Narrative:

I was on an IFR flight plan from sussex county airport, de, ged to hgr. Part of the routing clearance was taking the 321 degree radial from EMI and then intercepting the 089 degree radial inbound to hgr. I was using a garmin 530 GPS to navigation with, which is an IFR certified system and had a current GPS database card. Basically, the routing ATC had given me was to take me around P-40 (camp david). Somewhere east of P-40 and flying wbound, potomac advised that I should turn immediately 40 degrees right to avoid P-40 camp david. I checked the GPS display and the moving map showed me on a track that would clear P-40 to the north. However, I decided to take ATC's advice and turn 40 degrees right. It was then that I noticed that the moving map image was frozen -- the aircraft did not change position on the map. At that time I was using the obs (or hold) feature on the garmin 530. When I switched to the automatic sequence mode, then the map indeed read correctly again. After some troubleshooting, I found that the garmin 530 display would 'freeze' whenever I used the obs feature, but would read ok on the automatic-sequence. Apparently there seems to be some sort of software glitch. Although there was no violation on penetrating P-40, my GPS had a malfunction which would have led me into a problem. Thankfully, potomac ATC advised me in time and a violation was avoided. I thought it would be a good idea to make a report in case there are other users who may come across the same problem. I've made contact with garmin and explained the error situation. This particular glitch is a puzzlement to them as well. They suggested that there may be some type of GPS scrambling or jamming going on with the signals in sensitive areas like P-40. Garmin said that many of the GPS complaints like mine seem to come from the washington, dc area (langley AFB, too). Shortly after my incident I continued to experiment with the GPS in all different modes and it worked 100%, all the time. So, did this 'anomaly' go away, or is there some type of signal scrambling going on near P-40/camp david?

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Original NASA ASRS Text

Title: PLT OF BE20 IS DISTRESSED TO LEARN THAT HIS GARMIN 530 GPS SYS MAP DISPLAY LOCKS UP IN THE VICINITY OF P-40. UNABLE TO DUPLICATE IN SUBSEQUENT TESTS OUTSIDE OF THE VICINITY OF THE PROHIBITED AREA.

Narrative: I WAS ON AN IFR FLT PLAN FROM SUSSEX COUNTY ARPT, DE, GED TO HGR. PART OF THE ROUTING CLRNC WAS TAKING THE 321 DEG RADIAL FROM EMI AND THEN INTERCEPTING THE 089 DEG RADIAL INBOUND TO HGR. I WAS USING A GARMIN 530 GPS TO NAV WITH, WHICH IS AN IFR CERTIFIED SYS AND HAD A CURRENT GPS DATABASE CARD. BASICALLY, THE ROUTING ATC HAD GIVEN ME WAS TO TAKE ME AROUND P-40 (CAMP DAVID). SOMEWHERE E OF P-40 AND FLYING WBOUND, POTOMAC ADVISED THAT I SHOULD TURN IMMEDIATELY 40 DEGS R TO AVOID P-40 CAMP DAVID. I CHKED THE GPS DISPLAY AND THE MOVING MAP SHOWED ME ON A TRACK THAT WOULD CLR P-40 TO THE N. HOWEVER, I DECIDED TO TAKE ATC'S ADVICE AND TURN 40 DEGS R. IT WAS THEN THAT I NOTICED THAT THE MOVING MAP IMAGE WAS FROZEN -- THE ACFT DID NOT CHANGE POS ON THE MAP. AT THAT TIME I WAS USING THE OBS (OR HOLD) FEATURE ON THE GARMIN 530. WHEN I SWITCHED TO THE AUTOMATIC SEQUENCE MODE, THEN THE MAP INDEED READ CORRECTLY AGAIN. AFTER SOME TROUBLESHOOTING, I FOUND THAT THE GARMIN 530 DISPLAY WOULD 'FREEZE' WHENEVER I USED THE OBS FEATURE, BUT WOULD READ OK ON THE AUTO-SEQUENCE. APPARENTLY THERE SEEMS TO BE SOME SORT OF SOFTWARE GLITCH. ALTHOUGH THERE WAS NO VIOLATION ON PENETRATING P-40, MY GPS HAD A MALFUNCTION WHICH WOULD HAVE LED ME INTO A PROB. THANKFULLY, POTOMAC ATC ADVISED ME IN TIME AND A VIOLATION WAS AVOIDED. I THOUGHT IT WOULD BE A GOOD IDEA TO MAKE A RPT IN CASE THERE ARE OTHER USERS WHO MAY COME ACROSS THE SAME PROB. I'VE MADE CONTACT WITH GARMIN AND EXPLAINED THE ERROR SIT. THIS PARTICULAR GLITCH IS A PUZZLEMENT TO THEM AS WELL. THEY SUGGESTED THAT THERE MAY BE SOME TYPE OF GPS SCRAMBLING OR JAMMING GOING ON WITH THE SIGNALS IN SENSITIVE AREAS LIKE P-40. GARMIN SAID THAT MANY OF THE GPS COMPLAINTS LIKE MINE SEEM TO COME FROM THE WASHINGTON, DC AREA (LANGLEY AFB, TOO). SHORTLY AFTER MY INCIDENT I CONTINUED TO EXPERIMENT WITH THE GPS IN ALL DIFFERENT MODES AND IT WORKED 100%, ALL THE TIME. SO, DID THIS 'ANOMALY' GO AWAY, OR IS THERE SOME TYPE OF SIGNAL SCRAMBLING GOING ON NEAR P-40/CAMP DAVID?

Data retrieved from NASA's ASRS site as of July 2007 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.