B727 flight crew has altitude deviation when autoplt disengaged to re-trim aircraft and not reengage...

Attributes
ACN	335130
Time
Date	199605
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lit
State Reference	AR
Altitude	msl bound lower : 30600 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 2000
ASRS Report	335130
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : far non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At cruise altitude (FL310) on long flight, center controller stated that it appeared we were 400 ft low. Indeed we were at 30600 ft. Captain (PF) disengaged autoplt and climbed back to assigned altitude. Captain had recently disengaged autoplt to re- trim aircraft and apparently did not reengage altitude hold mode and none of us caught it. Two main contributing factors were 1) apparently none of the three crew members were monitoring flight instruments closely and, 2) company policy and procedure is to verbally announce any change to autoplt mode. This did not happen, but if followed could have drawn my attention to autoplt control panel where it would have been obvious that the altitude hold was not engaged.

Original NASA ASRS Text

Title: B727 FLC HAS ALTDEV WHEN AUTOPLT DISENGAGED TO RE-TRIM ACFT AND NOT REENGAGED.

Narrative: AT CRUISE ALT (FL310) ON LONG FLT, CTR CTLR STATED THAT IT APPEARED WE WERE 400 FT LOW. INDEED WE WERE AT 30600 FT. CAPT (PF) DISENGAGED AUTOPLT AND CLBED BACK TO ASSIGNED ALT. CAPT HAD RECENTLY DISENGAGED AUTOPLT TO RE- TRIM ACFT AND APPARENTLY DID NOT REENGAGE ALT HOLD MODE AND NONE OF US CAUGHT IT. TWO MAIN CONTRIBUTING FACTORS WERE 1) APPARENTLY NONE OF THE THREE CREW MEMBERS WERE MONITORING FLT INSTS CLOSELY AND, 2) COMPANY POLICY AND PROC IS TO VERBALLY ANNOUNCE ANY CHANGE TO AUTOPLT MODE. THIS DID NOT HAPPEN, BUT IF FOLLOWED COULD HAVE DRAWN MY ATTN TO AUTOPLT CTL PANEL WHERE IT WOULD HAVE BEEN OBVIOUS THAT THE ALT HOLD WAS NOT ENGAGED.

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.

B727 flight crew has altitude deviation when autoplt disengaged to re-trim aircraft and not reengaged.