Widebody transport flight crew inadvertently descended below and overshot assigned altitude.

Attributes
ACN	291611
Time
Date	199412
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : tag
State Reference	FO
Altitude	msl bound lower : 22800 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : rktt
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 120 flight time total : 8500
ASRS Report	291611
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	horizontal : 18000 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATC gave us an altitude change with a new heading and TA all at the same time. The altitude change was from FL250 to FL240. Please note both autothrottles and pms were inoperative/MEL for this flight. After I started my descent, and at FL228, I asked crew what was our altitude limit. I looked up to find a conflict with the awi setting. Crew stated altitude limit was FL240 and at this time, I started a climb back to FL240. ATC asked us what our altitude was, and captain said we were returning to FL240. ATC advised us of traffic and, at this point, we received an RA to descend. Captain and so had traffic so we climbed back to FL240. RA received at 23500 ft. For just a few seconds, as we leveled off, RA stopped. Normal flight after we returned to FL240.

Original NASA ASRS Text

Title: WDB FLC INADVERTENTLY DSNDED BELOW AND OVERSHOT ASSIGNED ALT.

Narrative: ATC GAVE US AN ALT CHANGE WITH A NEW HDG AND TA ALL AT THE SAME TIME. THE ALT CHANGE WAS FROM FL250 TO FL240. PLEASE NOTE BOTH AUTOTHROTTLES AND PMS WERE INOP/MEL FOR THIS FLT. AFTER I STARTED MY DSCNT, AND AT FL228, I ASKED CREW WHAT WAS OUR ALT LIMIT. I LOOKED UP TO FIND A CONFLICT WITH THE AWI SETTING. CREW STATED ALT LIMIT WAS FL240 AND AT THIS TIME, I STARTED A CLB BACK TO FL240. ATC ASKED US WHAT OUR ALT WAS, AND CAPT SAID WE WERE RETURNING TO FL240. ATC ADVISED US OF TFC AND, AT THIS POINT, WE RECEIVED AN RA TO DSND. CAPT AND SO HAD TFC SO WE CLBED BACK TO FL240. RA RECEIVED AT 23500 FT. FOR JUST A FEW SECONDS, AS WE LEVELED OFF, RA STOPPED. NORMAL FLT AFTER WE RETURNED TO FL240.

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.