B747 crew had altitude overshoot in rctp class a airspace.

Attributes
ACN	487858
Time
Date	200010
Day	Tue
Local Time Of Day	1201 To 1800
Place
State Reference	FO
Altitude	msl bound lower : 34800 msl bound upper : 35000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B747-100
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Route In Use	enroute airway : a1.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : multi engine pilot : instrument
Experience	flight time last 90 days : 120 flight time total : 10000
ASRS Report	487858
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : multi engine pilot : instrument
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot conflict : airborne critical non adherence : clearance non adherence : published procedure
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude flight crew : took evasive action none taken : anomaly accepted
Miss Distance	horizontal : 30000 vertical : 1600
Supplementary
Problem Areas	Flight Crew Human Performance Company Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

As aircraft was descending from FL390 to FL350, the autoplt was slow to level off at FL350. At 200 ft above leveloff (FL352) the yoke was gently pulled back manually and power was added manually (autoplt and pms still engaged). Aircraft leveled at FL348.5 and climbed back to FL350 with slight back pressure applied to yoke with autoplt and pms still engaged. When back pressure was removed from yoke, aircraft stabilized straight and level for approximately 5 seconds at FL350. Aircraft then pitched rapidly nose down and descended before autoplt and pms could be disengaged and aircraft returned to FL350. 1 RA was received when aircraft pitched over (slow descent). In retrospect autoplt should have been disengaged when aircraft was slow to level at FL350. It is common practice, however, to help autoplt (manually) when it is slow to respond.

Original NASA ASRS Text

Title: B747 CREW HAD ALT OVERSHOOT IN RCTP CLASS A AIRSPACE.

Narrative: AS ACFT WAS DSNDING FROM FL390 TO FL350, THE AUTOPLT WAS SLOW TO LEVEL OFF AT FL350. AT 200 FT ABOVE LEVELOFF (FL352) THE YOKE WAS GENTLY PULLED BACK MANUALLY AND PWR WAS ADDED MANUALLY (AUTOPLT AND PMS STILL ENGAGED). ACFT LEVELED AT FL348.5 AND CLBED BACK TO FL350 WITH SLIGHT BACK PRESSURE APPLIED TO YOKE WITH AUTOPLT AND PMS STILL ENGAGED. WHEN BACK PRESSURE WAS REMOVED FROM YOKE, ACFT STABILIZED STRAIGHT AND LEVEL FOR APPROX 5 SECONDS AT FL350. ACFT THEN PITCHED RAPIDLY NOSE DOWN AND DSNDED BEFORE AUTOPLT AND PMS COULD BE DISENGAGED AND ACFT RETURNED TO FL350. 1 RA WAS RECEIVED WHEN ACFT PITCHED OVER (SLOW DSCNT). IN RETROSPECT AUTOPLT SHOULD HAVE BEEN DISENGAGED WHEN ACFT WAS SLOW TO LEVEL AT FL350. IT IS COMMON PRACTICE, HOWEVER, TO HELP AUTOPLT (MANUALLY) WHEN IT IS SLOW TO RESPOND.

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.