GBU-10/12 Delay fuse

[The_Tau]

Is there any way to delay fuse on GBUs to make bomb first to penetrate bunker before explosion? N/T fuse option change in profile results in invalid fuse msg...

[Rainmaker]

That would be something that’s Hard mounted in the bomb, you either have the fuze set to delay or you don’t. I guess they ‘could’ fudge that in the same way the laser code is, but it apparently isn’t. N/T regulates which wires are pulled on release. In the case of a GBU, IIRC, the nose fuse arms the seeker and the tail pulls either the fins or the arming wire lanyard. In either case, not pulling all the lanyards would be a bad thing in terms of having an operable bomb.

 

There are some weapons dudes around here that can correct anything that I may have gotten wrong on the above.

Edited October 5, 2020 by Rainmaker

[The_Tau]

Idk, in other planes it seem to be simple Nose/tail switch... nose for impact and tail for delay... and it works, it explodes after some time when in tail

[Rainmaker]

Don't know what to tell you about 'other planes'

 

http://www.navybmr.com/study%20material/14313a/14313A_ch1.pdf

 

FMU-139

 

"... four functioning

delay settings (10, 25, and 60 milliseconds,

and instantaneous)"

 

"...functioning delay must be set during weapon

assembly"

 

See attached pic. That center plug between the two lugs is your arming wire. Only one wire in that case.

 

 

EDIT:

 

Looking further into it, apparently the Navy has a secondary option of a Mk-22 initiator. Perhaps your 'other aircraft' is referring to navy-type aircraft? Apparently this offers 'pilot-selectable' options via a coax cable. Not and Air Force thing that I've ever heard of so perhaps this is your 'difference' between the two?

 

https://www.fighterpilotpodcast.com/musing/understanding-the-fmu-139-and-its-employment-options/

Edited October 5, 2020 by Rainmaker

[Frederf]

It's perfectly possible to set up two fuzes in a bomb and wire one to each fuze solenoid. Each fuze could have a different delay so dropping only the penetration fuze armed would give penetration action and both fuzes would give instant action. I don't think that's terribly common though. I think it's much more common to have the bomb configured for instant or delayed before flight.

 

FMU-139 for example the action is controlled by physical pellets in the fuze and can only be set on the ground. FMU-139 also has HD/LD sensing and so can behave different depending if a high drag device is deployed or not. It's theoretically possible to have a FMU-139 delay action for LD and instant action for HD. FMU-139 can only go in the rear fuze well but there are other nose fuze models which can double fuze a bomb for independent settings.

 

On the other hand a DSU-33 is a proximity device which can be armed or not to select airburst or contact action. This does provide in flight selection and is quite common. Also fancy fuzes like FMU-152 can be fully programmed in the air to select any option. Reprogramming FMU-152 requires a 1760 interface, i.e. the same interface JDAM needs.

 

Right now there isn't any part of the airplane systems that suggests delay detonation settings for fuzes. It's simply not relevant to the A-10 in the sense the bomb flies the same path and arms in the same time either way.

 

Delay action fuzes would have to be baked into the bombs themselves, hopefully user-configurable, and you would know how it behaves under various arming wires (if that matters at all).