A B727 PIC allows the aircraft to descend out of assigned altitude of 11000 ft while on autoplt altitude hold during a large speed reduction 35 mi west of bos, ma.

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Attributes
ACN	486330
Time
Date	200009
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bos.airport
State Reference	MA
Altitude	msl bound lower : 10680 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : atp pilot : commercial technician : fcc
Experience	flight time last 90 days : 140 flight time total : 3600 flight time type : 940
ASRS Report	486330
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft Environmental Factor
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On arrival en route to bos, controller requested speed reduction of 100 KTS. Autoplt was engaged with altitude hold. During the reduction, the autoplt lost 320 ft of altitude. I had been distraction and did not catch the deviation until immediately after aircraft had descended. I disengaged the autoplt and returned to our assigned altitude. Upon leveling at 11000 ft, the controller issued a clearance to descend to 10000 ft. The controller did not mention that we had caused any problems, and I continued the arrival/approach without autoplt engaged. Contributing factors were: crew fatigue, large speed change, crew distraction. In the future, when I am issued large speed reductions, I will either hand fly the aircraft or closely monitor the autoplt and not let the other crew members distract my monitoring of the situation.

Original NASA ASRS Text

Title: A B727 PIC ALLOWS THE ACFT TO DSND OUT OF ASSIGNED ALT OF 11000 FT WHILE ON AUTOPLT ALT HOLD DURING A LARGE SPD REDUCTION 35 MI W OF BOS, MA.

Narrative: ON ARR ENRTE TO BOS, CTLR REQUESTED SPD REDUCTION OF 100 KTS. AUTOPLT WAS ENGAGED WITH ALT HOLD. DURING THE REDUCTION, THE AUTOPLT LOST 320 FT OF ALT. I HAD BEEN DISTR AND DID NOT CATCH THE DEV UNTIL IMMEDIATELY AFTER ACFT HAD DSNDED. I DISENGAGED THE AUTOPLT AND RETURNED TO OUR ASSIGNED ALT. UPON LEVELING AT 11000 FT, THE CTLR ISSUED A CLRNC TO DSND TO 10000 FT. THE CTLR DID NOT MENTION THAT WE HAD CAUSED ANY PROBS, AND I CONTINUED THE ARR/APCH WITHOUT AUTOPLT ENGAGED. CONTRIBUTING FACTORS WERE: CREW FATIGUE, LARGE SPD CHANGE, CREW DISTR. IN THE FUTURE, WHEN I AM ISSUED LARGE SPD REDUCTIONS, I WILL EITHER HAND FLY THE ACFT OR CLOSELY MONITOR THE AUTOPLT AND NOT LET THE OTHER CREW MEMBERS DISTRACT MY MONITORING OF THE SIT.

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.