Altitude deviation altitude excursion -- aircraft equipment problem -- air carrier flight crew did not take timely action when the autoflt system malfunctioned and this allowed the aircraft to climb 800 ft above the assigned altitude.

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Attributes
ACN	314163
Time
Date	199508
Day	Sun
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : egl
State Reference	FO
Altitude	msl bound lower : 35000 msl bound upper : 35800
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : eggx
Operator	common carrier : air carrier
Make Model Name	B747-100
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : atlantic enroute airway : eggx
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 210 flight time total : 10540 flight time type : 750
ASRS Report	314163
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Automatic stabilizer trim B warning light illuminated, followed by autoplt B disengaging and nose pitchup. Aircraft climbed 800 ft (35800 ft) -- recovered back to cleared altitude (FL350) immediately. Callback conversation with reporter revealed the following information: this so was on a B747-100 on a night, overwater flight when the event occurred. He said that the most disturbing aspect of the experience was the length of time that it took the pilots to react to the excursion. The so did not regard the event as an upset though he did agree that it was uncommanded. The so recommended that pilots be trained to be more aggressive toward maintaining control of the aircraft. They should have acted more swiftly.

Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION -- ACFT EQUIP PROB -- ACR FLC DID NOT TAKE TIMELY ACTION WHEN THE AUTOFLT SYS MALFUNCTIONED AND THIS ALLOWED THE ACFT TO CLB 800 FT ABOVE THE ASSIGNED ALT.

Narrative: AUTO STABILIZER TRIM B WARNING LIGHT ILLUMINATED, FOLLOWED BY AUTOPLT B DISENGAGING AND NOSE PITCHUP. ACFT CLBED 800 FT (35800 FT) -- RECOVERED BACK TO CLRED ALT (FL350) IMMEDIATELY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS SO WAS ON A B747-100 ON A NIGHT, OVERWATER FLT WHEN THE EVENT OCCURRED. HE SAID THAT THE MOST DISTURBING ASPECT OF THE EXPERIENCE WAS THE LENGTH OF TIME THAT IT TOOK THE PLTS TO REACT TO THE EXCURSION. THE SO DID NOT REGARD THE EVENT AS AN UPSET THOUGH HE DID AGREE THAT IT WAS UNCOMMANDED. THE SO RECOMMENDED THAT PLTS BE TRAINED TO BE MORE AGGRESSIVE TOWARD MAINTAINING CTL OF THE ACFT. THEY SHOULD HAVE ACTED MORE SWIFTLY.

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.