACE IN A SMALL COCKPIT BUT WOULD HAVE PROVIDED BETTER USER READABILITY. THE AMOUNT OF COMPUTER DESKTOP SPACE LIMITS THE SIZE OF CHARTS READABLE AREA. AS A RESULT; ZOOMING AND SCANNING AREAS OF A CHART IS REQUIRED WHEN SMALL TEXT OR MORE DETAIL IS NEEDED. THIS ACTION TAKES TIME AND ATTN.

Data retrieved from NASA's ASRS site as of January 2009 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.