VictorInThePacific
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Joined: 10/30/2008
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Warning: This gets into hardcore logistic details 
All aircraft have a basic range. This is the distance the aircraft can fly before it falls out of the sky.
Generally, you want to get your aircraft back to base before that happens, and Harpoon tends to push you in that direction, so there are other important ranges, and all of this depends on what the aircraft is carrying.
Tankers have an important range (call it the tanking range), which is the distance the tanker can fly and still be able to refuel other aircraft. In Harpoon, the tanking range is considerably less than half its basic range.
In real life, a tanker carries a certain amount of fuel. That fuel can be used for two purposes: to keep the tanker flying, and to keep other aircraft flying. The fuel available for other aircraft and the fuel available for the tanker are not physically separate quantities. Rather, the tanker and all the aircraft it refuels draw from the same supply. I believe that this is true for all tankers, or at least almost all tankers.
A tanker could in principle refuel many aircraft, and it could transfer varying amounts of fuel to those aircraft.
Harpoon uses a simplified procedure. A tanker may only refuel one group, and there are further restrictions to this. A tanker may refuel a group only once without returning to base. Keeping these restrictions in mind, and bearing in mind that you usually don't have a lot of tankers, you need to plan the refueling procedures with some care.
In real life, a tanker could use up 45% of its fuel, then give another aircraft 10% of its initial load, and still have 45% of its initial load to get back to base. In Harpoon, this is not possible. Because the fuel transferred in Harpoon for each tanker is a fixed amount and a large fraction of the tanker's initial load, that fuel is absolutely not available to the tanker - until the tanker ceases to function as a tanker. If you set things up in such a way that the tanker is forced to draw on the "other aircraft" amount, then you are no longer allowed to use that plane as a tanker without returning to base.
The way this works in Harpoon is that, when a tanker is at about 49% above bingo fuel, it will transfer fuel to other aircraft in its group. If there other aircraft present, well and good, they get the fuel, but if the tanker happens to be alone, too bad, the tanker reverts to being a normal plane. At that point, in either case, the tanker acts as though it had given away its "other aircraft" amount and attempts to return to base. Of course, you can force the tanker to keep flying around, and it still has plenty of fuel, which makes sense if the tanker didn't actually refuel anyone. However, if the tanker did transfer fuel, then it does need to return to base immediately, but you can cheat by keeping it in the air, even if it no longer functions as a tanker.
For example, in EC2000 Battle for the Norwegian Sea, a common US tanker, the F/A-18C/D, has a basic range of 1050 nm with the tanker loadout. It could fly 500 nm from its base and return with a bit of fuel to spare. However, it reaches 49% bingo at about 340 nm from base, so, for practical purposes, it will be unable to refuel any planes further than about 325 nm from its base.
Now if your aircraft are stationed within 325 nm of the base, that's fine, but what if you want to make sure that you engage approaching forces further away?
Here is a more specific example:
You have a pair of F-14Ds 425 nm from the base, and you really don't want to station them any closer in, and you can't afford to just bring them home and replace them with a new pair.
What you need to do is set up a rendezvous somewhere within 325 nm of the base. You can't just send the F-14s there and call for the tanker, because that takes the F-14s away from their station too long. You can't just send the tanker there and call for the F-14s, because by the time the F-14s arrive, the tanker may have gone below 49% bingo. So you have to calculate a flight plan for both groups to ensure that they arrive at the rendezvous at the same time.
You can do the following calculations exactly with a calculator, but you should be assigning some contingency anyway, so it is OK to work with approximate numbers.
The first contingency is to have the rendezvous 300 nm from the base.
An F-14 cruises at 650 kn, so it will need .2 h to travel 125 nm. An F/A-18 cruises at 650 kn, so it will need .5 h to travel 300 nm. The F-14 needs to loiter somewhere for .3 h. It loiters at 300 kn, so it will use up about 100 nm of fuel. Each of these calculations has its own contingency. As you get more comfortable with this calculation, you may want to shave the contingencies down. If you assign a further 75 nm of contingency, you need to call for the tanker AT THE LATEST when the F-14s have (125 + 100 + 75 = 300) nm of fuel left. 15 min later, send the F-14s to the rendezvous. Everybody should arrive in good order, and you can group the planes and let the automatic routines take over.
< Message edited by VictorInThePacific -- 7/15/2009 5:19:50 AM >
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