Narrative:

Departed lga gate. Short taxi to runway 31, #1 for immediate takeoff, aircraft on 3 mi final approach to runway 31. Wind out of the north at about 15 KTS, right crosswind. Did not note HSI runway alignment. Took off with ATC clearance to turn right to 340 degree at approximately 800 ft. Departure instructed us to turn right to 340 degree. First officer was flying aircraft. I looked at HSI read 340 degrees and crosschecked rni at 340 degrees, and told departure that we were heading 340 degrees. ATC advised that he showed us on center line. I then checked magnetic compass which involved using a rearview mirror mounted on glare shield turning on standby compass light, aligning both to read standby cmpass. Read 310 degrees on standby compass, reset captain's RMI, then instructed first officer to match his RMI to mine by matching RMI to his HSI. Then instructed first officer to turn right to 340 degrees and notified ATC that we had a compass misalignment and had corrected problem and were now heading 340 degrees. ATC noted new heading end of event. There is a note in company airport advisory page warning against magnetic irregularities affecting compass headings during takeoff, particularly from gates a and B on short taxies. Our short taxi time did not allow enough time for the compasses to resynchronize to correct heading. In communicating with the chief pilot I discovered that the jetways need to be demagnetized. This should be done without delay. I wouldn't want this scenario to be repeated on a cold dark winter night in icing conditions. Needless to say I will take the time in the future to confirm compass alignment with runway prior to takeoff. (Since both compasses slewed 30 degrees to the right of magnetic heading the aircraft instrument comparator system did not annunciate the problem).

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Original NASA ASRS Text

Title: MLG DEPARTS WITH UNCORRECTED COMPASS SYNCHRONIZATION.

Narrative: DEPARTED LGA GATE. SHORT TAXI TO RWY 31, #1 FOR IMMEDIATE TKOF, ACFT ON 3 MI FINAL APCH TO RWY 31. WIND OUT OF THE N AT ABOUT 15 KTS, R XWIND. DID NOT NOTE HSI RWY ALIGNMENT. TOOK OFF WITH ATC CLRNC TO TURN R TO 340 DEG AT APPROX 800 FT. DEP INSTRUCTED US TO TURN R TO 340 DEG. FO WAS FLYING ACFT. I LOOKED AT HSI READ 340 DEGS AND XCHKED RNI AT 340 DEGS, AND TOLD DEP THAT WE WERE HEADING 340 DEGS. ATC ADVISED THAT HE SHOWED US ON CTR LINE. I THEN CHKED MAGNETIC COMPASS WHICH INVOLVED USING A REARVIEW MIRROR MOUNTED ON GLARE SHIELD TURNING ON STANDBY COMPASS LIGHT, ALIGNING BOTH TO READ STANDBY CMPASS. READ 310 DEGS ON STANDBY COMPASS, RESET CAPT'S RMI, THEN INSTRUCTED FO TO MATCH HIS RMI TO MINE BY MATCHING RMI TO HIS HSI. THEN INSTRUCTED FO TO TURN R TO 340 DEGS AND NOTIFIED ATC THAT WE HAD A COMPASS MISALIGNMENT AND HAD CORRECTED PROB AND WERE NOW HDG 340 DEGS. ATC NOTED NEW HDG END OF EVENT. THERE IS A NOTE IN COMPANY ARPT ADVISORY PAGE WARNING AGAINST MAGNETIC IRREGULARITIES AFFECTING COMPASS HDGS DURING TKOF, PARTICULARLY FROM GATES A AND B ON SHORT TAXIES. OUR SHORT TAXI TIME DID NOT ALLOW ENOUGH TIME FOR THE COMPASSES TO RESYNCHRONIZE TO CORRECT HDG. IN COMMUNICATING WITH THE CHIEF PLT I DISCOVERED THAT THE JETWAYS NEED TO BE DEMAGNETIZED. THIS SHOULD BE DONE WITHOUT DELAY. I WOULDN'T WANT THIS SCENARIO TO BE REPEATED ON A COLD DARK WINTER NIGHT IN ICING CONDITIONS. NEEDLESS TO SAY I WILL TAKE THE TIME IN THE FUTURE TO CONFIRM COMPASS ALIGNMENT WITH RWY PRIOR TO TKOF. (SINCE BOTH COMPASSES SLEWED 30 DEGS TO THE R OF MAGNETIC HDG THE ACFT INST COMPARATOR SYS DID NOT ANNUNCIATE THE PROB).

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.