The most common reason is a combination of low altitude, incorrect bomb fuse for that altitude and incorrect settings on the bomb arming panel.
I'm going to go out on a limb here and assume you're trying some low-level attacks in true Jabo fashion, so here's how to make it work.
First of all, you need to select the low altitude fuse. There are two of them, use the one that the Stuka uses by default.
Then, you need to make sure that this fuse is set to the correct profile because it has two available settings to choose from. I vaguely remember reading here that the way it was done was to send an electrical charge to a capacitor when arming the bombs: the bombs would arm after dropping depending on how fast the capacitor discharged.
In terms of bombs there are two control panels in the cockpit. One is for selecting which bombs to drop (in aircraft with more than one bomb like the Stuka and the 110), the other is for arming the bombs.
So, take a look at the weapon arming panel in your cockpit. If you can't find it, press the keys/stick buttons you've set for master arm and see which switch moves. It's a three way switch, when it points upwards the bombs are not armed. However, there are two modes of arming. One is for low level attacks and labeled "Sturz" (meaning dive) and is the one you want, the other is for dropping from higher altitudes.
Setting it to Sturz mode sets the bomb fuse to arm with a shorter delay when leaving the bomb rack and the subsequent detonation delay of 14 seconds that comes with this fuse lets you escape the blast.
So how do you do it? I don't remember if i've mapped anything to it in the controls so i do it with the mouse. If you hover the pointer over it a tooltip will appear that reads "toggle short delay" or something like that (that's probably how it's called in the controls section too, in case you want to map the function to a key/button).
Just clicking on the 3-way switch will select your preferred mode, even if the switch is still pointing up and the master arm is off.
When you click it you'll see an on-screen message (if you haven't disabled the on-screen blue text messages that give you information on secondary controls, eg gear/flaps/etc) saying "short delay on" (faster arming, the low altitude mode) or "short delay off" (longer arming delay for higher altitude drops):
a) If your master arm was already on, doing so will flip the switch from one arming position to the other (it alternates between dive bombing/low level and higher altitude bombing modes).
b) If your master arm wasn't on you won't see the switch move yet, but as soon as you enable the master arm it will move to the position that corresponds to what you selected.
Initially i didn't know about this either so i came up with a good dive profile to land bombs on trains and ships in the 110, releasing in a 30-40 degree dive from about 700 meters with the high altitude mode.
However, i recently tried this online and the low altitude arming works a treat, i released bombs at less than 100 meters and sunk a tanker.
|