Narrative:

I took off approximately at xa:30 tue, october, 1988, on an IFR flight from boeing field to port angeles, wa, about 40 minutes away. I used runway 13R at boeing, and learned later I unintentionally turned right far enough to cross the approach path of the sea-tac airport, a few miles to the south and west of boeing. After landing, departure control told me that there was an aircraft on final approach and my airplane flew over the top of the other craft closely enough to be classed as a near miss. I never saw the other plane. My clearance was via the kent 2 departure SID, which states 'fly runway heading for vectors...'. I set the number one radio on the localizer for the boeing ILS and identified it, in case I needed to return to the airport. I set the number two radio on the seattle VOR, which cannot be identified on the ground at boeing. The seattle VOR is the NAVAID for both the lost comm procedure on the SID and the victor airway for my route. I set the directional gyro, during run-up, to the magnetic compass heading of 155 degrees and the heading bug for the autopilot on 130 degrees, the runway heading. I was cleared into position, turned on the transponder and set the heading of the dg to the runway heading of 130 degrees. When cleared for takeoff, I noted the time to be xa:27. During the climb (somewhere between 1000-1500 FPM), I noticed the dg showed 125 degrees so consciously entered a slight right turn to get back to runway heading, 130 degrees. This happened two or three times. I engaged the autopilot at approximately 800' MSL and monitored it for proper operation. I also was looking for other traffic until entering less than VFR conditions at about 1000' MSL, although I flew through scattered clouds at lower altitudes. Instrument departures from boeing are usually handed off to approach between 500-800' MSL. The tower controller this night was occupied with a traffic watch airplane and a helicopter. At 1,500' MSL, I asked for a frequency change and was finally approved to contact approach, on 119.2. Radio contact with approach was made at about 1600' MSL, or approximately 1 and a half minutes after takeoff. The controller said 'say heading.' I knew immediately the question would not be asked if I had been on course. The dg still showed 130 degrees but I noticed the magnetic compass indicated wsw, about 230 degrees. The controller questioned the discrepancy between headings when I told him the two instruments disagreed and then gave me a no-gyro vector. He later informed me I had flown through the sea-tac approach corridor. I mentally transitioned to no-gyro partial panel timed turns as the controller subsequently gave me headings and altitudes. I disconnected the autopilot immediately when the heading error was discovered. The dg processed badly, +/-30 degrees within less than a minute, for the next five to ten minutes, and then worked properly the rest of the flight. The autopilot also functioned normally when later engaged. I had navaids I could have utilized to detect the heading change, i.e., the sea VOR, the LOM, the localizer. But the time frame is so short and the workload so great at takeoff until reaching 1500' that these clues are not easily utilized. The SID only states fly states 'fly runway heading.' after talking to our mechanics and avionics technicians, I believe the dg malfunctioned. They also said they have heard of this problem--a quick precess of such magnitude--happening before. I want to stress the action was completely inadvertent, unplanned and as much of a surprise to me as to the approach controller. Because of errors inherent in the magnetic compass, mainly acceleration in this case, it was not part of my scan during takeoff. I will include it now, but its accuracy is questionable and should be verified by a NAVAID (the localizer in this case). I hope the kent 2 departure (and the needle 4 departure also) SID from boeing field is changed to include tracking the localizer course. With two airports so close, and the approach altitude for sea-tac the same as the takeoff altitude forboeing, course guidance should be a part of the departure procedure. Callback conversation with reporter revealed the following: this has happened to this aircraft again and they have found the reset knob was sticking in when released and this of course kept gyro caged. Also ascertained the distance from other aircraft was 200 ft vertical but horizontal not given but estimated less than 500 ft. FAA is making investigation of incident.

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Original NASA ASRS Text

Title: NMAC BETWEEN DEPARTING SMA AND ARRIVING UNK ACR AT CLOSE PROX ARPT CAUSED BY TRACK DEVIATION BY SMA.

Narrative: I TOOK OFF APPROXIMATELY AT XA:30 TUE, OCTOBER, 1988, ON AN IFR FLIGHT FROM BOEING FIELD TO PORT ANGELES, WA, ABOUT 40 MINUTES AWAY. I USED RUNWAY 13R AT BOEING, AND LEARNED LATER I UNINTENTIONALLY TURNED RIGHT FAR ENOUGH TO CROSS THE APPROACH PATH OF THE SEA-TAC AIRPORT, A FEW MILES TO THE SOUTH AND WEST OF BOEING. AFTER LANDING, DEPARTURE CONTROL TOLD ME THAT THERE WAS AN ACFT ON FINAL APPROACH AND MY AIRPLANE FLEW OVER THE TOP OF THE OTHER CRAFT CLOSELY ENOUGH TO BE CLASSED AS A NEAR MISS. I NEVER SAW THE OTHER PLANE. MY CLRNC WAS VIA THE KENT 2 DEPARTURE SID, WHICH STATES 'FLY RUNWAY HEADING FOR VECTORS...'. I SET THE NUMBER ONE RADIO ON THE LOC FOR THE BOEING ILS AND IDENTIFIED IT, IN CASE I NEEDED TO RETURN TO THE AIRPORT. I SET THE NUMBER TWO RADIO ON THE SEATTLE VOR, WHICH CANNOT BE IDENTIFIED ON THE GND AT BOEING. THE SEATTLE VOR IS THE NAVAID FOR BOTH THE LOST COMM PROCEDURE ON THE SID AND THE VICTOR AIRWAY FOR MY ROUTE. I SET THE DIRECTIONAL GYRO, DURING RUN-UP, TO THE MAGNETIC COMPASS HEADING OF 155 DEGREES AND THE HEADING BUG FOR THE AUTOPILOT ON 130 DEGREES, THE RUNWAY HEADING. I WAS CLRED INTO POSITION, TURNED ON THE TRANSPONDER AND SET THE HEADING OF THE DG TO THE RUNWAY HEADING OF 130 DEGREES. WHEN CLRED FOR TAKEOFF, I NOTED THE TIME TO BE XA:27. DURING THE CLIMB (SOMEWHERE BETWEEN 1000-1500 FPM), I NOTICED THE DG SHOWED 125 DEGREES SO CONSCIOUSLY ENTERED A SLIGHT RIGHT TURN TO GET BACK TO RUNWAY HEADING, 130 DEGREES. THIS HAPPENED TWO OR THREE TIMES. I ENGAGED THE AUTOPILOT AT APPROXIMATELY 800' MSL AND MONITORED IT FOR PROPER OPERATION. I ALSO WAS LOOKING FOR OTHER TFC UNTIL ENTERING LESS THAN VFR CONDITIONS AT ABOUT 1000' MSL, ALTHOUGH I FLEW THROUGH SCATTERED CLOUDS AT LOWER ALTITUDES. INSTRUMENT DEPARTURES FROM BOEING ARE USUALLY HANDED OFF TO APPROACH BETWEEN 500-800' MSL. THE TWR CTLR THIS NIGHT WAS OCCUPIED WITH A TFC WATCH AIRPLANE AND A HELI. AT 1,500' MSL, I ASKED FOR A FREQUENCY CHANGE AND WAS FINALLY APPROVED TO CONTACT APPROACH, ON 119.2. RADIO CONTACT WITH APPROACH WAS MADE AT ABOUT 1600' MSL, OR APPROXIMATELY 1 AND A HALF MINUTES AFTER TAKEOFF. THE CTLR SAID 'SAY HEADING.' I KNEW IMMEDIATELY THE QUESTION WOULD NOT BE ASKED IF I HAD BEEN ON COURSE. THE DG STILL SHOWED 130 DEGREES BUT I NOTICED THE MAGNETIC COMPASS INDICATED WSW, ABOUT 230 DEGREES. THE CTLR QUESTIONED THE DISCREPANCY BETWEEN HDGS WHEN I TOLD HIM THE TWO INSTRUMENTS DISAGREED AND THEN GAVE ME A NO-GYRO VECTOR. HE LATER INFORMED ME I HAD FLOWN THROUGH THE SEA-TAC APPROACH CORRIDOR. I MENTALLY TRANSITIONED TO NO-GYRO PARTIAL PANEL TIMED TURNS AS THE CTLR SUBSEQUENTLY GAVE ME HDGS AND ALTITUDES. I DISCONNECTED THE AUTOPILOT IMMEDIATELY WHEN THE HEADING ERROR WAS DISCOVERED. THE DG PROCESSED BADLY, +/-30 DEGREES WITHIN LESS THAN A MINUTE, FOR THE NEXT FIVE TO TEN MINUTES, AND THEN WORKED PROPERLY THE REST OF THE FLIGHT. THE AUTOPILOT ALSO FUNCTIONED NORMALLY WHEN LATER ENGAGED. I HAD NAVAIDS I COULD HAVE UTILIZED TO DETECT THE HEADING CHANGE, I.E., THE SEA VOR, THE LOM, THE LOC. BUT THE TIME FRAME IS SO SHORT AND THE WORKLOAD SO GREAT AT TAKEOFF UNTIL REACHING 1500' THAT THESE CLUES ARE NOT EASILY UTILIZED. THE SID ONLY STATES FLY STATES 'FLY RUNWAY HEADING.' AFTER TALKING TO OUR MECHANICS AND AVIONICS TECHNICIANS, I BELIEVE THE DG MALFUNCTIONED. THEY ALSO SAID THEY HAVE HEARD OF THIS PROBLEM--A QUICK PRECESS OF SUCH MAGNITUDE--HAPPENING BEFORE. I WANT TO STRESS THE ACTION WAS COMPLETELY INADVERTENT, UNPLANNED AND AS MUCH OF A SURPRISE TO ME AS TO THE APPROACH CTLR. BECAUSE OF ERRORS INHERENT IN THE MAGNETIC COMPASS, MAINLY ACCELERATION IN THIS CASE, IT WAS NOT PART OF MY SCAN DURING TAKEOFF. I WILL INCLUDE IT NOW, BUT ITS ACCURACY IS QUESTIONABLE AND SHOULD BE VERIFIED BY A NAVAID (THE LOC IN THIS CASE). I HOPE THE KENT 2 DEPARTURE (AND THE NEEDLE 4 DEPARTURE ALSO) SID FROM BOEING FIELD IS CHANGED TO INCLUDE TRACKING THE LOC COURSE. WITH TWO AIRPORTS SO CLOSE, AND THE APPROACH ALTITUDE FOR SEA-TAC THE SAME AS THE TAKEOFF ALTITUDE FORBOEING, COURSE GUIDANCE SHOULD BE A PART OF THE DEPARTURE PROCEDURE. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THIS HAS HAPPENED TO THIS ACFT AGAIN AND THEY HAVE FOUND THE RESET KNOB WAS STICKING IN WHEN RELEASED AND THIS OF COURSE KEPT GYRO CAGED. ALSO ASCERTAINED THE DISTANCE FROM OTHER ACFT WAS 200 FT VERTICAL BUT HORIZONTAL NOT GIVEN BUT ESTIMATED LESS THAN 500 FT. FAA IS MAKING INVESTIGATION OF INCIDENT.

Data retrieved from NASA's ASRS site as of August 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.