I have a fairly significant correction to make on what we've been thinking regarding part of the fuel system.
Last night, we noticed a massive fuel usage disparity between two 110 pilots who flew the same sortie from the same base, and landed together. It was identified as being the result of them taking very different fuel loads from the airfields. Other pilots had their usage stats checked, and they matched up perfectly with the amount of fuel that they had taken. The campaign was not giving the unspent fuel on board at the end of the sortie to the airfield which they landed at. It was, however, giving the airfield all unused bombs and ammunition in exact quantity, and of course the aircraft itself.
I went digging into the code and was pretty convinced I found the section that controls the exchange of resources between aircraft and airfields. And sure enough the fuel section looked wrong, or at least different than the sections for the other three resources. I changed the format to match with the group, and was fully expecting to see my fuel given to the airfield like everything else when I landed. Unfortunately, it failed to do so.
Then, while browsing through HR's updated FAQ section on their site, I found the answer I did not want to find. The game simply does not provide anything for the campaign to pick up on as far as how much fuel you have on board at the end of a sortie. It knows how much you took off with, but that's the last time the campaign can take your fuel load into account. For whatever reason, CLOD makes the info for ammunition and bombs on board available at landing, but not the fuel. HR's explanation refers to a campaign setting that had never made sense to me before, but is now crystal clear why it exists, and what it does.
Given this shortcoming of the game, HR set up a configurable time limit, which essentially draws a line in your sortie. If you land before this time, you give the airfield back all the fuel that you took from it, including what you have used during the sortie. If you land after this time, you give none of it back, even if there's plenty left in the tank. It's an all or nothing system for returning fuel. By default they had it set to 300 seconds, or 5 minutes.
This setting makes sense for when something requires you to quickly return to base without doing anything that could be considered a normal sortie. Maybe you have just taken off and forgot to open the radiator and blew it, or maybe you forgot to grab the bombs you were supposed to take. You just turn around, land, and you haven't wasted your entire fuel load. On the other hand, it needs to be quite short of a grace period (I'd say if not 5, not more than 10 minutes), to prevent people from doing quick strike and return sorties, while not actually consuming any fuel from the airfield. It's got to be quick enough that you typically can't perform anything that would be considered a worthwhile sortie. This is of course not an exact definition, and so there's no perfect setting. But somewhere there needs to be a balance of not forcing you to waste a whole tank of fuel for a few minutes of flight, while also not letting you get away with productive sorties without using a drop from your airfield fuel stores.
This also makes it very important to not take more fuel than you'll need. Carefully consider your fuel load for the sortie you are planning. Not that you can perfectly predict such things, but it's best to not take fuel that will last 2 hours, if you expect to be back down much earlier than that. Because when you land, whatever you took out, is gone.
Hptm. Stecher, Staffelkapitän