Narrative:

The flight that day was part 91 with the aircraft full of passengers consisting of one non flying pilot in the front right seat as per company policy. Upon completion of all pre-takeoff checklists take off clearance was given and we took off. The initial clearance was to maintain a heading of 130 and climb to 2;000 ft and the flight proceeded accordingly. On climb out while completing the after takeoff checklist I noticed on my primary instrument for heading; my HSI 1; that my heading had deviated to the left I corrected back to a heading of 130 degrees; thinking I must have inadvertently turned while completing the checklist items. Finishing the turn; crosschecking HSI 1 with my RMI and HSI 2 on the copilot side I found a discrepancy. My GPS track was not as apparent due to the high winds aloft that day so it wasn't of much help. Upon completing the turn after the compass had settled down from its turning error I was able to find that it was most likely my HSI 1 that was showing the discrepancy and my instruments slaved to the secondary heading system were showing the correct heading. Immediately after I had realized this discrepancy; center requested a turn of 25 degrees to the left which I immediately complied with. Continuing to fly the airplane while complying with center I re-slaved; in other words reset the slave of my HSI 1 and the indication immediately swung 20 degrees; correcting itself to 130 which is the direction center had cleared us and turned us back to what my secondary heading instruments depicted. Having fixed the discrepancy in my instrumentation and taking into consideration the aircraft's HSI 2 and RMI I chose to proceed with the flight. Also; we were soon given a turn to the west and then the north; both of which allowed for visual reference to the ground and surrounding terrain (in other words VFR conditions) all the way to destination as another means of crosschecking. On our initial climb out we had been pointed directly at a building layer of clouds to the south. With our pitch up attitude at that time visual reference to the ground was difficult if at all possible. The HSI discrepancy did not repeat itself for the rest of the flight. We continued to destination; canceling our IFR flight plan and landed under VFR. I have since had an a&P mechanic check into the instrument's heading discrepancy finding nothing wrong with the instrument or system. We are still not sure what magnetic/electrical disturbance could have caused the discrepancy. I had informed all my passengers to turn off their electronic devices but you can never be sure if someone had forgotten a phone in their purse or just plain managed to sneak one by me. Looking back at this situation as to what would have helped catch and correct the error earlier I will make a few observations. Upon finding the initial heading deviation checking my back up HSI a little sooner might have helped. At that time I was trying to comply with my clearance which was a heading but seeing the error on both sides along with the RMI would have helped me to see that there was a discrepancy sooner but still wouldn't have verified which instrument was in error. Checking my instruments against the compass sooner would also have helped although in a nose up attitude and beginning a correcting turn; there are some inherent errors in a compass to consider. Checking the compass was really the only real reliable way to find out which system was the one in error; which did become apparent after the plane was rolled wings level.

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Original NASA ASRS Text

Title: King Air pilot discovers a HSI heading error shortly after takeoff but not before making a heading correction using the faulty instrument. ATC issues a heading correction and the HSI is adjusted to the magnetic heading with no further problems reported.

Narrative: The flight that day was Part 91 with the aircraft full of passengers consisting of one non flying pilot in the front right seat as per company policy. Upon completion of all pre-takeoff checklists take off clearance was given and we took off. The initial clearance was to maintain a heading of 130 and climb to 2;000 FT and the flight proceeded accordingly. On Climb out while completing the after takeoff checklist I noticed on my primary instrument for heading; my HSI 1; that my heading had deviated to the left I corrected back to a heading of 130 degrees; thinking I must have inadvertently turned while completing the checklist items. Finishing the turn; crosschecking HSI 1 with my RMI and HSI 2 on the copilot side I found a discrepancy. My GPS track was not as apparent due to the high winds aloft that day so it wasn't of much help. Upon completing the turn after the compass had settled down from its turning error I was able to find that it was most likely my HSI 1 that was showing the discrepancy and my instruments slaved to the secondary heading system were showing the correct heading. Immediately after I had realized this discrepancy; Center requested a turn of 25 degrees to the left which I immediately complied with. Continuing to fly the airplane while complying with Center I re-slaved; in other words reset the slave of my HSI 1 and the indication immediately swung 20 degrees; correcting itself to 130 which is the direction Center had cleared us and turned us back to what my secondary heading instruments depicted. Having fixed the discrepancy in my instrumentation and taking into consideration the aircraft's HSI 2 and RMI I chose to proceed with the flight. Also; we were soon given a turn to the west and then the north; both of which allowed for visual reference to the ground and surrounding terrain (in other words VFR conditions) all the way to destination as another means of crosschecking. On our initial climb out we had been pointed directly at a building layer of clouds to the south. With our pitch up attitude at that time visual reference to the ground was difficult if at all possible. The HSI discrepancy did not repeat itself for the rest of the flight. We continued to destination; canceling our IFR flight plan and landed under VFR. I have since had an A&P Mechanic check into the Instrument's heading discrepancy finding nothing wrong with the instrument or system. We are still not sure what magnetic/electrical disturbance could have caused the discrepancy. I had informed all my passengers to turn off their electronic devices but you can never be sure if someone had forgotten a phone in their purse or just plain managed to sneak one by me. Looking back at this situation as to what would have helped catch and correct the error earlier I will make a few observations. Upon finding the initial heading deviation checking my back up HSI a little sooner might have helped. At that time I was trying to comply with my clearance which was a heading but seeing the error on both sides along with the RMI would have helped me to see that there was a discrepancy sooner but still wouldn't have verified which instrument was in error. Checking my instruments against the compass sooner would also have helped although in a nose up attitude and beginning a correcting turn; there are some inherent errors in a compass to consider. Checking the compass was really the only real reliable way to find out which system was the one in error; which did become apparent after the plane was rolled wings level.

Data retrieved from NASA's ASRS site as of April 2012 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.