Upside Down Subs
After the BHA has been pumped down, some guns may fire without any problems, but at some point on the BHA an issue could cause one or more guns to be unable to fire. In other cases it is possible for a gun to appear to fire normally, but not actually fire correctly. After adjustments are made to try to restore the gun to firing order without success, the BHA should be pulled out of hole to inspect.
After pulling the BHA, and disarming the guns, it should be inspected to find the cause of the error. In this case, after tearing down the BHA, an incorrectly installed sub is identified. Occasionally, pre-installed subs are incorrectly installed by the manufacturer, which allows fluid to migrate into the carrier upon firing the gun below. This fluid blocks the detonating cord from initiating properly.
Once the cause of the issue is determined, the entire crew should be made aware of the issue and reminded of the measures that need to be taken when inspecting guns. Communication with the manufacturer is also recommended to try to resolve the issue before the guns ever leave the factory for use. This should help prevent this issue from occurring in the future.