Narrative:

At approximately XA40Z near krena intersection on V100 west of obk VOR, I had an altitude deviation. I had been cleared to descend to 11000 ft from FL230. I was flying the airplane on the autoplt. Out of 12000 ft, our TCASII gave a TA, an inbound B737 into ord. This traffic was maintaining 10000 ft and was approaching us on a 1 O'clock to 7 O'clock path. My co-captain got a visual on the traffic and I rolled in some nose-up trim to slow our vertical closure with the traffic. This was my first mistake. As the boeing passed in front of us and off our left side and I took my attention off the flight director and observed it (mistake #2), as I looked back at the EFIS I saw the flight director had not captured 11000 ft and was continuing our descent. I disengaged the autoplt and pitched up. We descended to about 10700 ft and were probably 2 or 3 mi behind the B737. As we returned to 11000 ft, center asked for a verification of our altitude. This was very embarrassing and humbling and could have easily had very serious consequences. In hindsight, there were several human factors. First, was my failure to use the proper technique in applying trim when the airplane is being flown by the flight director. Every airplane I have flown will disconnect altitude capture if you manually trim while the flight director is trying to capture an altitude. Why I did this and didn't see the annunciation that I had lost altitude capture is a mystery to me. This is one 'gotcha' that won't bite me in the future. My second mistake was to avert my attention from my airplane and a failure to closely monitor the autoplt's flying. I violated the cardinal rule of a pilot -- 'fly your airplane.' if I had been watching my instruments instead of the B737, I would have noticed our airplane was not going to level off at 11000 ft and could have taken appropriate and timely actions to do so. Personally, this failure is the most damning and shows a breakdown of personal discipline, something I have always strived for. It has caused a self-examination of my flying habits, priorities and judgement. I feel pretty badly about this incident and the areas where I was deficient. I pledge to do much better in the future.

Related reports:

Google
 

Original NASA ASRS Text

Title: A CPR JET, DSNDING, OVERSHOT ITS ASSIGNED ALT WHEN DISTR BY PASSING TFC. THE ALT CAPTURE WAS NULLIFIED BY THE CAPT'S MISUSE OF THE ACFT'S HORIZ STABILIZER'S TRIM WHEEL.

Narrative: AT APPROX XA40Z NEAR KRENA INTXN ON V100 W OF OBK VOR, I HAD AN ALTDEV. I HAD BEEN CLRED TO DSND TO 11000 FT FROM FL230. I WAS FLYING THE AIRPLANE ON THE AUTOPLT. OUT OF 12000 FT, OUR TCASII GAVE A TA, AN INBOUND B737 INTO ORD. THIS TFC WAS MAINTAINING 10000 FT AND WAS APCHING US ON A 1 O'CLOCK TO 7 O'CLOCK PATH. MY CO-CAPT GOT A VISUAL ON THE TFC AND I ROLLED IN SOME NOSE-UP TRIM TO SLOW OUR VERT CLOSURE WITH THE TFC. THIS WAS MY FIRST MISTAKE. AS THE BOEING PASSED IN FRONT OF US AND OFF OUR L SIDE AND I TOOK MY ATTN OFF THE FLT DIRECTOR AND OBSERVED IT (MISTAKE #2), AS I LOOKED BACK AT THE EFIS I SAW THE FLT DIRECTOR HAD NOT CAPTURED 11000 FT AND WAS CONTINUING OUR DSCNT. I DISENGAGED THE AUTOPLT AND PITCHED UP. WE DSNDED TO ABOUT 10700 FT AND WERE PROBABLY 2 OR 3 MI BEHIND THE B737. AS WE RETURNED TO 11000 FT, CTR ASKED FOR A VERIFICATION OF OUR ALT. THIS WAS VERY EMBARRASSING AND HUMBLING AND COULD HAVE EASILY HAD VERY SERIOUS CONSEQUENCES. IN HINDSIGHT, THERE WERE SEVERAL HUMAN FACTORS. FIRST, WAS MY FAILURE TO USE THE PROPER TECHNIQUE IN APPLYING TRIM WHEN THE AIRPLANE IS BEING FLOWN BY THE FLT DIRECTOR. EVERY AIRPLANE I HAVE FLOWN WILL DISCONNECT ALT CAPTURE IF YOU MANUALLY TRIM WHILE THE FLT DIRECTOR IS TRYING TO CAPTURE AN ALT. WHY I DID THIS AND DIDN'T SEE THE ANNUNCIATION THAT I HAD LOST ALT CAPTURE IS A MYSTERY TO ME. THIS IS ONE 'GOTCHA' THAT WON'T BITE ME IN THE FUTURE. MY SECOND MISTAKE WAS TO AVERT MY ATTN FROM MY AIRPLANE AND A FAILURE TO CLOSELY MONITOR THE AUTOPLT'S FLYING. I VIOLATED THE CARDINAL RULE OF A PLT -- 'FLY YOUR AIRPLANE.' IF I HAD BEEN WATCHING MY INSTS INSTEAD OF THE B737, I WOULD HAVE NOTICED OUR AIRPLANE WAS NOT GOING TO LEVEL OFF AT 11000 FT AND COULD HAVE TAKEN APPROPRIATE AND TIMELY ACTIONS TO DO SO. PERSONALLY, THIS FAILURE IS THE MOST DAMNING AND SHOWS A BREAKDOWN OF PERSONAL DISCIPLINE, SOMETHING I HAVE ALWAYS STRIVED FOR. IT HAS CAUSED A SELF-EXAM OF MY FLYING HABITS, PRIORITIES AND JUDGEMENT. I FEEL PRETTY BADLY ABOUT THIS INCIDENT AND THE AREAS WHERE I WAS DEFICIENT. I PLEDGE TO DO MUCH BETTER IN THE FUTURE.

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.