Narrative:

We were on a maintenance test flight to check pressurization and gear warning. The pressurization check was done above FL250 and the gear check at 12000 ft. The pressurization check was done with crew on oxygen. During the flight while the checks were performed the copilot was coordination with the mechanic and I was handling the aircraft and working the radios. After takeoff, the HSI selector was set to RNAV but later on, at FL280, center had us on vectors and the HSI was in heading mode. After the pressurization check, we proceeded direct to lisse intersection (RNAV). Approaching lisse, we requested to maintain 12000 ft and reduce airspeed to do the landing gear warning check. We were vectored off the arrival (heading mode), then vectored to hobby followed by a visual approach and landing. Approaching hou I noticed my magnetic heading on the HSI was incorrect and I had a red flag in my RMI but no flags in my HSI. We were on visual approach with hobby in sight so no action was taken. After landing, a 1 amp circuit breaker for the captain's RMI was noticed pulled on the captain side console. The oxygen mask on the captain's side connects behind the captain's seat and the line lies along the side console. We believe the action of putting on the mask pulled the circuit breaker. I also believe that if the copilot had not been coordinating the checks with the mechanic, perhaps he would have picked up on the heading difference I had missed. On the sabre, the #1 HSI is slaved off the #1 RMI and as no heading warning flag was shown on the HSI, this made detection more difficult. At no time did the controllers advise us that our assigned headings were a problem. Perhaps they were allowing for our deviation in their heading deviation assignments. Our HSI was approximately 30 degrees in error.

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Original NASA ASRS Text

Title: POSSIBLE TRACK DEV.

Narrative: WE WERE ON A MAINT TEST FLT TO CHK PRESSURIZATION AND GEAR WARNING. THE PRESSURIZATION CHK WAS DONE ABOVE FL250 AND THE GEAR CHK AT 12000 FT. THE PRESSURIZATION CHK WAS DONE WITH CREW ON OXYGEN. DURING THE FLT WHILE THE CHKS WERE PERFORMED THE COPLT WAS COORD WITH THE MECH AND I WAS HANDLING THE ACFT AND WORKING THE RADIOS. AFTER TKOF, THE HSI SELECTOR WAS SET TO RNAV BUT LATER ON, AT FL280, CTR HAD US ON VECTORS AND THE HSI WAS IN HDG MODE. AFTER THE PRESSURIZATION CHK, WE PROCEEDED DIRECT TO LISSE INTXN (RNAV). APCHING LISSE, WE REQUESTED TO MAINTAIN 12000 FT AND REDUCE AIRSPD TO DO THE LNDG GEAR WARNING CHK. WE WERE VECTORED OFF THE ARR (HDG MODE), THEN VECTORED TO HOBBY FOLLOWED BY A VISUAL APCH AND LNDG. APCHING HOU I NOTICED MY MAGNETIC HDG ON THE HSI WAS INCORRECT AND I HAD A RED FLAG IN MY RMI BUT NO FLAGS IN MY HSI. WE WERE ON VISUAL APCH WITH HOBBY IN SIGHT SO NO ACTION WAS TAKEN. AFTER LNDG, A 1 AMP CIRCUIT BREAKER FOR THE CAPT'S RMI WAS NOTICED PULLED ON THE CAPT SIDE CONSOLE. THE OXYGEN MASK ON THE CAPT'S SIDE CONNECTS BEHIND THE CAPT'S SEAT AND THE LINE LIES ALONG THE SIDE CONSOLE. WE BELIEVE THE ACTION OF PUTTING ON THE MASK PULLED THE CIRCUIT BREAKER. I ALSO BELIEVE THAT IF THE COPLT HAD NOT BEEN COORDINATING THE CHKS WITH THE MECH, PERHAPS HE WOULD HAVE PICKED UP ON THE HDG DIFFERENCE I HAD MISSED. ON THE SABRE, THE #1 HSI IS SLAVED OFF THE #1 RMI AND AS NO HDG WARNING FLAG WAS SHOWN ON THE HSI, THIS MADE DETECTION MORE DIFFICULT. AT NO TIME DID THE CTLRS ADVISE US THAT OUR ASSIGNED HDGS WERE A PROB. PERHAPS THEY WERE ALLOWING FOR OUR DEV IN THEIR HDG DEV ASSIGNMENTS. OUR HSI WAS APPROX 30 DEGS IN ERROR.

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.