Narrative:

During descent into pittsburg, we were cleared to 10,000 and 250 KTS at grace intersection. The captain was flying the aircraft and I was working the radios and conducting the PNF duties. The captain had been on vacation for approximately 1 month previous to this trip. At 11,000' I called out 11 for 10 and said to the captain his descent rate was high. He replied ok. He had the autoplt set to level off at 10,000' and he expected it to capture but I knew it would not because of his high (5000 FPM) descent rate. At 10,300' I again said 10,000 to remind and verify with him that we were required to stop our descent at 10,000'. At 10,000' it was obvious to me that we were not going to stop at 10,000. The captain then realized the autoplt was not going to level off so he disengaged the autoplt and started to pull up manually. I saw that we were going through 10,000 and took the controls to help pull up to stop our descent. I felt this was necessary because we were going to level off at approximately 9000' and we were IMC. The captain yelled 'what are you doing' and I said 'ten thousand' as I pulled up. At that point I felt he had control again so I let go and the aircraft continued to descend and pitched down again loosing more altitude. At that point I again assisted by pulling up again on the yoke until the aircraft leveled off at 9600' and started to climb back to 10,000'. I feel the captain should have taken more aggressive action to stop the descent rate. People flying passenger forget that being smooth on the controls has a time and place and it is not when you're going through assigned altitude in IMC conditions. I fly aerobatic aircraft for pleasure and competition and I am a rated instructor. I am familiar with g-loads and the consequences associated with them. The g-load I used to level the aircraft was nowhere near the limit of the aircraft. The fasten seatbelt sign had been on for at least 5 minutes (since 18,000') and the F/a's had been alerted for landing. I feel the failure of the captain to recognize his high sink rate and failure to take action immediately caused the altitude incursion. This resulted in my taking action and leveling the aircraft and bringing it back to assigned altitude. The captain had been on a different aircraft prior to this and thought the autoplt would capture the altitude. This coupled with the fact he had not flown for approximately 1 month also contributed to this altitude incursion. In general I feel that pilots need to fly airplanes and not be led around by the autoflt systems. Complacency due to autoflt systems had let to a lack of proficiency and judgement ability when the situation needs both.

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Original NASA ASRS Text

Title: ACR LGT ALT DEVIATION OVERSHOT DURING DESCENT.

Narrative: DURING DSCNT INTO PITTSBURG, WE WERE CLRED TO 10,000 AND 250 KTS AT GRACE INTXN. THE CAPT WAS FLYING THE ACFT AND I WAS WORKING THE RADIOS AND CONDUCTING THE PNF DUTIES. THE CAPT HAD BEEN ON VACATION FOR APPROX 1 MONTH PREVIOUS TO THIS TRIP. AT 11,000' I CALLED OUT 11 FOR 10 AND SAID TO THE CAPT HIS DSCNT RATE WAS HIGH. HE REPLIED OK. HE HAD THE AUTOPLT SET TO LEVEL OFF AT 10,000' AND HE EXPECTED IT TO CAPTURE BUT I KNEW IT WOULD NOT BECAUSE OF HIS HIGH (5000 FPM) DSCNT RATE. AT 10,300' I AGAIN SAID 10,000 TO REMIND AND VERIFY WITH HIM THAT WE WERE REQUIRED TO STOP OUR DSCNT AT 10,000'. AT 10,000' IT WAS OBVIOUS TO ME THAT WE WERE NOT GOING TO STOP AT 10,000. THE CAPT THEN REALIZED THE AUTOPLT WAS NOT GOING TO LEVEL OFF SO HE DISENGAGED THE AUTOPLT AND STARTED TO PULL UP MANUALLY. I SAW THAT WE WERE GOING THROUGH 10,000 AND TOOK THE CONTROLS TO HELP PULL UP TO STOP OUR DSCNT. I FELT THIS WAS NECESSARY BECAUSE WE WERE GOING TO LEVEL OFF AT APPROX 9000' AND WE WERE IMC. THE CAPT YELLED 'WHAT ARE YOU DOING' AND I SAID 'TEN THOUSAND' AS I PULLED UP. AT THAT POINT I FELT HE HAD CONTROL AGAIN SO I LET GO AND THE ACFT CONTINUED TO DSND AND PITCHED DOWN AGAIN LOOSING MORE ALT. AT THAT POINT I AGAIN ASSISTED BY PULLING UP AGAIN ON THE YOKE UNTIL THE ACFT LEVELED OFF AT 9600' AND STARTED TO CLIMB BACK TO 10,000'. I FEEL THE CAPT SHOULD HAVE TAKEN MORE AGGRESSIVE ACTION TO STOP THE DSCNT RATE. PEOPLE FLYING PAX FORGET THAT BEING SMOOTH ON THE CTLS HAS A TIME AND PLACE AND IT IS NOT WHEN YOU'RE GOING THROUGH ASSIGNED ALT IN IMC CONDITIONS. I FLY AEROBATIC ACFT FOR PLEASURE AND COMPETITION AND I AM A RATED INSTRUCTOR. I AM FAMILIAR WITH G-LOADS AND THE CONSEQUENCES ASSOCIATED WITH THEM. THE G-LOAD I USED TO LEVEL THE ACFT WAS NOWHERE NEAR THE LIMIT OF THE ACFT. THE FASTEN SEATBELT SIGN HAD BEEN ON FOR AT LEAST 5 MINUTES (SINCE 18,000') AND THE F/A'S HAD BEEN ALERTED FOR LNDG. I FEEL THE FAILURE OF THE CAPT TO RECOGNIZE HIS HIGH SINK RATE AND FAILURE TO TAKE ACTION IMMEDIATELY CAUSED THE ALT INCURSION. THIS RESULTED IN MY TAKING ACTION AND LEVELING THE ACFT AND BRINGING IT BACK TO ASSIGNED ALT. THE CAPT HAD BEEN ON A DIFFERENT ACFT PRIOR TO THIS AND THOUGHT THE AUTOPLT WOULD CAPTURE THE ALT. THIS COUPLED WITH THE FACT HE HAD NOT FLOWN FOR APPROX 1 MONTH ALSO CONTRIBUTED TO THIS ALT INCURSION. IN GENERAL I FEEL THAT PLTS NEED TO FLY AIRPLANES AND NOT BE LED AROUND BY THE AUTOFLT SYSTEMS. COMPLACENCY DUE TO AUTOFLT SYSTEMS HAD LET TO A LACK OF PROFICIENCY AND JUDGEMENT ABILITY WHEN THE SITUATION NEEDS BOTH.

Data retrieved from NASA's ASRS site as of August 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.