Procedures are laid down on how to statistically determine weights for passengers and baggage. These procedures are published by IATA/ICAO and JAR OPS.
They produce weights that fall within a 2% confidence range for passengers and 1% confidence range for bags.
This effectively means that the actual weight of every bag on your aircraft is likely to be at the standard weight or somewhere between -1% and +1% of the standard weight.
The same applies to passenger weights.
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{If as you say your weights mean a big diffence between actual/atandard then you company has a problem! Do you notice performace deviations to justify this? Green dot speeds and altitudes not being attained?}
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Which means that the figures you see on the loadsheet for passengers and baggage are about as accurate as you can get (without weighing everyone and each bag separately)which still happens on small aircraft.
Figures differ carrier by carrier if they elect to survey their own passengers/baggage as opposed to adopting those figures presecried by their CAA/DGCA.
However, a carrier must adopt only one set of figures for use on all its flights and cannot mix actual/standard weights on a flight. Special circumstances may void standard weights such as large gruops of particualr traffic - military/sports people etc.
Dont forget that the SG of your fuel will and does differ day by day region by region, yet the loadsheet will probably be based on 0.8kg/L only and this will mean the weight shown is correct, however due to increased volume or decreased volume of the fuel in tanks your trim data will perhaps not be as accurate as possible.
Some EDP systems have multiple fuel tables for other then your elected standard SG and can get round this (most dont!) and manual documents will be based on only one SG.
The only thing you guys need to worry about is the competence of the guy and/or system calculating the weight and balance.
[This message has been edited by Icarus (edited 11 January 2001).]