The proliferation of drone-delivered munitions over the battlefields of Ukraine has forced a rapid and often improvised evolution in one of the least visible yet most critical components of any warhead: the fuze. As both sides scaled up their use of dropped grenades and FPV kamikaze drones, the fuzing solutions available at the start of the war , mostly repurposed from existing grenades, proved insufficient for the task, both in volume and in the specific demands of the new platforms. What followed was a scramble to field fuzes in large numbers, across a wide range of applications, at a price point and production speed that conventional defense industry was ill-suited to meet. The results have been mixed: cheap 3D printed inertial fuzes, factory grade designs with pyrotechnic arming delays, and jury-rigged contraptions that would not look too out of place among some of the IED documentation coming out of the Middle East over the past decade.
All of those different solutions are used all at once in the great mess that is today’s battlefield in Ukraine.
In this article we’ll try to explore most of the different kinds of fuzing solutions used today in Ukraine.
There are two main categories of fuze in use for drone munitions: mechanical and electric, each with their own variants in initiation method. Mechanical fuzes use a physical striker upon impact to strike a detonator and initiate the warhead, while electric fuzes rely on an electric current passing through a blasting cap to achieve initiation.
Within mechanical fuzes, there are two distinct operating principles. The first and likely the most intuitive is the percussion fuze. In such a design, the fuze is mounted at the front of the munition; upon impact with a surface, a striker is physically driven forward by the end cap, striking a detonator which initiates the main charge.
When first adapted for drone use, these solutions were mostly relying on repurposed existing fuzes such VMG-M or VMG-K from VOG-17 and VOG-25 being modified to remove the need to be fired in order to be armed, sometimes fitted with different end cap to work more reliably on softer terrain and then fitted with stand off probes to optimise fragment dispersal. One of such end caps popular on the Russian side is known as the Volga, it uses 3D printed components and a nail to replace the original VMG-M striker.
But with the ever increasing consumption of drone munitions converting existing ordnance for drop wasn’t enough, new munitions had to be made from scratch and with that requiring new purpose made fuzes.
The development of purpose-made percussion fuzes diverged along two paths: safer but more complex and expensive designs on one hand, and basic, low-cost designs with fewer safety features on the other.
Among the cheaper models, many can be produced in workshops using 3D printers and basic hardware, sometimes relying on professionally manufactured detonators or salvaged ones from existing fuzes and sometimes more “handmade” solutions are used. The Volga end cap previously mentioned was also declined in variants to be used whole percussion fuze itself, in this case coupled with a detonator like MD2 or KD8A and adaptors to be screwed on anything wanted.
Other kinds of cheap percussion fuzes will be produced in factories but remaining as simple as possible like PG-1 used on SAB-0.27 and SAB-0.5, coming with both a protective cover and a pin as safety.
Higher end factory-made percussion fuzes represent the other end of the spectrum. This is an area where the Russian company Pribor, one of the largest drone warhead manufacturers, has placed considerable emphasis, particularly with their OFSP product lines, beginning with the A133 and B133 and followed by the more recent P133.
All of these rely on a safety pin that, once removed, starts an arming timer ranging from 2 to 20 seconds depending on the model, providing meaningfully improved safety for the operator .The A133 and B133 were originally designed exclusively for dropped munitions, with the pin held in place during installation and throughout flight and released automatically at the moment of drop, triggering the arming timer. The A133’s relatively long arming delay of 4 to 7 seconds imposed a minimum drop altitude of around 250 metres, a constraint with real implications for accuracy.
When adapted for Kamikaze FPV use, however, the fuzes are typically armed manually, with the operator removing the pin by hand before takeoff, a procedure they were not designed for. It is this improvised use that earned the A133 and B133 their poor reputation for showering the user’s hands with small metal fragments upon pin removal.
One downside of percussion style fuzing can be the small area of contact with the target, which in some cases against cage or nets can lead to failure to initiate the warhead. Also the fact that such fuzes are mounted to the front end of the warhead, impacting target in first, is an issue for shaped charges munitions, which requires an initiation at the base of the warhead.
The second type of mechanical fuze used on drone munitions is the inertial fuze. These share the same basic initiation mechanism as percussion types, a striker hitting a detonator upon impact, but here the assembly is located at the rear of the munition. The key difference is that it is not the direct contact of a cap against a surface that transfers energy to the striker; instead, the fuze exploits the sudden deceleration of the munition itself, primarily through two different approaches.
One approach employs a heavier striker held away from the detonator, typically by a spring. Upon impact, as the warhead undergoes sudden deceleration, the striker retains its inertia and is driven forward into the detonator. This mechanism generally requires the fuze to be oriented more or less in line with the direction of travel so that the inertia effectively drives the striker to a stop, though this depends on the specific design. The inertial fuze used in the HFB series of drop munitions for example operates exclusively on this principle.
Some other designs are slightly less dependent on a perpendicular approach to the target surface, moving away from a purely tubular design by incorporating balls and concave striker holders.
The most widespread example of this type of inertial fuze is the UDZ, originally used in the RGO/RGN impact hand grenades. It relies on a lead-weighted ball to retain inertia during impact and drive the striker into a detonator. For drone use, the fuzes need to be modified by removing the self destruction mechanism so that the warhead doesn’t detonate after few seconds.A common practice on top of that is to fit the fuze with an additional time fuze under the form of a match cord, a white cable burning slowly until it reaches the impact arming pyrotechnical delay and start it. This method provides the users with an actual safety timer, duration depending on the time fuse used and its length, but roughly enough time so that the drone can fly away from the users positions before it is armed.
Copying part of the UDZ mechanism, Russian manufacturers began producing a cheap and simple series of inertial fuzes using 3D printed components and basic hardware such as nails and springs, released under the designation UDD in several minor variants, all sharing the same operating principle. One noted drawback of this system is relatively poor sensitivity, requiring a considerable impact force to reliably initiate. A somewhat common Russian workaround has been to mount two UDD fuzes on the same warhead, improving the odds of initiation at the cost of added complexity and weight.
The second inertial approach does not use the inertia of a weight to strike the detonator directly, but rather to release a spring-loaded striker. This is the principle behind the well-known UDIV-DD fuze, where an off center weight retains inertia during impact, releasing the spring-loaded striker which then detonates the warhead. Fuzes of this design tend to be considerably more sensitive, requiring far less energy to trigger: the UDIV-DD, for example, requires a drop of only 50 cm to initiate, compared to the UDD which requires at least 1.5 m. This heightened sensitivity, combined with the UDIV-DD’s rather sparse safety features, has given it a fearsome reputation for being dangerous to handle or, as one serviceman put it: “it is top tier to kill yourself.”
While many inertial impact fuzes in use in Ukraine are designed to be cheap and workshop-producible, factory-made examples with more robust safety mechanisms do exist. NPO Pribor that we mentioned earlier for their percussion fuze lineup has two widely fielded inertial models: the A668, used on the KZSP-0.5, and the P795, used on the KOZBCh-1.8.
Both share a key feature with the Pribor percussion fuzes discussed previously: a pyrotechnic arming delay that meaningfully improves safety for the operator. The A668 follows the same logic as the A133 and B133, being intended for dropped munitions, and uses a comparable arming delay of 1 to 2 seconds, in line with the B133.
The more recent P795 shares its safety architecture with the P133, featuring an external pyrotechnic arming delay module that screws onto the fuze body and is initiated by pulling a short cord. It offers a substantially longer delay of up to 25 seconds and most importantly it was developed with FPV use explicitly in mind. According to the manual, the warhead is to be mounted with the arming mechanism facing downward; the cord is then attached to a fixed peg or weighted object, and the safety pin removed. As the FPV climbs away on launch, the cord pulls taut and triggers the arming delay. This is a simple , purpose-built solution that removes the need for any manual arming by the operator at the moment of takeoff.
Another major name in the Russian production of professionally manufactured fuzes is Bazalt, which, alongside Pribor, stands as one of the largest producers of drone warheads, here in the 2 to 90 kg range, and produces the fuzes to go with them. Their two best known models are the UZ and the UZ-2. Both rely on inertial action for initiation and are armed in flight via an electric impulse. The primary difference between the two is size and weight: the UZ appears to have been designed with larger UAVs in mind such as the Geran while the UZ-2 lighter profile makes it better suited to smaller platforms like FPVs. Both fuzes are specified to require an impact velocity of at least 30 m/s to reliably trigger, which can be a limiting factor on slower UAVs.
Bazalt’s most recent fuze, developed for smaller UAVs such as FPVs and the Molniya, is the VM-KP. Its most notable feature is its dual-mount capability: it can be installed either as a nose fuze functioning as a percussion fuze or as a base fuze, functioning as an inertial fuze. For the arming mechanism, it departs from the electric impulse approach of the UZ and UZ-2, instead using a pull cord in the same vein as the P-795 and P-133 discussed earlier. This removes the need to modify the drone’s power supply to deliver current to the warhead, making the VM-KP considerably more ”plug and play” in practice. The catalogue lists a required velocity of 30 m/s for reliable triggering , a figure that, based on feedback from operators, appears to apply primarily to the base fuze configuration. When mounted as a nose percussion fuze, it is reportedly far more sensitive to impact and initiates considerably more reliably on small obstacles.
An important difference between percussion impact fuzes and inertial impact fuzes will lie in their sensibility. Taking Pribor offering as an example, again, their catalogue lists that the minimum velocity to trigger B-133 is a mere 2m/s while P-795 requires over 10m/s to reliably go off. This will of course vary from fuze to fuzes but generally warheads relying on inertial fuzes will require a noticeably stronger impact to detonate. This is something which can be an issue for some drones flying at lower velocities like Fiber Optic FPVs often progressing at a lower pace. The need for that sharp deceleration can also be an issue against soft terrain for dropped munitions, an issue already known in the case of cluster bomblets for decades, and for kamikaze UAVs it is mostly nets which can tamper with their reliability, softening the deceleration it can catch drones without them being set off.
We now turn to the initiation of drone warheads which instead of using the mechanical force of a striker impact on a detonator, rely on an electric input to an electrical detonator as a means of initiating the warhead.
The first initiation method worth covering is likely the best known: contact wire initiation, referred to by both Russian and Ukrainian as “whiskers.”
The principle is straightforward. An electric circuit is held open by keeping bare wires separated from one another, typically coiled loosely around each other or arranged so they remain in close proximity without touching. Upon contact with a surface, the wires bend and make contact, closing the circuit. This usually sends power to an electronic component, the initiation board, which sends an electric current to the electric detonator, setting off the warhead.
It is not rare to see the contact wires being mounted directly on the drones as part of the FPV package like for the Ukrainian “Vyriy” company lineup of drones.
An increasingly common alternative to coiled bare wires is the use of cheap limit switches, which keep the circuit open until closed by physical contact. To compensate for the shorter reach than many contact wire mounting solutions, they are sometimes attached to probes, increasing the standoff.
One inherent risk of relying on cheap switches or inexpensive electrical components more broadly for anything related to initiation is that a defective part can have catastrophic consequences with very little warning. This is why many operators invest considerable time testing every component individually before committing it to a live system. The video below is a case in point: a Russian drone operator venting his frustration after testing the switches supplied in a KVN drone kit, finding them to be defective with the circuit registering as closed at all times.
Initiation boards serve more than just the function of triggering the warhead, they can also incorporate safety features and self-destruction mechanisms. Taking the Russian MDV as an example: it is fitted with a physical safety pin; once removed, a two-minute safety timer begins during which the warhead will not detonate even if the circuit is closed. LEDs and/or audible signals are often used as status indicators, showing whether the board is armed or not, and can flag issues during the arming process, such as an unintended contact between the bare wires or a closed switch, that must be resolved before proceeding.
demonstration of MVD initation board
Another method of sensing target contact and initiating the warhead is through an accelerometer, often integrated directly into the initiation board. If a sudden deceleration is recorded, the electric detonator is activated. The sensitivity of the accelerometer must be carefully calibrated, responsive enough to trigger at lower impact velocities, but not so sensitive as to fire during aggressive maneuvering. Some manufacturers claim to use software filtering to separate out drone vibration from genuine impact signals, reducing the potential for false positives.
Test of sensibility of the PIU-1 inertial iniation board
Many such boards now also incorporate a self-destruction mechanism triggered after a set period of time, commonly 30 or 60 minutes, though some go significantly longer, such as the POPCORN board by Vyriy, which offers up to 48 hours, reducing UXOs threat on the battlefield which has tactical and long term significance.
Another capability becoming increasingly common on initiation boards is command detonation, the ability for the drone pilot to trigger the detonator directly. This opens up two valuable options: airburst detonation against a target, or disposal of the UAV and its munition when no target has been found, reducing the risk of leaving behind an unexploded device. The airburst option is of particular interest against infantry in the open: paired with the right warhead, it can deliver a lethal fragmentation effect significantly larger than a ground detonation would produce.
It is worth noting that command detonation demands very precise timing to be fully effective. The more directional the warhead’s effect, focused fragmentation or EFP for example, the greater the impact even a small input delay will have on terminal effectiveness.
This is where contactless initiation becomes especially valuable. The term tends to carry different meanings depending on context: in remote mining discussions it usually refers to magnetic or seismic sensors, but in the context of kamikaze or bomber UAVs it most commonly refers to optical proximity sensors. In this application, the sensor triggers when the munition closes within a set distance threshold of an obstacle, guaranteeing airburst detonation at the desired standoff. This is useful both for anti-personnel tasks where it optimizes fragment distribution and for anti-armor applications where increased standoff can enhance the penetration performance of a shaped charge and may also help defeat certain improvised armor add-ons fitted to armored vehicles.
A strong example of such a system is the Ukrainian company Laser Deton, which markets contactless initiation modules for both drone-dropped munitions and kamikaze UAVs. Their Kamik model offers multiple selectable standoff distance settings, providing meaningful flexibility for the operator.
The sheer variety of fuzing solutions seen on today’s battlefield is a direct consequence of the scale at which drones are being deployed, day after day, in numbers that continue to grow month on month, driving a demand for fuzes that is nothing short of enormous. As with so many aspects of this war, soldiers were forced to adapt long before industry could catch up: recycling detonators from existing munitions, 3D printing components for improvised fuzes, and engineering their own solutions from whatever was at hand, while manufacturers worked to scale up production of more complex and reliable alternatives.
A broad divide has emerged between the two sides. The Russian approach has leaned heavily toward mechanical fuzing solutions, driven in large part by their two principal producers, Pribor and Bazalt and by its easier plug and play approach. The Ukrainian side, by contrast, has predominantly gravitated toward electric detonators paired with initiation boards, triggered through a variety of methods.
Despite these differences, operator safety remains a primary concern on both sides, and one encouraging trend is the increasing prevalence of self-destruction mechanisms on initiation boards. Hopefully, these will go some way toward limiting the vast quantities of unexploded ordnance that will otherwise be left to litter Ukrainian soil for generations to come.
Beyond Ukraine’s contaminated soil, another concern arise:
While the wide array of homemade fuzing solutions has so far had a mainly practical impact in Ukraine,meeting demand for drone warheads and increasing the variety of unexploded ordnance, a wider view could suggests that some of these practices are likely to spread beyond Eastern Europe.
Large volumes of material already circulate online in Russo-Ukrainian groups: detailed guides on converting existing ordnance in simple workshop conditions, often paired with STL files for 3D printed fuze parts, adapters, mounting solutions and so on. Combined with the recent rise in strike-UAV use by non-state actors, this could amplify the threats posed by the growing availability of such platforms.