LR-45 CAPT DESCRIBED HEADING FAILURE INCIDENT DURING ATC VECTORS TO PWK; INDICATING SUPER COLLIDER LOCATION AS POSSIBLE CAUSAL FACTOR.

Narrative

ON APCH VECTORS FROM CHICAGO APCH CTL FOLLOWING AN UNEVENTFUL FLT FROM ZZZ TO PWK; WE WERE ON A HDG OF 340 DEGS ABOUT 15 NM ON THE 290 DEG RADIAL OFF OF OBK. CHICAGO GAVE US A HDG CHANGE TO 030 DEGS AND WHEN THE TURN WAS STARTED WE RECEIVED A HDG FAILURE MESSAGE WHICH READ 'HDG' ON THE #1 AND #2 DIRECTIONAL GYROS ON THE RESPECTIVE DISPLAY UNITS. THE MFD MAP ALSO HAD A 'HDG' MESSAGE IDENTICAL TO THE DISPLAY UNITS. THERE WERE NOT ANY CAS MESSAGES OR CWP MESSAGES ASSOCIATED WITH THIS FAILURE. WHEN WE LEVELED WINGS ON A 030 DEG HDG; CHICAGO GAVE US A 140 DEG HDG TO INTERCEPT THE RWY 16 LOC INTO PWK. WE COULD NOT ACCEPT THIS PROC DUE TO THE LOSS OF OUR NAV EQUIP SO INSTEAD WE OPTED FOR THE VISUAL. WHILE TURNING INBOUND THE COMPASS WAS FLUCTUATING STRANGELY. IN TURNS FROM 090 DEGS TO 140 DEGS; THE COMPASS WAS READING 360 DEGS AND TURNING IN THE WRONG DIRECTION. ONCE ESTABLISHED ON A 140 DEG HDG; THE COMPASS SPUN 180 DEGS TO THE CORRECT HDG. WHEN ON FINAL AND FLAPS WERE SET TO 8 DEGS ALL FLAGS WENT AWAY AND THE AHRS IMMEDIATELY WENT BACK TO NORMAL. THIS IS THE SECOND TIME THIS FAILURE HAS HAPPENED IN THE SAME AREA TO THIS ACFT. ON THE FIRST EVENT; MAINT; MGMNT AND PLTS WERE ADVISED. THE AREA WHERE BOTH INSTANCES HAPPENED IS ABOUT 15-20 MI N OF THE SUPER COLLIDER W OF CHICAGO. AFTER DISCUSSIONS WITH CREW AND MAINT; WE BELIEVE THAT SOME SORT OF MAGNETIC INTERFERENCE OR ANOMALY MAY HAVE TAKEN PLACE DURING THOSE TIMES OF OPS.