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Anti Helicopter Mines - AHM's

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posted on Jan, 20 2006 @ 12:34 AM
Since a brief search reveals nothing on-topic and it seems our forces are suffering a new 'freedom of operations' (mobility) impediments courtesy of the insurgents aptitude for improvisation, I thought I would gather what I could in an outline on the 'History And Application' of the Anti Helicopter Mine (hereafter referred to as the AHM). This will be followed by another section 'Discussion' which I will offer some thoughts on what can be done to improve rotary wing platform's survivability in current conditions. I will then 'Conclude' with some thoughts as to where we are headed and what must happen before we get there.

It seems that there are four main types of threat which can be directed at helicopters from the ground.

The first is fires based and includes such things a preregistered mortars and hidden MG pits directed at landing zones, downed pilots or other 'attractants' to helicopter use. These are differentiated principally from typical antiaircraft fires by the fact that they are localized in their density and response to ONE area, often with the intent of catching the helicopter at it's most vulnerable, slowing down or speeding up with limited vision and often mission-critical events (troops deplaning, a rescue in progress) on-going. They may also be employed against FARPS and FOBS where adequate (sensor watch, counterbattery, countermeasure and patrol) efforts are not maintained to provide operational safety to airframes and ground crews. Tellingly, it also appears possible for modified tank HEAT rounds with an airburst fuze responsive to rotor doppler to engage helicopters in bobup hides or otherwise behidn masking. Early 1980's German research quickly being duplicated by all Western NATO partners (U.S. round being the M830A1 HEAT-MP-T). Whether the Russian CLGP (ATGW) rounds of the Kobra through Songster generations have given them special insight into the nature of these weapons remains unclear.

The second type of threat relevant to the helicopter seems to rely on the use of both deliberate and improvised boobytraps at ground level near to expected operations/landing zones. Explosive systems are typical but where ground cover is dense (as in the elephant grass of SEA) simple sharpened stakes, cables or deadfalls may also be used to snag the helicopter's landing gear/skids, entangle rotor systems or impale fuselages completely thru the main cabin (fuel cells) and into the 'doghouse' of roofmounted engine and transmission areas.

Deadfalls are usually loosely placed treeboles which fall under rotor disturbance and as often as not are also triggers linked to specific secondary kill devices such as handgrenades or AT mines. The latter may include weapons designed to explode in tree tops as the helicopter approaches or passes through a given predictor zone (approach or transit choke). Improvised explosives may involve simple direct action (passage) based systems or be designed to respond to direct downwash effects as with a pinless grenade wrapped tightly in paper which is subsequently stripped. It should be noted that only one Russian design depicts a Claymore type device mounted on a tripod with deliberate intent to provide a wide arc of coverage from behind masking foliage or camouflage as with an off-route mine, presumably because this requires a more complicated siting technique and/or direct activation.

Obviously, most of these systems are not reliable and have small lethal radii which require as a precondition the rotary wing aircraft's direct approach to an associable terrain feature (flat ground with low vertical obstacles in reasonable proximity to a desired ground objective = LZ) and can be avoided by creating random or multiple landing zones on short notice or outright avoiding air mobile operations outside controlled areas. Their simplicity however does not rule out their use in multiple (seemingly) random encounter modes and so they must not be discredited as possibly present in any engagement.

The third category of AHM use belongs to 'pop up' or 'directed' (fragment stream) airburst weapons which are associated with systems designed to engage aircraft and potentially cruise missiles from some small degree of standoff in their primary flight (high speed) state. Either as a function of driving them higher into secondary engagement by large-caliber/guided systems. Or again as a desultory attack based on passage kills through predictable terrain chokes (something of particular relevance in hot'n'high desert or mountainous areas). It is these systems which are apparently of most interest to the current war as Iraqi's appear to be employing old anti-aircraft artillery shells to to drive off or assassinate attack helicopters (previously one of the most difficult target sets) as a 'statement' of controlling ground areas through denial of aerial overwatch.

At this point I will include two LINKS-

Link 1

Link 2

Which purport to illustrate AHMs but which require JED Member Access Passwords to look at, full scale.

As well as two more-

Which to show an AHM in comparison with what was previously known as the 'WAAM' or Wide Area Anti-Armor Mine. One of the many 'brilliant' munitions designed in the later phases of the Cold War to interdict large numbers of Warsaw Pact Armor from remote artillery or CBU emplacement. Clearly there is a familial resemblance in that the M93 Hornet shown has much the same Acoustic Horns and a center munition (Skeet SFW) which would be ejected over a ground target to orient it's explosively formed projectile at the vehicle roof via an onboard IR cell.

According to this LINK-


The Russian AHM, rather than employ a 'bouncing betty' methodology (using a microcharge to eject to a matching height) is acoustically pointed, on-mount, and then explode directly with an IR sensor to fire the 3km/sec EFP up to a target height of 200m.

This LINK-

Survival Of Modern Helicopters

Agrees that this is the major operating mode for all four of the non-U.S. producers of AHMs: Bulgaria, Austria, the UK and the FSU. Even as it confirms that the majority of the weapons use Acoustic cue and IR characterization to fuze the weapon rather than any (RF) 'proximity fuze' effect as is being attributed to Iraqi improvised 57mm and 85mm AAA shells.

This clearly raises some interesting principle variables for further consideration but before I go on, I will include the following LINK-

Origins Of Mines Pt.II

Which both affirms the VC/NVA first use of anti-rotary wing explosives (I would be most interested in hearing of anecdotal proofs earlier on in Korea, Africa or even the latter phases of the Pacific action). While providing an reference point for the last and probably most dangerous of all 'mines' (where such is defined as an unattended system capable of independent sensor-triggered lethal action) devices, the guided/powered weapon. Though nominally a Spetznatz conversion of the SA-7/14 to standalone use, the remote pedestal system has since been adapted to both the Swedish RBS-90 and the BAe/Short Bros Starburst/Skystreak VSHORADS systems and offers an ability to engage targets beyond any reasonable counter-detection threshold and above any reasonable ceiling of say 1-2,000m standoff. It must be a fairly large (tall) emplacement to clear the sight optics and allow for full rotation and elevation of the 40-50 inch missile tubes. But it is 'the next step' in a world where contempt of engagement (COE) tactics seem to be increasingly the rule by which small forces avoid losing cadre expertise.

I would only add that while the U.S. has nominally abandoned AHM research in favor of elements of the ADI (Air Defense Initiative) known as 'Mountain Top', the JLENS surveilance aerostat from the LCCMD effort and MALI kill vehicle systems-

Which admittedly allow pursuit of targets over local horizons (by tens of miles in the case of slowmo rotary wing aircraft), may also have allowed our enemies to pirate a cheaper technology to inflict nuissance casualties on our forces.

Now, what does this say for our ability to perform 'counter mine' activties in the presence of this threat?

IMO, the first prerequisite is to discover just how these makeshift weapons are crafted and emplaced. The original WAAM efforts required a significant seismic sensor network assist to work at their best capacity and the U.S. AHM effort, while indeed originally based on WAAM also envisioned the weapons as having a major _ISR_ role when applied with a trigger function. Counting'em in and out as it were, both to track friendly ops, passively by in-place networks. And to judge threat high utilization threat navigation routes and safe passage corridors relative to overall activity levels and in development of a counter-air plan.

If the enemy is using a simple, one-shot, mortar system (like a firework cannon) there must be significant material expense and machining efforts to pack the charge in tube which is either readily buried or able to be stood on end to acommodate a relatively large caliber round with ease. The latter must be safe to transport yet also have easy access to either a nose or base mounted proximity delay. If the fuze is internally set by acceleration there may need to be further modifications for 'soft launch' at much lowever MVs.

If this is not present as a trackable signature (indicating recovery by AHM 'teams' of hunters) or if actual debris from AHMs are being recovered to indicate advanced manufacturing capabilities, we must consider that these are being assembled or at least /designed and fabricated as sub assemblies/, out of country. With likely professional advice in their use as well as assembly.

Obviously, if the weapons do blip-up and there are no activity sensors such as an acoustic fuze to cue this action, a hardwire or remote connect option must be available which would require that these 'mines' be in fact attended as the difficulty in remote observation triggering would be fairly high and there might also be fratricidal concerns under some engagement conditions. This would greatly increase the activity cue inherent to their emplacement and use.

If weapon activation is based on an RF proximity fuze signal there should be a detectable signal and peak threshold during launch which should respond to techniques similar to those employed by Warlock and Shortstop jamming systems (intended for use against cell phone and mortar round proximity fuzes respectively). If the system is acoustic based (which IMO involves a whole order of magnitude improvement in threat electronics conversion and calibration capabilities relative to a conventional AAA round) then a system which throws rotor harmonic resonances (blade beat first and second order frequency overlaps) slightly out of phase must be rigged. Obviously 'the trend' is already in place-

But the question must be whether (if acoustics are a problem) a QRC or Quick Response Capability 'bootstrap' option might not be a better option.

Of course before go there, we must answer another dilemma which is why USAr Helos in particular are not simply flying over the threat floor. As indeed Air Cav did in SEA, when it was felt that surprise was not worth the desultory fires. Often topping out at 3,000 or even 5,000ft to avoid the majority of low caliber weapons while keeping everyone together until just prior to the LZ. Even a 1,500 foot AGL would almost certainly remove the helos from both the AHM and most tube weapons under 12.7mmm the text here-

Would have us believe that it is because the Iraqi's present a higher threat at medium altitudes. To which I say bunk. The RPG, with it's complex trajectory and without guidance should be just next to useless on all threats much over 300ft or so. While the use of true MANPADS must be questioned as both a function of initial inventory (1:100:1,000 was the ratio I was taught for AK-47, RPG/RPK and SA-7 presence in these kinds of theaters).

It _may_ be a simple function of supporting ground troops or 'patrolling' with limitied depression arcs or mangnification on aged TADS/MMS optics but if so, the question to be answered is why the USMC is able to do as well with equally aged TSU or (NTS) modified systems on their AH-1W's? A more likely reason here is limited available flight hours for all but 'emergencies' and thus too few gunships in the orbit over hot sites. Particularly if there is additional trolling-for-fire going on.

In any case there are some basic cures:

1. If you are afraid of the high altitude threat, don't drive a 'black helicopter'. Seriously, the CARC based OD of yesteryear may be a good basic corrosion preventative and European camouflage when seen against a darker horizon in Europe or the U.S.. But it has no place in a war defined by operations above the skyline. As indeed USMC ops are standardized (ghost on ghost) around. There are a few grey Apaches visible in photos coming out of theater, but far too few, IMO.
Link to image
Link to image

2. U.S. RF and especially EO countermeasures are pathetic. The ALQ-144 is a ca, 1980, 360`, IR pulse puffer that scintillates a diffuse stream of IR 'dots and dashes' across a broad spatial arc and bandwidth curve without focusing enough sectored energy on any one threat bearing to defeat ANY of the later (Egyptian or Chinese) SA-7 mod seekers. Let alone those associated with the three generations of later (Gremlin/Gimlet/Grouse) Soviet MANPADS that came after. Or their knockoffs and clone 'equivalents' from Europe and the Far East (these weapons actually like the look of the beacon and will home on it).

Similarly, the AAR-47 plume warner, when installed is a dated system with a lot of clutter problems and limited saturation (active threshold gains) in a multishot environment while the later AAR-57 CMWS, while 'technically downselected' as the winner of the SIRFC along with the ATRJ and ALQ-212 ATIRCM, has not exited phased development. Except on SOCOM choppers. Which now use 'the loser' in the ATIRCM competition as the BAe Sanders AAQ-24 Nemisis with two or more turret packages installed as free standing DIRCM or Directed Infra Red Countermeasure mounts which, having their own MAWS, require NOTHING but aircraft power and on-switch activation (admittedly through the IHADS/MATT in the MH-53). There are also only 2 M130 dispensers on the AH-64 when in point of truth ANY use of (larger caliber) flares in an active COIN environment means accepting vastly less than the nominal 30 rounds of Chaff which the buckets can pop. The Israeli systems for their mod-D Apaches include another bunch of dispensers forward. As do the British WAH-64D. The AH-58 is even worse off, lacking both power and airframe points to mount many more systems.

If proper countermeasures were available to defeat 'proper' S2A threats, U.S. helicopter drivers might not be as unwilling to leave the NOE.

3. Equiping with Dropfire Weapons. Though not nominally trained with them, almost all helicopters can at least /release/ light weight bombs in the 250-500lb range. It would stand to reason that increasing the number of Finder and Viper Strike type options on-airframe would both serve to 'certify' these devices more quickly and provide alternatives to direct engagement at low levels and short standoffs. They may even (for a short while) decrease the incentive to move towards A-UAV.

4. Active Free Flight Decoys.
Both the USAF and Navy have experimented with POET and GEN-X expendable systems which are possessed of the ability to float down while generating specific 'transponder mode' decoy signatures relavent to certain S2A systems. It should be theoretically possible to rig an equivalent for preemptive use against RF prox threats which go active-out-of-barrel. Whether you drop one and let it whizz down before commiting run in and out while dropping a continuous stream of them. Or employ a scatterable system by artillery.

5. Cable Decoys.
In many ways these offer the most hope IMO because while they function like the ALE-50/55 they don't need to separate or deploy cleanly in a multi-hundred knot airstream but can simply be anchored, like a slingload cable to the bottom of the aircraft or an outboard pylon and rely on a drogue not unlike the paravane in naval clearance, to keep the device roughly vertical to the slipstream. Clearly, if you are taking fire from other threats, airspeed and maneuver limiter issues may be a problem (keeping the device out of the tail rotor and in-axis with a rising threat. But the advantages would be enormous given a 20ft cable may have enough line to mount BOTH acoustic transducers and an RF bird as well as perhaps a single MAWS cell to cue 'start the music' on a dummy loaded pod.

6. Smoke and Mirrors.
Smoke is the most basic of military deceptive aids and provided your deconfliction is good, it can be delivered from considerable range in relatively builtup areas with simple 105mm field guns. It has the bonus' of somewhat muting sound and blocking human vision _at a level_ (burst charge) which allows fighting to continue underneath the screen. And without blocking IIR based sensors. This could be of particular import if the enemy are using human observation of ambush zones or if the helicopters are forced by terrain or structures to fight lower than they might otherwise.

Mirrors refers to self-reflection. Most aviators will be able to sit down at an ops chart, look at the mission maps and plot out the likeliest routes too and from given high activity areas where they are 'routinely' heavily engaged. If you can spot a pattern, so can your enemy. And it is up to YOU to exploit /their/ OODA loop in getting them to commit to actions which you later use to get inside a decision cycle. The obvious method is announcing 'heavy air patrols' in response to continuing attacks at X. And then placing remote sensors, observer teams or drone air to allow for tracking and possibly capture of AHM specialist units.

At the least, such a deceptive misinfo and maneuver would permit the use of 'cable draggers' (perhaps 100-300ft long if deliberate MCM aircraft) as mine clearance birds deliberately sweeping those same approach corridors. While mission aircraft either were commited elsewhere or took an alternative route. Depleting the enemy resources and morale in a false operation.

There is a growing trend of belief that the last day of the armed helicopter as a battlefield asset is fast approaching if not already here. This LINK-

Would suggest that the vulnerability of the average vehicle to ORM or IED/VBIED threats is such that there is no point in continuing the development of even armored vehicles. To which the obvious counterarguments are inherent to military systems ability to exploit other than predictable roads and chokepoints. And the difficulty in targeting such vehicles in densely populated urban environs peopled with hundreds more civillian equivalents. Indeed, while the loss /rate/ may certainly be greater in surface vehicles, the individual real value and perceived technical superiority of what are merely 'jeeps and trucks' is much less in the minds of Americans and The World. Making it easier to trade such systems on a many vs. one exchange rate with rotary wing equivalents. I would even go so far as to say that survival of personnel in ground vehicles is relatively if not overwhelmingly high 'per sortie' where such are engaged by improvised explosives. Whereas comparitive loss of a rotary wing aircraft, at any point in the envelope where speed or altitude or lift (rotor disk disintegration) denies an autorotation, seems to statistically imply almost total loss of all onboard. Irrespective of sortie density.

As another point in the debate it appears that the first cracks may be appearing in the Key West doctrine-

The Army would be allowed to retain aviation assets for reconnaissance and medical evacuation purposes.

By which (ERMP) Army use of fixed wing combat assets is denied. In this, certainly the short range responsiveness of helicopters is becoming questionable compared to land vehicles, under 10nm from objective or crisis. While their absolute radius of influence and the time it takes for them to reach a given linear distance in that sphere vs. the total number available or required to ensure their own safety is bordering on extreme and unsupportable in the mid-ranges (over 50 miles). Relative to the continuous dangers faced (minutes or hours) in transiting a threat envelope they never quite leave and for which 'owning the night' is no longer adequate excuse or protection, the long range capabilities of helicopters are starkly lacking. And so must additionally be held to account as a much more difficult to repair as well as replace asset.

Where a small drone has equal speed performance but as much as 10 times as many flight hours endurance, completely above the threat floor, the question may be rightly asked if not answered: "Sure, what goes up must come down but where and how high for how long inbetween" as a more valid measure of the ability to depart a conventional takeoff and landing base, reach a given point in the theater and simply /stay/ there. Until a need arises. Before coming back home (even if that RTB is in fact to another country). All without suffering the distraction of self-engagement. Traditionalists and those jealous of the Army's remaining assets (still the third or fourth largest 'air force' in the world IIRR) will point out that fixed wing aircraft are also highly limited in their ability to deliver point fires and particularly to drop multiple PGMs within feet of friendlies 'in total synch' with a highly fluid ground situation.

Truth be told, this may be a bit optimistic, even for trained helicopter pilots used to working such a high-friction role. It almost certainly does not pay heed to the latest generation of Viper Strike-

And similar weapons designed to do EXACTLY what the army always has with CAS: delivering very small munitions with superb accuracy. Without worrying about being shot at in turn. Something no current helicopter can lay claim too.

If there is, in turn, a threat to the unmanned system or high altitude strikes from conventional runways that it represents, such probably lies most immediately in other, lethal, drones that cost twice or more what a MANPADS does. The farther furture being a misty unknown lit with the intermittent promise of directed energy weapons.

In any case, so long as we must deny modernization and transformation for the exigencies of the current conflict, we must continue to support the use, not simply of 'all available' airpower assets suitable for prosecuting CAS-as-COIN. But those best suited to job through minimal-cost improvements that match our enemies ingenuity, measure for measure.

Unfortunately, much of what is available on the recent losses in Iraq is very non-specific in generating specific ideas for improvement. If someone has comments or additional LINKS please post so that we can expand on more solid details where possible.

Thanks For Your Time...KPl.

Edit to fix long URL links

[edit on 20-1-2006 by SimonGray]
[edit to fix caps lock title]

[edit on 20-1-2006 by dbates]


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