Air carrier DC10 flight crew descends below assigned altitude reporting equipment and cabin distrs.

Attributes
ACN	422290
Time
Date	199812
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : vkz
State Reference	FL
Altitude	msl bound lower : 19700 msl bound upper : 20000
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	422290
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

The autoplt was engaged and the altitude was armed for FL200 and the first officer was flying the leg. During the leveloff period just before FL200, a flight attendant reported a jet fuel odor in the lower galley. While addressing that problem, I noticed the autoplt was not leveling off at FL200 and advised the first officer who leveled the aircraft off at FL200. We first descended approximately 300 ft below FL200. I then noticed that although the altitude was still armed and set properly that the autoplt somehow was in the control wheel steering mode on the paddle switch. No response was given by center, so we believe the deviation was not alerted. Just the same, we are reporting for protection. The lesson here is that now we have to check that the autoplt did not enter a control wheel steering mode. A disconnect would be easier to notice with lights and aural warnings.

Original NASA ASRS Text

Title: ACR DC10 FLC DSNDS BELOW ASSIGNED ALT RPTING EQUIP AND CABIN DISTRS.

Narrative: THE AUTOPLT WAS ENGAGED AND THE ALT WAS ARMED FOR FL200 AND THE FO WAS FLYING THE LEG. DURING THE LEVELOFF PERIOD JUST BEFORE FL200, A FLT ATTENDANT RPTED A JET FUEL ODOR IN THE LOWER GALLEY. WHILE ADDRESSING THAT PROB, I NOTICED THE AUTOPLT WAS NOT LEVELING OFF AT FL200 AND ADVISED THE FO WHO LEVELED THE ACFT OFF AT FL200. WE FIRST DSNDED APPROX 300 FT BELOW FL200. I THEN NOTICED THAT ALTHOUGH THE ALT WAS STILL ARMED AND SET PROPERLY THAT THE AUTOPLT SOMEHOW WAS IN THE CTL WHEEL STEERING MODE ON THE PADDLE SWITCH. NO RESPONSE WAS GIVEN BY CTR, SO WE BELIEVE THE DEV WAS NOT ALERTED. JUST THE SAME, WE ARE RPTING FOR PROTECTION. THE LESSON HERE IS THAT NOW WE HAVE TO CHK THAT THE AUTOPLT DID NOT ENTER A CTL WHEEL STEERING MODE. A DISCONNECT WOULD BE EASIER TO NOTICE WITH LIGHTS AND AURAL WARNINGS.

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.