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F-35, F-22 and B-2 vs China's Underground Airbases

Everything Old is New Again

Air Power Australia - Australia's Independent Defence Think Tank

Air Power Australia NOTAM

  16th February, 2011
© 2011 C. L. Mills

WGCDR Chris Mills, AM, BSc, MSc(AFIT), RAAF (Retd)

Contacts: Peter Goon
Carlo Kopp

Mob: 0419-806-476 Mob: 0437-478-224

The PLA's forty plus “super-hardened” underground air bases are tunnelled horizontally into the sides of hills, these bases are unusually difficult to destroy and permit concealed preparations for operation, as fuelling, weapons loading and runup activity is invisible to orbital and airborne ISR assets (Chinese Internet).

March of the Chinese People's Liberation Army (PLA Choir)

Assessing PLA Underground Air Basing Capability
APA Analyses Journal Monograph APA-2011-01

People's Liberation Army (PLA) Air Power According to Sun Tzu1:
The general who is skilled in defence hides in the most secret recesses of the earth; he who is skilled in attack flashes forth from the topmost heights of heaven. Thus on the one hand we have ability to protect ourselves; on the other, a victory that is complete.

In making tactical dispositions, the highest pitch you can attain is to conceal them; conceal your dispositions, and you will be safe from the prying of the subtlest spies, from the machinations of the wisest brains.

By discovering the enemy's dispositions and remaining invisible ourselves, we can keep our forces concentrated, while the enemy's must be divided.

The good fighters of old first put themselves beyond the possibility of defeat, and then waited for an opportunity of defeating the enemy.
16 October 1964 was a momentous day of China. At 07:00 GMT, it exploded its first nuclear bomb called ‘596’ – named after the year and month the nuclear weapon program started. On 17 June 1967, China successfully exploded its first Hydrogen Bomb. It took the United States more than seven years from its first A-bomb test to its first hydrogen bomb test, the USSR, four years, and the UK, four and a half years. In China, it only took two years and two months.

After the ravages of World War II, China made a remarkable recovery. However, after assessing the devastation at Hiroshima and Nagasaki, and participating in the Korean War where USA forces pushed back to the 38th parallel and monumental air battles raged, the Chinese leadership must have felt that their country, and especially their armed forces, people and cities, were nakedly exposed to conventional and nuclear attack.

Their response was breathtaking in its scope and execution – tunneling into many mountains and building airbases with underground hangars, equipped with blast doors at the entrances. Aircraft could be hidden, maintained, armed and launched in complete safety from attack by period nuclear weapons. Personnel and armaments have a place safe from attack. No doubt the Chinese were aware of the use of the ‘Tallboy’ to attack the German submarine pens and underground factories, and would have made provision in the design for resistance to attack from ‘earthquake’ bombs. The use of licensed T-14/VB-13 “Grand Slams” dropped by B-29s in Korea by the US Air Force would have been observed very carefully by the PLA.

In terms of effective military defences, these airbases with underground hangars rank with the Great Wall of China, built to hold back the barbarians invading from the north. The Great Wall was a huge impost on the population in terms of cost of construction and cost of garrisons; in the case of airbase with underground hangars, the cost is ‘sunk’ and the cost of these defences is a fraction of equally safe protection of military assets exposed on the surface – an ongoing military bargain. Sun Tzu had some advice, not for China, but for a nation contemplating attacking the installations:
Thus the highest form of General-ship is to balk the enemy's plans; the next best is to prevent the junction of the enemy's forces; the next in order is to attack the enemy's army in the field; and the worst policy of all is to besiege walled cities.

The rule is, not to besiege walled cities if it can possibly be avoided.
The monograph ‘Assessing PLA Underground Air Basing Capability’ by Sean O’Connor and Dr Carlo Kopp is a seminal study of the history and modern use of  China's Super-Hardened Underground Basing. Far from being a relic of the Cold-War, these facilities confer a substantial capability to China in its ability to generate substantial air power and protect the force-in-being. In an era of ‘Spy Satellites’, the recording of normalcy patterns and observation of preparation for offensive and defensive air and aerospace operations is completely denied. If a country wishes to effect a ‘capability and operational surprise’, underground basing is an invaluable resource. Air Power Australia’s recent ‘Long March’ NOTAM illustrates this point.

However, there is no such state as ‘invulnerability to attack’. An assessment of weaknesses in these underground installations can be made by Western observers using a process called ‘Red Force Analysis’ in which the vulnerabilities to attack are examined, likely attack profiles assessed, and necessary responses identified – all from a Chinese perspective. This process is repeated until the Analyst is satisfied that one of two conditions is reached: the installations are acceptably safe from attack, or that they cannot be reasonably or economically defended, and alternative military capabilities are sought. The process is often called ‘Capability Gap identification and closure’.

We can return to Sun Tzu’s ‘The Art of War’ for guidance:
Now the general who wins a battle makes many calculations in his temple ere the battle is fought. The general who loses a battle makes but few calculations beforehand. Thus do many calculations lead to victory, and few calculations to defeat: how much more no calculation at all! It is by attention to this point that I can foresee who is likely to win or lose.

In respect of military method, we have, firstly, Measurement; secondly, Estimation of quantity; thirdly, Calculation; fourthly, Balancing of chances; fifthly, Victory.

Using this discipline is called ‘Weaponeering’ which is part of the ‘Targeting Cycle’:

(© 2011, Carlo Kopp)
If the Commander’s Objective is to neutralize or destroy PLA-AF air combat capability, it will be necessary to destroy aircraft in the air or on the ground. With China’s air combat fleet becoming more numerous, more survivable and lethal, and more youthful by the day, and the USA’s fewer, less survivable and lethal, and more geriatric and/or uncompetitive by the day, destroying aircraft on the ground is more likely to succeed. This objective inherently requires attacking the underground bases.

Attacking mountains, even with airburst nuclear weapons, is futile. The entrance to an underground base is its weakest point, and the US has several weapons for the task, and recent experience in successful attacks on Hardened Aircraft Shelters (HAS). Generally, these are a bomb or warhead with a hardened case capable of penetrating several metres of rock before delay-fusing an ‘energetic’ explosive. The Monograph identifies several weapons ranging from the 285 lb GBU-39 Small Diameter Bomb, through larger bombs in the 2,000-4,800 lb class which can be delivered by some tactical aircraft, to the modern equivalent of the ‘Grand Slam’ - the Massive Ordnance Penetrator GBU-57A/B, only deliverable by large bombers such as the B-52, the B-1B and the B-2.

The US also has cruise missiles such as the RGM/UGM-109E Tomahawk Land Attack Missile and the AGM-158 JASSM with specially designed penetrating warheads.

Defence against these weapons starts with passive measures such as blast doors, tunnel design that blocks overpressure waves, and ‘burster slabs’ that deflect the bomb and blast away from vulnerable areas of the underground bases. While videos of the penetrating weapons look impressive, passive defences such as burster slabs and deflection grids are cheap, effective and quickly replaceable.

Using a ‘layered’ system of defence, China might employ active point defences with systems such as the LD-2000, based on the Type 730 CIWS “Sino-Goalkeeper”, or imported Russian Tor-M2E and Pantsir S. Adaptations of the HQ-6D Aspide and HQ-7B Crotale are also feasible.

Such “Counter-PGM” systems are designed to detect, track and destroy swarms of Precision Guided Munitions (PGMs). Placing systems such as the Pantsir S in pre-determined locations with good detection-views and arcs-of-fire would destroy inbound PGMs during an attack with a high kill probability. Some would still get through the defences, but in terms of the Targeting Cycle, this would increase the number of attacks needed to achieve the required level of effectiveness.

Bunker Busting Munitions

Earthquake Bombs

Therein lies the next problem for US Air Campaign Planners – surviving the ingress and egress. For air-delivered weapons, current planning says they will have a choice of aircraft such as: F-15E, F-22A, F-35A/C, B-52H, B-1B and B-2. China has an extensive and highly Integrated Air Defence System (IADS), and with sensors operating on frequencies from HF to X-Band. Only ‘Low Observable’ aircraft with the necessary combination of range and payload are employable, as early detection and well prepared and capable air forces will detect and destroy ‘strikers’ inbound and the survivors outbound. Depth-of-penetration matters in deep strike, creating many more opportunities for detection and fire against threats compared to the environment of fighting along a FEBA (Forward Edge of Battlefield Area). An attacker also exposes the rear hemisphere of the aircraft as defences are bypassed and any weaknesses in observability from these aspects, as is the case of the from-below-abeam and back-end views of the F-35 JSF, increases the chances of loss. This survivability requirement effectively limits the choice to the B-2A, F-22A and the F-35, if escorted by F-22As to clear defences along the way.

Each aircraft has its own strengths and vulnerabilities. The B-2A has the size to achieve the necessary ‘Low Observability’ across the spectrum of IADS search frequencies, and has the necessary range and payload, and can carry the vital GBU-57/B MOP “earthquake bomb”. But with less than 20 operational aircraft and a requirement for many sorties, tactically repeated as the attacked facilities are repaired and reopened, mounting a successful campaign with such a small number of platforms is problematic at best. The aircraft is large and limited to about Mach 0.85, so intercept, while having a low probability of success, is possible and would have dire consequences in a fighter versus unarmed bomber engagement.

Tactical planners would quickly find that 20 B-2As is insufficient to mount a campaign against a target set of more than 40 airbases with underground hangars. Fortunately, there is a simple, low cost and timely solution: build more aircraft. The tooling is intact, and with the high development cost ‘sunk’, the cost of ‘new-build’ B-2Bs would be a fraction of the cost attributed to B-2As, where the huge development cost was distributed across only 21 aircraft.

Employment of high-value assets such as the B-2 generates a unique set of risks – a baited trap being one. Sun Tzu advised:
All warfare is based on deception.

Hold out baits to entice the enemy. Feign disorder, and crush him.
By exposing high levels of activity at a particular air base and revealing a set of attractive targets, plus some inventive cyber-war mis-advice, could entice an attack. A B-2’s attack, like that of a silent submarine is an ‘indiscretion’, and when the bomb-bay doors open and the weapons fall, the attacked then know that a B-2 is in the vicinity. Swarms of fighters can then be launched and seek out the B-2 Spirit. Even though the probability of an intercept by an individual aircraft is low, when that probability is multiplied by the number of interceptors, the chances of the B-2 being intercepted become significant. This is another argument for additional aircraft – an ability to sustain losses and maintain an effective capability.

The F-22A has the required ‘Low Observability’ in higher frequencies of the IADS search spectrum, but not in the lower bands, and its operations would be restricted to those few hours where, say, HF Skywave Radar is ineffective. As the larger penetrators such as the BLU-113 cannot be carried internally, its ordnance is restricted to the smaller 1,000 lb AUP penetrator and 285 lb SDB penetrator bombs. The Raptor also has a lesser range and payload, introducing more vulnerabilities as more sorties would be required to achieve the Commander’s Intent, and support from Air-to-Air refuelling would be necessary on most missions. Following an outbound F-22A home with an aircraft like the J-XX/J-20 and ambushing it and the refueller during the tanking operation is a high-yield tactic – one used by the Luftwaffe against RAF bombers many times over with considerable success, during the 1940s.

Proponents of the F-35 JSF will suggest its use as a strike weapon. This aircraft has even more limitations in basic performance to those of the F-22A, but it is hoped to provide carriage of the larger 2,000 lb penetrators such as the BLU-109/BLU-116/BLU-118. (Release of this ordnance has yet to be demonstrated). Air Power Australia has made a detailed assessment of the ability of an F-35 JSF to penetrate a well defended target such as this system of underground and protected air bases, and reached the conclusion that it would suffer high attrition levels because of its much higher levels of ‘observability’ compared with the F-22A, and much slower penetration speeds, at much lower altitudes (Please refer: http://www.ausairpower.net/APA-2009-01.html).

The reason for assessing the F-35 JSF as unsuitable, is that the Underground Air Bases, themselves high value facilities, are generally situated near, and connected to, airbases with exposed runways, taxiways and buildings. These facilities would be protected in times of war by longer range SAMs such as the HQ-9, the S-300PMU2 and in future, the S-400.

These assessments of the relative worth of the penetrating capability of the F-22A and the F-35 can be best explained by the substantial kinematic superiority of the F-22A in terms of speed, altitude and manoeuvrability/agility. Speed is vital as a supercruise at Mach 1.5 greatly reduces exposure time compared with a Mach 0.85 ingress and egress. HF Skywave has daily ‘outages’ because of shifts in the ionosphere and requires a dwell time to search designated cells for targets – so the longer you linger, the higher the chance of detection and interception.

Operating over two miles higher and 700 knots faster than the F-35 JSF, the Raptor shrinks the engagement envelope of Surface to Air Missiles (SAMs) and fighter aircraft. If the attackers are fired on by SAMs and these missiles are turning to intercept, the high agility of the F-22A gives it a far greater chance of avoiding the incoming missile. Finally, there is the weapons release distance from target using glide bombs – considerably further in the case of the F-22A at Mach 1.5 and 60,000 feet in comparison with an F-35 JSF at Mach 0.85 and 35,000 feet. There is a huge difference in the kinematics of an F-22A and an F-35, and a corresponding huge difference in survivability – the essential precursor to lethality.

This chart shows the pronounced asymmetry between the PLA's robust basing infrastructure, in comparison with that of the United States, and its principal WestPac allies, Japan and Australia. The chart excludes civil airfields, dual use airfields and PLA military airfields in the two Western MRs. The PLA has available around 150 military airfields, divided not quite evenly between superhardened bases with underground hangars, bases equipped with revetments or HAS, and unhardened bases. In a “PGM-centric” warfighting environment, bases with revetments qualify as unhardened. With around seven times the number of military airbases available, the PLA has a major advantage over the US and its allies, in terms of its ability to rapidly relocate combat units, or redeploy if a base is severely damaged. The number of superhardened bases with underground hangars alone is around twice the total number of operational bases used by the United States, and its principal WestPac allies, Japan and Australia. Whether we consider scenarios involving pre-emptive attacks, or sustained air wars of attrition, China has an enormous advantage over the United States, and its allies, as the asymmetry in basing infrastructure produces a strong asymmetry in military effort required to degrade airbase operational capability, attrit aircraft on the ground, or render basing unusable (© 2011, C. Kopp).

Lastly, there is the ‘tit-for-tat’ response. If China’s airbases, underground or conventional, are attacked, then there is likely to a retaliatory response. Here Sun Tzu has some advice:

To secure ourselves against defeat lies in our own hands, but the opportunity of defeating the enemy is provided by the enemy himself.

With China operating from more than forty well defended, underground bases, and the US from a small number of airbases with no or minimal hardening and defences, and a reliance on vulnerable air-to-air refuelling to provide the necessary range, there is considerable asymmetry in the vulnerability – and susceptibility – between the two sides. As China increases its ‘Low Observable’ strike range and payload with aircraft like the J-XX/J-20, it can win a war of attrition in a ‘tit-for-tat’ situation.

Finally, we should address an even more pernicious outcome of the asymmetry between China, and the US and it’s Allies, to resist a full scale conventional weapons assault – a fallback to the “Dr Strangelove Mineshaft Gap” days of ‘Mutually Assured Destruction’ (MAD) and the constraints that balance-of-destructive-power so successfully imposed. If the Hawks propose a ‘Nuke ’em ‘til they Glow’ last resort, they should consider which country has large and substantial Underground Bases, capable of sustaining life through a nuclear attack and the aftermath until the level of radioactivity subside to a survivable level. And at that time, that country could emerge with clear capability advantage in terms of armies of people and numbers of conventional and nuclear weapons, together with air and missile delivery platforms. Sun Tzu’s advice?
It is only one who is thoroughly acquainted with the evils of war that can thoroughly understand the profitable way of carrying it on.
Combining the layers of defence to make destruction by offensive capabilities nigh impossible is a sound stratagem, and one that China seems to have done in ‘recycling’ its Cold-War nuclear-hardened underground air bases to provide a safe haven for its modernised and highly capable air force.

Let Sun Tzu have the last word, across 2,600 years of time:
If you know the enemy and know yourself, you need not fear the result of a hundred battles.

If you know yourself but not the enemy, for every victory gained you will also suffer a defeat.

If you know neither the enemy nor yourself, you will succumb in every battle.

Northrop B-2A Spirit (US DoD).


1 Sun Tzu, The Art of War, URI: http://www.chinapage.com/sunzi-e.html.
2 O'Connor S., Kopp C., Assessing PLA Underground Air Basing Capability, Air Power Australia Analysis 2011-01,  16th February 2011, URI: http://www.ausairpower.net/APA-2011-01.html
3 Kopp C., Hardening RAAF Air Base Infrastructure, APA Analyses, Vol. V APA-2008-02, URI: APA-2008-02.html; Kopp C., The GBU-28 Bunker Buster, Technical Report APA-TR-2005-0501, URI: GBU-28.html; Kopp C., GBU-39/B Small Diameter Bomb I, Technical Report APA-TR-2007-0106, URI: APA-SDB.html.
4 O'Connor S., Underground Airfields: The DPRK, GEIMINT Blog, URI: http://geimint.blogspot.com/2010/07/underground-airfields-dprk.html.
5 Stillion J., Fighting Under Missile Attack, Air Force Magazine, Vol. 92, No. 8, August, 2009, URI: http://www.airforce-magazine.com/MagazineArchive/Pages/2009/August%202009/0809fighting.aspx
6 Kopp C., People's Liberation Army Air Force and Naval Air Arm Air Base Infrastructure, Technical Report APA-TR-2007-0103, January, 2007, URI: APA-PLA-AFBs.html.
7 O'Connor S., Chinese Military Airfields, GEIMINT Blog, URI: http://geimint.blogspot.com/2008/12/chinese-military-airfields.html.

Assessing PLA Underground Air Basing Capability
APA Analyses Journal Monograph APA-2011-01


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