DCS F16 GND vs GND DLY settings on GBU31v3b

[Tj1376]

Can anyone clarify (or point me to the manual) on what the difference is between GND and GND DLY on the GBU31v3b?

I have a test mission where we use GBU31v3bs to take out an ammo depot.

Prior to the 12/22 patch, you had to put the GBU31v3bs into GND DLY to kill the ammo depot with 2 bombs on the F16.

Post the 12/22 patch, you now have to put the GBU31v3bs into GND to kill the ammo depot with 2 bombs on the F16. 

Im sure this is all still WIP, so no bug report, but was curious what the 'correct' procedure will end up being. 

TJ

GBU31fromF16withGroundDelayNotKillingBunkers.trk GBU31fromF16withGroundKillingBunkers.trk GBU31fromF18withGroundDelayKillingBunkers.trk

[Frederf]

It depends on if it is a FMU-148 or FMU-152 fuze on the bomb. The AIR/GND/GND DLY setting is for informing (-148) or choosing (-152) the type of terminal function set on the fuze. AIR means airburst means DSU-33 which is impossible on the -31v3 because it can't have anything bolted on the front as it is a penetrator warhead. The -31v1 can though. GND means the delay is essentially instant, a few milliseconds. GND DLY is for longer delays, seconds to hours.

If memory serves the cutoff time between GND and GND DLY is 1.5 seconds with everything shorter being GND and longer GND DLY. I believe the idea is that the bomb will will have come to a halt after 1.5s.

I'm no weaponeer but it makes sense that optimum penetration is probably 180-250ms or so to breach the earthen or concrete part of the bunker and be in the juicy middle space before detonating. Letting the bomb penetrate as much as it can until it comes to a stop could easily have it continue past the interior space and be less destructive. If the bomb was going fast and shallow it could easily have burrowed outside the lateral confines of the target given enough time which could really reduce its effectiveness. Unless you're trying to lay a sort of time delayed mine I don't see the utility in GND DLY.

The FMU-148 (or FMU-139 non-hardened target fuze which might be in a -31v1) is set on the ground. It's going to arm and function however it was configured without any pilot control. The most a pilot can do is enable/disable a DSU-33 by pulling/not pulling the arming lanyard on release. The reason for telling the jet the config is for information like frag clearance, fuze time.

The FMU-152 is a smart fuze connected by the 1760 bus. When it's connected and communicating it will show up as an extra option to do extra settings. If it's not communicating then the extra option is blanked. From memory we don't have the JPF menu so it should be assumed it's FMU-148 with fixed settings or it's JPF but not complete in implementation which makes seeing/changing those settings similarly impossible.