Technology Explained – The Air Land Battle Part I

The Luftwaffe is an interesting case study for various reasons, but in this instance it usefully illustrates the first force structure built around CAS/BAI.

Western air forces have traditionally seen their role as strategic and have never seriously structured for CAS/BAI. WW2 saw CAS operations flown by RAF Typhoons, Hurricanes and Spitfires and US Army P-38s, P-47s and P-51s. All of these aircraft were, however, initially air superiority aircraft and even if later dedicated operationally to CAS, suffered from restricted payload and vulnerability to ground fire.

Operationally, CAS involved a technique not unlike that pioneered by the Germans, with ground observers calling in strikes against targets offering resistance to advancing armour and infantry. The Pacific theatre largely reflected Western strategy in Europe, more so in that much of the CAS and interdiction work was done by carrier based forces equipped by default with fighters and dive bombers. The Russians, always ready to emulate the Germans, structured their tactical air forces almost exclusively about CAS and BAI aircraft. The 11-2 Shturmovik, Pe-2 and Tu-2 all reflected this philosophy and formed the backbone of Russia’s tactical air forces until the late 1940s.

During the Korean War Western air forces flew a great many CAS/BAI sorties, the by then obsolete F-51 being the mainstay of the United Nations effort, but nothing new was attempted in the area of CAS/BAI strategy or technology. The late 1950s saw CAS drift out of sight as Western air forces spent heavily on strategic and tactical nuclear strike capabilities. The USAF Tactical Air Command (TAC) had by the early sixties structured its force about F-105s and planned F-111s, both types designed to deliver internally carried nuclear bombs against theatre targets. Armageddon was first and foremost in the minds of force planners. Only the US Marine Corps, by role committed to amphibious assault, maintained a serious CAS capability with squadrons of naval tactical aircraft.

The Russians also spent most of the fifties building up nuclear capabilities, but quickly recognised the potential of theatre tactical ballistic missiles with nuclear or chemical warheads. By the sixties a comprehensive warfighting strategy was formulated, which involved initial nuclear missile strikes against theatre targets, followed up by massive armoured thrusts into the devastated territory. All tanks and personnel carriers became nuclear-biological-chemical (NBC) warfare capable. Pockets of resistance would be annihilated by air strikes, the primary role of the Frontal Aviation (FA WS).

To some degree this strategy made a virtue out of a constraint, as the principal tactical fighters of the day, the MIG-21 Fishbed and Su-7 Fitter, lacked the payload radius performance for any other role than CAS and BAI.

The US involvement in Vietnam was a major milestone in the development of Western CAS/BAI strategy. The Americans had to quickly relearn the lessons of Korea and WW2 and in doing so laid the foundations of much of today’s operational practice and tactics.

Initially CAS operations involved South Vietnam’s VNAF supported by US advisers, flying a motley collection of WW2 and fifties piston aircraft. The T-28B/C and the B-26 Invader were without doubt the workhorses of the early campaigns, but these aircraft had severe payload radius limitations, a growing structural fatigue problem and their response times in the remoter areas were unsatisfactory, given the slow transit speeds. The elusive enemy may have disappeared into the jungle by then. After several T-28s shed their wings pulling out of dive bombing runs, the US replaced them with 25 dual control A-1E and a number of single seat A-1H Skyraiders (Profiled in our July edition) drawn from inactive stocks in the US. These sturdy naval strike aircraft served for the duration of the conflict and ultimately played a major role in the formulation of a formal CAS strategy.

As the war escalated through the sixties, the Americans deployed newer and newer hardware. Early entries were two squadrons of B-57s, a US derivative of the Canberra. These were shortly followed by the F-100 Super Sabre, by then clearly obsolete as an air superiority aircraft. By late J99q a further five F-100 squadrons were assigned to South Vietnam,: supported by Marine Corps F-4B Phantoms and the TAC’s 12th TFW with its F-4C aircraft. The tactical jets carried substantial payloads, offered rapid response times and were fast enough to avoid fire from VC and NVA automatic weapons and anti-aircraft artillery (AAA). But their speed over the targets, often small and hidden, severely penalised accuracy. While the piston fighters could turn at low level and keep their targets in sight, the tactical jets were too fast. Tactics had to evolve and as a result, increasing use was made of former Army Cessna 0-1 Birddog Forward Air Control (FAC) aircraft. Fitted with white phosphorus ‘Willie Pete’ rockets and flown by experienced USAF pilots, these frail aircraft skimmed the tree tops searching for V C targets, calling in tactical jets and then marking the targets with rockets. Underpowered and vulnerable to small arms fire, the tiny Cessnas understandably suffered high casualty rates.

It was clear by the end of 1967 that more capable FAG aircraft were needed so the 0-1 was superceded by the larger and faster Cessna O-2A, better known to most readers as a Milspec C-337 Skymaster. The beginning of 1968 also saw the debut of the Rockwell OV -1O Bronco, a sturdy twin boom light GAS aircraft which soon assumed an important role in the South, flying both GAS and FAG sorties.

As the war escalated, the intensity and radius of operations increased. The Ho Chi Minh trail, a massive communist resupply zone, came under increasing USAF scrutiny. While it is beyond the scope of this discussion, it is worth noting that trail interdiction missions forced a whole range of innovative technological developments such as night vision equipment, remote acoustic intrusion sensors and even direction finding receivers to track the interference from automotive ignition systems. By 1970 most strikes were flown by tactical jets, relying upon FAG aircraft, with the piston A-1s flying largely special operations work in support of heliborne troops. The principal munitions used were napalm and white phosphorus incendiaries, iron bombs, the then new cluster bombs and unguided rockets. Accuracy was not always spectacular and a high standard of airmanship was required to avoid hitting friendly troops.

The Spring Offensive in 1972 saw a major change in the nature of operations, when the NVA deployed over 500 T-54, T-34 and PT-76 tanks. These were small hard targets which largely resisted the anti-personnel munitions in use until then.

It was at this time that interdiction of NVA supply routes within the Ho Chi Minh trail and South Vietnam assumed the character of modern BAI operations, as the communists fielded shoulder launched SA-7 Grail SAMs, a wide range of AAA weapons of substantial calibre and in some areas, even large SA-2 Guideline SAMs.

A key weapon in the battle was the new Texas Instruments Paveway I laser guided bomb, which was used against bridges, rail communications and supply depots in the North, and against supply depots and armour in the South. Openly exposed columns of tanks and trucks were destroyed by TAC fighters en masse, halting the flow of men, munitions and weapons to the battlefront. The battlefront itself saw the debut of another weapon destined for a long career – the TOW optically tracked wire guided antitank missile, fired from several hastily fitted UH-1B Iroquois assault helicopters.

As the NVA offensive ground to a halt and eventually reversed, the operational philosophy consolidated and the US began to seriously reconsider how they would fight any battle in Europe.

The experience gained in crushing the very Russian style of massed armour assault carried out by the NVA indicated that a two pronged strategy would be most practical – missile firing helicopters and dedicated tank busting GAS aircraft for immediate GAS and precision guided munition (PGM) carrying tactical jets for BAI. This philosophy has persisted until the late eighties and continues to have strong support from the US Army who consider it best suited to their needs.

The principal new element in the GAS strategy was the Fairchild A-10 Thunderbolt II. TAC had come to recognise as early as 1966 that an aircraft with the payload and manoeuvring performance of the A-1 but with turbofan propulsion, substantial armour and dedicated tank killing weapons was a must. In 1970 Northrop and Fairchild were contracted under the A-X program to build two competitive designs, aircraft with the ability to carry 12,000lb of payload on full internal fuel and with substantial resilience to ground fire through armour and systems redundancy. The A-10 defeated the Northrop A-9 in 1973, with production commencing in 1975. TheA-10 is a large 24,000lb (10,896kg) empty weight aircraft powered by two GE TF 34 9,000lb class turbofans, cruising at345kt (640km/h) and limited to 450kt (835km/h). Its only internal weapon is a massive 7 barrel 30mm GAU-8 gatling gun firing high velocity depleted uranium core shells. The pilot sits in a titanium armour tub, while most vital systems are armoured and redundant. The fuel system uses polyurethane foam to reduce the hydrostatic shock of direct hits and rigid foam is applied around the tanks to prevent external fires from reaching the 10,650lb of fuel. The engines are wide apart and their exhausts shielded from short wavelength heatseeking SAM seekers by the horizontal and vertical tail surfaces.

The big wing of the A-10 is designed for tight turning at low level, allowing a sustained 2,600ft (793m) turn radius at 300kt (556km/h), zero flap and 3,000Ib (1,360kg) of payload. This also translates into the ability to operate from poor quality forward deployed strips as short as 1,200ft (366m) at 30,000lb (13,620kg). Eleven stations allow the carriage of up to 16,000lb (7,264kg) of payload, keeping within the MTOW of 45,560Ib (20,685kg). The A-10 is very much the mud basher’s dream.

The deployment of the A-10 during the late seventies was welcomed by many, but was also not without criticism. The Israeli experience of 1973 was fresh in the minds of many observers. The Yorn Kippur War saw over one hundred Israeli tactical fighters destroyed in a matter of days when they attacked Arab targets covered by heavy concentrations of SA-6 radar guided SAMs and mobile ZSU-23-4P 23mm AAA systems.

TAC’s response to the threat of Russian SAMs developed as the tactics of operating the A-10 were defined. It was soon evident that conventional tactics would expose the aircraft to SAMs and AAA, and the operating environment was soon constrained to well below 500ft AGL. At these altitudes the A-1O would exploit terrain masking to remain below the visual and radar horizon of hostile air defences, popping up only briefly to acquire and fire at a target. Typical high noon engagement scenarios between the A-10 and SA-8 or ZSU-23 described in the seventies involved a rapid pop up to over 1,000ft, acquisition of the SAM/AAA system and the firing of the 30mm gun, followed by an immediate dive to low level, all accomplished in less than the acquisition and tracking time of the defending SAM/AAA system. To aid in acquiring such targets, the A-10 was fitted with the Pave Penny laser spot tracker, which projects a spot on the HUD where the laser illumination by ground observer or other aircraft marks the target. To reduce visual detectability the USAF soon discarded the two tone air superiority grey and after brief experimentation with various mottled camouflages, settled on a wrap around green/ dark green/grey European One scheme. Munitions were another area of evolution. While initially iron bombs and cluster bombs were preferred, these were soon supplanted by laser guided bombs and TV/infra-red-guided AGM-65 Maverick missiles. The most recent addition to the inventory are balloon retarded 2,000lb (908kg) Mk 84 bombs, designed for level release at very low altitudes.

Operations in the European theatre are largely coordinated with the US Army, who will employ their AH-1S Cobra and AH-64A Apache attack helicopters in nap-of-the-earth (NOE) tank killing operations. The AH-64 fires laser guided Hellfire antitank missiles, while the AH-1 force carries both the Hellfire and older TOW missiles. The division of labour involves the helicopters operating below treetop altitude, with the A-10 working from treetop level up to 500ft AGL. In theory the helos would approach and ambush advancing armour, providing defence suppression fire for the inbound A-1Os. With large payloads of heavier weapons the A-10i:; would then inflict maximum damage. This philosophy relies largely upon laser destination of targets for both missile attacks and A-10 strikes. It is however limited very much to daytime operations due to the absence of night vision systems in the A-10.

At this time it appears that this philosophy has reached the end of its effective usefulness. The last half decade has seen the deployment of the mobile radar guided SA-11 Gadfly and newer SA-6 derivatives, both capable of hitting targets in ground clutter, supplemented by all aspect heatseeking SA-13, SA-14 and SA-16 SAMs. With monopulse radar seekers and sophisticated infrared seekers these missiles are quite difficult to jam and manoeuvre is often a necessary supplement to defeating these weapons. The low and slow A-10, devoid of internal ECM, is likely to sustain high loss rates if engaged by these weapons. The USAF response has been to shift the role of the A-10 toward armed FAG for fast moving tactical jets. BAI has also made significant strides since the 1970s. A major gain was the introduction of the agile F-16 to supplement and later replace the ageing F-4E fleet. With superb manoeuvring performance, good payload range and accurate nav attack, the F-16 is a potent strike fighter. Where it missed out was in its lack of night vision equipment and a laser designator.

This has now changed with the deployment of the Lantirn pod set. Lantern was initially meant for the F-16C and A-10, but as the A-1O’s survivability declined in the eyes of TAC, the pods initially assigned to the A-10 were allocated to the new F-15E Strike Eagles. The Lantirn pod set is comprised of a Navigation Pod containing an advanced J-band terrain following radar and navigation Flir projecting on to the HUD, and a Targeting Pod with a two field of view Flir bore-sighted with a laser designator/rangefinder. By fitting two pods to an F-16C/D it acquires a penetration capability much like that of dedicated bombers such as the F-111 fitted with Pave Tack. The implications of Lantirn are significant, as it exposes Warpac ground forces to BAI strikes around the clock in all weather conditions, while releasing the F-111s and F-15Es previously committed to battlefield strikes for deep interdiction missions. The US Army however demands that a significant GAS capability be available for its land forces and has strongly resisted the USAF’s attempts to phase out the A-10. The USAF response to the declining survivability of the A-10 has been to open discussion on the subject of GAS/BAI with the view that the two roles should be merged and preferably flown by one aircraft type alone, carrying specific weapons for specific missions. BAI would be flown by Lantirn-equipped F-16s and GAS by A-16s with dedicated night vision equipment and 30mm gunpods.

In the context of winning an air battle, the USAF strategy is superior in that the F/A-16s inherently retain excellent air superiority performance and thus could be flexibly tasked with air superiority, air defence, BAI and GAS missions. This would allow a theatre commander to concentrate air assets as required and as we all know concentration tends to win air battles most effectively. The USAF position is further reinforced by an interest in keeping the F-16 production line open until 1997, when ATF (F-22/23) deliveries commence.

This approach is, however, exactly what the Army seeks to avoid, as at that instant that specialised GAS assets are replaced by multirole assets, the Army can never be certain that aircraft will be available for GAS when it needs them. In addition, the pilots who fly only treetop altitude GAS are likely to be more proficient at it than ‘knuckleheads’ who would much rather be stencilling red stars under their cockpits. By insisting on dedicated GAS airframes the Army is attempting to guarantee both the availability of airframes and of specialist aircrew.

The political fallout from this disagreement has provided politicians and bureaucrats alike with ample fodder, with the resulting increase in the complexity of the decision to be made. At the time of writing the A-10 vs F-16 debate had expanded to include the re-engined A-7F, re-engined A-10, AV-8B Harrier and F-18.

US defence contractors, facing a bleak future insofar as new contracts go, have responded promptly to this situation. General Dynamics, in conjunction with GEC in the UK and Texas Instruments, have trialled an F-16B aircraft fitted with a helmet-cued Flir turret. The Texas Instruments Falcon Eye Flir turret tracks the pilot’s line of sight and the image viewed by the Flir is projected upon a GEC Avionics Cat’s Eyes night vision goggle eyepiece combiner glass mounted on the helmet. As the turret projects from the upper forward fuselage, its perspective is much like that of the pilot, providing a very natural view of the outside world.

This is very relevant for GAS work, where the pilot must often turn about the target while keeping it in sight. Interdiction systems such as Lantirn are cumbersome in this application, as they are designed for the typical interdiction profile of a straight run in followed by a pop-up, inverted roll to acquire the target, roll level and a shallow dive bombing run to weapon release (usually employing CCIP delivery mode). While the Flir turret is the principal sensor, a Martin Marietta Pathfinder forward facing navigation Flir is also fitted, projecting a forward view image on the pilot’s HUD. Additional nav information is provided by a British Aerospace Terprom terrain profile matching· cove. rt navigation system, which much like cruise missile nav systems compares radar altimeter readings with stored digital map data. The final major element in the mission suite is the Rockwell-Collins Automatic Target Handoff System {ATHS). The ATHS is a datalink receiver which places a box symbol on the HUD (or helmet combiner glass) over a target designated by a forward air controller on the ground or in a suitably equipped scout helicopter. This removes any ambiguity in the identification of targets to be attacked. The single modified A-168 airframe has been extensively tested by GD and also participated in a series of TAC flight demonstrations of the F-16C in the GAS role conducted in late 1988. Seven F-16Cs were fitted with Pave Penny laser spot trackers, painted green and flown in 268 sorties at Nellis and Ft Hood directed by ground controllers and OV-10, OH-58D and AH-64 FACs. AGM-65D missiles and GPU-5/A 30mm gunpods were carried but not fired although live Mk 82 and cluster bombs were dropped. In a parallel development program, the USAF reconfigured in 1987 its well used AFTI F-16 development prototype for GAS development work.

The AFTI (Advanced Fighter Technology Integrator) airframe is the F-16 preproduction airframe fitted with canards, a thickened dorsal spine and a digital flight control system; it has logged over a thousand hours since 1982, evaluating the tactical performance of integrated flight and fire control systems and unconventional manoeuvring techniques, eg direct lift and sideforce control. A key system in the ground attack tests was the Automated Manoeuvring and Attack System (AMAS) which allowed the aircraft to aggressively manoeuvre during the terminal phase of a bombing run, thus foiling the linear and quadratic fire control prediction algorithms used by AAA and SAM fire control systems. Initial GAS tests in the AFTI evaluated the performance of the Rockwell-Collins ATHS, a Westinghouse Flir/ laser targeting system and a Harriss digital terrain map with a Sandia inertial terrain aided nav algorithm, these tests were followed by evaluation of the GEC tercom nav and three ground collision avoidance systems. In addition, TAC evaluated its Litton Digital Communications Terminal (OCT) system which was designed to transfer messages between FACs, ground observers and ground based command posts. The OCT is functionally similar to the ATHS although using different communication protocols between its computers; unlike the ATHS it was not initially optimised for FAG to GAS air-air communication. At the time of writing the AFTI was being refitted at the GD Fort Worth facility with a current Block 40 F-16C quadruplex digital flight control system and having its canards removed. Subsequent testing will involve the GEC/TI Falcon Eye Flir, the intention is to test a fully integrated suite using AMAS, night vision equipment and ATHS/ DCT.

The A-7 upgrade program involves reengining the Air National Guard (ANG) fleet of about 330 A-7D Corsair strike aircraft with afterburning P&W F100 or GE F110 turbofans (a further 400 Navy A-7Es are currently being placed in storage). The TF-41 (Spey) powered A-7D has a poor thrust/weight ratio which restricts both acceleration and sustained turn rate performance, thus leaving the A-7D vulnerable to SAM attack particularly during run in to the target. Increasing the thrust/weight ratio provides the ability to pull high G turns at combat weights, while also allowing the aircraft to egress a target area at transonic speeds. In addition the added power improves payload/range and short field performance.

The upgrade program is currently confined to two prototypes, which have been modified from A-7D aircraft. The modifications are not trivial. Fuselage plugs are inserted forward and aft of the wing, the wing is reskinned, the aft fuselage is redesigned to accept either new engine with an external cowl for the afterburner nozzle and the tail surfaces are redesigned. The vertical tail is taller to compensate for the increased forward fuselage area and the stabilators are swapped left to right to provide 5. 25 degrees of anhedral. In addition small strakes are added to the wing root to improve high AoA performance, the flaps are improved to reduced approach speeds and spoilers are added to improve short field performance.

The new A-7F is thus much closer in performance to its ancestor, the F-8 Crusader, with the ability to sustain 650kt (1,204km/h) speeds and 6G turns at 0. 9M which compares well against the 539kt (999km/h)/4G at 0. 7M performance of the A-7D. The added thrust is most apparent in acceleration performance, where the A-7F accelerates from 400kt (741km/h) to 550kt (1,020km/h) in 15sec, six times faster than the A-7D. While the A-7F is heavier with an empty weight of 23-24,000lb (approx 10,600kg), its fuel capacity is increased to 17,800Ib (8,081kg), payload to 17,380Ib (7,890kg) and MTOW to 46,000lb (20,885kg) compared with 42,000lb (19,070kg) for A-70. The penalty is in a reduced fatigue life of 5,000hr which still provides a useful life of 20 years at current usage rates.

The re-engining of the A-10 is another interesting alternative, although it is unlikely to substantially improve the survivability of the aerodynamically limited airframe. The proposal revolves about the replacement of the 9,065lb TF34 fans with non-after-burning 11,000lb GE F404 low bypass fans. It is however much cheaper than building more F-16s or rebuilding A-7s and is strongly favoured by the US Army. The remaining alternatives, the AV-8B Harrier Il and F-18 Hornet, are unlikely to be successful due to high acquisition and life cycle cost; the USAF would also have to develop additional logistical infrastructure to support these types.

Another player in this game, albeit an outsider, is Scaled Composites Inc, who are testing a low cost 6,200lb (2,815kg) gross weight mudfighter designated the ARES (Agile Responsive Effective Support). The ARES is a 300kt (556km/h) twin boom canard design fitted with a GAU-12/U 25mm gun and powered by a 2,950 lb JT15D-5 turbofan. Funded internally, the design may not be particularly successful even if it flies well, given the position held by TAC.

The outcome of the CAS/BAI debate will be known by the end of this year, it will most likely be a case of the F-16 against the A-7, with the A-7 having a slight advantage in cost and from the Army viewpoint, specialisation. To the Australian observer this whole Issue underscores the difficulties in developing an appropriate force structure for Army support missions. Air forces by their nature have a commitment to air superiority and interdiction and will thus seek technology which supports these roles, the multirole fighters of the seventies and eighties underscore this trend. With aircraft usable in both air superiority and strike operations, an airforce can concentrate its resources as most appropriate at the time. End users of air force services, such as army land forces, can however be disadvantaged if aircraft are unavailable through diversion to other missions and will always have an interest in specialised airframes which are unusable elsewhere, as this secures their availability.

The only service which appears to have resolved this issue successfully is the US Marine Corp, with its CAS/BAI force of AV-8 Harriers and F-18s. That is the subject of Part 2.