Flight crew descends through assigned altitude.

Attributes
ACN	314331
Time
Date	199508
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mkg
State Reference	MI
Altitude	msl bound lower : 22300 msl bound upper : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 180 flight time total : 18000 flight time type : 500
ASRS Report	314331
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 220 flight time total : 8000 flight time type : 400
ASRS Report	314494
Events
Anomaly	altitude deviation : overshoot non adherence : clearance non adherence : far
Independent Detector	other flight crewa
Resolutory Action	other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared to FL230, to be level by giber, which was approximately 20 ahead and we were at FL280. The first officer was flying, after the descent started and the altitude capture mode armed, I told the first officer and flight engineer I would make the last PA to the passenger. When I got done with the PA we were descending through FL240 and the first officer told me we were cleared direct to polar. We were using the #1 INS and #1 autoplt because the #2 autoplt was inoperative. So I had to verify the polar coordinates on the #1 INS. I was doing this and noticed we were going through FL230. I inquired about the altitude, thinking we may have been cleared lower than FL230. The first officer said no, it's FL230 and took the autoplt off at about FL225 and bottomed out at FL223. Climbed back up to FL230. There was no conflict with any other traffic and center didn't mention it at all. During the time we were going through FL230 there was a frequency change also. The reason we went through the set altitude, I believe, is because we descended at a high rate of descent, 3500 FPM, to make the restr. I think the first officer changed the vertical speed to help the autoplt level off but it had captured the altitude just prior to him doing that so when he changed the vertical speed that put the autoplt in a vertical speed mode and just continued down at a lesser rate of descent.

Original NASA ASRS Text

Title: FLC DSNDS THROUGH ASSIGNED ALT.

Narrative: WE WERE CLRED TO FL230, TO BE LEVEL BY GIBER, WHICH WAS APPROX 20 AHEAD AND WE WERE AT FL280. THE FO WAS FLYING, AFTER THE DSCNT STARTED AND THE ALT CAPTURE MODE ARMED, I TOLD THE FO AND FE I WOULD MAKE THE LAST PA TO THE PAX. WHEN I GOT DONE WITH THE PA WE WERE DSNDING THROUGH FL240 AND THE FO TOLD ME WE WERE CLRED DIRECT TO POLAR. WE WERE USING THE #1 INS AND #1 AUTOPLT BECAUSE THE #2 AUTOPLT WAS INOP. SO I HAD TO VERIFY THE POLAR COORDINATES ON THE #1 INS. I WAS DOING THIS AND NOTICED WE WERE GOING THROUGH FL230. I INQUIRED ABOUT THE ALT, THINKING WE MAY HAVE BEEN CLRED LOWER THAN FL230. THE FO SAID NO, IT'S FL230 AND TOOK THE AUTOPLT OFF AT ABOUT FL225 AND BOTTOMED OUT AT FL223. CLBED BACK UP TO FL230. THERE WAS NO CONFLICT WITH ANY OTHER TFC AND CTR DIDN'T MENTION IT AT ALL. DURING THE TIME WE WERE GOING THROUGH FL230 THERE WAS A FREQ CHANGE ALSO. THE REASON WE WENT THROUGH THE SET ALT, I BELIEVE, IS BECAUSE WE DSNDED AT A HIGH RATE OF DSCNT, 3500 FPM, TO MAKE THE RESTR. I THINK THE FO CHANGED THE VERT SPD TO HELP THE AUTOPLT LEVEL OFF BUT IT HAD CAPTURED THE ALT JUST PRIOR TO HIM DOING THAT SO WHEN HE CHANGED THE VERT SPD THAT PUT THE AUTOPLT IN A VERT SPD MODE AND JUST CONTINUED DOWN AT A LESSER RATE OF DSCNT.

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.