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A
747-400 MAINTENANCE MANUAL
 TASK 31-41-00-315-167
 4. Weight and Balance System - Calibration (Alternative)
_____________________________________________________
 A. General
 (1)  
Use this procedure as an alternative method to calibrate the weight and balance system after landing gear replacement or overhaul. Steps in this procedure are the same as those in the Weight and Balance System - Calibration (Recommended). The step sequence is the only difference. This step sequence puts the load sensor zero value calibration done with an airplane flight after the data is collected. After this flight, you must complete the calibration before nine more flights occur.

 (2)  
During the calibration procedure you will collect data, calculate calibration data, and put the calibration data into the calibration module. You will also make a written record of the calibration data.

 (3)  
First, you must do the zero adjustment on jacks.

 (4)  
You will then collect four sets of data from the scales and the WBC.

 (a)  You will collect wheel weights from the scales and sensor counts from the WBC. Each time you read the weight on a wheel, you must read the counts for the adjacent load sensor at the same time.
 NOTE: Wheel weights must be recorded in pounds (lbs.).
____
 NOTE: Counts are values retrieved from the 16-bit A to D
____ converter in the WBC. Counts have a range of 0 to 65535.
 (b)  The first, third, and fourth sets of data are collected at normal strut pressures. The second set of data is collected at low wing landing gear strut pressures. Between the third and fourth sets of data, you will decrease and then increase the strut pressures of the body landing gear to prepare the WBC for the fourth data collection.
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747-400
MAINTENANCE MANUAL

 (5)  
Then, you will find the zero values for the load sensors. To find the zero values, you must set the WBC to 100% autozero mode, let the airplane make at least one flight, and then read the zero values.

 (6)  
From the zero values and the four sets of data you will calculate the span and offset values for each load sensor.

 (7)  
You will use the WBC to read the load sensor resistance values. (The WBC uses resistance data to correct for temperature variation.)

 (8)  
You will use the WBC to put this data into the calibration module:

 (a)  
The calculated span and offset values.

 (b)  
The load sensor resistance values.

 (9)  
You will do a check to make sure that the calibration is correct. Finally, you will make a written record of the calibration data.

 (10)
 A software calibration procedure with instructions is available directly from Honeywell. This procedure lets you record and calculate calibration data automatically. You can also keep the data for each airplane in a digital format. Speak to the Honeywell Customer Support Engineering Representative for the Weight and Balance System to get this procedure.

 B. Equipment
 (1)  Airplane Scales that can measure individual wheel weights
 C. References
 (1)  
AMM 09-11-00/201, Towing

 (2)  
AMM 12-15-03/301, Wing Landing Gear Shock Strut Servicing

 (3)  
AMM 12-15-04/301, Body Landing Gear Shock Strut Servicing

 (4)  
AMM 12-15-05/301, Nose Landing Gear Shock Strut Servicing

 (5)  
AMM 24-22-00/201, Manual Control (Apply Power)

 (6)  
AMM 27-51-00/201, Trailing Edge Flap System

 (7)  
AMM 27-81-00/201, Leading Edge Flap System

 (8)  
AMM 28-26-00/201, Defueling

 (9)  
AMM 29-11-00/201, Main Hydraulic Supply System

 (10)
 AMM 32-00-30/201, Landing Gear Door Locks

 (11)
 AMM 32-11-20/401, Wing Gear Positioning Actuator

 D. Access
 (1)  Location Zones
 118 Electrical and Electronics Compartment, RH
　
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