Flight crew deviates from assigned altitude.

Attributes
ACN	309960
Time
Date	199506
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : bae
State Reference	WI
Altitude	msl bound lower : 34600 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau tower : sat
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : on vectors enroute airway : zau
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 180 flight time total : 10000 flight time type : 600
ASRS Report	309960
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

First officer was flying level at FL350. Aircraft was on autoplt with altitude hold. The first officer kicked off the autoplt to retrim the airplane. I watched his trimming and he turned the autoplt back on. He left the altitude hold switch off. I noticed that, but I also saw he was 100 ft high. Assuming he was descending to level at FL350, I turned my attention back to the PA I was going to make. My so was busy with an ACARS message. My PA was finished and ATC called to ask if we were level at 35000 ft. I looked up to see that we were at 34600 ft and quickly noticed that the altitude hold green light was not on. The first officer quickly corrected his mistake and climbed us to FL350 and engaged altitude hold. He said he forgot the switch after trimming the aircraft. It is another case of '1 step at a time' or 'complete 1 task first, before starting another.' I should not have assumed he (first officer) would re-engage altitude hold.

Original NASA ASRS Text

Title: FLC DEVIATES FROM ASSIGNED ALT.

Narrative: FO WAS FLYING LEVEL AT FL350. ACFT WAS ON AUTOPLT WITH ALT HOLD. THE FO KICKED OFF THE AUTOPLT TO RETRIM THE AIRPLANE. I WATCHED HIS TRIMMING AND HE TURNED THE AUTOPLT BACK ON. HE LEFT THE ALT HOLD SWITCH OFF. I NOTICED THAT, BUT I ALSO SAW HE WAS 100 FT HIGH. ASSUMING HE WAS DSNDING TO LEVEL AT FL350, I TURNED MY ATTN BACK TO THE PA I WAS GOING TO MAKE. MY SO WAS BUSY WITH AN ACARS MESSAGE. MY PA WAS FINISHED AND ATC CALLED TO ASK IF WE WERE LEVEL AT 35000 FT. I LOOKED UP TO SEE THAT WE WERE AT 34600 FT AND QUICKLY NOTICED THAT THE ALT HOLD GREEN LIGHT WAS NOT ON. THE FO QUICKLY CORRECTED HIS MISTAKE AND CLBED US TO FL350 AND ENGAGED ALT HOLD. HE SAID HE FORGOT THE SWITCH AFTER TRIMMING THE ACFT. IT IS ANOTHER CASE OF '1 STEP AT A TIME' OR 'COMPLETE 1 TASK FIRST, BEFORE STARTING ANOTHER.' I SHOULD NOT HAVE ASSUMED HE (FO) WOULD RE-ENGAGE ALT HOLD.

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.