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Last Updated: Mon Jan 27 11:18:09 UTC 2014

Strategic Tanker/Transports for Australia

Dr Carlo Kopp, MIEEE, MAIAA, PEng
Originally published Air Power International  Vol.6 No.1
March, 2000

© 2000, 2001,  2005 Carlo Kopp

During the late 1970s the 747-100 tanker conversion was developed for the US Air Force ACTA program, in competition with the DC-10-30. Several were built and later exported (Boeing photos).

Part 1
Issues and Choices

Australia has been arguably in the unique position, for many decades, of being geographically separated from areas of significant strategic tension. During the Cold War, the nearest Soviet bases were in Vietnam. Tensions with Indonesia, Australia's nearest neighbour, abated after the collapse of the Soviet aligned Sukarno regime during the mid sixties. As a result of these circumstances, Australia enjoyed the luxury of modest defence budgets, of the order of 2% GDP or less, over a period of more than three decades.

This favourable situation is now unravelling, as we see gradual shifts in the balance of economic and military power in Asia, and resulting realignments in the perceived interests of regional players.

Of most immediate interest has been a substantial change in the relationship between Indonesia and Australia. Indonesia, an archipelagic multi-ethnic, multi-religious nation state scattered across an island chain from Sumatra to New Guinea, came into existence after the Second World War. Javanese nationalists forced the departure of the Dutch colonial administration, and set up their own state under the leadership of the volatile President Sukarno. Sukarno, an ardent nationalist, participated in the Japanese occupational government in Indonesia and like many Indonesian nationalists, collaborated with the Japanese occupiers whom they regarded to have liberated them from Dutch colonial rule. The new Indonesian state was indeed patterned in many respects upon the Japanese WW2 model of government, with the Army occupying many key positions of power in the civil administration.

The strategic importance of Indonesia to Australia cannot be understated. If occupied by a hostile power, Indonesia becomes the springboard for launching air and naval attacks into Australia's economically vital but sparsely populated north. During WW2, the Japanese Imperial Naval Air Forces and Army Air Forces sortied from Indonesian territory to bomb Darwin and other Australian targets in the far north. In a contemporary scenario, Indonesian territory is ideal for launching air, naval and Intermediate Range Ballistic Missile attacks against targets in Australia. Of no less importance is that much of the heavy shipping carrying raw material and gas exports from Australia to destinations in Asia must travel through the straits in Indonesia, and air traffic to key Asian hubs such as Singapore, Hong Kong, Bangkok and Japan usually passes through Indonesian air space.

By the same token, access to airfields and ports in Indonesian territory provides a valuable geographical advantage to Australia in resisting any external incursion into Australia's area of interest, such as that achieved by Japan in 1942.

Australia's relationship with the developing Indonesia was seldom stable, and governments of the period tended to align with US policy positions on Indonesia, aimed at placating the Sukarno regime and avoiding complete seduction by the expansionist Soviet regime of the period. This policy, which saw the Dutch portion of New Guinea ceded to Indonesia in the late fifties, proved to be ineffective. Indeed it would appear to have actually encouraged the ambitious Sukarno, who by the early sixties engaged in a policy termed "Konfrontasi", aimed at intimidating and destabilising the fragile new state of Malaysia, still recovering from the trauma of a long running communist insurgency. Australian and British troops and air power played a decisive role in crushing the Beijing sponsored Malaysian communists.

Konfrontasi saw a Soviet backed Indonesia sabre rattling with shiny new MiG-21s, Il-28s, Tu-16s and SA-2s, opposed by a RAAF equipped with subsonic CAC Sabres and GAF Canberras and an RAF sorely tasked with balancing the Soviet threat in Europe. Australian and British SAS, and British Gurkhas engaged and destroyed a great many Indonesian insurgent raiding parties into Malaysian territory, while deployments of RAF V-bombers from the UK deterred the Indonesian regime from escalating beyond low level infiltration and sabotage operations. Indeed this was the historical context in which the Australian government ordered 24 GD F-111C strategic bombers, intended at the time to provide the capability to deliver conventional and if necessary, nuclear weapons against Indonesian targets. The prospect of battling 180 million belligerent, Soviet backed Indonesians, was a serious concern to Australian governments of that period.

By the mid sixties Indonesia changed its alignment, as a communist led coup against the Army dominated regime was crushed by the Army, the ABRI, which is alleged to have massacred several hundred thousand communists and their sympathisers. The Indonesian domino in the Soviet grand strategy to control the world's shipping choke points fell to the West, as the war in Vietnam escalated with increasing US and Australian deployments of troops and air assets.

The new Indonesian regime quickly aligned with the US, and was supported with military aid from the US and Australia in following years. Indeed, the strategic position of Indonesia was deemed so important, that successive Australian governments turned a blind eye to ongoing Indonesian violations of human rights, and the illegal annexation of the former Portuguese colony of East Timor in 1975. This policy of "appeasement" continued until very recently, with Australian governments providing extensive training and advice to the Indonesian military, the TNI. A stable and strong Indonesia was seen as an important buffer, and a means of minimising defence expenditure.

The policy of engagement with Indonesia began to unravel with the economic collapse in South East Asia, and the continuing growth of nationalist independence movements in various Indonesian provinces, especially East Timor. Timor became Jakarta's Vietnam, an ongoing insurgency with popular support sapping increasingly scarce military resources, while damaging Indonesia's reputation in the US and EU, key sources of economic aid and investment. Australia became heavily involved in the political effort to resolve the Timor issue peacefully, as such a resolution was seen to be vital to maintaining Indonesia's stability and long term economic growth.

The UN sponsored independence ballot in East Timor precipitated a serious political breakdown between Canberra and Jakarta, as the Jakarta regime, largely controlled by the TNI, opted for a scorched earth policy in Timor. TNI led militias burned out most towns in East Timor, killing large numbers of civilians. Under significant pressure from the UN and the US, Jakarta conceded and allowed the entry of an Australian led UN peace-enforcement force, Interfet. Indonesia's TNI rapidly vacated the field, in the knowledge that a direct confrontation with Australia's highly capable and modern military was a no win proposition. In any escalation, Australian air assets operating from Darwin and Tindal would have rapidly resolved the outcome in the favour of the UN.

Indonesia's ultra-nationalists and the rather narcissistic TNI leadership were politically humiliated at home and abroad, and Jakarta continues to maintain a very frosty diplomatic relationship with Australia, despite ongoing political overtures from Canberra.

The long term outcome in the region is unclear. Indonesia still faces the potential for Balkanisation, with Java playing the role of a Serbia trying to maintain control of an increasingly unstable empire. Of no less concern was the ambivalent role in this crisis played by the Malaysians, whose President Dr Mahatir opted to exploit the situation to continue with his ongoing theme of throwing public insults at all things Australian.

Neither Indonesia nor Malaysia have the capability to threaten Australia, indeed both countries have been long term recipients of extensive Australian military aid. Of much greater concern are events further afield, as India and the PRC continue to escalate their ongoing conventional and nuclear strategic arms race. At the time of writing India had acquired via lease former Soviet Tu-22M3 Backfire bombers, Ilyushin Il-78/A-50 Mainstay AWACS, while continuing negotiations for further purchases of Su-30MKI Flankers and a former Soviet CTOL carrier, the Gorshkov, with an air wing of MiG-29K fighters. The PRC has initiated the acquisition of the Il-78/A-50I AWACS, using a Russian airframe equipped with a state of the art Israeli ELTA L-band phased array, previously bid for Australia's Wedgetail AWACS requirement, while ordering up to 60 Su-30MKK multirole Flankers on top of extant orders for up to 300 or more Su-27SK Flankers. Both are shopping for inflight refuelling assets.

While the arms race between India and the PRC will not peak out until 2010-2015, it is of major concern since both players are clearly building up the force structures required for a modern air expeditionary force. While neither have the capability at this time to properly exploit their latest purchases, 10-15 years of training effort and expected evolution in doctrine will see this change.

Why this should be of concern in Australia, and is curiously enough completely ignored by most Australian foreign policy commentators in the lay media, is because South East Asia is likely to become an area of direct strategic competition between India and the PRC. The fundamental cause lies within the economic growth of India and China which are both developing an increasing dependency upon imported oil, since neither have significant domestic reserves. Indeed a CIA assessment some years ago suggested that the combined needs of the PRC and India by the mid 21st century could be double the world's current consumption. Therefore the PRC will be increasingly dependent upon the super-tanker traffic through the straits of Malacca and Sunda, bringing oil from the Persian Gulf. Shutting off this flow in a future confrontation between India and the PRC could cause decisive damage to the PRC's economy and military posture.

It takes little effort to conclude that a fragmented, politically and militarily weak Indonesia and Malaysia would be highly susceptible to political and military pressure in the charged political atmosphere of a confrontation between India and the PRC.

Effective deterrence to any moves by India or the PRC, or both, into South East Asia could be readily effected by deploying RAAF assets into bases in Malaysia and Indonesia. However, should current political trends persist, this prospect is very unlikely. Indeed, between the time of the Timor crisis and the writing of this article, Indonesia's recently elected President Wahid has made two visits to Beijing amidst repeated statements about realigning Jakarta, and forming a close relationship with the PRC, at the expense of relations with its hitherto principal benefactor, the West. Indonesia could thus be expected to deny Australian access to the region, to curry favour with Beijing, in any such crisis situation.

For Australia to maintain the level of strategic security it held until recently, will henceforth require the ability to cover those portions of South East Asia which were previously accessible from bases in the region, directly from bases on the Australian continent. Without access to runways in Malaysia and Indonesia, the only choice is to deploy sufficient Air-Air Refuelling (AAR) assets to cover the same geography from the chain of RAAF airfields across the north of the continent, since the prospect of deploying multiple CTOL carriers is not economically within Australia's reach.

Analysis performed by the author indicates that this could be effectively achieved with a modestly sized force of large widebody, strategic tankers. A strategic tanker is an aircraft in the payload radius performance of the DC-10, L-1011 or 747, such as the RAF Tristar or the USAF KC-10A Extender. A number between 12 and 16 aircraft, subject to the offload performance of the type, would allow useful numbers of RAAF combat aircraft to cover radii of about 2,000 NMI from the Australian coastline. This would provide direct deterrence in the vital region surrounding the Straits of Malacca and Sunda, the most likely future strategic flashpoint in the region.

A very useful political side effect of deploying such a strategic tanker force is that it denies both Indonesia and Malaysia the political bargaining chip of withholding basing access in any future crisis. Having access to their runways would be convenient but not essential for Australia to maintain a credible deterrent posture against any possible future Indian or PRC strategic incursions into the region.

In this manner a strategic tanker force resolves a number of developing political and strategic problems (the following portions of this article are derived from RAAF APSC Working paper 81, by the author, to be published early in 2000. The previous portions were commissioned by Air Power International/Strike Publications).

There is another strategic consideration. Should the difficulties experienced to date with Australia's Collins class SSKs persist, there is genuine potential for a lack of long range maritime interdiction capability in the coming decade. The deployment of a strategic tanker force of substantial size provides insurance against future problems with the class.

Considering that the aggregate Harpoon loadout for 82 WG is between 80 and 140 rounds, the latter assuming Harpoon capable F-111Gs, the aggregate maritime strike firepower is of a similar order to the 138 (23 x 6) Harpoons or torpedos carried by the Collins SSKs. However, the Collins has a combat radius of the order of 3,000 NMI or better. Therefore to offset the loss in capability which may result from future problems with the submarines, enough AAR capability must exist to support the F-111 to a similar combat radius, in adequate numbers.

Supporting a pair of F-111s to 3,000 NMI will require a large widebody tanker. Therefore to match the firepower of four Collins SSKs at 3,000 NMI, we require about twenty four F-111s and twelve large widebody tankers. It is a convenient coincidence that this number closely fits the parallel needs of deterrence operations within a 2,000 NMI radius.

As noted earlier, and evidenced by recent events in Ambon, Borneo and Aceh, we are seeing an ongoing breakdown in the functions of civil and military authority in Indonesian provinces. This situation may or may not stabilise, and much will depend upon future political decisions in Jakarta.

The rise of Islamic fundamentalism in Aceh could well stimulate problems in the Southern Phillipines. The result may be any number of localised "Timor contingencies" in the region, which regional governments may not be able to manage themselves, if current trends continue.

Under these circumstances it may be necessary to rapidly airlift in a peace enforcement or peacekeeping force. Whether such a force comprises primarily Australian personnel, or South East Asian personnel, the circumstances will most likely require the very quick insertion of a force of several thousand troops and supporting equipment. For such a force to be effective it needs to be at least the size of one to two brigades, mostly comprising infantry, special forces, police and supporting vehicles, the heaviest of which would be armoured personnel carriers.

Given existing US commitments it is not reasonable nor prudent to expect the immediate "on-call" availability of USAF Air Mobility Command assets. This would especially true if the US is managing another crisis elsewhere in the world.

Only Australia has the skills base in the region to to lead and manage such an operation, and therefore if it is to perform a leadership role, it will have to provide the heavy airlift.

While commercial transports modified as AAR tankers are mostly not well suited to carrying heavy equipment like armoured personnel carriers and tanks, required for high intensity combat operations, they are adequate for the transport of most of the equipment required for peacekeeping operations. Situations where heavy equipment does need to be lifted into theatre will most likely arise in the context of a larger, coalition campaign, where access to USAF C-141, C-5 and C-17 aircraft will be available. Experience during the nineties indicates that only 5-20% of the total airlift capacity requires the use of specialised RORO and short field / outsize cargo capable military airlifters. Indeed the principal impediment to the wider US military use of commercial freighters during the nineties was a shortage of deployable ground loading equipment, thereby forcing the use of specialised military airlifters. This has been remedied by the USAF's fielding of the capable SEI 60K Tunner mobile loader, in 1997. The Tunner can service all USAF airlifters and commercial freighter types.

It may be argued that commercial freighter types are less suitable for such airlift operations since many of the runways in the immediate areas of interest are of poor quality, and only accessible by military airlifters such as the C-130 and C-17. This is true, but mostly irrelevant, since it is not operationally prudent nor sensible to fly heavy airlifters into a marginally secure area, where they could be exposed to MANPADS, AAA, small arms and even mortar fire on the ground. Indeed the USAF's intended 21st century airlift strategy uses a two tier scheme, with C-17 for heavy lift into secure major airfields and C-130 for distribution to less secure forward operating bases.

A single large widebody transport can lift between 300 and 500 troops, which means that a dozen such aircraft can move a brigade in the time to takes to load, cover the distance, unload, and return. When carrying equipment and supplies, each will typically lift between 75 and 110 tonnes. Therefore a dozen such aircraft can move between 900 and 1320 tonnes of equipment and supplies in the time to takes to load, cover the distance, unload and return.

The participation of Australian personnel in other UN sponsored peacekeeping operations is highly probable, and likely to be in far flung parts of the world. We can thus expect a strong and ongoing demand for extended range airlift, especially of personnel and supplies. Lifting refugees proved to be demanding during the Kosovo crisis, and similar contingencies are likely to arise again. The rapid delivery and distribution of humanitarian aid is another very likely contingency, again one where the ability to rapidly move bulk freight is of considerable value. The evacuation of Australian nationals from foreign countries in crisis situations is another scenario where a rapid demand for passenger lift may arise at very short notice.

It is another convenient accident of circumstance, that the required fleet size of strategic tankers for deterrence operations and long range maritime strike operations happens to closely fit the sizing needs of an airlift force required to support likely ground force operations in the region.

A useful opportunity thus exists to provide the RAAF with a substantial AAR tanker fleet while fulfilling developing airlift requirements. Equipping strategic airlift capable freighter aircraft with booms, hose/drum equipment and lower deck fuel cells, means that the ADF could exploit these airframes to plug a long extant gap in RAAF capabilities.

Therefore, by appropriate choice of aircraft type it is possible to address the future needs for strategic AAR and strategic airlift with a single package of aircraft, which offers very significant economies across the board.

A factor which should not be discounted is the utility of air power in supporting ground forces on regional peacekeeping deployments, should the political conditions under which such a force is deployed later deteriorate. Using a dual role strategic tanker/transport force rather than a dedicated RORO airlifter force means that any Bosnia-like scenario can be deterred or resolved by the focussed application of air power, directly from the Australian mainland.

Because the performance requirements of a strategic tanker are more demanding than those for a widebody troop and freight transport, these must be the driving constraints in the choice of airframe. Therefore the following analysis focusses on meeting the needs of strategic AAR first and foremost.

Issues and Choices for a Strategic Tanker/Transport Force

The choice of an airframe for a Strategic Tanker/Transport Force will necessarily involve some compromises in AAR capabilities, and airlift capabilities. This is an inevitable reality where the only choice is the adaptation of existing airframe designs.

The capabilities required for an AAR tanker aircraft vary strongly with the intended mission profiles. Where operational radius is modest, inside 500-1,000 NMI, the best choices are small or medium sized airframes, since these allow for larger numbers of tankers and much greater flexibility in operational planning. This is especially true when supporting small reactive defensive CAPs, or defensive point intercepts beyond the range of the CAP fighters, since the cost in fuel burn of putting up the tanker is minimised. However, as we extend the required operational radius out to 1000 NMI and beyond, the fuel offload performance of the aircraft becomes increasingly important, favouring larger airframes. The disadvantages of larger tankers are thus bigger operating costs for shorter range, small offload missions, and greater demands upon runway strength and length, assuming similar generation powerplants.

Therefore, the use of a heavyweight strategic tanking capability imposes an implicit reduction in operational flexibility for many shorter ranging roles, and a potentially large increase in the operating costs of the AAR capability for such operational employment, and peacetime training. This will be offset by reduced crewing and thus crew training requirements of heavyweight strategic tankers, an advantage which increases with the increasing capability for offload performance.

Proponents of small and medium sized tankers can correctly argue that big strategic tankers will cost more to operate per aircraft in training use, however in any wartime situation, small to medium sized tankers lack the offload performance to support large strike packages over substantial distances without the substantial use of tanker to tanker refuelling.

The classical case study of what happens with small tankers when long range sorties are required is the 1982 Black Buck series of Vulcan strikes, where typically fifteen Victor tankers were required to support a single Vulcan bomber !

To robustly place a package of combat aircraft over a target at 2,000 NMI, and repeat this process as needed by operational circumstances, will require genuine strategic tankers. This is a reality which cannot be escaped.

The issue of flexibility and training costs could be offset to a large degree by the adoption of a two tier model, in which a heavyweight large widebody airframe is employed for the operational strategic tanking role, and heavy airlift. A much smaller narrowbody aircraft with low offload performance and low fuel burn is then employed in small numbers for the reactive, low offload role, and for most of the training activity.

The latter requirement could be fulfilled by re-engining the extant Boeing 707-338C with the highly fuel efficient CFM-56, and by fitting booms. A costlier alternative in the short term, which yields a better return in fuel burn costs in the longer term, is the acquisition of a newer narrowbody airframe equipped with a boom and a fuselage hose/drum/drogue unit.

Two obvious candidates would be the KC-757 proposed by Boeing as a KC-767 supplement, or a variant of the Boeing 737, i.e. a KC-737 or 737-TT. Both of these aircraft provide excellent operating costs, the 737 is widely used in Australia, the 757 offers common cockpit ratings to the 767, which is also widely used in Australia. Both would incur the expense of a new AAR conversion design and testing.

The capabilities required for a strategic airlifter also vary with the intended mission profile. Where the transport of personnel and palletised supplies are the principal priority, and long runways of adequate strength are available, widebody passenger transports and freighter conversions of such types are the cheapest and most practical choice. However, if we wish to move heavier equipment items such as the ASLAV (LAV-25) armoured personnel carriers, artillery pieces, or even very large items such as Main Battle Tanks (MBT), the demands upon the aircraft in terms of cargo bay floor strength and loading door sizes increase significantly.

In practical terms this is reflected in established types of aircraft used for the AAR tanker and strategic airlift requirements. The USAF KC-135 reflects optimisation for AAR operations, with a limited secondary personnel and freight carrying capability. The USAF KC-10A reflects a requirement which combined AAR support for fighters on long deployments, with the associated ground support equipment carried as freight, to reduce demands upon dedicated airlift assets. The C-141, C-5 and C-17 reflect optimisation for the strategic airlift requirement, with no secondary capability to provide AAR.

The dilemma for Australia in selecting a type lies in finding a suitable compromise which provides sufficient capability in both strategic AAR and airlift to be able to address the requirements of both roles adequately. Since the only production strategic airlifter at this time is the C-17 which is both too expensive, too capable, and lacks the payload-radius and thus offload performance for genuine strategic tanking, the only practical choice is an adaptation of a commercial widebody airliner airframe.

In a sense Australia has little if any choice in this game, since the acquisition of a large number of medium sized tankers would not be competitive against a smaller number of heavyweight tankers, given the need to offload large amounts of fuel at long ranges. Deploying such a fleet in parallel with dedicated airlifters would clearly involve prohibitive expenditure.

A significant operational benefit to the use of a common type is that when performing the airlift role, the aircraft can refuel their own fighter escorts, thereby reducing the temptation an opponent may have to sortie a long range fighter such as the Su-27/30 to engage the airlift. In effect, a heavyweight strategic tanker/transport opens up the possibility of an "aerial convoy", whereby the transports are accompanied by their own escort fighter force.

The considerations which must be applied in the selection of an aircraft type may be summarised thus:

  • The ability to support a refuelling boom, to refuel the F-111, the F-16 (RNZAF, SAF, USAF), the F-15 (USAF) the Wedgetail AEW, USAF tankers and transports, and to avoid imposing constraints upon any fighter selected under AIR 6000.
  • The ability to support one or more hose/drogue refuelling units, to refuel the F-18 (RAAF, USN), the F-14 (USN), and to avoid imposing constraints upon any fighter selected under AIR 6000.
  • Sufficient offload performance to support strike packages operating to combat radii of 2,000 NMI or more, with a minimal number of airframes.
  • The ability to support a receptacle to accept fuel from other boom equipped tankers, thereby improving operational flexibility.
  • Best possible short field performance and minimal demands upon runway load carrying capability, and smallest possible span to maximise handling flexibility on the ground.
  • Highest possible economic cruise speed and dash speed, to provide best possible flexibility and survivability.
  • Four or three engines are preferable to two engines, for extended over water operations.
  • Cabin volume for relief crews, and if possible for racks of supplementary communications relay equipment, such as satellite link or HF to UHF relays.
  • Largest possible main deck internal volume, especially width and height, to accommodate bulky medium or low density freight.
  • Sufficient lower deck volume to accommodate dedicated fuel cells and associated plumbing to provide a large, high flow rate AAR capability.
  • Freight doors large enough to accommodate the ASLAV (LAV-25) and if possible, M-113 APCs. The ASLAV has a height of about 2.7 metres, a length of about 6.5 metres, and a width of about 2.62 metres. The M-113 has a height of about 2.4 metres, a width of about 2.7 metres, and a length of about 5.3 metres.
  • Floor load bearing capability sufficient to accommodate the ASLAV (LAV-25) and if possible, M-113 APCs. The ASLAV weighs about 11 tonnes empty and 13 tonnes full.
  • Minimal requirements for additional maintenance support in Australia, thereby decisively favouring types already in service with local commercial operators.
  • Minimal requirements for aircrew training infrastructure in Australia, thereby decisively favouring types already in service with local commercial operators.
  • Minimal Non Recurring Expenses (NRE) to implement a freight handing conversion, involving floor strengthening, freight door installation and powered freight handling equipment installation. This will favour those types for which existing freighter and combi conversion programs are active.
  • Minimal NRE to implement an AAR boom and AAR hose/drogue hardware installation. This will favour those types for which AAR tanker variant conversions have been performed, and are or have been flown operationally.
  • Should used airframes be employed, these should have preferably been used for long haul operations to minimise the number of accrued landing and takeoff cycles.

These criteria may be employed for comparing types which are currently available as new or used airframes in the commercial marketplace.

Boeing/MDC DC-10/MD-11 Derivatives - KDC-10 and KMD-11

The Boeing DC-10/MD-11 family of aircraft are the basis of the USAF KC-10A Extender, and the Dutch RNeAF KDC-10-30CF tanker transports. These aircraft provide suitable offload performance if equipped with lower deck fuel cells, and load carrying capability for both AAR, freight and personnel airlift roles.

The USAF KC-10A has been flight tested with a pair of wing mounted Mk.32B refuelling pods, in addition to the internal Sargent Fletcher hose/drum/drogue unit and the AAR boom installation. The current build MD-11 and DC-10-30 and -40 can be readily adapted as freighters, as Boeing maintain an active conversion program. The available lower deck floor strength provides for about 42 tonnes of auxiliary fuel in the DC-10-30/40 models, and about 50 tonnes of auxiliary fuel in the MD-11 models.

However this family of aircraft is not operated in Australia, and thus there is no established base of aircrew nor any domestic support infrastructure. Moreover, the standard freight door is not of sufficient height to load Army APCs, thereby limiting the usefulness of the aircraft in airlift operations to personnel, freight and small vehicles.

Another factor is longer term supportability, since the DC-10 has been out of production for some years now and the MD-11 is being phased out. This is already cause for some concern in USAF circles about the longer term economics of supporting the KC-10A Extender, since it is expected that most commercial operators will begin to wind down their DC-10 fleets between 2010 and 2015, resulting in a contraction of the commercial support base and resulting growth in support costs.

For these reasons the DC-10/MD-11 family of aircraft are not a particularly suitable choice for this application.

Lockheed L-1011 Tristar Derivatives

The Lockheed L-1011 is the basis of the RAF's Tristar tanker fleet. While a much better performer than the competing DC-10 airframe, the Tristar has been out of production for many years now and the remaining pool of airframes is tired. Therefore long term supportability will be an issue for the Tristar. Like the DC-10 derivatives, it is limited in the size of main deck freight, and is not flown by any operator in Australia. No boom conversion exists. Therefore it is even less suitable a choice than the DC-10.

Boeing 767 Derivatives - KC-767

The Boeing 767 family of aircraft, specifically the -200C/F, -300C/F and -400C/F models, have been proposed by Boeing as a replacement for the KC-135 family of aircraft, and have been vigourously marketed by Boeing. However at this time no AAR tanker conversion exists, and significant NRE would be incurred. In terms of offload performance, the proposed Boeing KC-767 modestly outperforms the standard KC-135R, yet it provides a far superior ability to carry main deck freight.

Therefore, for a smaller fleet the KC-767 is inadequate for the outer radius envelope and thus not competitive with a larger widebody airframe such as a KC-10A. The other important limitation of the KC-767 is the limited freight door size and main deck width which preclude the loading of Army APCs. Current costs in the used aircraft market for the 767-300ER vary between USD 51M and 88M, depending on the age and condition of the aircraft. In terms of speed its Mach 0.8 performance is modest, compared to the Mach 0.85 or better performance of the RAAF's Boeing 707 aircraft.

Therefore the KC-767 also is not a good fit for the defined requirements.

Airbus A310 Derivatives - MRTT

The Airbus Industrie MRTT (MultiRole Tanker Transport) is a variant of the established Airbus A310-300 or -600 series airframe, which has been proposed and actively marketed as a European alternative to existing US AAR tankers. At this time no AAR conversion exists, and significant NRE would be incurred. This aircraft falls below the Boeing 767 in offload performance and would also be marginal in the airlift role.

The remaining large widebody type to consider is the Boeing 747. Part 2 will explore the significant potential of the 747 in the strategic tanker/transport role.

For representative images refer:

Volume II - APA-2005-02 Carlo Kopp and Brian Cooper KC-33A: Closing the Aerial Refuelling
and Strategic Air Mobility Gaps (PDF)

Figure 1. RAAF/Boeing 707-338C tanker. The RAAF's extant fleet of four Mk.32B pod equipped 707s provide a training and limited operational capability to support the F/A-18A. Fitted with thirsty sixties technology fans, they burn around 15,000 lb/hr, yet lacking lower deck fuel cells they provide poor offload performance against the similar KC-135R, and lacking a boom they cannot refuel the regionally important F-16 and the RAAF F-111. Interestingly, a late seventies upgrade proposal for the KC-135 would have seen the retrofit of the larger 707 wing, but the USAF settled for the life extension of the existing wing.

Figure 2. Boeing KC-135R Stratotanker. The Stratotanker is the backbone of the USAF's tanker fleet, providing a fast airframe and respectable offload performance. The aircraft have undergone a major program to replace lower wing skins, the retrofit of CFM-56 engines, and are now being retrofitted with glass cockpits under the Pacer CRAG program. Some aircraft have received a new design boom, and the fleet is being progressively retrofitted with new, safe dry running fuel pumps. At this time the only concern is the possible impact of airframe corrosion on fleet life,

Table 1.

Table 2.

Table 3.

Figure 3. Boeing KC-10A Extender (USAF).

The USAF operates 60 KC-10A Extender aircraft, to supplement the KC-135. The KC-10 is a genuine strategic tanker, and has adequate freight handling capacity to usefully supplement the USAF's C-5, C-141 and C-17 fleets. Standard KC-10A are equipped with a boom and single hose drum units, while airframes are also plumbed and wired for wing mounted Mk.32B pods. A major issue for the USAF will be supporting the fleet after 2010, as the commercial operator base collapses with the retirement of much of the commercial fleet.

Figure 4. RNeAF Boeing KDC-10-30CF (Boeing).

The Royal Netherlands Air Force operates several converted DC-10-30CF tanker transports to support their F-16 fleet. These aircraft provide much lower offload performance than USAF KC-10As, due to the absence of lower deck fuel cells. Like the KC-10A, support costs for this type are expected to increase in coming years.

Figure 5. Boeing KC-767 Tanker/Transport (Boeing)

The KC-767 has yet to fly, but is being actively marketed by Boeing. This aircraft provides a respectable unit replacement for the KC-135R, offering slightly better offload performance and significantly better freight capacity. Its limitation in the Australian context is offload performance, since a fleet size of 20-25 aircraft would be required, and freight handling size, limited by the low ceiling height to smaller vehicles and palletised freight. Strategic Tanker/Transports for Australia.

Part 2
The Boeing KC-25/KC-747 Strategic Tanker/Transport

In Part 1 of this two part series we explored the evolving strategic context in South East Asia and identified a developing need for Australia's RAAF to acquire a substantial strategic/tanker transport force. Analysis indicates that about 12-16 large widebodies would provide a good fit for deterrence operations, long range maritime strike, air support of regional peacekeeping deployments, and the airlift and ongoing resupply of a brigade sized ground force element.

Applying a basic list of criteria against available airframe in the commercial market indicates that the 767 and Airbus 310 derivatives are too small. DC-10 and Tristar derivatives will be difficult to support in Australia, moreso beyond 2010 when commercial fleets begin to down-size, despite the adequate performance of these types as tankers. The only remaining type in the required size and performance class is the Boeing 747, and this aircraft is the subject of this final part of the series.

The Boeing 747 family of aircraft is used both by Qantas and Ansett in Australia, and Air New Zealand. Qantas flies it in passenger and freighter variants. The Boeing 747 design is a derivative of a sixties Boeing proposal for a military airlifter, which lost out to the Lockheed C-5A Galaxy. The aircraft was later evaluated against the DC-10 as part of the USAF Advanced Tanker / Cargo Aircraft program, losing out to the McDonnell Douglas KC-10A proposal despite its superior performance. Photographs exist of the 747 refuelling even the SR-71A during these trials.

Several AAR boom and receptacle equipped 747-100B tankers were supplied to Iran during the mid to late seventies, these including lower deck fuel tanks, and two US military variants exist with AAR refuelling receptacles.

The conversion package for Iran was performed with the expectation that other clients would be found, and a full production standard documentation package was generated as a result. Therefore a current retrofit of the basic KC-135 boom to the 747 incurs minimal Non Recurring Expenditure (NRE). The Iranian aircraft employed an operator with direct view as per the KC-135 design, but located behind a recessed rear fuselage window in the aft pressure bulkhead, rather than in a protruding fairing as used by the KC-135.

A cheaper alternative to produce, at the expense of some NRE, would be the remotely operated boom as used on the KDC-10-30CF. The "classic" KC-135 boom was recently re-engineered in a number of areas to employ current production techniques such as extrusion rather than riveting. Booms supplied on recently delivered KC-135R conversions have been based on this newer implementation which would be used in any new build 747 retrofit.

The lower deck volume of the -100/200/300 and -400 models available for container freight provides ample space for additional auxiliary fuel cells, which would be essential to extract the full offload potential of the aircraft as a tanker. Since intercontinental variants of the 747 carry a generous internal fuel load, at MTOW for most variants only about 20 to 40 tonnes would need to be carried in auxiliary lower deck fuel cells, with crossfeed from the main tank employed.

A typical implementation for a lower deck fuel cell would resemble a reduced height LD2 type freight container. Without potentially expensive structural reinforcement of the lower lobe floor, the auxiliary fuel cells are weight rather than volume limited. The aggregate gross weight limit for fore and aft lower lobe compartments is 47.7 tonnes, assuming an evenly distributed load, which bounds the available capacity of lower deck tanks. The US FAA requires the tanks withstand loads of 9G. Typical contemporary implementation employs a rigid double walled tank design, rather than the older " fuel bladder inside a metal box" style.

Offload performance at a 1,900 NMI radius would be about 95 tonnes of fuel or better, for a Combi or Freighter configuration with lower deck auxiliary fuel cells. Such performance is superior to the KC-10A.

US military 747-200B variants are designated C-25A, such as the VC-25A "Air Force One". The designation C-19A is reserved for 747-100 aircraft committed to the CRAF scheme. Therefore a 747-200B tanker/transport variant could be designated a "KC-25A", with a different suffix applied for a different 747 variant, examples being a "KC-25B" for 747-SP model or a "KC-25C" for a 747-300 model.

A simple measure of the Boeing 747 against other established tankers is that it delivers offload performance potentially superior and payload-range superior to the KC-10A Extender, yet it is fast like the KC-135R or Boeing 707 tankers, cruising at 0.84-0.85 Mach.

Therefore this aircraft is the only type which satisfies the requirement of an existing domestic operator base, the requirement for an established boom equipped AAR conversion, and delivers the long range AAR offload performance and volumetric requirements needed for the strategic AAR and airlift roles, respectively.

Freighter conversions of the four basic versions are very widely used in the commercial air freight market, indeed the current industry trend is for older 747-100 and -200 airframes to be retrofitted into freighter configuration by the addition of a large aft fuselage Side Cargo Door (SCD), and installation of the freighter floor. Designated a 747 "Special Freighter" (747SF or 747-100SF/200SF), conversions are performed by Boeing Wichita, GATX-Airlog, Pemco Aeroplex, Israel Aircraft Industries and HAECO with costs depending on the scope of the conversion package. Typical costs are between USD 12M and 20M per airframe.

Boeing 747-100 and 747-200

Five basic models of this aircraft exist, manufactured from about 1970. The 747-100 and -200 are the oldest models and given accrued airframe fatigue many airframes may not be a viable consideration for a large long term investment given the cost of airframe life extension. The last -200F freighters were built during the early nineties and may have acceptable fatigue life. Typically the fatigue life of older 747s can be extended through Section 41 reworks, and Pylon and D checks, with the cost of such a work package reaching up to USD 10M per aircraft. Engine overhauls typically cost USD 1.5M each at intervals of 1,200 to 1,500 cycles. The market value of 747-100 and older -200 aircraft varies between USD 4.6M and 7.7M, with later build 747-200 variants commanding between USD 13.8 and 26.2M apiece.

Boeing 747-300

The 747-300 is the extended upper deck variant of the late build -200B airframe, manufactured between the early eighties and nineties. With the advent of the extended range -400 model, the demand for this model in the commercial market has declined and it is readily available, while accrued fatigue life will be modest for examples flown mostly on long haul routes. Of particular interest is the fact that at this time there is a glut of used 747-200B/C and -300B/CF aircraft in the market, of which a good proportion are Combis, which are already fitted with the large SCD freight door and would thus incur lower costs to convert to a tanker/transport configuration. Typical unit costs fall between USD 39.4 and 50.8M, but will vary with the age, condition and fit of the aircraft. Given the saturation of the market, it may be feasible to acquire aircraft at prices well below the actual value of the aircraft.

The extended upper deck on the 747-300 series aircraft provides the means of carrying up to 85 economy class passenger seats in addition to main deck freight, but does so at the expense of reducing the ceiling height of the main deck fore of the wing, thereby imposing some limits on the carriage of taller freight items. A 747-300 is thus more flexible in terms of its ability to mix freight and troop loads, but is less flexible in the mix of freight item sizes it can accommodate, in comparison with a 747-200 derivative.

Boeing 747-400

The 747-400 is the current production model, introduced in the early nineties, available in passenger, Combi and Freighter versions. It features the extended upper deck of the -300, and a new extended wing, fitted with winglets. Since it is available either new build, or with a service life under 10 years, fatigue life is not an issue for the 747-400 at this time.

The 747-400 offers the best load carrying performance of any 747 variant, but its larger MTOW imposes the need for better runways, and due to its large wingspan ground handling can be an issue on some sites. It is also expensive in the used aircraft market, as it remains strongly in demand, with typical used aircraft worth between USD 92.5M and 158.5M.

Boeing 747-SP

The Boeing 747-SP is a high performance, lightweight, long range variant, manufactured between 1976 and the late eighties. Only 45 were built. The aircraft was specifically designed for very long range, low load factor routes, as a replacement for the long range variants of the Boeing 707. It employs a shortened fuselage, lighter structure and enlarged tail surfaces. Until the advent of the extended range -200B variants and the -400 it was the 747 variant with the best range performance.

As the -400 has penetrated into the commercial market, the demand for the 747-SP has fallen very strongly and as of July, 1999, seven were in storage and four dismantled for structural spares. Qantas continues to operate two examples. No less than fifteen 747-SPs are currently on the market, including some VIP transports, with a unit cost cited between USD 5.3M and 7.7M apiece37. Because of the poor profitability of the 747-SP on most routes, it is considered to be worth more as scrap than as an commercial asset. As the 747-SP was almost exclusively used for long haul operations, the number of cycles on the airframes will mostly be excellent, in relation to the age and accrued flight hours of the aircraft, typically between 9,000 and 13,000 cycles on aircraft aged around 18 years. Such numbers are more typical for 747 aircraft of 12-15 years of age.

However, the general condition of many of the available aircraft is unclear, and considerable refurbishment, and corrosion repair effort may be required in addition to the required AAR hardware modifications. Providing that candidate airframes are adequately investigated prior to purchase, this risk can be managed reasonably precisely.

The 747-SP has the best short field take off performance of any 747 variant. Most large widebodies require about 3,100 metres of runway, the 747-SP typically requires 2,350 to 2,750 metres at MTOW, reflecting the lower MTOW and load carrying performance of this variant.

As a tanker the 747-SP provides an internal fuel capacity of 148 to 153 tonnes, and lower lobe floor strength to accommodate about 30 tonnes of auxiliary fuel. Given existing MTOW limits on the aircraft this yields about 74-80 tonnes of offload at 1,900 NMI which is competitive performance against the KC-10A. Clearing the aircraft for a 4% increase in MTOW would bring offload closer to 85 tonnes under these conditions.

The limitation of the 747-SP as a tanker/transport airframe is its low structural payload limit of 38 tonnes in the standard configuration, and the need to perform a Combi or Freighter conversion, neither of which were standard build options. A production option was an increased structural payload limit of 45 tonnes, and it may be feasible to further improve upon this. The issue is thus the NRE of such structural work, and the NRE associated with adapting the standard 747-200/300/400 freight floor and SCD installation. Given the low cost of basic airframes, such modifications are well worth exploring, especially since they are based upon standard components used in the 747-200B/CF/300CF freighter conversions.

In terms of initial acquisition costs and performance as a pure tanker, the most suitable 747 variant is the 747-SP. With lower deck fuel cells its offload performance is competitive against the KC-10A, yet the cost of the basic airframe is 1/4 to 1/3 of current DC-10-30CF costs, and it offers superior short field performance and cruise speed. This competitive advantage must be balanced against its limited performance as a freighter, typically of the order of 40% to 50% of the structurally limited payload of a 747-200/300 series aircraft, and 50% to 60% of a KC-10A aircraft.

Biasing the requirement toward airlift, and factoring in availability and fatigue life, the most suitable 747 variants for a strategic tanker/transport role would be the 747-200B/CF/300CF, should examples with suitable maintenance histories be selected.

An issue for any Boeing 747 AAR tanker conversion will be the provision of hose/drogue refuelling hardware, as no current user (Iran) has had such fitted. The simplest alternative is the installation of one or two fuselage hose/drum unit, in a manner akin to the KC-10A or RAF Lockheed Tristar, preferably using the same hardware. Refuelling of the C-130J and larger RAF assets imposes the constraint that such a fuselage installation be used.

The need for redundant hose/drogue systems to account for possible failures enroute indicates that the preferred configuration would employ either a pair of fuselage hose/drum units, or a three point arrangement with a single fuselage hose/drum unit and a pair of wing mounted Mk.32B pods as used on the RAAF's Boeing 707-338Cs. The latter would be more attractive operationally but a much more expensive choice since the overheads of design, wing modification to accommodate fuel lines, and flight testing would be incurred.

The Engineering, Manufacturing and Development contract for adding wing-mounted "hose and drogue" refueling pods to the KC-135R Stratotanker cost approximately USD 24.4M. The cost of conversion kits to fit Mk.32B pods to USAF KC-135R aircraft is about USD 2.55M per aircraft, excluding the cost of the pods. The cost for a KC-25/747 kit would be slightly higher due to the longer fuel lines required. Given that Boeing have performed the adaptation of both the KC-135R and KC-10A for wing mounted Mk.32B pods for the USAF, it is reasonable to assume that much of the design work could be directly adapted to a KC-25/747 design, thereby reducing the magnitude of the NRE required. The all up cost of equipping a dozen KC-25/747 aircraft with pods would be thus of the order of USD 50M, excluding the cost of 24 pods and appropriate spare components.

The 747 as an Airlifter

A very attractive aspect of the standard Boeing 747-200CF/300CF and 400F Combi and Freighter conversions is the size of the standard rear fuselage SCD freight door. It provides a vertical clearance suitable for a 3 metre high load, and a horizontal clearance suitable for a 2.5 metre wide load. The door is 3.4 metres wide, but some allowance must be made for swinging the load around as it is inserted. Refer Table 1. for comparison with the C-130, C-141, C-5 and C-17.

The floor width is 6.13 metres, which means that on paper both the standard ASLAV and M-113 can be loaded, albeit with some care required during insertion. Clearances will need to be verified by a load check since the ASLAV is 18 cm wider and 45 cm longer than the standard 2.44 x 6.05 metre freight pallete. Specialised variants of the ASLAV, such as the command vehicle and ambulance may not fit through the 747 freight door due to their bulkier and higher profile.

Unlike a conventional military airlifter allowing Roll-On/Roll-Off (RORO) loading, the Boeing 747 would require that the ASLAV be first tied on to a 6.05 metre pallete, and then handled and loaded into the aircraft as if it were an 11 tonne, 6.05 metre contoured freight container. A forklift would be used to load empty palletes on to the loader, for roll-on loading of the vehicle on to the pallete. Once the vehicle is secured to the pallete it may be loaded into the aircraft. For unloading, the "palletised" vehicle is released off the pallete and driven away, and a forklift is used to remove the empty pallete from the loader.

Since the vehicle is slightly longer than the standard pallete size, the locked down positions of the pallete would have to be slightly different to a standard load of 6.05 metre containers or palletes. On paper, this arrangement would allow four or more ASLAVs to be loaded, side by side, together with other freight.

Unlike conventional military airlifters which have loading ramps and a very low floor height, the Boeing 747 requires specialised support equipment for loading and unloading. The height of the 747 main deck is between 4.67 and 5.33 metres, depending on the weight of the aircraft. Therefore, if the aircraft were to be operated into airfields which are not equipped to handle containerised freight, such equipment would need to be either prepositioned, carried in by the 747 strategic transport, or delivered by other aircraft prior to the arrival of the 747 strategic transports. Ground based loading equipment may be fully mobile container handling equipment like the 30 tonne capacity USAF/SEI 60K Tunner, or the 13 tonne capacity SEI 25K loader series, or much cheaper collapsible frame container and pallete elevators, like those employed by the USAF with the KC-10A. Fully mobile loaders are the most flexible in use but more difficult to deploy, e.g. the USAF Tunner requires either C-141, C-5 or C-17 lift. Smaller loaders are compatible with the C-130.

New build Boeing 747-200CF/300CF/400F Freighters and many Combis have been delivered with a lifting Nose Door, similar in concept to that used on the C-5 Galaxy. This door has size limitations, primarily the vertical clearance limit of 2.49 metres imposed by the floor of the cockpit and upper deck section. This is inadequate for the ASLAV but may be sufficient for the M-113. It would however be convenient for roll-on/roll-off loading and unloading of 4WD vehicles and smaller trucks with heights under 2.45 metres, using a loader to lift them level with the aircraft main deck.

The Freighter/Combi Nose Door is however attractive insofar as it allows the aircraft, with minor modifications, to carry the Boeing On Board Loader device, which is stowed in the nose of the aircraft and deployed once on the ground to provide autonomous freight handling. This device takes 30 minutes to deploy or stow, weighs 6.6 tonnes and can handle payloads of up to 13.6 tonnes. When stowed it displaces two 2.44 x 6.05 metre containers or 6.7% of main deck capacity. The Boeing On Board Loader may be disconnected from the aircraft nose and used as a free standing loader. It is designed to load and unload 2.44 x 6.05 metre palletes or containers, using either the Nose Door or the Side Cargo Door. The loader is powered from the aircraft's electrical system at either door, or by a ground based generator.

An interesting side note is that the design of the loader was paid for by the Iraqi national airline during the late eighties. They were the sole client for this piece of equipment. We can but speculate upon reasons for the Iraqis wanting to be able to load and unload large 13 tonne containers at unprepared sites.

This loader is not suitable in its basic configuration for the handling of the ASLAV and M-113 and would require some design changes for this purpose. Slight modification of the loader design to increase its width and length would thus be required. Nominal time to load or unload an aircraft using this device is about one hour, assuming the device is already deployed.

An important limitation of the Nose Door is that the nose refuelling receptacle design would need to be adapted to use a flexible or articulated connection to the fixed fuel lines in the forward fuselage, or shifted above the cockpit, thereby incurring some additional NRE.

The feasibility of retrofitting the Nose Door as part of the freight modification needs to be further investigated, as this would provide more flexibility in the choice of airframes which otherwise must be selected from the limited pool of Nose Door equipped Combis available in the marketplace. Another alternative is to rework the design of the Boeing On Board Loader to allow it to be deployed from the SCD rather than the Nose Door. The final option is a mixed fleet with only some aircraft fitted with the Nose Door.

There may be some scope for faster reconfiguration time between the airlift and troop carrying configuration, by using dedicated 2.44 x 6.05 metre palletes fitted with fixed canvas troop seats, rather than commercial Combi airliner seating. This could be implemented in a manner which saves considerable weight, against commercial seating, thereby allowing more troops and freight to be loaded into the aircraft.

A simple measure of the Boeing 747-200CF/300CF/400F as an airlifter is that it provides payload range performance in the class of a C-5 Galaxy, but its freight loading door limits payload items to sizes similar to those carried by a C-130 Hercules or C-141 Starlifter. With the exception of length, the Boeing 747 SCD can handle items slightly larger than either the C-130 or C-141. Therefore any Army assets air portable by C-130 will almost certainly be portable by 747, thereby taking a significant load off the RAAF C-130 fleet.

Its principal limitation in comparison with purpose built airlifters is inferior short field performance, greater runway strength required, and the need for external loaders. For bulk strategic airlift of personnel and palletised freight into secure areas with suitable surfaces, using the C-130 for forward distribution, the 747 outperforms all airlifters other than the C-5.

Crew and Passenger Access

An issue of some inconvenience is the absence of a door or hatch and internal ladder for crew and passenger access to the aircraft at sites without appropriately sized boarding facilities for airliners. The solution is to employ a modification used on the USAF's Boeing E-4B NEACP airborne command post and the VC-25A VIP aircraft. These aircraft carry a deployable set of airstairs stowed in the forward lower lobe cargo bay.

Installing deployable airstairs would remove at least one fuel cell in the forward bay. Given the load carrying capacity of the lower lobe lobe floor and MTOW limits in both the 747-200B/CF/300CF and 747-SP models, this would not impair the potential offload performance, as a single cell amounts to 10% or less of the lower deck capacity.

Integration of the deployable airstairs will render some small portion of the main deck floor above the forward lower lobe cargo bay unusable for freight, so as to provide space for a hatch to access the airstairs. Since retractable stairs must be installed to provide access between the main deck and the upper deck, these should be located adjacent to the hatch to the airstairs to minimise the loss to main deck floor space.

The airstairs provide the ability to load and unload passengers, as well as providing access for the crew, regardless of site facilities and should be a serious consideration for all aircraft in the fleet.

Implementation Issues

While a Boeing 747 based strategic tanker/transport is not the ideal solution for the strategic airlift requirement, it is an excellent basic platform for a strategic tanker, it is readily available via the modification of units from the large pool of used commercial airframes, and it is much more affordable than any new build alternative.

In terms of variants, it would appear that a mix of 747-SP and 747-200B/CF/300CF models, given examples of suitable condition can be located, would be the most practical choice.

The 747-200B/CF/300CF is the better strategic tanker and transport by virtue of its higher MTOW, better offload performance and ability to carry heavy freight. The 747-SP offers much lower initial acquisition costs, and slightly lower fuel burn47. It also offers better operational flexibility per total fleet offload performance and better short field performance, with the limitations of slightly lower unit offload performance, the inability to carry freight without modification and similar crewing and support requirements to the 747-200/300.

Therefore the 747-200/300 offers a better longer term return on investment, with a much greater initial acquisition cost. The proportions of any mixed fleet would therefore have to be based upon a careful analysis of the point in the fleet lifecycle where the difference in initial acquisition cost favouring the 747-SP is balanced by the lower return in airlift capability given similar crewing and support costs.

Determining the number of aircraft to provide the capability will require some detailed modelling of AAR performance for the ranges in question, and some analysis of the airlift requirement. A first order estimate indicates that between 12 and 14 747-200/300 aircraft would be required, depending on the offload performance achievable for a given configuration, runway capabilities available and aircraft empty weight after the installation of AAR hardware and freight modifications. For the same fleet offload performance, 12 to 16 747-SP aircraft would be required. Some spares would be required.

The 747-200/300 could be, according to Boeing-Wichita information, modified into a freight configuration with a lead time of only several months.

Conversion for this dual role capability would require the following modifications:

  1. Installation of an AAR boom and operators' station.
  2. Installation of two fuselage hose/drum/drogue units, or a single fuselage hose/drum/drogue unit and a pair of wing mounted Mk.32B pods.
  3. Installation of AAR fuel pumps, valves, manifolds, plumbing and operator controls.
  4. Installation of lower deck auxiliary fuel cells.
  5. Installation of AAR receptacle for tanker-to-tanker refuelling.
  6. Installation of single point ground refuelling receptacle for lower deck auxiliary fuel cells.
  7. Installation of the forward lower deck internally stowed airstairs and retractable upper deck stairs.
  8. Installation of at least two observers' bubble windows, replacing aft upper deck windows.
  9. Installation of dual TACAN beacons and formation lighting.
  10. Installation of military UHF communications equipment, preferably with crypto capability, IFF and JTIDS equipment.
  11. Installation of military GPS navigation equipment.
  12. Installation of IFF interrogator.
  13. Installation of a suitable intercom system.
  14. Installation of Echidna RWR and DECM package, possibly also IRCM on engine pylons49.
  15. Installation of the Side Cargo Door if not already fitted.
  16. Strengthening of the main deck floor to freighter standard and installation of freight handling hardware.
  17. For aircraft with extant Nose Door installations, modification to support the Boeing On Board Loader, and supply of these devices, modified as required.

Serious consideration should be given to the use of a standard configuration, if possible, whereby all aircraft are fitted with the airstairs, Nose and Side Cargo Doors, the Boeing On Board Loader, and refuelling receptacles.

Whether to retrofit the aircraft cockpits to a current standard "glass cockpit" arrangement is open to debate. While this would increase the unit conversion cost, it offers the longer term economy of a two person flight crew, against a three person flight crew, assuming a dedicated AAR operator. Given that most commercial models now have glass cockpits, maintenance of currency for reservists flying commercial models would indicate that a glass cockpit would be preferable. This would also provide the opportunity to standardise the inertial navigation and communications equipment fit across the fleet. A FANS compatible system would be desirable.

There may be some merit in retrofitting all aircraft to a common engine type, should airframes of suitable quality not be fitted with such. Qantas will be well equipped to advise on the performance and idiosyncrasies in supporting specific engine types. Overhauled used engines of suitable quality may be acceptable, since the aircraft in RAAF service would not be operated at the tempo of a commercial operator outside periods of war or other contingencies.

The commercial aspect of such an acquisition is of modest complexity, since with the exception of the AAR conversion, multiple sources exist for freight conversions, airframe life extension and engine overhaul or retrofit. The only extant and flight tested AAR conversion was performed by Boeing. While other vendors such as IAI may be competent to engineer an AAR conversion, they will incur the full engineering overheads and development risks of a new design.

Therefore Boeing will have a significant competitive advantage over any other vendor, and this may also be true of a comprehensive modification package incorporating all changes.

There may be considerable potential for domestic offsets by performing portions of the structural work and modification at the Avalon facility, which has the runway and hangar sizes required. ASTA performed structural work on 747 aircraft some years ago.

Whether the best strategy is to release an RFP for the supply of fully modified 747 aircraft to a specified configuration, and place responsibility for the choice of airframes upon the vendor, or to acquire the aircraft directly off the commercial suppliers, and then release an RFP for the modifications remains to be determined. We could expect that shifting the burden on to the vendors will have some impact on the price tag as they would want to cover any risks they might incur. The availability of suitable airframes and pricing in the market will vary and this should be a consideration, since the pool of available aircraft and prices will fluctuate as older airframes are absorbed into the freighter market.

The total expense for the acquisition phase of the program would comprise the cost of the used airframes, the cost of any re-engining, zero-timing and corrosion repair, the total cost of the required AAR, and where applicable, freighter modifications as detailed above. Since the program would involve a reasonable number of aircraft, some economies of scale in the production phase could be achieved.

This issue of which runways to upgrade, and whether to include them in a project budget, is an interesting one. Strategically the two most important sites are Darwin for airlift and air support of peacekeeping forces, and Learmonth for deterrence and maritime operations. Neither would require substantial runway work to support operational detachments, although some upgrades to the fuel replenishment infrastructure may be needed to sustain high intensity operations.

Learmonth would require a modest 10% runway extension to support the 747-200/300 at MTOW. The runway strength at Curtin is not adequate for high gross weight operations, and its remoteness makes the resupply of large quantities of fuel to support tanker deployment difficult. Darwin would provide a better runway than Tindal for 747-200/300 operations. Townsville would require a new parallel runway rated for the 747, while Amberley could operate the aircraft with some gross weight limitations applied. All of the major civilian airports in Australian capitals could support the aircraft.

Amberley would appear to be the best prospect, with weight limits imposed, for a squadron home base capable of supporting training flights only.

From a practical perspective, the full MTOW capacity will be required only for long range or long endurance AAR operations, or for heavy lift transport operations. The former category of operations is geographically confined primarily to Learmonth and Darwin, both of which have adequate runways. The latter category would be confined mostly to Darwin and Townsville.

Crewing the aircraft will be a major issue. If we assume a fleet size of twelve aircraft, with a glass cockpit and two person flight crew, and assume two sets of crews for the fleet, we end up with a requirement for 48 pilots, of which half are qualified as aircraft commanders. Maintaining currency, given the hourly operating costs of such aircraft, would be by any measure expensive. Simulators, no matter how good, are not a substitute for time in a real cockpit.

Therefore it will be necessary to explore other alternatives. One possibility worth exploring is that of hiring out the aircrew to the airlines, at such a rate where the offer is attractive to commercial operators. The contractual arrangement would be such that these pilots would fly regular operations for the airline in the same manner as the aircrew employed by the airline, however they could be recalled by the RAAF at very short notice to crew the strategic tanker/transport fleet.

Such a strategy has several attractions. The first is that it is an unbeatable attraction in the recruiting game, for those applicants with long term aspirations of a airline career. The second is that the crews get to maintain a high level of currency on the basic aircraft, and long haul overseas flight experience in the process. For the airlines, there is the advantage of simplified recruiting of junior pilots, who will have acquired their ab initio, early flight training and some multi-engine time in the very rigourous RAAF training regime. Contractual arrangements would need to be such, that the airline can recoup the training investment in such aircrew after they complete their service in the RAAF. The arrangement would have to be such to make "poaching" of such aircrew impossible before their contracted service periods run out. The aircrew would periodically fly the RAAF aircraft to maintain proficiency in AAR flight operations, but would gather most of their hours on commercial aircraft.


This paper argues the case for the acquisition and deployment of a substantial strategic tanker/transport force for Australia, comprising a fleet of modified variants of the Boeing 747 transport.

The Boeing 747 makes for an excellent strategic tanker, but not an ideal airlifter. However it is the only aircraft type which will allow Australia to deploy a large strategic tanker/transport force with a modest initial expenditure, while exploiting the established training and support base.

To provide a general measure of capability, one dozen 747-200B/C/300CF derivative KC-25 strategic tanker/transports provide the cruise speed and offload performance equivalent to around thirty KC-135R tankers, and can lift the payloads of a dozen C-17A airlifters over about a 60% greater distance, all at about 1/3 of the total acquisition cost of the combined packages of KC-135R and C-17A aircraft. A mixed KC-25 fleet including some 747-SP derivatives yields similar offload performance and lesser airlift performance, with even lower acquisition costs. A mixed fleet of C-17A and KC-25s yields inferior offload performance, but would provide a superb airlift capability, with a penalty in acquisition costs.

In summary it is fair to say that the strengths of the 747-200B/CF/300CF and 747-SP as a strategic tanker/transport outweigh its limitations, especially in comparison with other alternatives derived from commercial airframes. While its weaknesses are most prominent in the airlift role, it performs this role far better than other commercial types.

Whether Australia's political leadership is prepared to commit to a strategic tanker/transport force of the required size remains to be seen. The case for this capability is irrefutable from a political and military strategic perspective, and the economics are clearly within Australia's budgetary reach, should the 747 be used as the basic platform.


This paper is based primarily on RAAF APSC Working Paper 82, to be published early in 2000. The author gratefully acknowledges the assistance of S/L Murray Warfield (ret) of Qantas, who originated this idea, the RAAF School of Air Navigation at Sale, Capt Kurt Todoroff, USAF (ret), Capt Perry Beor, Army Reserve, and Boeing Australia for their advice and assistance with this project.

For representative images refer:

Volume II - APA-2005-02 Carlo Kopp and Brian Cooper KC-33A: Closing the Aerial Refuelling
and Strategic Air Mobility Gaps (PDF)

Figure 1. Imperial Iranian Air Force (IIAF) Boeing KC-25/ KC-747-100 Strategic Tanker/Transport refuelling an IIAF 747-100 (Boeing).

Figure 2. KC-135R Improved Refuelling Boom structural assembly (Boeing).

Figure 3. The IIAF KC-25/KC-747-100 boom installation under test. This is an unusually clean installation, with the operator's station recessed in the fuselage. Note the fuselage stiffeners (Boeing).

Figure 4. Comparison of proposed Boeing KC-25/747 Variants (EPS Author).

Figure 5. Boeing KC-25 (747-200/300CF) Tanker/Transport Refuelling Points

Figure 6. Boeing 747 Main Deck Geometry for ASLAV.

Figure 7. KC-10A Freight Loaders (USAF).

Figure 8. Boeing 747-200F Freighter Nose Door installation being used for container loading. Lufthansa were the lead customer for the 747-100F and remain a major user of the 747-400F (Lufthansa).

Figure 9. The VC-25A and E-4B both carry internal airstairs to provide crew and passenger access at sites without airliner boarding facilities.The airstairs deploy from the forward cargo door (USAF).

Figure 10. Comparison of Boeing KC-25 (747-200CF/300CF) and GD F/RF-111C/G sizes (Author).

Figure 11. Boeing On-Board Loader (Boeing).

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