Peter - Often, and at distances greater than 50 miles.
Don
Tac nets are usually assigned for each division. The criteria for establishing a division include: one, a size that allows the division supervisor to walk the perimeter in one day and two, being able to communicate on a simplex frequency with all the units on the division. Sometimes, due to the size of a fire and the availability of command resources, these objectives can't be met. In most cases, when additional resources arrive those objectives are then met.
During the Yellowstone fires of 1988, in spite of the 9600 firefighting personnel present, there weren't enough resources to staff divisions so everyone was starting to work at levels above their qualifications and divisions were too big to meet objectives explained above. This resulted in division supervisors handling some of the tasks of branch directors, strike team leaders performing as "sub division supervisors," and crew bosses making decisions normally made by strike team leaders. For example, my crew and I were sent inside the fire line to make it more fire resistant (covering it with old fire shelters and adjacent trees and fuel). The wind, smell of the smoke and my instincts told me the situation was tenuous and when fire behavior began to change I made a unilateral decision to pull out my crew out. I could not contact my strike team leader to pass along my observations or my decisions because I could reach anyone on tac net due to topography and distance. The division supervisor sent a Type I helicopter, brought in to make bucket drops on spot fires, to relay his direction to pull out and what route to travel with our bus, once we made the 2 mile trek back to it. I had already made these decisions without him due to the wind making a 180 degree shift and not being able to raise anyone on tac net. I did this not knowing the behavior and location of the fire in other portions of the division. I had already sized up my area and knew where my safety zone was going to be if I needed it, but I could not give the bus driver, who was sitting in the bus, any direction because we didn't have enough radios to provide bus drivers with them. By the way we lost the division and had a "little" slopover fire of 27,000 acres that afternoon, but when the size of the fire exceeding 400,000 acres at the time, this was just a little fire across the line!
The size of divisions, difficulties with tac net and stretching the qualifications of supervisory personnel was known and discussed at briefings, but resource utilization on the national level had exhausted the supply of them. The 1988 northern Rockies fire situation was very unusual and this is the only time I encountered this type of situation. I don't think any injuries resulted due to this situation as everyone really stepped up to the plate and handled it. However, at times fire behavior was such that it was sufficient to make some young men a little incontinent!
I hope this provides some insight on how tac nets are affected by topography and the design of the command structure.
***EDIT*** I don't think the Yellowstone situation would be allowed currently. The protocol of LCES (lookouts, communications, escape routes and safety zones) that requires documentation prior to deployment governs now. In my Yellowstone situation a person relaying traffic for us should have been provided at a location where someone could act as a human repeater and lookout. I don't recall if a safety zone and escape route had been discussed that day but it was pretty clear to me what those would be when I arrived, even though the escape route for the bus was real sketchy .
