Narrative:

I received a clearance from midway tower for takeoff on runway 31C and was instructed to, after takeoff, turn to a heading of 250 degrees and climb to an altitude of 3000 ft. At this point, before commencing my takeoff roll, the heading bug was placed on 250 degrees. After takeoff and having cleared all obstacles, I began the left turn to 250 degrees. Crossing 1200 ft, I engaged the heading autoplt and let the autoplt continue the left turn to 250 degrees so meanwhile I could focus on transitioning the aircraft from a takeoff confign to a climb confign, mainly setting power levers, propeller levers, manage fuel flow, egt, fuel pumps, etc. I was constantly scanning the flight instruments to assure myself that the aircraft was climbing and turning to 250 degrees. As the autoplt began the rollout on a heading of 250 degrees, midway tower asked to contact chicago departure, and at this precise moment it seemed to me that a turn of 60 degrees (from 310 to 250) was a bit long. On initial contact with chicago departure I indicated that I was climbing through my present altitude for 3000 ft and that I was assigned 250 degrees by the tower. The controller acknowledged my transmission. I immediately proceeded to check my magnetic compass to verify the heading I was on, but because I've just rolled out of a turn, it was unreliable. At the same time chicago departure got back on the frequency and asked what heading I was on. I replied 250 degrees. Chicago now indicated that my aircraft was heading sse and there was traffic 2 mi ahead on final approach at midway. Immediately I started a right turn towards the west. Chicago asked again what heading I was showing now, but because I have just rolled into a turn and was confused, I replied: stand by. Once established on a 250 degree heading by use of the magnetic compass, departure control requested an explanation. I did not exactly know quite yet what went wrong so my first thought was an autoplt malfunction only to find out later that the equipment was operating fine. I discovered that the problem was caused by a gyro-slaving failure. By pressing the fast slave button the directional gyro was again operating normally, although throughout the remaining of the flight was off by 10 degrees. Chicago advised me that my aircraft became close to a jet traffic on final approach at midway but I don't know by how much. Even though I have checked my gyro with the magnetic compass during my preflight and pre taxi checklist, I've failed to double-check my heading with the runway heading prior to beginning my takeoff roll. I did set the heading bug but I did not look to see if I was showing 310. Also, even though the WX was marginal I should have used outside references to aid my orientation. I should point out that I don't know whether the failure occurred during taxi or after liftoff.

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Original NASA ASRS Text

Title: PLT OF AN SMT TWIN ENG ATX FRT ACFT FAILED TO STOP TURNING AFTER TKOF TO THE ASSIGNED HDG RESULTING IN LTSS WITH ANOTHER ACFT ON APCH.

Narrative: I RECEIVED A CLRNC FROM MIDWAY TWR FOR TKOF ON RWY 31C AND WAS INSTRUCTED TO, AFTER TKOF, TURN TO A HDG OF 250 DEGS AND CLB TO AN ALT OF 3000 FT. AT THIS POINT, BEFORE COMMENCING MY TKOF ROLL, THE HDG BUG WAS PLACED ON 250 DEGS. AFTER TKOF AND HAVING CLRED ALL OBSTACLES, I BEGAN THE L TURN TO 250 DEGS. XING 1200 FT, I ENGAGED THE HDG AUTOPLT AND LET THE AUTOPLT CONTINUE THE L TURN TO 250 DEGS SO MEANWHILE I COULD FOCUS ON TRANSITIONING THE ACFT FROM A TKOF CONFIGN TO A CLB CONFIGN, MAINLY SETTING PWR LEVERS, PROP LEVERS, MANAGE FUEL FLOW, EGT, FUEL PUMPS, ETC. I WAS CONSTANTLY SCANNING THE FLT INSTS TO ASSURE MYSELF THAT THE ACFT WAS CLBING AND TURNING TO 250 DEGS. AS THE AUTOPLT BEGAN THE ROLLOUT ON A HDG OF 250 DEGS, MIDWAY TWR ASKED TO CONTACT CHICAGO DEP, AND AT THIS PRECISE MOMENT IT SEEMED TO ME THAT A TURN OF 60 DEGS (FROM 310 TO 250) WAS A BIT LONG. ON INITIAL CONTACT WITH CHICAGO DEP I INDICATED THAT I WAS CLBING THROUGH MY PRESENT ALT FOR 3000 FT AND THAT I WAS ASSIGNED 250 DEGS BY THE TWR. THE CTLR ACKNOWLEDGED MY XMISSION. I IMMEDIATELY PROCEEDED TO CHK MY MAGNETIC COMPASS TO VERIFY THE HDG I WAS ON, BUT BECAUSE I'VE JUST ROLLED OUT OF A TURN, IT WAS UNRELIABLE. AT THE SAME TIME CHICAGO DEP GOT BACK ON THE FREQ AND ASKED WHAT HDG I WAS ON. I REPLIED 250 DEGS. CHICAGO NOW INDICATED THAT MY ACFT WAS HDG SSE AND THERE WAS TFC 2 MI AHEAD ON FINAL APCH AT MIDWAY. IMMEDIATELY I STARTED A R TURN TOWARDS THE W. CHICAGO ASKED AGAIN WHAT HDG I WAS SHOWING NOW, BUT BECAUSE I HAVE JUST ROLLED INTO A TURN AND WAS CONFUSED, I REPLIED: STAND BY. ONCE ESTABLISHED ON A 250 DEG HDG BY USE OF THE MAGNETIC COMPASS, DEP CTL REQUESTED AN EXPLANATION. I DID NOT EXACTLY KNOW QUITE YET WHAT WENT WRONG SO MY FIRST THOUGHT WAS AN AUTOPLT MALFUNCTION ONLY TO FIND OUT LATER THAT THE EQUIP WAS OPERATING FINE. I DISCOVERED THAT THE PROB WAS CAUSED BY A GYRO-SLAVING FAILURE. BY PRESSING THE FAST SLAVE BUTTON THE DIRECTIONAL GYRO WAS AGAIN OPERATING NORMALLY, ALTHOUGH THROUGHOUT THE REMAINING OF THE FLT WAS OFF BY 10 DEGS. CHICAGO ADVISED ME THAT MY ACFT BECAME CLOSE TO A JET TFC ON FINAL APCH AT MIDWAY BUT I DON'T KNOW BY HOW MUCH. EVEN THOUGH I HAVE CHKED MY GYRO WITH THE MAGNETIC COMPASS DURING MY PREFLT AND PRE TAXI CHKLIST, I'VE FAILED TO DOUBLE-CHK MY HDG WITH THE RWY HDG PRIOR TO BEGINNING MY TKOF ROLL. I DID SET THE HDG BUG BUT I DID NOT LOOK TO SEE IF I WAS SHOWING 310. ALSO, EVEN THOUGH THE WX WAS MARGINAL I SHOULD HAVE USED OUTSIDE REFS TO AID MY ORIENTATION. I SHOULD POINT OUT THAT I DON'T KNOW WHETHER THE FAILURE OCCURRED DURING TAXI OR AFTER LIFTOFF.

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.