<< >> NASA ASRS Report 665968, July 2005

An A300 in the profile descent mode indicated proper FMA altitude capture annunciations; but failed to capture the programmed altitude.

Attributes
ACN	665968
Time
Date	200507
Local Time Of Day	0001 To 0600
Place
Locale Reference	navaid : zzz.vor
State Reference	US
Altitude	msl bound lower : 23600 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	A300
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Route In Use	arrival star : zzzzz
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp pilot : cfi
Experience	flight time last 90 days : 30 flight time total : 1200 flight time type : 600
ASRS Report	665968
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

On arrival to ZZZ; on xxxxx arrival. First officer was flying. Cleared to descend to FL240; aircraft was in profile descent mode. Captain was reviewing arrival chart when altitude deviation warning went off. I (captain) looked away from chart to see aircraft was now at FL236. First officer; who was flying; was looking down at his chart. I immediately took control of aircraft; clicked autoplt off; and climbed back up to FL240. Approach didn't say anything and event was over within 5 to 10 seconds. Aircraft will always not perform properly while in profile mode. Complacency especially in profile mode should be avoided; especially prior to aircraft leveloff. Additional; crew was awake for approximately 24 hours at the time of event. Callback conversation with reporter revealed the following information: reporter stated that in this event both the MCP altitude set and the FMC contained FL240 as the constraining altitude. The aircraft was slightly past the constraint point and was attempting to meet the fix requirement but dropped the altitude for some unknown reason. The autoplt did not overspeed trying to meet the constraint.

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Original NASA ASRS Text

Title: AN A300 IN THE PROFILE DSCNT MODE INDICATED PROPER FMA ALT CAPTURE ANNUNCIATIONS; BUT FAILED TO CAPTURE THE PROGRAMMED ALT.

Narrative: ON ARR TO ZZZ; ON XXXXX ARR. FO WAS FLYING. CLRED TO DSND TO FL240; ACFT WAS IN PROFILE DSCNT MODE. CAPT WAS REVIEWING ARR CHART WHEN ALT DEV WARNING WENT OFF. I (CAPT) LOOKED AWAY FROM CHART TO SEE ACFT WAS NOW AT FL236. FO; WHO WAS FLYING; WAS LOOKING DOWN AT HIS CHART. I IMMEDIATELY TOOK CTL OF ACFT; CLICKED AUTOPLT OFF; AND CLBED BACK UP TO FL240. APCH DIDN'T SAY ANYTHING AND EVENT WAS OVER WITHIN 5 TO 10 SECONDS. ACFT WILL ALWAYS NOT PERFORM PROPERLY WHILE IN PROFILE MODE. COMPLACENCY ESPECIALLY IN PROFILE MODE SHOULD BE AVOIDED; ESPECIALLY PRIOR TO ACFT LEVELOFF. ADDITIONAL; CREW WAS AWAKE FOR APPROX 24 HRS AT THE TIME OF EVENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT IN THIS EVENT BOTH THE MCP ALT SET AND THE FMC CONTAINED FL240 AS THE CONSTRAINING ALT. THE ACFT WAS SLIGHTLY PAST THE CONSTRAINT POINT AND WAS ATTEMPTING TO MEET THE FIX REQUIREMENT BUT DROPPED THE ALT FOR SOME UNKNOWN REASON. THE AUTOPLT DID NOT OVERSPEED TRYING TO MEET THE CONSTRAINT.

Data retrieved from NASA's ASRS site as of January 2009 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.