<< >> NASA ASRS Report 433914, April 1999

A B737-400 required excessive trim for takeoff and landing due to a weight and balance computer error.

Attributes
ACN	433914
Time
Date	199904
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : pit.airport
State Reference	PA
Altitude	agl bound lower : 0 agl bound upper : 100
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : pit.tower tower : mco.tower
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	climbout : takeoff descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	other personnel
Qualification	other
ASRS Report	433914
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem none taken : detected after the fact
Consequence	other
Supplementary
Problem Areas	Company
Primary Problem	Company
Situations
Publication	Operations Manual

Narrative:

Stabilizer trim for computerized weight and balance data showed 3.9. Captain advised dispatcher had to use 8.5 units of trim to get aircraft airborne -- 6.2 units of trim for landing. Cargo distribution was verified by arrival station personnel. Problem may be with new computer system and the procedure used for seat assignments of passenger. Operations engineering to be advised of this problem. Callback conversation with reporter revealed the following information: the reporter stated this computer problem of calculating the wrong aircraft trim has occurred several times and is being corrected. The reporter said the computer is supposed to assign seats to balance the aircraft but instead randomly assigned seats that when used in the trim calculation caused a large error.

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Original NASA ASRS Text

Title: A B737-400 REQUIRED EXCESSIVE TRIM FOR TKOF AND LNDG DUE TO A WT AND BAL COMPUTER ERROR.

Narrative: STABILIZER TRIM FOR COMPUTERIZED WT AND BAL DATA SHOWED 3.9. CAPT ADVISED DISPATCHER HAD TO USE 8.5 UNITS OF TRIM TO GET ACFT AIRBORNE -- 6.2 UNITS OF TRIM FOR LNDG. CARGO DISTRIBUTION WAS VERIFIED BY ARR STATION PERSONNEL. PROB MAY BE WITH NEW COMPUTER SYS AND THE PROC USED FOR SEAT ASSIGNMENTS OF PAX. OPS ENGINEERING TO BE ADVISED OF THIS PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THIS COMPUTER PROB OF CALCULATING THE WRONG ACFT TRIM HAS OCCURRED SEVERAL TIMES AND IS BEING CORRECTED. THE RPTR SAID THE COMPUTER IS SUPPOSED TO ASSIGN SEATS TO BAL THE ACFT BUT INSTEAD RANDOMLY ASSIGNED SEATS THAT WHEN USED IN THE TRIM CALCULATION CAUSED A LARGE ERROR.

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.