A scale modeler's guide
Since its introduction to combat in 2004, the GBU-38 has given air forces across the globe the ability to hit ground targets with greater precision and confidence to avoid unnecessary collateral damage. It is capable of being delivered from every tactical fighter in the US inventory as well as several air frames that have since been retired. The GBU-38 has also been cleared for use on an assortment of foreign aircraft. Such widespread use means that a modeler who intends to build a subject of a modern jet fighter that has been involved in the Global War on Terror stands a great chance of being able to mount the JDAM on their kit. Having the right references for just such a circumstance is key.
The BombTogether the US Navy and Air Force conceived requirements for a new precision guided munition at the end of the first Gulf War. The venture was named JDAM, for Joint Direct Attack Munition and soon found success using GPS assisted inertial navigation systems that could be packaged into guidance kits and attached to legacy "dumb bombs". These JDAM kits could be fitted to a variety of bomb bodies thus giving existing munitions a powerful new ability.
The foundation of the typical GBU-38 is the Mk82 bomb body but may also be the BLU-111 (identical to the Mk82 except that it contains PBXN-109 explosive filler rather than Tritonal) or the composite case warhead BLU-129.
|Mk82 500 lb bomb body capable of being converted to a GBU-38 JDAM. This particular one is inert as shown on the stencil.|
|Two BLU-129/B composite bomb bodies about to receive their guidance packages to become JDAMs. The yellow diamonds denote the high explosive hazard of the munitions and denote that they are composite cased warheads.|
Part of the process for turning a "dumb bomb" into a more intelligent munition involves adding a few accessories to improve its accuracy. Several features on the nose of the GBU-38 are distinct and make them easy to identify from other munitions.
|Each GBU-38 is fitted with aerosurfaces, or strakes, that are strapped around the nose of the bomb body. This improves aerodynamics. Typical USAF versions feature a copper colored ring into which the conical nose plug is installed as you see above.|
|The MXU-735 solid nose plug may also be painted in olive drab as seen in this photo.|
|Here you can more easily see the DSU-33 and copper colored ring in these GBU-38's inside the bomb bay of a B-2.|
|This GBU-38 is loaded on an F-18 Hornet and also features the prominent DSU-33 proximity sensor. You can see the NAVAIR versions do not use the copper colored ring used by the USAF.|
Of course, it is only the aerosurfaces that determine the weapon is a GBU-38. The conical nose plug, the MXU-735 and the DSU-33 are not unique to the JDAM and do not factor in the bomb's status as a smart munition. However, such features help distinguish the GBU-38 from its brother, the GBU-54 which has similar characteristics.
The KMU guidance kit is probably the most important part of the JDAM as it contains the actuating fins, GPS antenna and umbilical receptacle to interface with the aircraft.
|This munitions technician is adjusting the positioning of the umbilical receptacle. This is configured depending on the air frame or pylon the munition will be loaded on. It interfaces to the aircraft with a Mil Standard 1760 cable.|
|Here you can see where the fins are able to actuate, thus guiding the bomb to the target. At the rear of the KMU is the GPS antenna.|
Thermally Protected vs Non Thermally Protected
Eduard recently released two sets of 1/48 GBU-38's, one being thermally protected, the other not. But what does this mean for the modeler? As mentioned briefly above, the US Navy applies an ablative coat to their munitions, a requirement after the 1967 fire aboard the USS Forrestal that killed 134 sailors. It essentially lengthens the cook off time for munitions should they be enveloped by fire, allowing fire fighters more time to douse the flames.
|These bombs clearly have the ablative thermal coating applied. Two dead give-aways of this feature are the incredibly rough textured appearance and the dual set of yellow stripes.|
|More recent NAVAIR bombs show applications of the thermal coat that are much more smooth and grey in color, such as these GBU-38's on an F-18.|
|A closer look at this NAVAIR version shows the slight texture of the thermally protective coat, as well as a DSU-33 on the nose.|
While the thermal coating is a requirement for shipboard operations, the NAVAIR style bombs are not exclusive to US Navy and Marine Corps use.
|USAF personnel are assembling NAVAIR style GBU-38's that even feature a yellow stripe along the back third of the bomb body.|
So, while companies like Eduard specify between USN and USAF versions, in some cases, the difference does not matter. Ultimately, the ordnance in the ammo dump will be used by whatever air component needs it.
The GBU-38 is compatible with every tactical fighter and bomber in the US inventory and can be hung from an assortment of different pylons and bomb racks, to include B-52's, smart racks, and Digital Improved Triple Ejector Racks.
|An A-10 flies in support of Operation Inherent Resolve, loaded with several GBU-38's, among other things.|
|A pair of GBU-38's on an F-18's smart rack on the right wing.|
|GBU-38's on a B-52.|
|A pair of GBU-38's on an F-16's BRU-57 smart rack.|
|Certainly capable of carrying more, this F-15E only shows two GBU-38's loaded.|
|A USMC AV-8B with two GBU-38's on the right wing loaded to a new DITER supporting Operation Inherent Resolve, 2017.|
The features of an inert GBU-38 are the same as a live except they do not contain explosive filler. Visually they are identified by either a blue stripe or a completely blue BDU-50 bomb body.
|An inert GBU-38 being assembled. The single blue stripe indicates this munition is inert and not for flight. This will likely be used as a load crew trainer or to train munitions personnel on assembly.|
|Inert GBU-38's with completely blue BDU-50 bomb body. These are capable of being flown and dropped by aircraft and are about to be loaded on the F-16 in the background.|
|An inert GBU-38 on an F-18.|
|You may also see an inert DSU-33. In some cases, though not all, non functioning sensors may have a blue stripe as well.|
Some Final Shots
|Norwegian Air Force F-16 being loaded with a GBU-38|
|Republic of Singapore F-15 with inert GBU-38's loaded.|
|A Japanese Mitsubishi F-2 with GBU-38 loaded.|
|Spanish AV-8 with GBU-38.|