Assessing
PLA Underground Air Basing Capability
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PLA-AF
Shenyang J-8 Finback fighters being towed into one of the PLA's many
“super-hardened” underground air bases. 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. Note the open exterior blast door (Chinese Internet).
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Abstract
The PLA's network of around forty underground airbases provides a
unique and indeed superlative capability to withstand a large scale
counter-air campaign,
as significant effort with penetrating munitions of large mass would be
required to close such bases down for the duration of the campaign, or
permanently render them unusable.
As these bases deny surveillance by orbital, airborne or ground based
ISR assets, they provide an inherent capability to perform covert
preparations for combat operations, be it in times of conflict, or in
the period immediately preceding a conflict.
The hangaring capacity of these underground bases is of the order of at
least 1,500 combat aircraft, possibly greater, if more than basic
internal
tunnel arrangements have been employed. This capacity represents
more
than the total number of modern combat aircraft currently operated by
the PLA.
In strategic terms, the PLA's underground airbase infrastructure
provides a capability to deny at this time even
the United States the opportunity to inflict massive early attrition
upon the PLA's fleet of combat aircraft, while these are on the ground.
This would force any opponent, including the United States, into a
protracted aerial war of attrition, before decisive losses could be
inflicted upon the PLA combat
aircraft fleet.
The inherent survivability of the
PLA's impressive underground airbase infrastructure has not been a
major consideration in the ongoing debate in the United States on the
utility, and indeed intended design, of the replacement heavy bomber
aircraft. If the defeat of the PLA's underground airbase infrastructure
is part of the intended role of this future aircraft, then this
aircraft will need to combine the survivability needed to repeatedly
penetrate what is becoming the most capable Integrated Air Defence
System in
existence, with the ability to deliver heavy “earthquake bombs”.
Anything less will result in unsustainable combat attrition.
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Introduction
A unique feature of China's air power
basing environment, compared to
other major air forces, is the widespread use of underground or
“super-hardened” hangars, of which more than forty have been
identified from open source and declassified KH series reconnaissance
satellite imagery.
Intended to maximise the survivability of aircraft and critical
operational infrastructure under air attack, underground hangars have
historically been used mostly by smaller air forces, such as those in
Sweden, Switzerland, the DPRK, the former Yugoslavia, and the former
socialist Albania. The motivation, typically, was to survive in a
threat environment where the defending air force was numerically, and
often, also technologically uncompetitive against the threat.
Deeply buried infrastructure, such as production and maintenance
facilities, proved highly survivable during the Second World War, when
Germany constructed a myriad of underground production lines, for
critical material including A-4 ballistic missiles and fighter
aircraft. These facilities proved highly resistant to carpet bombing
using
standard unguided munitions. The handful of successful attacks on
similar underground targets involved exclusively the Royal Air Force
617 SQN,
dropping
Tallboy or Grand Slam “earthquake bombs”1.
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Saumar
Tunnel after attack by earthquake bombs in 1944 (RAF).
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The advent of nuclear weapons in 1945, airburst at low or medium
altitudes, produced considerable interest in
hardened shelters and underground hangars during the late 1940s and
1950s, as the West and the Warsaw Pact expanded their nuclear warstocks
and
adapted their doctrine.
Aircraft parked on tarmacs, in WW2 style revetments, or on pads with
earthwork berms, were vulnerable to nuclear blast overpressures,
involving both direct pressure loading, or lifting and overturning by
the
passing shock transient. Glasstone documents several examples of
structural damage from overpressure effects2.
Glasstone states that blast overpressure transients of 1 to 2 psi
produce damage to exposed aircraft. Higher overpressures, typically
from 4 to 10 psi, resulting from higher weapon yields or closer
proximity to the epicentre, will typically produce damage beyond
economical repair.
Thermal radiation from nuclear blasts would have a limited effect on
unpainted anodised aluminium aircraft skins due to the high infrared
reflectance of aluminium, but is capable of igniting painted components
and other airframe materials, as well as fuels. Glasstone details
radiant intensities for 24 kiloton, 1.4 megaton and 20 megaton
airbursts in Table 7.40.
Initial gamma radiation and neutron flux for early weapons presented
primarily a threat to personnel, while bomb residue and other fallout
could render aircraft and equipment unsafe for use.
Underground hangars therefore provided a very robust passive defence
against nuclear blast, thermal and gamma radiation, electromagnetic
pulse (EMP) effects and neutron flux,
while permitting the whole operational servicing, refuelling and
loading area, and aircraft storage to be protected from fallout.
Protection against fallout in turn presented the opportunity to also
protect the aircraft and personnel from exposure to biological and
chemical weapons, both of which were widely deployed for operational
use
during that period.
While the primary imperative behind underground hangar designs was
protection of aircraft, personnel, POL, munitions warstocks and support
equipment against
conventional bombing, nuclear bombing, and chemical and/or
biological agent deliveries, they presented another important advantage.
Underground hangars provide a measure of covertness absent in
conventional basing, as operational activity can only be established
once aircraft roll out of the caverns to depart on sorties. Fuelling,
servicing, loading, testing and other activities can be conducted out
the sight of airborne, orbital and surface observers.
The use of underground hangars is not without disadvantages. Unless a
naturally occuring cavern is expanded or modified, the cost of
tunnelling can be considerable, especially if the rock is of a hard
igneous type, rather than soft sedimentary type. While the former
offers much better protection than the latter, availability depends
wholly on the local geology available.
Other unique and ongoing maintenance issues exist. One is ensuring that
water does not penetrate or accumulate inside the tunnels. Trees
growing near entrances or other surface features may damage the rock or
concrete through root penetration. Vermin, such as birds and bats may
seek shelter or nesting inside the tunnels, presenting a risk of
contagion, but also presenting the potential for damage to equipment by
FOD (swallowed stones) or corrosive guano.
China started constructing underground hangars as part of its large
scale 1950s airfield construction effort, and declassified KH-4 Corona
IMINT collected in 1962 - 1963 shows construction of such basing well
under way at that time, including auxiliary alert runways and/or
taxiways now known to lead to the hangar entrances.
China's Underground Airbases,
Geographical Placement (red - PLAAF, blue - PLANAF, green -
unidentified tenant afiliation) [Click to enlarge][KMZ Download].
KH-4 Corona wet film imagery of Chanzing AB
in Nanjing MR, collected 1962-1963, showing underground hangar access
under
construction (US DoD via FAS).
A number of PLA airbases explored more recently using high resolution
Google Earth IMINT indicate that some bases were specifically sited
with the intent to construct underground hangars, which may have been
commenced but was not completed. On other sites there is evidence of
construction work on taxiways or hangar entrances, suggesting ongoing
maintenance or construction effort. Some sites, such as the well known
PLANAF base at Lingshui on Hainan Island, are optimally located next to
a suitably large hill, but there is no evidence of underground hangar
construction or associated taxiways, which does not preclude the
construction of an underground hangar at a future date.
At this time a small number of the PLA's underground hangars are
derelict, typically as a result of the associated airfield being
converted to other than military operational use. Examples include the
abandoned Daishan Island fighter base, south of Shanghai, and the
completely overbuilt Yidu fighter base, converted to a warehousing
area.
Suburban encroachment appears to be the primary cause of PLA airfields
being abandoned, although many have also been converted in recent years
to civilian airports, often retaining some military use.
Most of the PLA's underground hangars appear to be in operational use
at this time.
China's most prominent Cold War period client states, Albania and the
DPRK, both constructed airbases with underground hangars patterned on
the PLA design.
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PLA
Airbase Design
Strategy, Base Construction and Capacity
The study of well in excess of 200 Chinese military, civil and dual use
airfields shows a disciplined and highly standardised approach to
airfield construction, with often identical runway, taxiway and tarmac
arrangements for given categories of airfield.
Broadly, all designs observed revolve around three basic
configurations, one for fighter bases, one for bomber bases, and one
for transport bases, with the caveats that some bomber bases started
life as fighter bases, and many transport, bomber and fighter bases
have
over the last decade been rebuilt into civil airports, which often
retain a dual-use capability.
As late entrants in the game of military airfield construction, the
Chinese had the benefit of extensive overseas experience, and most
military airfields are patterned on standard and very robust Warsaw
Pact fighter base designs of the 1950s period. There can be no doubt
that Warsaw Pact engineers, especially Soviet engineers, played a
pivotal role in establishing the PLA's airfield construction program
during the 1950s.
Good comparative examples of construction are the former
Soviet Frontal Aviation bases in Eastern Germany, such as Grossenhein, Templin-Gross, Altenburg-Nobitz, Tutow-Demin, Brand, Welzow,
Damgarten, Wittstock, Eberswalde-Finow, Zerbst, Hinsterwalde, Juterbog, Merseburg, Rechlin and Sperenberg.
PLA AF Quzhou AB in the Nanjing MR.
Quzhou is atypical insofar as the revetments in the dispersal area are
connected by a full arc of taxiway, requiring multiple 'cuts' by an
attacker to close the taxiway. The revetment pads of typical PLA
airfields are 75 to 100 ft in diameter and can accommodate up to three
Farmer, Fantan or Fishbed fighters. or one or two Flankers. Dispersal
taxiways are typically 45
ft wide. At least one Badger base has pads sized to fit a single
aircraft, but no berms were installed. The
PLA's approach to the construction of semi-hardened and hardened basing
closely follows the Soviet Cold War model (US
DoD).
Given a highly standardised approach to airfield layout, typically
employing a single primary runway with a parallel taxiway, the latter
often usable as a redundant runway, the principal differences between
PLA fighter bases are typically to be found in the dispersal area
arrangements, and whether the base employs an underground hangar.
Mostly, fighter bases with underground hangars do not employ networks
of taxiways and dispersal revetments, although dual taxiways to the
hangar system are common. Most bases have alert aprons at
either end of the main runway.
The “classical” Warpac style bases are well hardened by the standards
of the era predating PGMs, usually employing horseshoe shaped earthwork
berms around individual dispersal pads, thus making these difficult
targets for low altitude strafing, rocket and dive bombing attacks.
This dispersal arrangement has been observed at fighter bases, H-5
Beagle bases, and H-6 Badger bases.
At this time the global availability of PGMs capable of often very
precise steep trajectory attacks largely defeats the Warpac era
dispersal scheme, as individual revetments can be hit, and the linear
or looped taxiway arrangement can be easily cut with a modest number of
rounds. While the latter problem can be cheaply corrected by adding
additional taxiway paths, the use of revetments at this time provides
benefit only in reducing fratricide from exploding and burning aircraft.
TAB-V
Hardened
Aircraft
Shelters
at Kadena
AFB,
Okinawa, are
not designed to survive hits from bunker buster
penetrating munitions. Most PLA HAS are similar in appearance to TAB-V
shelters (US Air
Force image).
Hardened
Aircraft
Shelters
at
Suixi
AB
and
Xiangshui
Hsu
AB
(Google
Earth).
PLA fighter bases with underground hangars have been constructed where
local geography permitted, and we can surmise that the construction of
the softer “classical” Warpac style bases simply reflected the
geographical unavailability of suitable mountains, hills or hillocks in
areas where an airbase needed to be constructed.
An interesting geographical feature of much of the eastern seaboard of
mainland China is that very flat areas are frequently punctuated by
isolated hills or mountains, or short chains of same, and it is at such
sites that the PLA constructed most of its underground hangars in the
Shenyang, Beijing, Jinan, Nanjing and Guangzhou MRs.
The arrangement of the airfield proper and the underground hangars
varies widely, and clearly the engineers designing these sites sought
to exploit the local geography to every extent possible. A factor which
clearly impacted the placement of runways relative to the hill
concealing the hangar was the flatness of terrain in close proximity to
the hill. As a result, while many such bases have the runways and
aprons placed within a hundred metres of the hill, in some instances
the distance is as great as kilometres, a major impediment in
sustaining high sortie rates.
A very useful feature observed in a good number of these bases is the
construction of an auxiliary takeoff only runway in place of one of the
dedicated taxiways, or a full capacity second runway fully capable of
recovering aircraft. These auxiliary runways have one end usually
placed
immediately at one of the underground hangar entrances, which has an
apron at the entrance, or within a few
hundred yards, to permit aircraft to taxi out, line up, and immediately
roll into a takeoff. Upon returning from a sortie the aircraft would
land on the main runway, and then taxi or be towed along the auxiliary
runway or taxiways back to the underground hangar. Usually a paved pad
or apron is also sited at the midpoint of the auxiliary runway, or
taxiway
between the runway and hangar, to permit takeoffs while aircraft are
being returned to the hangar. These sites are
easily identified as the auxiliary runway is much wider than a standard
taxiway, and is straight unlike many taxiway sections. At some
sites, the auxiliary runway is in a state of
disrepair, and at one site it is clearly overgrown with vegetation.
Auxiliary takeoff only runways are installed at Chifeng AB, Zunhua AB,
Jinzhou Xiaolingzi AB, Yinchuan / Xincheng AB, Lihue AB, Anqing AB,
Changzing AB,
Daishan Island AB, Feidong
AB, Guiyang AB, Taihe AB, Yiwu AB, Foluo Northeast AB, Jiyuan AB,
Leng Shui Chi AB, Yaotian AB, Guodu AB, Jiyuan AB, and Luyang
AB, which constitute around 50 percent of known bases with
underground hangars. It is likely that bases without such runways and
having
long taxiways simply lacked suitably flat local terrain for second
runway construction.
Taxiways into underground hangar entrances reflect the placement of the
entrances, which are mostly situated at opposite sides of the hill
being used, although a modest number have entrances on the same side,
up
to 200 m apart. Mostly two entrances are employed, and the taxiways
fork in a Y pattern, following the contours of the base of the hill. A
small number of sites employ one entrance, but Guiyang AB in Nanjing
MR, and Yinchuan AB in Lanzhou MR, each have four entrances in a single
hill.
J-6A Farmers (Chinese Internet).
Both the J-8
Finback
and J-7
Fishbed
are
compatible
with
the “fighter-sized” underground hangars (Zhenguan Studio, ©
2010 Air Power Australia).
A H-5 (Il-28) Beagle, developed as
an analogue to the
Canberra and B-66 medium bombers, on display in the Datangshan
underground hangar (Zhenguan Studio, ©
2010 Air Power Australia).
The Luyang / Ranghe-Zhen AB site is employed at this time in part as a
mass storage site, and in part as a museum. It is unusual in that it
combines “MiG-sized” hangars,
“Beagle-sized” hangars
and one partially completed “Badger-sized” hangar.
Above, interior view of the “Badger-sized”
hangar, currently used to display early fighter aircraft . The
incomplete “MiG-sized” tunnel may have been
intended to connect to the remainder of the tunnel system
(Chinese Internet).
Comparative entrance sizes for PLA
underground hangars, scaled from imagery. Some fighter base entrances
are as narrow as 12 metres, while some “Badger-sized” base entrances
may be as
wide as 40 metres. There are eight known 35 - 40 metre wide
“Badger-sized” hangars, one of which is decommissioned, fourteen known
~22 metre wide “Beagle-sized” hangars, and seventeen known 12 to 14
metre wide “MiG-sized” hangars (C. Kopp).
- “MiG-sized”: 12 - 15 metre entrance widths
compatible with the J-4/MiG-15
Fagot, Q-5 Fantan, J-5/MiG-17 Fresco, J-6/MiG-19 Farmer,
J-7/MiG-21 Fishbed and later
J-8 Finback;
- “Beagle-sized”: ~22 metre entrance widths compatible
with the H-5 Beagle;
- “Badger-sized”: ~35 - 40 metre entrance widths
compatible with the H-6 Badger.
The entrance width most commonly observed is ~45 ft (~14 m), evidently
sized for
legacy PLA fighter aircraft but still compatible with the more recent
J-8
Finback and JH-7 Flounder. This explains why J-11A/B Flankers have not
been observed
operating from such hangars, as the Flankers' 48 ft 3 in (14.7 m)
wingspan is simply too great to permit entry.
Operating the
J-11A/B from these sites would require the retrofitting of the
Su-27K/Su-33/J-15 folding wing, or manufacture of new aircraft with
same, or excavation of the tunnel to a greater size.
The new Chengdu J-10A/S/B has a span of 31 ft 10 in (9.7 m) and will
comfortably fit all PLA underground hangars.
The prototype Chengdu J-20
would require folding wings, or at least wingtips, to fit the 14 metre
width entrances.
Many of the bases observed have ~22 metre width entrances, and
evidently were constructed for H-5 Beagle units, the span of this
aircraft being 21.5 metres. These could accommodate the J-11A/B,
Su-30MKK/MK2 and the J-20 without modification of the aircraft or
tunnels.
A half dozen of the known operational sites have 33 to 40 metre wide
entrances, permitting access
for the H-6 Badger, and thus compatible with all smaller types.
H-6 Badgers being towed from
an underground
hangar. Six of the known sites have 30 metre entrances permitting
access for the H-6 Badger (Chinese Internet).
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The Beijing Shahezhen AB
site, better known as the Datangshan Museum,
has an underground hangar sized for the Tupolev Tu-16 / Xian H-6
Badger. Datangshan is the only PLA underground hangar accessible to the
general
public.
Internal arrangements used in PLA underground hangars are mostly
unknown, as very few images exist in the public domain. Given the
nature of underground hangars, numerous possibilities exist in terms of
internal layouts.
Importantly, most sites with underground hangars are devoid of external
hangars which would in other basing be used for engineering work on
aircraft.
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Stowing fighter aircraft in underground hangars presents similar
challenges to those seen in aircraft carrier hangar decks, but with the
difference that hangar decks have width usually absent in underground
hangars. The PLA will therefore have developed numerous procedures for
aircraft handling in such confined spaces.
Significant increases in internal storage capacity and
supporting capabilities such as materiel storage and personnel
accommodation can be achieved by using complex rather than simple
internal topologies (C. Kopp).
The simplest internal arrangement which is compatible with the entrance
layouts of the known underground hangars is a simple straight, curved
or segmented tunnel connecting the two entrances. This is indeed the
arrangement at Datangshan, where the overall length of the hangar
between the entrances is just over 500 metres. Assuming H-6 aircraft
parked nose to tail, this site could accommodate at least a dozen
aircraft, which is a standard PLA-AF squadron.
If we consider a simple straight, curved
or segmented tunnel connecting the two entrances as the standard
internal layout, the linear distance between the entrances provides a
reasonable measure of internal capacity. For most of the sites, ~500
metres was measured, although some are up to 1,000 metres apart, and
some as little as ~300 metres apart. Sites with same-side entrances
will likely employ a horseshoe shaped loop4.
Annex B contains a preliminary and very conservative
assessment of the capacity available in the PLA's network of
underground hangars. This assessment does not consider the impact of
additional branching tunnels, or forks and parallel tunnels, which
could significantly expand capacity for aircraft and materiel. As such
it may underestimate extant hangar capacity, and certainly
underestimates the potential capacity, were the PLA to expand these
hangars by additional enlargement of extant tunnels or further
tunnelling.
The seven known operational “Badger-sized” underground hangars have a
minimum capacity of
the order of 120 H-6 aircraft, which suggests on currently cited H-6
numbers, that the whole PLA H-6 fleet could be accommodated.
The fourteen known “Beagle-sized” underground hangars have a minimum
capacity of
the order of 600 Flankers, or 500 J-20 aircraft. Again, this would
accommodate all extant PLA Flankers with surplus capacity. Similar
numbers of the JH-7 Flounder could be also accommodated.
The seventeen known “MiG-sized” underground hangars have a minimum
capacity of
the order of 600 to 800 J-10 Sino-canard fighters, which is a
substantial fraction of the intended production numbers.
At least three more underground hangars are known, but given
limitations in currently available imagery, capacity cannot be reliably
assessed.
The aggregate number of combat aircraft which could be accommodated is
at a minimum of the order of 1,500, considering that the highest value
types would
be placed into such hangars under conditions where attacks on the
mainland were expected.
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Underground
Air
Base
Vulnerability
Of the available techniques for constructing hardened airfields,
underground airbases are the least vulnerable to both conventional and
nuclear weapons effects, and thus present as an attractive choice in a
environment where precision guided munitions have proliferated
globally. With pervasive orbital and airborne ISR capabilities, the
concealment of operational preparations afforded by underground hangars
is much more valuable than when these were initially constructed.
A detailed discussion of “bunker busting” free fall bomb and cruise
missile
warheads can be found in earlier publications3.
In summary, modern “bunker busting” weapons fall into several classes,
with varying
penetration performance, employing conventional and more recently
thermobaric explosive fillers. Refer Table 1.
| Small Diameter Bombs |
Standard Penetrators |
Deep Penetrators |
Heavy Penetrators |
GBU-39/B
SDB
I
(385
lb)
|
BLU-109/B (2,000
lb) |
BLU-113/B
(4,800
lb) |
GBU-57A MOP
(30,000 lb) |
| Luoyang
LS-6
(100
kg) |
BLU-116/B AUP
(2,000 lb) |
BLU-122/B
(4,800
lb) |
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| Luoyang
LS-6
(50
kg) |
BLU-118/B (2,000
lb) |
KAB-1500
(1,500
kg) |
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KAB-500 (500 kg) |
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Table 1.
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Small Diameter Bombs and Standard Penetrators were
developed primarily to defeat Hardened Aircraft Shelters and other
hardened surface structures, primarily built using steel reinforced
high strength concrete. These weapons are known to penetrate 6 to 12 ft
of reinforced concrete, subject to the concrete strength and delivery
method. Such weapons
are sized for internal or external carriage by fighters.
Deep Penetrators were developed primarily to defeat
underground bunkers, and can penetrate up to 18 ft of reinforced
concrete, or less under some depth of soil or soft rock. These weapons
are sized for internal carriage by heavy bombers or external carriage
by heavy strike fighters, such as the F-111, F-15E, or Flanker.
Heavy Penetrators were developed primarily to defeat deep
underground bunkers, and represent a modern reimplementation of the
1940s “earthquake bomb” concept. They can only be lifted by heavy
bombers,
equipped with special adaptors. These weapons are intended to produce a
high velocity shock wave in the rock which will collapse bunkers,
tunnels or other deeper structures.
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Earthquake
Bombs
Past
and
Current
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RAF 617 SQN Lancaster
dropping a Tallboy. The aircraft had numerous modifications applied to
carry and target the demanding Tallboy and Grand Slam bombs, including
a unique sculpted bomb bay (RAF).
Tallboy after release, prior
to pitchover, and spin up (RAF).
12,000 lb Tallboy ground
handling (RAF).
30,000 lb GBU-57A/B Massive
Ordnance Penetrator, built for carriage by the B-1B, B-2A and B-52H
(Boeing).
GBU-57A/B Massive Ordnance Penetrator release
from a B-52H (DTRA).
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Tactics for counter-air strikes on airfields today mostly reflect the
Desert Storm model, but using contemporary aircraft and weapons. In
Desert Storm, Coalition F-117A and F-111F aircraft dropped pairs of
GBU-24/27/BLU-109B weapons on HAS, and GBU-10/Mk.84 on runways and
taxiways, while RAF Tornados did much the same using GBU-10/Mk.84, with
laser illumination provided by Tornado GR.1/TIALD or Buccaneer S.1/Pave
Spike “master bombers”.
In a contemporary conflict, the delivery platforms of choice would be
the F-22A Raptor armed with the penetrating GBU-39/B SDB and B-2A
Spirit armed with
the penetrating GBU-39/B SDB and/or deep penetrating GBU-31/B/BLU-116/B
AUP, as only these aircraft types
have the survivability to repeatedly penetrate a modern IADS without
incurring unsustainable attrition.
These weapons and tactics would provide some effect against a base
equipped with an underground hangar, but do not provide a high
probability of a robust
and unrecoverable kill.
In conventional steep terminal trajectories, these bomb types could be
used to
damage the hangar entrances and in some instances cause the entrance
roof to cave in, or mountainside above the entrance to collapse. There
is no guarantee that significant damage would be
inflicted on aircraft and other materiel inside the hangar, presenting
good odds that the site would be operational again in a day or so.
Damage to runways and taxiways can be repaired quickly, if planned for.
The ability of these munitions to penetrate the rock in proximity
to the hangar entrance, or above the hangar cavity, depends not only on
the design and terminal trajectory of the munition, but also on the
mechanical properties of the rock. Southern and Eastern China, where
most
underground hangars are situated, has an abundance of dense igneous
rock formations, many with high fracture toughness.
Where the weapon autopilot software permits a horizontal or very
shallow terminal trajectory, and entrance placement permits, the
weapon can be programmed to fly horizontally into
the hangar entrance and initiate deep inside the hangar. This mode of
attack, especially if the warhead has a thermobaric filler, presents
much better odds of success, as a large scale fire can be produced
which can destroy stored materiel, including aircraft, POL, and
stored munitions.
After such an attack the underground hangar will likely still be
repairable,
but may require significant rebuilding as fires will destroy or
severely
damage internal cladding, wiring looms and plumbing, while leaving
hazardous residues and UXO in the hangar cavities. In a high intensity
short duration conflict this mode of attack would render the target
unusable for the duration of the conflict.
The drawback of “flying the bomb in through the front door”
attacks is that in
many locations, the simple expedient of placing a berm, reinforced
concrete entrance blocker, or burster slab in front of the hangar
entrance would preclude such attacks.
This method is infeasible where the entry to the hangar is in a deep
canyon cut into a hillside, but such locations would in turn permit the
installation of sacrificial prestressed concrete burster slabs or
deflection grids over the entrance, to force the inbound weapon to
initiate early,
outside the main blast doors5.
At least one underground hangar equipped base in the DPRK, designed to
the PLA pattern, incorporates a blocking structure in front of the
hangar entrance6.
The notion that the PLA, being as well versed as it is in airfield
construction and passive defence, would not deploy such simple and
cheap protective
measures at such important sites is not realistic. The technology and
design technique for burster slabs and deflection grids is relatively
mature, and well within the reach of China's indigenous civil and
construction engineering capabilities. China has an abundance of
earthmoving equipment and experienced construction workers.
The “conventional” approach to
attacking hardened structures is from above or the sides. This example
shows attack into the rock above the entrances. The intent would be to
collapse the tunnels at either entrance from above.
The only robust “quick kill” tactic against an underground hangar with
a high probability of causing the hangar cavity to cave in, thus
rendering it
permanently
unusable, is the use of the GBU-57A/B Massive Ordnance Penetrator, or a
similar “earthquake bomb” class munition. In
well defended airspace, such as China's Eastern IADS sectors, this
would require delivery by very scarce B-2A
bombers. To effect a robust kill against a typical PLA underground
hangar would require multiple well placed GBU-57/B hits, reflecting the
extensive Royal Air Force operational experience of the 1940s using the
Tallboy and Grand Slam “earthquake bombs” to destroy underground
structures.
The British experience with the use of the
Tallboy and Grand Slam was that despite the exceptional penetration
performance of these weapons, many targets with unusually strong rock
or concrete roofs were difficult to defeat, as the weapon could not
penetrate the dense materials deeply enough to produce the intended
effect. This would be an issue for attack on underground hangars where
the hill or mountain was of an igneous rock composition, such as
granites, basalts, diorites or serpentines. Such rock is often both
hard and tough, which limits penetration depth strongly in comparison
with sedimentary rock types.
The strategy used by the British with considerable success was to put
the bomb next to the target, into softer materials, such that the shock
effect hit the target from the sides or below, where it was less able
to absorb the load and would collapse as a result.
Study of PLA underground hangar construction
shows tunnels with a weighted catenary arch cross section, intended as
in the design of bridges or other structures using catenaries, to
transfer compressive loads produced by the weight of the rock above,
outward into the lower sides of the tunnel. The compressive shock loads
even from large conventional bombs, or airburst nuclear weapon
overpressure, hitting above the tunnels would be transferred by the
catenary section into horizontal compressive loads in the rock.
The weakness of this design is that a latent tensile load exists in the
tunnel floors, resulting from the compressive force on the lower tunnel
walls.
Attack with a GBU-57A/B aimed at the apron infront of each tunnel
entrance would generate a shock pulse with a large component pushing
the tunnel floor upward, and thus increasing the tensile load on the
tunnel floors. While reinforced concrete has some tolerance for tensile
loads, rock typically does not, moreso if the load is cyclic, or
repeated. Such an attack therefore has the potential to collapse the
tunnel from below, by causing the floor to burst into the cavity. Even
modest damage levels would present difficulties by impairing aircraft
movements over a fractured floor, with significant potential for
spalling damage from delaminated concrete fragments.
The “Wallis” approach to attacking hardened structures
is from below and the side. This example shows attack into the apron
in front of the hangar entrances. The intent would be to collapse the
tunnels at
either entrance from below.
Counter-PGM weapons such
as this LD-2000 30 mm Gatling SPAAG (above) could significantly
complicate
defeat of PLA airbases equipped with underground hangars, by attritting
penetrating PGMs prior to impact. The LD-2000 is a derivative of the
Type 730 CIWS (below), itself a Chinese copy of the Thales Nederland
Goalkeeper, with the Type 730B gun a copy of the General Electric
GAU-8 Avenger 30 mm x 173 mm seven-barrel gun used
on the A-10 Warthog. The LD-2000 was recently integrated with a CBR to
perform the C-RAM role (Chinese Internet).
The Russian Kupol 9K332 Tor M2E / SA-15D Gauntlet was
specifically developed to engage and defeat saturation PGM attacks
against critical infrastructure, as a competitor to the KBP 96K6
Pantsir S1E / SA-22 SPAAGM. The PLA operates the earlier and less
capable 9K331M1 Tor M1 SAM. Depicted example is deployed (Strizhi.info).
The
high destructive effect and procurement cost of large munitions such as
the GBU-57A/B MOP would easily justify the use of area defence SAMs
such as the HQ-12 or HQ-9 to intercept such PGMs after release. Left:
HQ-12/KS-1A
TELs
and
H-200
engagement
radar;
right:
HQ-9
TEL
and
HT-233
engagement
radar
(via Chinese Internet).
Defensive Measures Available for
Survivability Enhancement of Underground Hangars
|
Measure
|
Category
|
Effectiveness
|
Cost
|
SDB
JDAM
|
MOP
|
Entrance
Burster Slabs
|
Passive
|
High |
Low |
Low
|
Entrance
Blocking Structures
|
Passive |
High |
Low |
Low
|
Entrance
Deflection Grids
|
Passive |
High |
Low |
Low
|
Redundant
Entrances and Access Tunnels
|
Passive |
High |
High
|
Site dependent
|
Procure/Deploy
9K332 Tor M2E / SA-15D Gauntlet SAM
|
Active
|
High |
High
|
High |
Procure/Deploy
96K6 Pantsir S1E / SA-22 SPAAGM
|
Active |
High |
High
|
High |
Evolve/Deploy
LD-2000 SPAAGM C-PGM Variant
|
Active |
High |
Low |
Modest
|
Evolve/Deploy
HQ-7B/FM-90 Crotale C-PGM Variant
|
Active |
High |
Low |
Modest |
| Evolve/Deploy
HQ-6D/LY-60 Aspide C-PGM Variant |
Active |
High |
Low |
Modest |
Redeploy
HQ-12/KS-1A Batteries
|
Active |
Low |
High |
Modest |
| Procure/Deploy
HQ-9 Batteries |
Active |
Low |
High |
Modest - High |
| Procure/Deploy
S-300PMU2 / SA-20 Batteries |
Active |
Low |
High |
High |
Table 2.
|
Active defence of airfields using AAA, SPAAG and SAM systems is a well
established aspect of PLA doctrine, and HQ-7 and HQ-6D/HQ-64 batteries
have been observed in close proximity to airfields, the intent being to
engage low flying aircraft and cruise missiles. Once the PLA follows
the Russian lead in deploying point defence
weapons, such as SPAAGs, SPAAGMs and SAMs, in the Counter-PGM role,
even a single battery of such weapons at each airfield would
significantly complicate the defeat of underground hangar equipped
airbases.
Importantly, a large PGM such as the GBU-57A/B MOP is valuable and
destructive enough in its own right to justify its engagement with an
area defence SAM system as early as possible after release. An
area
defence SAM system such as the HQ-12, HQ-9, S-300PMU/PMU1/PMU2 is
kinematically compatible with such a target, and the cost of two or
more rounds expended is easily justified given the damage effects such
a
weapon can produce7.
Passive defence measures for underground hangars, other than the use of
additional burster slabs, blocking structures and deflection grids at
entrances, include the simple expedient of adding additional hangar
entrances and access tunnels by further excavation, at extant sites.
Most PLA underground hangars employ two entrances only. Doubling the
number of entrances and access tunnels doubles the necessary effort to
disable these sites, with proportionate increases for further entrances
and access tunnels. This application of redundancy, in effect using
Lusser's product law, has the additional benefit of further increasing
hangar internal capacity, and yielding bulk spoil which can be employed
to further enhance passive defence measures elsewhere at the site.
Table 2 summarises available active and passive defensive measures, and
compares their effectiveness against smaller penetrating munitions,
such as the GBU-39/B and JDAM derivatives, and the much larger
GBU-57A/B MOP.
In pragmatic terms, the PLA's network of superhardened
underground airbases would present a genuine challenge to defeat
without the possession of a well sized fleet of stealthy heavy bombers,
and a very robust warstock of hundreds of GBU-57A/B rounds reserved for
this
purpose. As such, these superhardened
underground airbases are an extremely valuable strategic asset, without
peer globally, as they make a rapid “knockout blow” massed attack on
PLA airfields operationally infeasible even for the United States at
this time8.
How much effort is required to disable a typical PLA
airbase equipped with an underground hangar? This chart presents a
hypothetical targeting model for such a base, assuming the use of the
GBU-39/B SDB and GBU-57A/B MOP. No less than 51 SDBs are required cover
key airbase facilities, and two MOPs to defeat the underground hangar
system. While the MOP requires the use of the B-2A, the SDB could be
delivered by both the B-2A and the F-22A. No less than seven F-22A
sorties would be required to deliver the required number of SDBs. Forty
such bases would require forty-fold the number of weapons delivered
(S.
O'Connor).
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. An excellent analysis of this problem was produced by Stillion9.
|
Conclusions
The PLA's network of around forty
underground airbases provides a
unique and indeed exceptionally robust capability to withstand a large
scale
counter-air campaign,
as significant effort with penetrating munitions of large mass would be
required to close such bases down for the duration of the campaign, or
permanently render them unusable.
As these bases deny surveillance by orbital, airborne or ground based
ISR assets, they provide an inherent capability to perform covert
preparations for combat operations, be it in times of conflict, or in
the period immediately preceding a conflict.
The hangaring capacity of these underground bases is of the order of at
least 1,500 combat aircraft, possibly greater, if more than basic
internal
tunnel arrangements have been employed. This capacity represents
more than the total number of modern combat aircraft currently operated
by the PLA, and thus provides the PLA with the capability to protect
its best assets during any major conflict where opposing aircraft would
seek to attack PLA air bases.
At this time there is no evidence that the PLA has been favouring the
use of its underground basing in the operational deployment of units
operating newer combat aircraft, as these are operated both from bases
with and without underground hangars. However, peacetime deployment
patterns do not necessarily reflect intended deployment patterns in
times of conflict, or in the period immediately preceding a conflict.
The PLA has not shared its thinking on the use of these bases in
war, and is very unlikely to do so in the forseeable future.
In strategic terms, the PLA's underground airbase infrastructure
provides a capability to deny at this time any feasible opponent,
even the United States, the opportunity to inflict massive early
attrition upon the PLA's fleet of combat aircraft while these are on
the ground. This would force any opponent, including the United States,
into a protracted aerial war of attrition, in which repeat attacks on
hardened airbases would be required, over a period of many weeks or
months, before decisive attrition could be inflicted upon the PLA
combat aircraft fleet.
The inherent survivability of the PLA's superlative underground airbase
infrastructure has not been a major consideration in ongoing debate in
the United States on the utility, and indeed intended design, of its
replacement heavy bomber aircraft. If the defeat of the PLA's
underground airbase infrastructure is part of the intended role of this
future aircraft, then this aircraft will need to combine the
survivability needed to repeatedly penetrate what is becoming the best
Integrated Air Defence System in existence, with the ability to deliver
heavy “earthquake bombs”. Any lesser capability would result in
unsustainable
combat attrition.
While China's underground airbase infrastructure may well be an
artefact of the early Cold War period, it will clearly have an enduring
long term impact as one of China's invaluable national strategic assets.
|
Endnotes/References/Bibliography
- Saumur Tunnel, 9th June 1944,
Royal Air Force
website: URI: http://www.raf.mod.uk/bombercommand/saumur.html;
Royal
Air
Force
Bomber
Command
60th
Anniversary
Campaign Diary, June 1944, URI: http://www.raf.mod.uk/bombercommand/jun44.html.
- Glasstone S, Dolan P.J., The
Effects of Nuclear
Weapons, Third Edition, US DOD and ERADA, 1977, URI: http://www.atomicarchive.com/Docs/Effects/index.shtml.
- 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.
- Some measure of the effort
required to excavate a
single underground hangar can be gained by estimating the tonnage of
rock to be removed. If we assume a semicircular cross-section with a
diameter of 13 metres, and a length of 500 metres, the total volume is
~33,200 m3. At 2.5 to 3 tonnes per cubic metre, this is up
to 100,000
tonnes of rock per base, or more if a complex tunnel arrangement is
employed.
- Burster slabs are employed to force the penetrating
weapon to initiate early, and to deflect the blast overpressure, while
deflection grids are employed to impart a normal acceleration to a
penetrating munition to cause its casing to burst or bend, impairing
its ability to penetrate. Both are relatively simple to construct. A
good discussion of the design principles of these can be found in:
Slawson T.R. et al, Design of an Underground Facility Subjected to
CWE and Accidental Threats, Technical Report, US Army Corps of
Engineers, Omaha District, Omaha, NE, 61802-4901, August, 1994; and
Underwood J.M., EFFECTIVENESS OF YAW-INDUCING DEFLECTION GRIDS FOR
DEFEATING ADVANCED PENETRATING WEAPONS, Technical Report,
ESL-TR-92-61, ENGINEERING RESEARCH DIVISION, Air Force Civil
Engineering Support Agency, Civil Engineering Laboratory, Tyndall Air
Force Base, Florida 32403, April, 1995.
- O'Connor S., Underground
Airfields: The DPRK, GEIMINT
Blog, URI: http://geimint.blogspot.com/2010/07/underground-airfields-dprk.html.
- The likelihood of defensive missile attacks against
the GBU-57A/B indicates that self protective measures should be added.
This is not a new idea, as the Soviet AV-MF included self-protection
jammers on the P-500 Bazalt / SS-N-12 Sandbox cruise missile. Obvious
choices are an internal RF jammer, or a towed decoy.
- The strategic reality is that had the United States
built and deployed the initially planned fleet of 132 B-2A bombers, or
even half that number, this force structure gap problem would not exist
now.
- 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
- 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.
- O'Connor S., Chinese Military
Airfields, GEIMINT
Blog, URI: http://geimint.blogspot.com/2008/12/chinese-military-airfields.html.
- Bowie C.J., The Lessons of Salty
Demo, Air Force Magazine, Vol.92, No.3, March 2009, URI: http://www.airforce-magazine.com/MagazineArchive/Pages/2009/March%202009/0309salty.aspx
- Chinese Air Arms, Scramble.nl,
URI: http://www.scramble.nl/cn.htm
- Chris Lofting, Albanian Airbase Imagery (Photoessay),
Airliners.net,
URI: http://www.airliners.net/search/photo.search?id=1052618,1166446,1183226,1183229,1142666,1134330,1052623,1079196,1119821,1206364
- Holger Mueller, Albania 2006 (Photoessay),
MiG-21.de, URI: http://www.mig-21.de/english/newsarchive/albania2006.htm
- Stillion
J., Orletsky D.T., Airbase Vulnerability to Conventional
Cruise-Missile and Ballistic-Missile Attacks; Technology,
Scenarios, and U.S. Air Force Responses,
Monograph MR-1028, Project Air Force, RAND Corporation, URI: http://www.rand.org/pubs/monograph_reports/MR1028.html.
- Kopp C., EXPANDING
THE
ENVELOPE
-
Stealth
and
Other
Strike
Roles, Air
& Space
Power
Chronicles, Maxwell AFB,
July 2000, URI: http://www.airpower.maxwell.af.mil/airchronicles/cc/kopp.html.
- Bowie C.J., The Lessons of Salty
Demo, Air Force Magazine, Vol.92, No.3, March 2009, URI: http://www.airforce-magazine.com/MagazineArchive/Pages/2009/March%202009/0309salty.aspx
- Centner C.M., IGNORANCE IS RISK; THE BIG LESSON FROM
DESERT STORM AIR BASE ATTACKS, Airpower Journal, Winter 1992,
URI: http://www.airpower.maxwell.af.mil/airchronicles/apj/apj92/win92/centner.htm.
- Blake T.C., Improving the Ground Survivability of
In-Theater TACAIR, Air University Review, September-October
1975, URI: http://www.airpower.au.af.mil/airchronicles/aureview/1975/sep-oct/blake.html.
- Satellite imagery provided
courtesy of Google Earth.
- Imagery Sources: US DoD; PLA-AF, PLAN-AF;
MilitaryPhotos.net;
other Internet sources.
- Updated 23rd February, 2011, add Albanian imagery by
Holger Müller.
- Updated 28th February, 2011, add Albanian layout
diagrams by Roland Büchler; Annex C.3 with blast door designs.
|
The only current and planned US
assets capable of surviving China's growing IADS are the B-2A Spirit
and and F-22A Raptor. Intended numbers in the force structure are only
a small fraction of that necessary to defeat the growing capability
of
the PLA-AF (US Air Force image).
|
Acknowledgements
The
authors are greatly indebted to all
parties in Australia and overseas who
reviewed the draft of this
paper, for their cogent comments and valuable thoughts.
|
A formation of Harbin H-5 Beagle
bombers. At least fourteen underground hangar systems were
constructed
during the Cold War to protect these aircraft (via Chinese Internet).
|
Annex A
-
PLA
Underground Air Base Survey
The satellite images in this survey
were captured using Google Earth
in early 2011, and mostly
reflect LEO satellite imagery collected over the previous four years.
Image
quality varies and results in some uncertainty in some of the airbase
assessments. The survey datasets employed were produced by the authors
previously7, 8.
Criteria for determining the presence of an underground hangar were
thus:
- The hangar must be under a hill or other terrain with
credible elevation to provide viable protective depth of rock;
- Taxiways and where applicable an auxiliary runway of
appropriate width and surface quality must exist connecting the runway
system to the hangar entrances;
- Entrance geometry and size must be consistent with well
known PLA
underground hangars previously identified, and must match taxiway
widths and clearances;
- The airbase is a known PLA airfield with a prior history,
and reflects PLA design practice and layout;
- Where possible, supporting evidence such as declassified
KH-4 imagery is to be used to validate observations;
A number of sites were found which initially presented as possible
underground hangar sites, but were reclassified as weapons bunkers if
they did not meet the preceding validation criteria, and are not listed
in this Annex.
In most instances the underground hangar is situated within 1 to 2
kilometres distance from the taxiway exit from the runway system,
although a few notable examples involve greater distances.
A number of PLA airfields have been constructed within suitable
distance of a hill, mountain, or elevated terrain, for an underground
hangar to be constructed, but in the absence of taxiways or roads
connecting to the runway system, were assessed as bases without an
underground hangar. Such bases could be equipped with an underground
hangar at a future date.
Of the total number of airfields with identified underground hangars,
one is derelict and overbuilt, two appear to be mothballed or
unused, one requires repairs to the end of runway, and three
require taxiway or auxiliary runway repairs.
The authors make no warranty that this survey is complete, and that
other underground hangars do not exist at other locations in China.
|
- PLA-AF Fuxin AB
/
Shenyang MR
- PLA-AF Jichang
AB / Shenyang MR
- PLA-AF Jinzhou
Xiaolingzi AB / Shenyang MR
- PLA-AF Lihue
AB / Shenyang MR
- PLA-AF
Nangangzi
AB / Shenyang MR
- PLA-AF Beijing
Shahezhen AB [Datangshan] / Beijing MR
- PLA-AF
Chen-Chuan
AB / Beijing MR
- PLA-AF Chifeng
AB / Beijing MR
- PLA-AF Fengning
AB / Beijing MR
- PLA-AF Hohhot
AB / Beijing MR
- PLA-AF Jizhuang
AB / Beijing MR
- PLA-AF Pingquan
AB / Beijing MR
- PLA-AF Wenshui
AB /
Beijing MR
- PLA-AF Yongning
AB / Beijing MR
- PLA-AF
Zhangjiakou AB / Beijing MR
- PLA-AF Zunhua
AB / Beijing MR
- PLA-AF Urumqi
South AB / Lanzhou MR
- PLA-AF Yinchuan
/ Xincheng AB / Lanzhou MR
- PLA-AF Anqing
AB (An Ching) / Nanjing MR
- PLA-AF
Changzing AB / Nanjing MR
- PLA-NAF Daishan
Island AB / Nanjing MR
- PLA-NAF Feidong
AB / Nanjing MR
- PLA-AF Suzhou
West AB / Nanjing MR
- PLA-AF Taihe AB
/ Nanjing MR
- PLA-NAF Yiwu AB
/ Nanjing MR
- PLA-NAF Ledong
/ Foluo
Northeast AB / Guangzhou MR
- PLA-NAF
Guiping
Mengshu AB / Guangzhou MR
- PLA-AF Leng
Shui Chi
AB / Guangzhou MR
- PLA-AF Shaodong
AB / Guangzhou MR
- PLA-AF Shaoguan
AB /
Guangzhou MR
- PLA-AF
Wudangshan AB / Guangzhou MR
- PLA-AF Yaotian
AB / Guangzhou MR
- PLA-AF Guodu
AB / Jinan MR
- PLA-AF Jining
AB / Jinan MR
- PLA-AF Jiyuan
AB / Jinan MR
- PLA-AF Luyang / Ranghe Zhen
AB / Jinan MR
- PLA-AF
Neixiang AB /
Jinan MR
- PLA-AF Yantai
Southwest AB / Jinan MR
- PLA-AF
Yidu/Chijian AB / Jinan MR
- PLA-AF Guiyang
AB / Chengdu MR
- PLA-AF
Wenshan/Pinquan AB / Chengdu MR
|
Shenyang MR Underground Airbases,
Geographical Placement [Click to enlarge].
|
Coordinates: 42° 4' 44N 121°
39' 43E
Base Primary R/W: 08/280
Base Primary R/W Length: 7,200 ft
Base Status / Tenant: Unknown
Fuxin AB employs a conventional layout, but is devoid of an auxiliary
runway due to the very close proximity of the runway to the hangar
entrances. It is a fighter base with 15 metre hangar entrances.
|
Base Location: 43° 12'N 125° 53'E
Base Primary R/W: 08/26
Base Primary R/W Length: 7,100 ft
Base Status / Tenant: Unknown
Jichang AB is unusual in that it employs two
separate underground hangars in two hills adjacent to the main apron
and taxiway. This former H-5 Beagle base has four 22 metre entrances.
|
Base Location: 41° 6'3.98"N
121° 3'47.38"E
Base Primary R/W: 01/19
Base Primary R/W Length: 8,500 ft
Base Auxiliary R/W: 12/30
Base Auxiliary R/W Length: 5,800 ft
Base Status / Tenant: 3rd FA trainers
This base was constructed to house interceptors, and is equipped with
an auxiliary runway, and two 15 metre hangar entrances.
|
Base Location:
42°15'16.42"N / 125°42'19.39"E
Base Primary R/W: 04/22
Base Primary R/W Length: 7,200 ft
Base Auxiliary R/W: 16/24
Base Auxiliary R/W Length: 6,500 ft
Base Status / Tenant:
Lihue is an active fighter base, constructed
with a 40 m wide auxiliary runway and an underground hangar located in
a canyon between two mountains South of the base. Two entrances provide
access to an estimated 800 m hangar. Imagery resolution precludes at
this time accurate entrance width assessment, which could be in excess
of 20 metres. In addition the base has fifteen conventional revetments
at the southern apron.
|
Base Location:
43°48'56.35"N / 127°30'25.28"E
Base Primary R/W: 01/19
Base Primary R/W Length: ~6,400 ft usable
Base Status / Tenant: Unknown
Nangangzi AB is a former H-5 bomber base,
with two 20 metre entrances to an underground hangar in the mountain
immediately to the West of the runway system. There is no evidence of
recent operational activity, and the northern end of the main runway is
in a state of disrepair, with only ~6,400 ft of the 7,100 ft evidently
in usable condition. The internal length of the hangar is ~800 metres.
|
Beijing MR Underground Airbases, Geographical Placement [Click to
enlarge].
|
Base Location:
Base Primary R/W: XX/YY
Base Primary R/W Length: ZZZZ ft
Base Status / Tenant: XXth FD / YYth AR
Datangshan, situated in the outer Beijing
suburbs, has two 33 metre entrances for the H-6 Badger. The site has
been redeveloped as the China Aviation Museum, housing a large
collection of aircraft dating to the 1940s.
|
Base Location:
37°52'23.26"N / 110° 4'17.29"E
Base Primary R/W: 14/32
Base Primary R/W Length: 8,500 ft
Base Status / Tenant: Unknown
This base was initially constructed to
operate
the H-5, and is equipped with an underground hangar with two colocated
22 metre entrances, and an internal length of at least 600 metres. The
base does not display evidence of recent operational activity.
|
Coordinates: 42° 9' 32N 118°
50' 31E
Base Primary R/W: 02/20
Base Primary R/W Length: 8,100 ft
Base Auxiliary R/W: 01/19
Base Auxiliary R/W Length: 7,000 (5,900) ft
Base Status / Tenant: 1st FD J-7E / Unknown AR
The Chifeng fighter base employs an unusual placement for the auxiliary
runway, which appears to be under repair in available imagery, and
partly overgrown with foliage. Twenty
eight lightweight shelters have been constructed on the primary apron.
The two hangar entrances are 13 metres wide.
|
Base Location: 41°15'39.31"N /
116°37'8.91"E
Base Primary R/W: 17/35
Base Primary R/W Length: 7,500 ft
Base Status / Tenant: Unknown
Fengning is a fighter base, lacking an
auxiliary runway, with a dual
entrance underground hangar with 15 metre entrances.
|
Base Location: 40°44'19.38"N /
111°13'46.22"E
Base Primary R/W: 08/26
Base Primary R/W Length: 7,800 ft
Base Status / Tenant: J-7II, J-7E FD / unknown AR
Hohhot is a fighter base with two 15 metre
entrances colocated on
the southern side of the mountain, to the west of the runway system. At
least two squadrons of Fishbeds have been observed at this site.
|
Base Location: 38°35'50.20"N /
112°58'8.80"E
Base Primary R/W: 07/25
Base Primary R/W Length: 8,200 ft
Base Status / Tenant: Unknown FD
Jizhuang is a fighter base with two 15 metre entrances on southern side
of the mountain, to the northeast of the runway system. The estimated
minimal length of the hangar is 700 m.
|
Base Location:
40°53'52.41"N / 118°40'53.63"E
Base Primary R/W: 06/24
Base Primary R/W Length: 7,800 ft
Base Status / Tenant: Unknown
This former H-5 Beagle base has three 22
metre entrances on the
southern side of the mountain.
|
Base Location:
37°24'30.17"N / 111°57'55.62"E
Base Primary R/W: 06/24
Base Primary R/W Length: 10,400 ft
Base Status / Tenant: 8th
BD
H-6
Wenshui was until recently an operational
PLA-AF H-6 Badger base, with a large 10,400 ft primary runway. The site
is equipped with a 40 metre wide dual entrance underground hangar
located
under a mountain 3 kilometres NW of the Western end of the runway.
Estimated length of the hangar is ~600 metres.
|
Base Location:
40°30'14.69"N / 116° 6'22.71"E
Base Primary R/W: 05/28
Base Primary R/W Length: 7,500 ft
Base Status / Tenant: J-7 FD / Unknown AR
This former H-5 Beagle base has a pair of 22
metre underground hangar entrances, with the western taxiway
partly overgrown with foliage.
|
Base Location: 40°44'15.98"N /
114°55'51.02"E
Base Primary R/W: 11/29
Base Primary R/W Length: 8,100 ft
Base Status / Tenant: 7th FD / 9th AR J-11
Zhangjiakou is a fighter base equipped with
two underground hangars, each of which has a pair of 15 metre
entrances. The base lacks an auxiliary runway. While the base hosts a
J-11 Air Regiment, these are incompatible with the hangar system, which
was built
for the J-6/J-7.
|
Base Location: 40° 6'23.74"N /
117°53'10.20"E
Base Primary R/W: 07/25
Base Primary R/W Length: 7,900 ft
Base Auxiliary R/W: 02/14
Base Auxiliary R/W Length: 5,200 ft
Base Status / Tenant: 24th FD J-8 / Unknown AR
Zunhua is an auxiliary runway equipped
fighter base, with a pair of colocated 15 metre hangar entrances, at
the north end of the unusually wide auxiliary runway.
|
Lanzhou MR Underground Airbases, Geographical Placement [Click to
enlarge].
|
Base Location: 43°27'57.91"N /
87°31'56.45"E
Base Primary R/W: 09/27
Base Primary R/W Length: 9,100 ft
Base Status / Tenant: 37th FD / 110th AR (J-8F), 111th AR
(J-7II)
Urumqi is a remote fighter base, without an
auxiliary runway. The
underground hangar with a pair of colocated 15 metre entrances is 3.5
kilometres south of the base.
|
Base Location:
Base Primary R/W: 01/19
Base Primary R/W Length: 9,100 ft
Base Auxiliary R/W: 12/30
Base Auxiliary R/W Length: 6,500 ft
Base Status / Tenant: 6th FD / 140th AR (Su-27SK/UBK)
Yinchuan superficially appears to be a
typical fighter base with an auxiliary runway. The underground hangar
system is however equipped with four entrances, two of which are 15
metres wide, and two 22 metres wide. It is likely the base was
initially shared between J-6 and H-5 units. Twenty four lightweight
shelters are constructed on the central apron.
|
Nanjing MR Underground Airbases, Geographical Placement [Click to
enlarge]. |
Base Location:
Base Primary R/W: 06/24
Base Primary R/W Length: 9,500 ft
Base Auxiliary R/W: 14/32
Base Auxiliary R/W Length: 6,500 ft
Base Status / Tenant: 10th BD H-6, Y-8(EW)
An Ching was initially constructed as a
fighter base, equipped with an auxiliary runway and an underground
hangar, built with paired 15 metre entrances. The base was later
redeveloped and now hosts H-6 Badgers of the 10th Bomber Division.
While some sources claim an underground hangar for the H-6 aircraft,
there is no evidence of such.
KH-4 Corona wet film imagery of An
Ching AB in Nanjing MR, collected 1962-1963, showing underground hangar
access (US DoD via FAS).
|
Base Location:
30°58'14.07"N / 119°43'46.08"E
Base Primary R/W: 07/11
Base Primary R/W Length: 8,300 ft
Base Auxiliary R/W: 10/28
Base Auxiliary R/W Length: 4,500 ft
Base Status / Tenant: 3rd FD J-7II, J-10 / Unknown AR
This former H-5 Beagle base has a pair of 22 metre entrances, and an
auxiliary runway.
|
Base Location: 30°17'12.71"N
/
122°
8'34.30"E
Base Primary R/W: 02/20
Base Primary R/W Length: 7,500 ft
Base Auxiliary R/W: 10/28
Base Auxiliary R/W Length: 6,500 ft
Base Status / Tenant: Currently unused
The Daishan Island interceptor base was previously operated by the
PLAN, providing local air defence for the Shanghai Bay area. It has a
dual entrance underground hangar with narrow 13 metre entrances, one of
these is now blocked. The auxiliary and primary runways are in a state
of disrepair, and the taxiways are being used as sealed bitumen roads.
A 1962 KH-4 Corona image of the
Daishan Island interceptor base. To the top of the image is the hill to
the West of the runway system, and associated taxiway, which still
shows today evidence of excavations into the base of the hill, along
the Western base taxiway (US DoD via FAS).
|
Base Location: 31°54'39.07"N /
117°39'58.71"E
Base Primary R/W: 04/22
Base Primary R/W Length: 8,500 ft
Base Auxiliary R/W: 14/32
Base Auxiliary R/W Length: 5,600 ft
Base Status / Tenant: 4th FD / 12th AR (Su-30MK2)
This former H-5 Beagle base has a pair of 22 metre entrances, and an
auxiliary runway. Twenty four lightweight shelters have been
constructed on the central apron.
|
Base Location: 31°15'46.75"N /
120°24'8.00"E
Base Primary R/W: 18/36
Base Primary R/W Length: 8,200 ft
Base Status / Tenant: Unknown FD / 2 x J-6, 1 x J-7 AR
Suzhou West is a former H-5 Beagle base with
a pair of 22 metre entrances to an underground hangar, north-east
of the runway system.
|
Base Location: 26°51'30.16"N /
114°44'15.07"E
Base Primary R/W: 08/26
Base Primary R/W Length: 8,700 ft
Base Auxiliary R/W: 04/22
Base Auxiliary R/W Length: 5,900 ft
Base Status / Tenant: 2nd IR JZ-6
Taihe is a former H-5 Beagle base with a
pair of 22 metre entrances to an underground hangar, and an auxiliary
runway.
|
Base Location: 29°20'43.73"N /
120° 2'4.10"E
Base Primary R/W: 02/20
Base Primary R/W Length: 8,500 ft
Base Auxiliary R/W: 16/34
Base Auxiliary R/W Length: 6,000 ft
Base Status / Tenant: 6th GAD PLAN 17th AR JH-7; formerly
26th FD PLA-AF
Yiwu is a former H-5 Beagle base with a pair
of 22 metre entrances to an underground hangar, and an auxiliary runway.
KH-4 Corona wet film imagery of Yiwu AB in
Nanjing MR, collected 1962-1963, showing underground hangar access (US
DoD
via FAS).
|
Guangzhou MR Underground Airbases, Geographical Placement [Click to
enlarge].
|
Base Location: 18°41'34.56"N
/ 109° 9'40.84"E
Base Primary R/W: 04/22
Base Primary R/W Length: 9,300 ft
Base Auxiliary R/W: 14/32
Base Auxiliary R/W Length: 7,300 ft
Base Status / Tenant: 9th FD / 27th AR (JH-7A)
The Foluo NorthEast airbase on Hainan Island
is of an unusual configuration. While it has an auxiliary runway and
underground hangar in the fashion of a typical fighter base, the main
runway, auxiliary runway and underground hangar entrances are 40+
metres wide, sized for the H-6 Badger. Twenty four lightweight shelters
have been built on the main apron, for 27th Air Regiment JH-7A Flounder
aircraft.
Kristensen of FAS noted that the Foluo NE underground hangar was under
active construction circa 2005, but satellite imagery dated in 2002
already shows taxiways, auxiliary runway and entrances in place.
|
Base Location: 23°19'58.33"N /
110° 0'31.93"E
Base Primary R/W: 09/27
Base Primary R/W Length: 10,200 ft
Base Status / Tenant: 3rd BD / 8th AR (H-6D, HU-6D)
This base has a typical H-6 rated primary runway, and two 33 metre
underground hangar entrances at the northeastern corner of the runway
system, the easternmost of which has a taxiway in a poor state of
repair. The base hosts a squadron of Badger aerial refuelling tankers.
|
Base Location: 31° 6'24.33"N /
112°24'9.09"E
Base Primary R/W: 04/22
Base Primary R/W Length: 7,200 ft
Base Auxiliary R/W: 16/34
Base Auxiliary R/W Length: 6,900 ft
Base Status / Tenant: Unknown
This base is of an unusual configuration,
with the auxiliary runway almost as large as the primary runway and
clearly viable for takeoffs and landings. This, and the 15 - 20 metre
wide taxiways and entrances suggest this base was constructed for H-5
bomber operations. Poor image resolution precludes an exact assessment
of the base status, but a hangar length of at least 400 metres is
evident.
|
Base Location: 27°13'32.16"N
/
111°40'10.54"E
Base Primary R/W: 05/23
Base Primary R/W Length: 9,500 ft
Base Status / Tenant: 8th BD H-6A/E
Shaodong is a H-6 Badger base, which
includes an underground hangar with two 33 metre entrances, at the end
of a convoluted 3 km taxiway to the southwest of the base.
|
Base Location: 24°58'54.46"N
/
113°25'18.19"E
Base Primary R/W: 15/33
Base Primary R/W Length: 7,100 ft
Base Status / Tenant: 9th FD J-6
The Shaoguan airbase was constructed to
house
interceptors, and is equipped with two 12 metre hangar entrances, which
yield an estimated tunnel length of ~750 metres.
A 1962 KH-4 Corona LEO image of
the Shaoguan interceptor
base during construction. To the top of the image is the hill to the
North of the runway
system, with the taxiways visible, and runup bays occupied by
construction sheds
(US DoD via FAS).
|
Base Location: 32°23'21.74"N /
111°41'43.57"E
Base Primary R/W: 17/35
Base Primary R/W Length: 10,400 ft
Base Status / Tenant: 27th FD J-7 / Unknown AR
The Wundangshan base is unusual, in the
sense that it has a large
primary runway of the type commonly seen at bomber bases. There is
evidence of one incomplete 15 metre hangar entrance, and other, under a
foliage canopy which may or may not have been completed. The base
currently hosts a J-7 unit.
|
Base Location: 26°31'48.26"N /
112°50'38.01"E
Base Primary R/W: 04/22
Base Primary R/W Length: 9,500 ft
Base Status / Tenant: 8th BD H-6A/E, H-6U, H-6H; 2nd BD
PLAN HZ-5
Yaotian is a satellite airfield which is not
connected by a taxiway to
the Leiyang / Hsin Shi primary base, which hosts an Air Regiment of H-6
Badgers. The two airfields are separated by a river. The underground
hangar has two 33 metre entrances.
|
Jinan MR Underground Airbases, Geographical Placement [Click to
enlarge]. |
Base Location:
Base Primary R/W: 12/30
Base Primary R/W Length: 7,100 ft
Base Auxiliary R/W: 04/22
Base Auxiliary R/W Length: 6,300 ft
Base Status / Tenant: Unknown
The Guodu base was constructed as a H-5
bomber base, with an underground hangar equipped with two 20 metre
entrances, and an internal length of at least 500 metres. The auxiliary
runway is of sufficient length to permit both
landings and takeoffs, with the entrances difficult to attack in the
canyon between two mountains. There is no evidence of recent
operational activity, and this base is not equipped with typical
administrative and garrison buildings.
|
Base Location: 35°17'32.87"N /
116°20'48.66"E
Base Primary R/W: 08/26
Base Primary R/W Length: 9,500 ft
Base Status / Tenant: 19th FD / 55th AR (J-11, Su-27SK,
Su-27UBK); Unknown BD H-6
Jining was constructed as a bomber base,
with a dual 40 metre entrance underground hangar north of the main
apron area. It continues to host H-6 Badgers, but also the 9th Air
Regiment
of 7th Fight Division Flankers.
|
Base Location: 35° 7'11.06"N /
112°36'31.44"E
Base Primary R/W: 08/26
Base Primary R/W Length: 9,100 ft
Base Auxiliary R/W: 10/28
Base Auxiliary R/W Length: 6,500 ft
Base Status / Tenant: Unknown
Jiyuan was constructed as a H-6 bomber base,
but includes an auxiliary runway. An underground hangar is located
north of the runway system, and has two 33 metre entrances, one of
which is in a state of disrepair, as is the auxiliary runway.
|
Base Location: 33°41'4.62"N /
112°53'26.89"E
Base Primary R/W: 10/28
Base Primary R/W Length: 7,200 ft
Base Auxiliary R/W: 04/22
Base Auxiliary R/W Length: 5,200 ft
Base Status / Tenant: Storage facility / Museum
The Luyang site is an unusual configuration, employing a conventional
fighter primary and auxiliary runway, with an underground hangar. The
hangar has a pair of eastern 15 metre entrances connected to the
auxiliary runway. The western side has a single 22 metre entrance., and
a 35 metre entrance to a blind tunnel hangar. An
incomplete excavation for another 22 m entrance is south of the paired
eastern entrances. It is likely this site was intended to initially
host H-6, H-5 and J-6, J-7 aircraft. Detail imagery of blast doors is
available in Annex C.3.
|
Base Location: 32°58'21.77"N
/
111°53'7.01"E
Base Primary R/W: 17/35
Base Primary R/W Length: 9,100 ft
Base Status / Tenant: Unknown
This base, located at the southern boundary
of the Jinang MR, show clears evidence of an underground hangar system
to the West of the runway system, with an estimated tunnel length of
~800 metres under the mountain directly to the West. The smaller
mountain to the NW of the runway system may also contain an underground
hangar, although poor image resolution precludes a conclusive
identification at this time. The wide 30 metre taxiways, 9,100 ft main
runway, and characteristic apron pattern indicate this base was
constructed for H-6 Badgers.
|
Base Location: 37°24'3.03"N /
121°22'2.52"E
Base Primary R/W: 04/22
Base Primary R/W Length: 8,800 ft
Base Status / Tenant: 5th AD F/GAD Q-5
The Yantai SW base is an atypical fighter base, which incorporates both
an underground hangar and no less than 25 revetments with surrounding
berms, each protecting a pair of Q-5 Fantans. The underground hangar is
located a distance of 2.7 kilometres west of the runway system, and is
accessed via a 200 metre road bridge crossing a canal. Both hangar
entrances are 15 metres wide.
|
Base Location: 36°35'35.72"N /
118°31'43.69"E
Base Primary R/W: 18/36
Base Primary R/W Length: N/A ft
Base Status / Tenant: Abandoned / Derelict
Yida is former H-5 Beagle base. The runway
is covered with warehouse structures,
the site is no longer usable for flight operations.
|
Chengdu MR Underground Airbases, Geographical Placement [Click to
enlarge].
|
Base Location: 26°24'30.27"N /
106°32'5.62"E
Base Primary R/W: 17/35
Base Primary R/W Length: 8,200 ft
Base Auxiliary R/W: 02/20
Base Auxiliary R/W Length: 6,600 ft
Base Status / Tenant: XXth FD / YYth AR
Guiyang is a fighter base with an auxiliary
runway, and an underground hangar south of the primary runway system.
Four 15 metre entrances provide access to the hangar.
|
Base Location:
23°42'55.90"N / 103°49'31.40"E
Base Primary R/W: 14/32
Base Primary R/W Length: 8,000 ft
Base Status / Tenant: Unknown
This base shows characteristic construction
features for an underground hangar, including a prominent 15 - 20 metre
wide taxiway around the base of the hill to the North of the runway
system, and four likely entrances on the North side of the hill. This
presents as a similar arrangement to Luyang AB and Guiyang AB, and has
been used for H-5 and mixed basing arrangments. Entrance placements
indicate ~400 to ~800 metres of internal length. Poor image resolution
precludes an assessment of base status.
|
|
The abundance of mountainous and
hilly terrain across the eastern Military Regions of China created many
opportunities to site airfields with underground hangars. The compact
Chengdu J-10 Sino-canard fighter will fill all three hangar types (via
Chinese Internet).
|
Annex
B
-
Underground
Hangar
Capacity
Estimation
Estimating the capacity of the PLA's network
of underground hangars presents some challenges, in the absence of
published floorplans. While the cross-section of the entry tunnels can
be accurately estimated from imagery, absence of knowledge about
internal layouts, especially if the hangar comprises multiple branching
or parallel tunnels, presents a high risk of underestimating internal
capacity.
The small number of available images, and
publicly accessible Datangshan interior suggest that a simple
arrangement may be commonly employed, connecting entrances with a
single tunnel of constant cross-section, following an |-, L-, U- or
S-shaped pattern to connect the pair of entrances.
To test this hypothesis, we estimated tunnel lengths for all of the
sites listed in Table B.1, routing the tunnel under the peak of the
hill or mountain. Where the geometry permitted multiple footprints
consistent with the hypothesis, we looked at best case (longest) and
worst case (shortest) case paths.
Assuming a future PLA Orbat comprising a mix of H-6H/M/K/U,
J-11A/B/Su-30MKK/MK2, J-20 and J-10, we postulated reasonable
placements for all types, given prevailing tunnel widths.
While the results for the J-11A/B/Su-30MKK/MK2 and J-20 do not
correlate well with any arrangement employing the H-5 Beagle, given the
fundamentally different platforms of the newer swept wing types, this
should not be a surprise.
The results for the H-6 Badger, listed in Table B.1, typically fall
into integer multiples of 12 aircraft squadrons, with some spares. The
aggregate figure is ~140 aircraft, a number which is greater than
the ~120 which repeatedly appears in
unclassified assessments of the total strength of the PLA's H-6 fleet.
Prima facie this would suggest that the PLA maintains underground
hangar capacity for the whole of its H-6 Badger fleet. An additional
large hangar complex at Leng Shui Chi AB was excluded due to
uncertainties about status and capacity.
The underground hangars built for the legacy cloned MiG fighters
yielded interesting results for the J-10, despite its different
planform and slightly larger footprint. Most of the underground hangars
yielded numbers which were, yet again, integer multiples of 12 aircraft
squadrons, with some spares. The aggregate figure is ~600 up to ~800
aircraft,
which means that these underground hangars could protect around 3/4 of
the often cited target production quantity for PLA-AF/NAF J-10A/B/S
fighters.
At this time the Flanker is the primary air superiority and deep strike
fighter of both the PLA-AF and PLA-NAF. As a result, it is reasonable
to consider how many Flankers could be accommodated in H-5 sized
underground hangars. The resulting ~600 aircraft sits at the upper
bound of previously cited numbers planned for the PLA Flanker fleet,
and is well above the current total deployed in operational units.
The J-20 will likely become the spearhead of
the
PLA-AF's TACAIR fleet, and is thus a high value asset worthy of
considerable protection from counter-air strikes. The extant H-5 sized
underground hangars could accommodate ~500 J-20 aircraft, assuming the
aircraft's cardinal dimensions and planform do not change significantly
during development.
The estimation method employed is inherently
conservative, and will underestimate actual capacity, as in the absence
of data, no allowance could be made for branching tunnel capacity.
Comparative area occupancy for PLA
underground hangars, for Badger and Flanker variants. Former Badger
bases will be able to accommodate significant numbers of J-11A/B and
Su-30MKK/MK2 Flanker aircraft. An underground hangar sized to fit a
dozen H-6 Badgers could comfortably fit an Air Regiment of 36+ Flankers
(C. Kopp).
Hangars constructed with a 20 - 22
metre entrance/tunnel width to accommodate the H-5 Beagle provide an
ideal environment for hangaring the J-11A/B/Su-27SK Flanker B and
Su-30MKK/MK2 Flanker G. An example arrangement is a slanted row with
aircraft spaced 14 metres apart (C. Kopp).
Hangars constructed with a 20 - 22
metre entrance/tunnel
width to accommodate the H-5 Beagle would also be compatible with the
new J-20, despite its greater length compared to the Flankers. An
example arrangement is a slanted
row with aircraft spaced
19 metres apart (C. Kopp).
Hangars constructed with a 12 - 15
metre entrance/tunnel
width to accommodate the J-4 Fagot, J-5 Fresco, J-6 Farmer and J-7
Fishbed are less than optimal for stowing later types such as the J-8
Finback and J-10 series. The J-10 can be stowed nose to tail, or with
~20% higher packing density, stowed slanted (C.
Kopp).
|
Annex
C
- PLA Airbase Design and Construction in Detail
PLA airbase design is standardised to an
extent not observed in NATO
nations, or former Warpac nations. This Annex will provide additional
reference material detailing the external and internal design features
of these standard base
designs.
Annex C.1 -
General Site Layout and Design
A characteristic design feature of most PLA airbases is
the use of large alert aprons at either end of the parallel main
runway/taxiway system. Above J-6 Farmers on the alert apron, below H-5
Beagles (via Chinese Internet).
PLA airbases without underground
hangars usually have a central apron, adjacent to hangars used for
engineering work on the aircraft and systems. This base, hosting Q-5
Fantan close air support aircraft, displays camouflaged structures, a
common feature on Warpac style bases with revetted dispersal pads (via
Chinese
Internet).
Lightweight aircraft shelters have
been installed on the main aprons of many PLA airbases. Above,
below:
two
types
are
used
most
commonly. They provide
protection against weather and overhead ISR assets, but not against
PGMs (Chinese Internet).
China is the only nation,
globally, able to protect its aerial tanker fleet by concealment in
underground hangars. The Xian H-6 Badger remains in production as a
cruise
missile carrier and tanker. It is a reverse engineered Tu-16, itself a
descendant of the Boeing B-29, the Tu-16 developed initially to compete
against the British V-bombers (Zhenguan
Studio,
©
2010
Air
Power
Australia).
Shantou NE AB hosts the PLAAF 24th AR of the 9th FD, operating the
J-10A. It is an excellent example of a “classic” Warsaw Pact pattern
base with revetted dispersal areas, which have been hardened by the
installation of HAS on previously revetted dispersal pads.
Survivability of hangared aircraft will be determined by the ability of
the shelters to resist penetrating munitions like the GBU-39/B (S.
O'Connor).
Longtian AB is another excellent example of a “classic” Warsaw
Pact pattern base with revetted dispersal areas, which have been
hardened by the installation of HAS. Longtian and a number of other
bases have camouflage paint applied to the taxiways and ramps which
access the HAS, arguably a futile effort, given that the location has
been surveilled by satellite since its initial construction, evidenced
by the KH-4 image below (S. O'Connor, US DoD).
Feidong AB hosts the PLANAF 10th AR of the
4th FD,
operating the maritime strike Su-30MK2 Flanker G. Feidong is the
archetypal superhardened base, with an underground hangar and auxiliary
runway (S. O'Connor).
Detail of the Feidong AB main
runway, alert ramps and main apron with lightweight aircraft shelters.
The lightweight shelters offer protection from the elements but are not
hardened against penetrating munitions. (S.
O'Connor).
Detail of the Feidong AB auxiliary
runway, taxiway system, and underground hangar. Many bases with
underground hangars include turnaround points or aprons along the
auxiliary runway or taxiway to permit takeoffs while returning aircraft
are being towed back to the underground hangar. While the auxiliary
runway is long enough for a FLANKER-series aircraft to land on it,
there is
insufficient vertical clearance for go-arounds (S.
O'Connor).
Detail of the Feidong AB underground hangar entrance
and access taxiway. Many bases with underground hangars display
localised patches of debris and dirt on the taxiways, mostly likely the
result of mudslides or runoff from the mountainside during heavy
precipitation, the latter a common occurrence in eastern China. Many
bases also show active construction work on entry ramps or taxiways,
indicating maintenance efforts on these surfaces
(S. O'Connor).
Detail of the Feidong AB underground hangar
exit and
ramp, start of auxiliary runway, garrison buildings, and POL bulk
storage facility. The latter is unusual in that it is fully exposed
and may only be used for intermediate storage prior to transfer
to underground storage in a contingency (S.
O'Connor).
Detail of the Feidong AB underground hangar
area in synthetic three dimensional rendering. The reshaping of the
hillside near the entrance may reflect attempts to control runoff and
mudslides which might otherwise impair operations. The purpose of the
water catchment is unclear, and may simply be used to support
agricultural irrigation in proximity to the hangar.
It
has
been
present
since
2003 (S. O'Connor).
|
Annex C.2 -
Hangar Internal Design
|
Interior
imagery
of
PLA
underground
hangars
is
generally
scarce,
and
usually
of
poor
quality,
most
likely
intentionally
so.
The
PLA
has
nothing
to
gain
by
propagating
such
material,
other
than
to
provide
insights
to potential opponents on the weaknesses of the designs in use.
Interior view of concertina inner door arrangement
in the 14 metre wide underground hangar system at Gjadër /
Lezhë-Zadrima
AB in Albania.
In the foreground a Chinese supplied J-6 Farmer of the Albanian Air
Force, with NR-23 guns removed (Courtesy of Chris Lofting).
Exterior view of open convex external blast
door
arrangement
in the 14 metre wide underground hangar system at Gjadër /
Lezhë-Zadrima
AB in Albania. The primary convex external blast
doors
employ a reinforcing internal structural framework to transfer
overpressure loads into the outer frame. The upper external blast door
is closed (Courtesy of Holger Müller@MiG-21.de).
Another exterior view of open convex external blast
door
arrangement
in the 14 metre wide underground hangar system at Gjadër /
Lezhë-Zadrima
AB in Albania.
The upper door is hinged on the right hand side of the door. The
concrete arch over the main entrance is a characteristic feature
observed at Chinese sites. In the foreground a Chinese supplied J-6
Farmer of the Albanian Air
Force (Author unknown).
The alternative to imagery of sites in China proper is to explore sites
in other nations, built to the same design rules and specifications. A
number of client
states procured significant numbers of Chinese aircraft since the
1960s, but only the DPRK and the former Hoxha regime in Albania also
imported design data and constructed airfields with underground hangars
to the PLA specification. Albania received ongoing aid from China until
the late 1970s, when the relationship collapsed.
14 m underground hangar external blast door
geometry (© 2011, C. Kopp).
14 m underground hangar entrance and inner door
geometry (© 2011, C. Kopp).
Two excellent collections of high quality imagery of three Albanian
underground hangars at Tirana-Rinas AB, Gjadër / Lezhë-Zadrima AB and
Kuçovë AB, have been produced
by aviation photographers Chris
Lofting and Holger Müller, and are available, respectively, at Airliners.net
[Click
Here to view the full archive] and MiG-21.de [Click
Here to view the full archive].
Main tunnel of the 14
metre wide underground hangar at Gjadër / Lezhë-Zadrima AB in Albania.
In the
foreground Chinese supplied J-6 Farmers, with pitot probes in
characteristic stowed position. The area to the right is cleared for
vehicle movements (Courtesy of Chris Lofting).
Main tunnel of the 14
metre wide underground hangar at Gjadër / Lezhë-Zadrima AB in Albania.
The design is a
linear segmented arrangement. Note the sheetmetal cladding (Courtesy of
Chris Lofting).
Branching short tunnel in the 14
metre wide underground hangar at Gjadër / Lezhë-Zadrima AB in Albania.
This example is
being used for maintenance of a J-7 Fishbed, in this instance involving
an engine change (Courtesy of
Chris Lofting).
Another view of the same branching tunnel in the 14
metre wide underground hangar system at Gjadër /
Lezhë-Zadrima
AB in Albania (Courtesy of Holger
Müller@MiG-21.de).
Primary tunnel of the 14
metre wide underground hangar system at Gjadër / Lezhë-Zadrima AB in
Albania
(Courtesy of
Chris Lofting).
Primary tunnel in the 14 metre wide underground hangar
system at Gjadër /
Lezhë-Zadrima
AB in Albania, viewed closer to the bend in the tunnel. The J-7 Fishbed
aircraft are an early configuration (Courtesy of
Holger Müller@MiG-21.de).
Branching short tunnel in the 12
metre wide underground hangar at Tirana-Rinas AB in Albania. This
example appears to be ~60 metres in length, sufficient to hangar
four J-6 Farmers (Courtesy of
Chris Lofting).
A number of very useful observations can be made from this imagery:
- Layout: The primary tunnel connecting the paired
main entrances typically comprises linear segments, joined by gently
curved sections. This is one of the possible strategies for the layout,
and arguably the easiest to construct;
- Layout: Branching blind tunnels of ~60 metres length
are employed,
with entrances from the primary tunnel. These are used, in the Albanian
tunnels, to either perform deeper maintenance on single aircraft, or to
hangar multiple aircraft, parked nose to tail. The blind tunnel
junctions with the primary tunnel are at a right angle, in the
available imagery;
- Geometry: Two different tunnel cross-sections are
employed. One
is a ~12 metre wide simple catenary section, down to the tunnel floor,
used at the Tirana-Rinas site. The other is a ~14 metre wide compound
cross
section, with ~3.4 m high vertical walls and a catenary section
upper
lobe, with an overall internal height of ~6.3 metres. The latter is
used at the Gjadër / Lezhë-Zadrima AB and Kuçovë AB sites;
- Entrances and Inner Doors: The primary tunnel
entrances at Gjadër /
Lezhë-Zadrima AB
and Kuçovë AB are through
an inverted T shaped main door arrangement. Hinged external blast doors
are used, with a multiple segment
horizontally opening steel concertina inner door, supplemented by a
smaller vertically opening steel concertina
door used to seal the slit aperture for the aircraft's vertical
tail (refer illustrations above). It is
unclear whether this arrangement would seal well enough for operation
in an NBC environment, although maintenance of positive pressure inside
the hangar could alleviate seal problems when the inner door is closed.
The inner doors are certainly used to protect against adverse weather;
- External Blast Doors: The left and right main and
upper hinged blast doors are externally convex, where the
curvature is across the shorter dimension. Construction appears to be
steel. Available imagery suggests either a circular section or catenary
curvature, intended to transfer overpressure loads into the outer frame
of the blast doors. The doors swing outward on hinges, and the inner
side of the door aligns exactly with the left and right inner tunnel
walls. The blast doors and upper concrete wall structure are located
about 7 metres from the hillside entrance, to protect the open blast
doors;
- Inner Blast Doors: The Gjadër /
Lezhë-Zadrima AB and Kuçovë AB a second pair of hinged blast doors in a
plenum chamber arrangement as depicted by Roland Büchler (below). This
forms a defacto airlock arrangement at either end of the plenum chamber.
- Internal Construction: The internal walls of the
tunnels are
lined with reinforced concrete. The construction method would appear to
involve setting up a frame, with wooden planks to form a mold, and
pouring the concrete in short segments of ~2 to 3 metres. The ~12
m Tirana-Rinas AB tunnels show contiguous pouring of these
segments.
The ~14 metre Gjadër / Lezhë-Zadrima AB and Kuçovë AB have exposed
steel I-beam inner webs at intervals of ~3 metres in linear tunnel
segments, and as little as ~1 metre in tunnel bends. These are likely
to be reinforcement for the final structure, but also used to support
the formwork during construction. Portions of the
Gjadër / Lezhë-Zadrima AB tunnel show evidence of the molds sagging
during the pouring
of the concrete.
- Drainage: Water seepage is clearly evident in the
joins between segments in the tunnel liner, in sufficient quantities to
see pooling on the tunnel floors at both Gjadër / Lezhë-Zadrima AB and
Kuçovë AB;
- Surface Finishing: Portions of the tunnel walls at
Gjadër / Lezhë-Zadrima AB are clad with white or light coloured
enameled
sheetmetal, also observed in PLA tunnels; other tunnel walls at Gjadër
/ Lezhë-Zadrima
AB and Kuçovë AB are either unfinished, or smoothly finished. The
possible intent of the sheetmetal liner is to improve tunnel
illumination, but possibly also to improve VHF radio propagation along
the tunnel, or to provide a utilities corridor;
- Utilisation: The 14 metre tunnel floors are divided
by a white marking line, with ~10 metres along one wall employed for
aircraft storage, and the remaining ~4 metres clear for vehicular
movements along the length of the tunnel; PLA tunnels appear to use a
similar arrangement.
The 14 metre tunnel design is very common in Chinese installations and
is likely much newer by design than the 12 metre tunnel design. The
interior volume of the former is generous for the aircraft sizes
employed, and considerable freedom of movement is available for
refuelling truck, weapons dollie and other vehicular movements required
to sustain operations.
Layout diagrams for the Gjadër / Lezhë-Zadrima AB and
Kuçovë AB sites have been produced by Roland Büchler, following a site
visit. Both sites employ a horseshoe linear segmented arrangement, as
suggested by photographic evidence.
The Gjadër / Lezhë-Zadrima AB (above) and
Kuçovë AB (below) sites employ horseshoe / linear
segmented arrangement (© Roland Büchler).
The likely operating cycle is that aircraft are always towed into one
entrance, and launched from the other. Aircraft returning from sorties
would be placed at the beginning of a queue, and flow down the tunnel
receiving, progressively, flightline maintenance, fuel and munitions
loads, as they approach the other end of the tunnel. Aircraft requiring
more time consuming maintenance would be placed into branching tunnels
not to stall the servicing, fuelling and arming “pipeline” as it flows
down the tunnel.
The entrance external blast door design observed in Albania is similar
to some known images of Chinese hangar blast doors, but different from
others,
suggesting a number of different designs are in use. The Albanian
blast door design is clearly designed to survive overpressure events
and high velocity shrapnel and spall. It is unlikely that the
single blast
door design is robust enough to stop a modern penetrating munition such
as the GBU-39/B or BLU-116/B, and may well reflect the chronological
age of the design, constructed in the
era of “dumb” munitions. With inner and outer blast doors closed, the
inner door would likely stop smaller munitions which may have
penetrated the outer door.
The entrance inner concertina door design observed in these tunnels is
not
especially robust in a PGM threat
environment. A penetrating munition which has passed through the
external and inner blast doors would likely punch through the
inner concetina door
panels, or join between the panels, and even if the munition does not
penetrate inside the hangar, it would likely produce sufficient twist
in one or two door panels to preclude the concertina mechanism
from working, effectively jamming the door shut.
|
Annex C.3 -
Hangar External Blast Door Designs
|
Available open source imagery indicates that
a number of different blast door arrangements are employed, with at
least two types employed for “MiG-sized” hangars, at least one for
“Beagle-sized” hangars and one for “Badger-sized” hangars. These are
detailed below. Imagery courtesy of Roland Büchler.
The Luyan / Ranghe-Zhen AB site
has an accessible “Badger-sized” hangar with a sliding, segmented
external blast door arrangement. Tunnels normal to the entrance have
been excavated to provide stowage for the doors when open
(Chinese Internet).
Above, below: detail of Luyan /
Ranghe-Zhen AB “Badger-sized” external blast door
arrangement (Chinese Internet).
Luyan / Ranghe-Zhen AB (above) and
Zhangjiakou AB (below) “Beagle-sized” external blast door
arrangement. These two part sliding blast doors retract into normal
tunnels left and right of the entrance.
|
|
|
|
Air
Power
Australia
Analyses
ISSN
1832-2433
|
|
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