Narrative:

During the initial phase of the takeoff roll at about 60 KIAS, we got a 'fuel filter bypass left' message and aborted the takeoff. We taxied back to the service center and got the problem rectified. The mechanics left the aircraft pwred. After a second preflight, we verified all system again and finished all checks with no problems or failure messages. After takeoff we were told to fly heading 320 degrees and realized that we had a shift of all 3 heading references by 90 degrees. The initial runway heading of 014 degrees was now 284 degrees. We requested a 'no gyro' ILS back. After landing, we analyzed the situation again. No failure messages were present. Since there were no messages there is no checklist. We turned the 2 IRS platforms off and realigned them without problems. The following departure was uneventful and no anomalies were encountered during the flight back home. There may have been some inputs by maintenance that caused the heading shift right after departure. Maybe they used 'att' mode, not the 'navigation' mode to initially align the IRS platforms and then switched to navigation mode. This could have caused the drift during the acceleration phase during takeoff. In the 'att' mode no navigation outputs are provided, nor are velocity and wind data. We decided in the future we will totally de-power the aircraft when it comes out of maintenance since we do not know how mechanics align IRS platforms. Approach control did a marvelous job getting us back with no gyro.

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Original NASA ASRS Text

Title: C750 FLT CREW EXPERIENCES LOSS OF IRS HDG INFO AFTER TKOF AND PERFORMS NO-GYRO APCH RETURN LAND.

Narrative: DURING THE INITIAL PHASE OF THE TKOF ROLL AT ABOUT 60 KIAS, WE GOT A 'FUEL FILTER BYPASS L' MESSAGE AND ABORTED THE TKOF. WE TAXIED BACK TO THE SVC CTR AND GOT THE PROB RECTIFIED. THE MECHS LEFT THE ACFT PWRED. AFTER A SECOND PREFLT, WE VERIFIED ALL SYS AGAIN AND FINISHED ALL CHKS WITH NO PROBS OR FAILURE MESSAGES. AFTER TKOF WE WERE TOLD TO FLY HDG 320 DEGS AND REALIZED THAT WE HAD A SHIFT OF ALL 3 HDG REFS BY 90 DEGS. THE INITIAL RWY HDG OF 014 DEGS WAS NOW 284 DEGS. WE REQUESTED A 'NO GYRO' ILS BACK. AFTER LNDG, WE ANALYZED THE SIT AGAIN. NO FAILURE MESSAGES WERE PRESENT. SINCE THERE WERE NO MESSAGES THERE IS NO CHKLIST. WE TURNED THE 2 IRS PLATFORMS OFF AND REALIGNED THEM WITHOUT PROBS. THE FOLLOWING DEP WAS UNEVENTFUL AND NO ANOMALIES WERE ENCOUNTERED DURING THE FLT BACK HOME. THERE MAY HAVE BEEN SOME INPUTS BY MAINT THAT CAUSED THE HDG SHIFT RIGHT AFTER DEP. MAYBE THEY USED 'ATT' MODE, NOT THE 'NAV' MODE TO INITIALLY ALIGN THE IRS PLATFORMS AND THEN SWITCHED TO NAV MODE. THIS COULD HAVE CAUSED THE DRIFT DURING THE ACCELERATION PHASE DURING TKOF. IN THE 'ATT' MODE NO NAV OUTPUTS ARE PROVIDED, NOR ARE VELOCITY AND WIND DATA. WE DECIDED IN THE FUTURE WE WILL TOTALLY DE-PWR THE ACFT WHEN IT COMES OUT OF MAINT SINCE WE DO NOT KNOW HOW MECHS ALIGN IRS PLATFORMS. APCH CTL DID A MARVELOUS JOB GETTING US BACK WITH NO GYRO.

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.