OverRun et al,
First of all thanks for all the feed back on this.
If I can clarify the situation a little:
When I'm asked to do an assessment, it is more often than not to try to get an overall picture of the capacity of the airport/airfield in the event that we may need to use it, i.e. its not that we're scheduling an imminent arrival.
The aircraft selected in the event that we do need to use it will be based on the assessment. We have had an instance in the past (before my time...) where an a/c has sat on the ramp for three days because the required unloading equipment wasn't available.
I can't give specific examples of local terminology, but I'm trying to get an overall view on how this is assessed and how I might extract relevant data from officialdom.
Sorry if this is a little vague but I'm not a pro! I was tossed into this at the deep end...
Cheers to all