Narrative:

Takeoff at lga runway 13. Long delay (approximately 30 min) near approach end runway 13. Potential for compass problems due to pier. During line-up and takeoff both compasses ok. Upon initial turn to 180 degree (whitestone climb) flight director started to give bad information (turn left instead of right). Suspected compass problem and turned to approximately 180 degree heading for 2 1/2 DME and started left turn to 040 degree. Also suspected both compasses were off to some degree? Locked in rear view mirror at stand by compass (couldn't initially do this because of low altitude maneuvering and realized number 1 compass had drifted left approximately 50 degree and number 2 compass had drifted left approximately 30 degree. Departure control provided several left turns as we climbed out using basic instruments (no flight directors) and standby compass. Both compasses provided reliable heading information within approximately 5 mins. Flight proceeded to destination without any other problems. Suggestion: avoid long ground delays vicinity runway 13 pier due to strong possibility compass anomalies. No altitudes or speeds were busted but headings were off initially. This type problem could get you into trouble very quickly if you don't revert back to basic instruments in a timely manner! Callback conversation with reporter revealed the following information: PIC stated that he has known of this anomaly but had never experienced both compasses deviating, only one. Had he not had the flight director on he may have taken longer to determine that he had a problem with the heading on departure. The situation was created, in his opinion, by the long delay he had. ATC had him move from taxiway cc and taxi around through bb and back to cc behind other traffic. Total time of delay was 25 mins. At takeoff roll the compasses appeared normal. In the past when he noted one being off he resynchronized the system with no departure problem. During the initial and later stages of this event ATC did not note or appear to be aware of the problem. Reporter was to busy to advise departure controller but should have. He recommends: that ATC not have you hold near the piers when taking a delay for runways 13 or 22. If that is unavoidable, resynchronize the system prior to takeoff. That: the note on the preceding paragraph and presently on the departure chart regarding magnetic anomalies be placed on the airport chart as well for information dissemination purposes. Further: that departure controllers be aware that departure traffic off runways 13 and 22 may experience this anomaly and have them prepared for immediate vectors to keep departures on track.

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Original NASA ASRS Text

Title: A DEP MD-80 EXPERIENCES COMPASS/HSI PROBS WITH BOTH COMPASSES DRIFTING LEFT FROM 30 TO 50 DEGS DURING TKOF FROM RWY 13 FOR THE LGA 9 DEP AT LGA, NY.

Narrative: TKOF AT LGA RWY 13. LONG DELAY (APPROX 30 MIN) NEAR APCH END RWY 13. POTENTIAL FOR COMPASS PROBS DUE TO PIER. DURING LINE-UP AND TKOF BOTH COMPASSES OK. UPON INITIAL TURN TO 180 DEG (WHITESTONE CLB) FLT DIRECTOR STARTED TO GIVE BAD INFO (TURN L INSTEAD OF R). SUSPECTED COMPASS PROB AND TURNED TO APPROX 180 DEG HEADING FOR 2 1/2 DME AND STARTED L TURN TO 040 DEG. ALSO SUSPECTED BOTH COMPASSES WERE OFF TO SOME DEG? LOCKED IN REAR VIEW MIRROR AT STAND BY COMPASS (COULDN'T INITIALLY DO THIS BECAUSE OF LOW ALTITUDE MANEUVERING AND REALIZED NUMBER 1 COMPASS HAD DRIFTED LEFT APPROX 50 DEG AND NUMBER 2 COMPASS HAD DRIFTED LEFT APPROX 30 DEG. DEP CTL PROVIDED SEVERAL LEFT TURNS AS WE CLIMBED OUT USING BASIC INSTRUMENTS (NO FLT DIRECTORS) AND STANDBY COMPASS. BOTH COMPASSES PROVIDED RELIABLE HEADING INFO WITHIN APPROX 5 MINS. FLT PROCEEDED TO DESTINATION WITHOUT ANY OTHER PROBS. SUGGESTION: AVOID LONG GND DELAYS VICINITY RWY 13 PIER DUE TO STRONG POSSIBILITY COMPASS ANOMALIES. NO ALTITUDES OR SPEEDS WERE BUSTED BUT HEADINGS WERE OFF INITIALLY. THIS TYPE PROB COULD GET YOU INTO TROUBLE VERY QUICKLY IF YOU DON'T REVERT BACK TO BASIC INSTRUMENTS IN A TIMELY MANNER! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PIC STATED THAT HE HAS KNOWN OF THIS ANOMALY BUT HAD NEVER EXPERIENCED BOTH COMPASSES DEVIATING, ONLY ONE. HAD HE NOT HAD THE FLT DIRECTOR ON HE MAY HAVE TAKEN LONGER TO DETERMINE THAT HE HAD A PROB WITH THE HDG ON DEP. THE SIT WAS CREATED, IN HIS OPINION, BY THE LONG DELAY HE HAD. ATC HAD HIM MOVE FROM TXWY CC AND TAXI AROUND THROUGH BB AND BACK TO CC BEHIND OTHER TFC. TOTAL TIME OF DELAY WAS 25 MINS. AT TKOF ROLL THE COMPASSES APPEARED NORMAL. IN THE PAST WHEN HE NOTED ONE BEING OFF HE RESYNCHRONIZED THE SYSTEM WITH NO DEP PROB. DURING THE INITIAL AND LATER STAGES OF THIS EVENT ATC DID NOT NOTE OR APPEAR TO BE AWARE OF THE PROB. RPTR WAS TO BUSY TO ADVISE DEP CTLR BUT SHOULD HAVE. HE RECOMMENDS: THAT ATC NOT HAVE YOU HOLD NEAR THE PIERS WHEN TAKING A DELAY FOR RWYS 13 OR 22. IF THAT IS UNAVOIDABLE, RESYNCHRONIZE THE SYSTEM PRIOR TO TKOF. THAT: THE NOTE ON THE PRECEDING PARAGRAPH AND PRESENTLY ON THE DEP CHART REGARDING MAGNETIC ANOMALIES BE PLACED ON THE ARPT CHART AS WELL FOR INFO DISSEMINATION PURPOSES. FURTHER: THAT DEP CTLRS BE AWARE THAT DEP TFC OFF RWYS 13 AND 22 MAY EXPERIENCE THIS ANOMALY AND HAVE THEM PREPARED FOR IMMEDIATE VECTORS TO KEEP DEPS ON TRACK.

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.