A few things to keep in mind ..
(a) it is not difficult to automate the drawing of a trimsheet providing that you have some programming skills but why bother ? -
(i) the numbers can be generated very quickly in a spreadsheet
(ii) you can modify an existing sheet in a drawing package without too much effort
(iii) once the sheet is drawn, it doesn't need to be revised unless the configuration changes
(b) any loading calculation (manual, computer, trimsheet, whatever) is only as good as the data and care which go into its completion. We have all seen trimsheets presented with errors. It follows that any sensible system (from a pilot viewpoint) involves a pilot check at the end of the chain ....
Probably the best system I have seen for trimsheets was based on a circular trimsheet (looked a bit like a nav computer). Originally, I was sceptical about the presentation but the customer insisted .. after seeing it in action I was convinced of the value. Completing the calculation took only a few seconds. This operator's procedure was to have the load folk do the loading and prepare the documentation. Then the flight crew would do a recheck with one pilot reviewing the loadsheet data while the other ran the prayer wheel to check the trim. Near foolproof system.
However you do it loading is pretty critical. If the system doesn't have appropriate checks and balances then it is set up for a fright or two along the way. If the system's checks don't involve the crew .. then, if I were crew, I'd involve myself at the end regardless ..
(c) So far as the number of loading zones is concerned it really doesn't stop the careless person from running the trimsheet incorrectly. The ideal sheet is simple to use and a good balance of flexibility and speed. But, at the end of the day, it is very difficult to keep the idiot factor totally at bay. Concerning accuracy, a well designed trimsheet is as accurate as a longhand calculation for practical purposes .. but it does require appropriate technical care in the execution ... which also needs those using the system to have a reasonable idea of its requirements and limitations.
Last edited by john_tullamarine; 21st Dec 2005 at 21:42.