Descending with autoplt temporarily deactivated and speed brakes extended to facilitate a speed reduction during descent, the pilot elects to re-establish the autoplt, but finds the ensuing leveloff at the assigned altitude is beyond its capability. The result is an altitude overshoot.

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Attributes
ACN	524070
Time
Date	200109
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	intersection : sweet
State Reference	NJ
Altitude	msl bound lower : 6400 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach
Route In Use	arrival star : williams port
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 100 flight time total : 2740 flight time type : 360
ASRS Report	524070
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

The flight we were working was en route to ewr. The first officer was the PF. During the williamsport 1 arrival, while descending to cross sweet intersection at 7000 ft, the first officer had the autoplt engaged. Descending through 9000 ft (approximately), ATC asked us to reduce speed from 250 KTS to 210 KTS while descending. The first officer decided to use the speed brakes, with the autoplt still on. He then decided to temporarily disengage the autoplt to smooth the descent. I (the captain, PNF) was monitoring the descent progress while calling operations. 7000 ft was set in the altitude select. Approaching 7000 ft, with a descent rate of approximately 2500 FPM, the first officer released the button and the autoplt passed through 7000 ft. He (the first officer) retracted the speed brakes, and when I finally looked up a few seconds later, I observed 6400 ft on the altimeter. I immediately challenged him and simultaneously pulled back to initiate a climb. The autoplt was then disengaged completely and aircraft was hand flown to altitude.

Original NASA ASRS Text

Title: DSNDING WITH AUTOPLT TEMPORARILY DEACTIVATED AND SPD BRAKES EXTENDED TO FACILITATE A SPD REDUCTION DURING DSCNT, THE PLT ELECTS TO RE-ESTABLISH THE AUTOPLT, BUT FINDS THE ENSUING LEVELOFF AT THE ASSIGNED ALT IS BEYOND ITS CAPABILITY. THE RESULT IS AN ALT OVERSHOOT.

Narrative: THE FLT WE WERE WORKING WAS ENRTE TO EWR. THE FO WAS THE PF. DURING THE WILLIAMSPORT 1 ARR, WHILE DSNDING TO CROSS SWEET INTXN AT 7000 FT, THE FO HAD THE AUTOPLT ENGAGED. DSNDING THROUGH 9000 FT (APPROX), ATC ASKED US TO REDUCE SPD FROM 250 KTS TO 210 KTS WHILE DSNDING. THE FO DECIDED TO USE THE SPD BRAKES, WITH THE AUTOPLT STILL ON. HE THEN DECIDED TO TEMPORARILY DISENGAGE THE AUTOPLT TO SMOOTH THE DSCNT. I (THE CAPT, PNF) WAS MONITORING THE DSCNT PROGRESS WHILE CALLING OPS. 7000 FT WAS SET IN THE ALT SELECT. APCHING 7000 FT, WITH A DSCNT RATE OF APPROX 2500 FPM, THE FO RELEASED THE BUTTON AND THE AUTOPLT PASSED THROUGH 7000 FT. HE (THE FO) RETRACTED THE SPD BRAKES, AND WHEN I FINALLY LOOKED UP A FEW SECONDS LATER, I OBSERVED 6400 FT ON THE ALTIMETER. I IMMEDIATELY CHALLENGED HIM AND SIMULTANEOUSLY PULLED BACK TO INITIATE A CLB. THE AUTOPLT WAS THEN DISENGAGED COMPLETELY AND ACFT WAS HAND FLOWN TO ALT.

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.