AEW Airships for the RAAF?

The Australian requirement of course is in the hands of the RAAF who, one would imagine, are about as ready to give their maritime patrol and surveillance roles over to the Navy as they would be to hand their helicopter squadrons over to the Army, despite the push in recent times by the latter for just such a transfer of function.

The fact that Australia would be acquiring some form of AEW to complement our Jindalee OTHB radar system has long been known. It was only last December though when Defence Minister Kim Beazley formally issued the first official Request For Proposals (refer p. 79 Mar AA) that the concept of a RAAF-operated AEW system was given official credence. Primary contenders are Grumman with their proven E-2C, Lockheed with the AEW&C development of the Orion, Boeing with a version of the E-3A Sentry and a less expensive option in a modified 737 Surveiller and finally Airship Industries with what will be ttie Sentinel 7000.

What Airship Industries (Al) are offering is essentially a very much larger version of their Skyship 600 which was due for its first Australian flight as we went to press. The military range of Bond Corporation-owned Airship Industries’ airships are designated Sentinel and the version on offer to the RAAF is the Sentinel 7000, a design which is on offer to the USN for their Naval Air Ship Programme.

When we visited Al’s London headquarters specific design information was sketchy owing to the US RFP requiring solicitations to be of a classified nature. While this complicates research for an article, there is certainly enough data available to appreciate that the USN are seriously contemplating the use of such craft and that Australian-owned Al are favourite for the potentially lucrative contract.

What the USN require is different in task to what the RAAF seeks; though not in basic mission capability. The USN requirement is for an airship to operate as an organic part of the fleet. In other words the airship would be treated just like any other vessel in the task force only it would be airborne. The airship would operate at the extremities of the head of a task force in company mostly with a carrier battle group. The role of the airship would be to provide 24 hour AEW surveillance (and perhaps some ASW sonobuoy dropping in support of the ASW frigate screen as required) to detect cruise missiles, small surface vessels and of course intruding aircraft at great range. The Sentinel 7000 would carry aloft a Westinghouse phased array radar giving it similar surveillance capability to the E-2C while at a patrol altitude of only 10,000ft.

Since the Falklands proved the effectiveness of the new generation of sea skimming anti-ship missiles and the overall need for surface fleet AEW, the USN has been working hard to evolve a more permanent capability then that available from their E-2Cs. Not that these aircraft are deficient but rather a situation of the normal physical limitation of any fixed-wing aircraft combined with extending the protective umbrella of surveillance capability as far out from the core of the fleet as possible on a round-the-clock basis. By using an airship, virtually as a ”flying frigate”, the Navy can protect their flanks better than is possible with any fixed wing aircraft. In addition they intend to primarily use the airship as an AEW platform while handing over the more complex and fast-moving role of battle management to the more mobile E-2C.

The USN require their NASP airship to be on station for up to 60 days using a single crew complement, not unlike a normal surface combatant on extended patrol. The airship can refuel from a fleet replenishment tanker or any other ship as required while crew quarters are such that generally the accommodations are better equipped than many of the surface ships. The USN had been contemplating the NASP programme for several years and Al were lucky to this end to be able to participate with both the USN and USCG in a number of evaluation deployments with the Skyship 500 in recent years. These stemmed from the 1980 Patrol Airship Concept Evaluation (PACE) through to the more recent Maritime Patrol Airship Study (MPAS), all of which proved essentially that the modern airship had a place in USN colours.

NASP meanwhile is completing its first stage of definition with the July 1985 release of $US650,000 for concept design studies in an effort to mate three radar manufacturers with three air vehicle manufacturers. The radar teaming have evolved as Westinghouse with Airship Industries, Boeing with Wren Skyships (UK) and Litton and Sperry with Goodyear. It is intended that the US DoD will make a decision on two competing systems in order to perform a fly-off later this decade with the system offered in the initial NASP RFP. This decision was expected sometime before June though budgetary constraints (via Gramm Rudman) could well mean financing the development of a single system. Both Al and Westinghouse look to be well ahead of their competition as Westinghouse has the radar technology already in place, Al has the vehicle and a working relationship already exists with the client. If they should win then the ultimate value of the contract could exceed $US6bn in 1986 dollars as a fleet of up to a hundred Sentinels are ultimately required. When speaking in these terms in company with one of the world’s most respected military organisations then the enormity of the potential for airship development is appreciated. What is also appreciated is that several Sentinel 7000s operating off our northern coastline could provide an effective AEW screen in concert with Jindalee.

The NASP programme though is not the only arrow in Al’s bow Also under present evaluation is a USAF requirement for modernisation of the NORAD northern line which could well see a number of large airships performing the role now undertaken by remote, vulnerable to sabotage, and expensive to service ground radar stations. The US is also concerned about the defence its continental shoreline has against submarine-launched sea skimmers and is also investigating using airships to provide longrange look-down surveillance in the region of the larger coastal industrial enclaves.

Additional to this is a specific US Coast Guard requirement for a long endurance system- to assist in the detection of drug runners from the Caribbean region. Airship’s Skyship has already been working with the USCG and an order for such a system looks likely in the year ahead. All of these applications would use either existing Sentinel 600 versions or larger craft such as the 7000. Another asset with airship development is the low development cost of the base vehicle. They are essentially only inflatable (with helium) air vehicles while the gondolas do not need to be stressed to great loads as is the case with a conventional aircraft. Design can be conducted cheaply and rapidly while a gondola design can be tailored to a specific role requirement with ease by conventional aviation standards. This results in design flexibility, low development costs and a low design gestation period. Furthermore, once operational an airship is an extremely cost-effective vehicle, a Skyship 600 for instance uses less fuel in a 20 hour mission than a Nimrod ASW aircraft does in the takeoff run!

The US aren’t the only ones interested in airships though.

Britain’s Royal Navy is examining a modified Sentinel 600 for its Offshore Patrol Vehicle role as is France. Al have already completed a series of successful trials with the French Coast Guard and expect a decision later this year on whether the vehicle will get to wear the Tricolor. If the RAF’s AEW Nimrod programme is cancelled later this year in favour of a new system Al will then offer their NASP concept for this role also. Patrolling the Channel region, to the south of England, the Western approach and the all-important Faeroes Gap would provide ideal territory for such craft given their round-the-clock mission capability and long loiter potential in specific areas of threat.

Australian Aviation also belives that South Korea and Indonesia are interested in the larger Sentinel system. Certainly, the application on the volatile Korean Peninsula would provide an ideal environment for round the clock AEW protection, particularly when their greatest threat is the spectre of several hundred aged AN-2 biplanes flying at tree-top level through the valleys into South Korea carrying elite commandos to take and control key tactical objectives prior to the primary South Korean defence force being able to respond. In a land where your enemy is prepared to dig invasion tunnels beneath the border, the AN-2 scenario is virtual nightmare material in Seoul which is why a round-the-clock surveillance capability via the airship is considered worthy of further study.

Closer to home our major concern lies more in detecting low-flying aircraft and surface shipping off our northern coastline. A squadron of five airships can patrol on round-the-clock duty from Darwin to Derby and beyond depending upon the specific area of threat intensity. Each would be crewed as a long endurance craft, more like a small warship than an aircraft while the turbocharged diesels that provide primary propulsion (via vectoring ducted propulsors) and electrical generation not only use relatively little fuel but actually produce potable water as a byproduct of their exhaust. This leads to low operating costs and extended habitability. While patrol speeds would lie in the 40kt to 60kt region a dash speed to 90kt is available using two turboprop engines to augment the diesels. These would only be used though in a dash situation.

Again from the RAAF’s viewpoint, it is probably difficult to mentally perceive an aircraft operating at these speeds in such a region. From the navy’s viewpoint the airship takes on the role of a fast, indeed very fast, patrol frigate or radar picket. Inbuilt air force prejudices that it is not shining and capable of Mach 2 can be overcome perhaps by examining more openly the role requirement that the airship is attempting to achieve.

Some of the most obvious arguments against such craft are their vulnerability. Obviously, an airship, 500kms from Darwin is vulnerable to enemy aircraft. In fact almost any patrol-type aircraft would have to operate at some level of vulnerability at that range from a safe haven. The AEW airship though has the advantage of being able to detect its potential enemy at great range, 200nm plus depending upon aircraft type. With this knowledge, it will either call in protective fighters, which would be scrambled anyway as that is why the AEW platform is on station in the first place, or it would run for home like any other such aircraft. Obviously though, even at 80kts or so its journey will be slow compared with its adversary. To this end the airship can have a degree of self defence capability in the same way a patrol boat would. An airship armed with a simple forward/rearward firing Sidewinder AIM-9L system would not only have a reasonable measure of self-defence capability but more importantly would make an aggressor rethink his tactics in order not to get hit by the airship following his achieving a firing solution upon the airship.

What has to be remembered is that like the Harriers in the Falklands, the airship is a particularly agile creature and can stand and fight with a boresight capability unknown in any fighter other than the Harrier or the modern attack helo. We are not advocating it on purely cost grounds but longer-ranging Sparrow and Phoenix systems could also be linked up with the massive capability of the existing radar to provide a true thorn in the side for long-range patrol aircraft of an unfriendly power. In this way, perched at the extremities of the fixed wing patrol zone of a carrier battle group, or a major industrial enclave, the airship can take on the role of a viable air defence system in the airborne picket mode.

If the airship is hit it also has a level of inbuilt strength not found in other aircraft. Hit an aircraft with an accurate cannon burst or a missile and it will most probably go down. Even a giant 747 can be downed with a single Sidewinder-type missile as we sadly know. An airship though is largely a floating vessel of low-pressure helium, a totally inert non-volatile gas. Puncture the pressure envelope, even with 30mm fire and you simply have a low-level rate of leakage as the pressure ratio is a mere 0. 00703kg/cm2. Even a large gash would enable a Sentinel 7000 at 10,000ft up to an hour before gently settling onto terra firma. In the military role it might also be viable to provide the airship with some measure of damage control to keep it airborne till safely reaching its base. The use of long-range radar guided missiles is questionable as the airship has an extremely low radar signature (with its AEW radar off) as the large envelope is to all intents and purposes radar transparent while the infrared signature given off by the encased diesels is barely worth mentioning. In other words the airship is not as vulnerable as is often suggested, indeed give it a small measure of self-defence capability in. a simple Sidewinder fit and you up the ante for any intruder considerably.

Weather is another perceived problem and the number one killer of aircraft, military and civil alike. Probably the best use of airships in a theatre of war was with the USN patrolling convoys off the Atlantic coastline during WW2. When war commenced the USN operated four such craft, at the cessation of hostilities they had some 168 in their inventory and only ever lost one to enemy action. Furthermore, despite the treacherous weather of the North Atlantic the airship units operated on a better than 85% availability rate flying over 55,000 missions in ASW and fleet support duties. The USN also found no greater problems handling airships on the ground in heavy weather than would be encountered with regular aircraft under such circumstances. Indeed the airship is fairly self-supporting on the ground and only requires a mast from which to tether. Its low maintenance and extremely low DOCs enable it to be far more productive than many rival fixed-wing systems when employed in a long loiter mode.

In conclusion, this article has not been able to specifically provide a mass of data on the specific systems fit aboard the Sentinel 7000 due to soon-to-be-lifted security reasons. However, what we have attempted to do is to profile the basic capabilities of such a platform, using modern technology, and document the level of interest that this modern-day application of the airship is having on some of the world’s foremost defence and surveillance agencies.

To win the RAAF AEW contract the Airship Industries’ proposal will certainly have to be good, but if the USN, via NASP end up financing the bulk of its development then Australia could find itself with a locally owned and built winner.