2017/07/02

Attack helicopter survivability

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I do criticize the survivability of even gold-plated battlefield helicopters on a modern battlefield from time to time, and thus also their poor cost-efficiency.

What I consider relevant under this topic

Attack helicopters had simple origins ...
The title here is "Defence and freedom", and by "defence" I mean "defence", not "how to attack some country on a distant continent with few own casualties".
"defence" requires that the own nation or its defensive alliance are under attack. "under attack" means to me blockaded, bombarded or invaded by military or paramilitary forces.
Save for very, very few outright idiotic exceptions the only power that would possibly launch such an attack would be a power that has an idea for how to get away with it. How to "win", or in the case of a preventive war "how to lose less badly than by waiting to be attacked".
The bar is thus very high; only very capable military powers would attack a very capable alliance. Only powers which have nuclear munitions can dare to attack a nuclear-armed alliance.

The only possible attackers are thus powerful armed forces, backed by nuclear munitions. "Bothnians", a.k.a. Russians + Belorussians or at most Russians + PR Chinese + Belorussians fit the bill. No-one else does.

The threats

Russia has no perfect battlefield air defences, but they do almost certainly have the most powerful ones. The primary threat to a Western battlefield helicopter would be Russian fighters (MiG-29, Su-27 and derivatives) and the 2K22 Tunguska self-propelled (V)ShoRAD system.

The implausibly short published effective ceiling of Tunguska's missiles is almost certainly wrong in all but the most challenging scenarios, but I still don't have a good opinion of it because it's apparently radio command guided (though a beam riding guidance would be possible as well) and thus vulnerable to radio link jamming.

The 30 mm guns are more interesting; they can be considered to be very dangerous to any helicopter out to 3 or 4 km. No helicopter is armoured against this calibre and the combination of rate of fire, dispersion and helicopter's slowness makes hits very likely if the fire control got a proper lock on it.

Most man-portable air defence missiles appear to be mostly countered by infrared countermeasures. It's reasonable to expect that the most modern types of thermal seekers would be effective unless very elaborate IR countermeasures are employed, but the bigger challenge is another one anyway; such missiles are expensive, thus few - and helicopters that hover but a few metres above buildings or treelines could and would get away if engaged at any but rather short (under 2 km) distances with such missiles. Laser beamrider missiles are likely very effective against helicopters because very few countermeasures are effective against this guidance approach, but Russians and Chinese have no such ManPADS.

A substantial threat to helicopters are the low tech fully automatic and even bolt action weapons; machineguns, machinecannons, rifles. Overland powerlines are quite a threat, too.

Mines have been devised against helicopters as well. I remember a proposal for a barrage balloon "mine"; a balloon lifts up a kevlar cable and any helicopter flying into the cable would (supposedly) wind it up on its rotorhead and crash.
Here are some examples of anti.-helicopter mines, not all of them Russian or Chinese:
High survivability approaches
  • Battlefield helicopters are partially armoured. Armoured seats, armoured fuel lines and protected fuel tanks are common. Armoured windscreens are common on attack helicopters.
  • Some essential systems are redundant (the twin engine layout has become standard with battlefield helicopters, for example)
  • matte camouflage paints (sometimes with limited IR camo properties), flat windows to minimise glare
  • efforts to hide the hottest parts of the gas turbines from view of IR sensors, mixing of hot exhaust air with cool environmental air
  • The NOTAR system was never adopted for battlefield helicopters because it would be quickly rendered ineffective when perforated.
  • Rotor blades have (supposedly) been hardened enough to resist a 23 mm HEI hit.
  • infrared countermeasures have been employed
  • missile warners (UV and IR spectrum) have been employed
  • datalinks have been introduced so helicopter crews are more aware of threats
  • ManPADS have been carried by some helicopters as deterrent against other helicopters and maybe even fighters
  • laser scanners that provide collision warning regarding powerlines have been developed
Helicopters can often make a crash landing with all engines out (autorotation, crash protection seats), while very, very few battlefield helicopters have ejection seats.

The RAH-66 project was the most radical published project for helicopter survivability (we still don't know much about the spec ops helo that crashed in the UBL raid). The RAH-66 was meant to go beyond the then-typical IR stealth measures and it was an attempt to achieve a much-reduced radar cross section. It did not include the full suite of IR countermeasures (examples here), though. I never quite figured out the idea behind trying radar stealth in a helicopter, but maybe the low observability was expected to be much better and much more capable of delaying a lock-on by a Tunguska fire control radar than I thought. That would still leave the helicopter very vulnerable to horizon-scanning IR-based sensors, though.

... and they ended up in a gold plating dead end.*

What I think how an attack helicopter force could be optimised for survival in Eastern Europe

  • No use of emitting radar, not even millimetre wavelength radars
  • Mast-mounted infrared sensors capable of a quick horizon scan (panorama) with automatic detection of probable targets. This would allow a quick scan, with data being interpreted by machine and weapon systems operator while the pilot flies behind concealment and cover to a new vantage point.
  • Datalink (with AESA antennas) that allows for one helicopter to launch semi-active laser guided missiles, while another helicopter maintains the target designation after the launcher platform had to break contact. Same datalink would also allow sharing of target and threat info in general and triangulation of targets
  • Use of lock on after launch or at least very quick missiles against tanks.
  • A mast-mounted radar warning receiver with good direction finding
  • A data downlink (LINK 16) that informs the pilot about the air situation; any hostile fighters' location and movement within 300 km radius should be known to him. The air force wouldn't know about ALL such hostile fighters, of course.
  • VERY COMPREHENSIVE infrared countermeasures suite (DIRCM if possible)
  • 360° IR/UV missile approach warners that also warn about and categorise large muzzle flashes.
  • Radio command guidance and radio beam rider jamming.
  • Mast-mounted laser rangefinder/target designator should double as cable (powerline or tethered balloons) warning scanner.
  • Bulletproofing (level about as common today)
  • acoustic signature either minimised with Fenestron and blue edge rotor blades or mimicking lower value and lower threat helicopters (common utility helicopters) by using the same main rotor, tail rotor and engines
  • radar jammer module (optimised against Tunguska search radar to delay a lock-on and offer more safe time in line of sight)
  • access to aerial drone feeds that show the location of battlefield air defences and if possible the direction that Tunguska turrets are facing
  • laser warning receiver with direction finding (against laser rangefinders, laser target designators and laser beamriders that are already pointed at the helicopter)
  • sound sensors to detect (and possibly identify) hostile helicopters without line of sight (infrasound), also to detect and categorise gunfires
  • possibly large stub wings to increase the top speed (ability to avoid hostile helicopters)
Tactics and freedom of action

Such attack helicopters (all this effort would in no way be justified for utility helicopters) would hide on the ground (motionless, ideally with covers thrown over the turbines to hide the IR signature) whenever hostile fighters come too close (and too close is nowadays 100 km or so).

The threat of dedicated battlefield air defences would be minimised by avoiding line of sight most of the time. An attack helicopter would operate like an early Cold War submariner who rarely pierced the waves with a periscope, and only did so for a short duration. The helicopter would hide most of the time, change locations often and limit the time of LOS exposure to a few seconds that intelligence and operational research found to be safe enough.
Fire & forget infrared missiles that cannot be defeated by simple means would be defeated by concealing the helicopter behind an entire wall of flares and their smoke and thus breaking the lock-on.

The threat of improvised battlefield air defences (rifles up to IFV autocannons) would be minimised by staying at 2+ km horizontal distance, and preferably hovering above and amidst friendly ground forces. This in combination with ground-launched lock on after launch (and man in the loop) missiles and aerial drones means the gold-plated helicopter I'm writing about would be a substitute for two 3 ton lorries with rather cheap missiles and rather cheap aerial drones.

Only at night - when much less low end threats can see the helicopter - could attacks without protection by friendly ground forces be dared at moderate risk. Again, it would need to stay in placed where few threats can reach it. One example would be to hover over a large lake.

Stragglers, infiltrators and airborne forces that had landed days ago (and thus ran out of batteries) could be engaged from above, particularly if there is a suitable look-down chin IIR/+LRF sensor ball and an autocannon that can engage targets below (more like AH-64's gun than AH-1's, Tigre's or RAH-66's guns).

The threat of hostile attack helicopters would be countered by early (acoustic) warning and either withdrawal, luring the threat helicopter into an air defence trap or ambushing the threat helicopter with missiles and gun.

Some more problems**

There is extremely little that could be done for such a helicopter's survival if hostile land forces launched lock-on after launch missiles such as MICA VL with a good firing solution. The Russians do not appear to have such missiles in use as ShoRAD, but they are perfectly capable of developing and fielding such missiles within a few years.

Furthermore, battlefield helicopters require airspace deconfliction with high angle fires and drones in the area under current Western doctrines and regulations.They might get hit by friendly artillery otherwise, while observing deconfliction rules impedes their mobility.


And that's why I don't think that more than a handful attack helicopters make sense for alliance defence. The first few dozen force an aggressor to spend much more on battlefield air defences that a re suitable against attack helicopters. Any more attack helicopters NEED gold plating to survive at least when used with great caution. The damage they can do to intact hostile peer forces is small compared to the damage they do to the funding of friendly non-battlefield helicopter forces. Moreover, we have substitutes by now.


related:

S O
defence_and_freedom@gmx.de


*: I know it was supposed to be a scout and attack helicopter, but let's be honest; its base model would have had inferior sensor abilities to an updated Apache with Longbow radar and  the Comanche's firepower would have been on par with Cobra or Mangusta firepower. It was a light attack helicopter with low observability ambitions. A tempting, yet most gold-plated military helicopter ever.
**: There are more problems; fuel logistics, operating expenses et cetera, but this time I focused on survivability with some remarks on how this impairs lethality. 
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1 comment:

  1. I remain unconvinced by attack helicopters; they seem to be a distant solution in any role other than a corps level flying reserve anti-armor capability to deal with possible penetrations.

    The issue remains one of opportunity cost, an immensely powerful economic concept that is constantly ignored by military theorists and fan boys. For example, the U.S. AH-64 cost $20 million, which was almost the same as an F-16 with LANTIRN. The AH-64D longbow was far worse at the cost of $65M which exceeds the procurement cost of an F-15E with two LANTIRN pods (about $46M)!

    In every sense the F-16, hardly a standout fighter bomber, dominates the AH-64 in raw airframe performance, and the attack helicopter provides no useful contribution to the broader air campaign. The myth from the first Gulf War is that the AH-64s opened the SEAD campaign, by Kosovo, AH-64s required fixed wing aircraft and MLRS batteries to counter Serb air defenses.

    When we consider availability rates, sortie rates, ordinance delivery capabilities, airframe performance, and above all the opportunity costs, modern attack helicopters are money badly spent.

    GAB

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