Narrative:

Departed vny on the canoga 8 departure. While on a 320 degree vector and level at 4000 ft socal departure said climb to 15000 ft. Shortly after that the controller came back and restr us to 8000 ft for traffic at the 10 O'clock position. As I leveled off, the controller said to maintain 8000 ft, traffic at 10 O'clock position. I told the copilot I had traffic in sight, he concurred and hesitated to call traffic to the controller due to being overwhelmed. As I reached 8000 ft, the controller said to maintain 8000 ft and immediately came back and said to descend to 8000 ft. As the controller was talking I noticed the altimeter was flagged off and then flicked on and off in a rapid manner and then went to normal (flag off) and the altimeter rapidly climbed up. On recognition of this I immediately began descent to 8000 ft. The controller then instructed us to climb to 15000 ft and then changed us over to another frequency and that controller asked us to call socal on the phone for possible altitude deviation. This problem with the altimeter repeated itself briefly while descending. Upon landing, I grounded the aircraft and had maintenance work on the aircraft. They could not find the problem or get it to duplicate itself. They released the aircraft. On the next leg, the problems arose again, but only for a 2-SECOND period (flicker) and then returned to normal otherwise. I again grounded the aircraft and at sus found a problem with the sdc module (static defect correction module) and replaced it with an overhauled unit. The problem has not resurfaced since. Contributing factors: 1) problem with altimeter (static defect correction module), 2) looking for traffic, diverting attention away from instruments at critical time, 3) rapid sequence of events with inexperienced copilot (2ND flight in a jet). Human performance considerations: 1) copilot failed to recognize anything was wrong. 2) copilot failed to radio traffic in sight when instructed to.

Related reports:

Google
 

Original NASA ASRS Text

Title: AN LR35 PIC OVERSHOOTS HIS AMENDED ALT WHEN THE ALTIMETER BECOMES ERRATIC AND UNRELIABLE 25 MI NW OF VNY, CA.

Narrative: DEPARTED VNY ON THE CANOGA 8 DEP. WHILE ON A 320 DEG VECTOR AND LEVEL AT 4000 FT SOCAL DEP SAID CLB TO 15000 FT. SHORTLY AFTER THAT THE CTLR CAME BACK AND RESTR US TO 8000 FT FOR TFC AT THE 10 O'CLOCK POS. AS I LEVELED OFF, THE CTLR SAID TO MAINTAIN 8000 FT, TFC AT 10 O'CLOCK POS. I TOLD THE COPLT I HAD TFC IN SIGHT, HE CONCURRED AND HESITATED TO CALL TFC TO THE CTLR DUE TO BEING OVERWHELMED. AS I REACHED 8000 FT, THE CTLR SAID TO MAINTAIN 8000 FT AND IMMEDIATELY CAME BACK AND SAID TO DSND TO 8000 FT. AS THE CTLR WAS TALKING I NOTICED THE ALTIMETER WAS FLAGGED OFF AND THEN FLICKED ON AND OFF IN A RAPID MANNER AND THEN WENT TO NORMAL (FLAG OFF) AND THE ALTIMETER RAPIDLY CLBED UP. ON RECOGNITION OF THIS I IMMEDIATELY BEGAN DSCNT TO 8000 FT. THE CTLR THEN INSTRUCTED US TO CLB TO 15000 FT AND THEN CHANGED US OVER TO ANOTHER FREQ AND THAT CTLR ASKED US TO CALL SOCAL ON THE PHONE FOR POSSIBLE ALTDEV. THIS PROB WITH THE ALTIMETER REPEATED ITSELF BRIEFLY WHILE DSNDING. UPON LNDG, I GROUNDED THE ACFT AND HAD MAINT WORK ON THE ACFT. THEY COULD NOT FIND THE PROB OR GET IT TO DUPLICATE ITSELF. THEY RELEASED THE ACFT. ON THE NEXT LEG, THE PROBS AROSE AGAIN, BUT ONLY FOR A 2-SECOND PERIOD (FLICKER) AND THEN RETURNED TO NORMAL OTHERWISE. I AGAIN GROUNDED THE ACFT AND AT SUS FOUND A PROB WITH THE SDC MODULE (STATIC DEFECT CORRECTION MODULE) AND REPLACED IT WITH AN OVERHAULED UNIT. THE PROB HAS NOT RESURFACED SINCE. CONTRIBUTING FACTORS: 1) PROB WITH ALTIMETER (STATIC DEFECT CORRECTION MODULE), 2) LOOKING FOR TFC, DIVERTING ATTN AWAY FROM INSTS AT CRITICAL TIME, 3) RAPID SEQUENCE OF EVENTS WITH INEXPERIENCED COPLT (2ND FLT IN A JET). HUMAN PERFORMANCE CONSIDERATIONS: 1) COPLT FAILED TO RECOGNIZE ANYTHING WAS WRONG. 2) COPLT FAILED TO RADIO TFC IN SIGHT WHEN INSTRUCTED TO.

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.