When a component fails, ACARA estimates the delay until it is replaced with a spare. If a spare is immediately available at the site, the component will be replaced as soon as other conditions allow (e.g., available manpower). If no spare is available, ACARA will determine when one can be delivered, based on the following user-specified inputs:

• Period between deliveries of spares
  
  
• Resupply cutoff time required to order replacement
  
  
• Hardware production schedule
  
  
• Constraints on resources (e.g., delivery vehicle capacity)
  
  

Once these restrictions allow the component to be replaced, ACARA will determine the time-to-replace, and then estimate total downtime.