Atlas Impala

The Aermacchi or Macchi MB-326 is a light military jet trainer designed in Italy. Originally conceived as a two-seat trainer, there have also been single and two-seat light attack versions produced. It is one of the most commercially successful aircraft of its type, being bought by more than 10 countries and produced under licence in Australia, Brazil and South Africa. It set many category records, including an altitude record of 56,807 ft (17,315 m) on 18 March 1966. More than 800 MB-326s were constructed between 1961–1975.Angelucci and Matricardi 1980, pp. 269–271.

The MB-326 had been developed and ordered during a period in which "all-through" jet training was considered by many air forces to be the most cost-effective model for training of military pilots. It was intended to provide a single type of aircraft that could be used to perform both elementary and advanced training right through to a near combat-ready standard. In practice, it was soon discovered that the simplicity and economy of scale of operating just one type for all training purposes was outweighed by the purchase and operating costs of a large all-jet training fleet. Many operators soon switched to operating the MB-326 in conjunction with a cheaper piston-engined type for basic training purposes. Over time, the MB-326 found its primary role as a lead-in trainer to prepare pilots for transition to very high performance fighter aircraft.

Development

Origins

During the 1950s, a number of countries began to operate compact jet-powered trainer aircraft that possessed similar performance to frontline operational aircraft, often having been produced as two-seat adaptions of these aircraft. Recognising the potential to better fulfil this role, several different companies independently chose to commence the development of purpose-built aircraft to serve as trainers; these included the French Fouga Magister, the American Cessna T-37 Tweet, the British Jet Provost, and the Czechoslovakian Aero L-29. In the aftermath of the devastating Second World War, Italy spent a number of years recuperating and reestablishing its economy; as such, the nation found itself unable to prioritise the necessary financing for the independent development of high-end combat aircraft that would be competitive with the upcoming generation of supersonic interceptors or bombers; accordingly, Italian aviation company Aermacchi elected to instead focus its resources and development efforts upon the production of a line of light fighters and trainer aircraft.

What would become the MB-326 had its origins in a private venture project by Macchi; it was developed by a team headed by Italian aeronautical engineer Ermanno Bazzocchi, the company's technical director and chief engineer. Reportedly, Bazzocchi had considered many different configurations for the tentative trainer before the design team chose to proceed with a single-engined design. In accordance with its intended primary use, the airframe was a robust and light all-metal structure, being relatively simple and cheap to construct and to maintain. The design was also to be powered by the British Armstrong Siddeley Viper turbojet engine, an efficient powerplant for the time. The Viper engine had been originally designed as a short-life unit destined for use upon disposable target drones, however, the engine had showed itself to be far more reliable and useful in other roles. During 1954, initial representations by Bazzochi were made to the Italian Air Ministry. During 1953, the designed airframe and engine combination led to Macchi formally launching the MB-326 programme.

Around the time of the programme's launch, the Italian Air Force took interest in the proposed aircraft. The service was considering options for the potential replacement of its existing trainer fleet, thus, upon the commissioning of a competition to select a suitable successor, the MB-326 was an obvious early entrant. A detailed specification was released for the competition, the requirements stated included a maximum load of 7  g when flown at the maximum weight, a lifespan of 5,000 flight hours, an interval of at least 50–60 hours between servicing, ample warning in advance of stalls (to be at least 15 km/h (9 mph) above the aircraft's stall speed), the ability to take-off at maximum weight in 800 m (2,625 ft) over a 15 m (50 ft) high obstacle (or 500 m (1,640 ft) when flown at a light weight), being able to land within 450 m (1,480 ft) at minimum weight, a minimum speed of 110/130 km/h and a maximum speed of 700 km/h, a rate of climb at least 15 m/s (2,950 ft/min), and an endurance time of at least three hours at 3,000 m (9,840 ft).Jannetti 1987,

Interest in the proposed MB-326 led to the awarding of the development contract for three prototypes. The programme was subject to significant refinement around this stage, leading to several modifications being made. Amongst these changes was the elimination of the negative dihedral angle previously present on the horizontal tail surfaces and the substitution of a pair of wing-based airbrakes into one located at a ventral position. During 1956, the AMI gave its official approval of the project and issued a request for the production of a pair of prototypes (later designated as ''MM.571'' and ''MM.572'') as well as a single airframe for static tests. These prototypes were not intended to include several features, such as the ability to equip and deploy armaments or refinements such as cabin pressurization, however, Bazzocchi chose to introduce them regardless.

Into flight

On 10 December 1957, the first prototype performed its maiden flight, flown by Macchi's chief test pilot Guido Carestiato.Taylor 1969, p. 120. This prototype, designated as ''I-MAKI,'' was first publicly demonstrated over France. During its flight test programme, the MB-326 prototypes demonstrated highly favourable flight characteristics of the design; however, several of the modifications made had negatively affected the overall weight of the aircraft; allegedly, at one stage, the excess weight was 400 kg (880 lb) greater than that given in the initial estimates. The original Viper 8 engine was capable of producing 7.8 kN (1,750 lbf) of thrust; to address the increased weight, the more powerful Viper 9 model was adopted instead, which was capable of generating 0.7 kN (147 lbf) more thrust.

On 22 September 1958, the first prototype was joined by the similarly-configured second prototype.Angelucci and Matricardi 1980, p. 269. It did feature some differences from the earlier aircraft; chiefly, it was powered by a newer model of the Viper engine, the Viper 11, which had been rated to produce 11.1 kN thrust (1,134 kgf, 2,500 lbf). The Viper 11 would be the same standard of engine used on subsequent production standard aircraft. Direct competition to the MB-326 came in the form of the Fiat G.80; this aircraft was both more powerful and was the first real Italian jet, having flown five years earlier. However, the G.80 had several disadvantages, including being heavier, considerably larger and more expensive than its rival; as such, it ultimately lost the trainer contest and remained without a market.

On 15 December 1958, having been suitably impressed, the Italian government placed an order for a batch of 15 pre-series examples on behalf of the AMI. A production line was established at Macchi's facility in Masnago, Varese, Northern Italy. Shortly thereafter, the AMI issued its first order for the MB-326 for an initial group of 50 production standard aircraft. During 1960, a larger follow-on order for 100 aircraft was received by Macchi; this sizable commitment was viewed as being a major step towards establishing the company's supremacy in jet trainer market.

Design

The Aermacchi MB-326 was a low-wing monoplane with an all-metal structure composed of light alloys. It was one of the first jet trainers to be developed with the aim of catering to both for ab initio and advanced instruction. As originally developed, the MB-326 functioned as a refined but simple aircraft capable of covering the considerably wide range of performance characteristics required to cover both ab initio training and advanced instruction alike; other major characteristics of the type included the capacity to deliver a high rate of utilization in conjunction with minimised servicing and maintenance requirements. According to Flight International, the type was suitable for the teaching of the majority of advanced flying techniques. In addition to being relatively easy to fly, a high degree of safety was also intentionally built into it, including adoption of new Martin-Baker-built ejection seats.

The MB-326 was powered by a single Rolls-Royce Viper non- afterburning turbojet engine, initial production aircraft were powered by the Viper 11 model, capable of generating up to 2,500 lb of thrust. The engine possessed multiple favourable attributes, including its general simplicity and robustness, relatively low revolutions per minute (RPM) and turbine entry temperature (TET), rapid acceleration, ease of installation, and its somewhat forgiving nature to mishandling in the air by students.''Flight International'' 20 September 1961, pp. 492, 494. Air was provided to the engine via a pair of low-profile intakes set into the wing roots. The Viper was produced under licence by Italian aviation company Piaggio following an agreement established with its original manufacturer, the British engine firm Bristol Siddeley, during 1959.''Flight International'' 20 September 1961, p. 492.

In a structural perspective, the MB-326 was relatively straightforward. Both the fuselage and the wing were constructed in three sections; of these, the centre section of the wing was integral to the fuselage. The fuselage was divided into a forward, central, and rear section; the forward section contained the nose wheel and radio systems; the centre part, accommodated the cockpit, fuel tanks and the engine; and the rear section which comprised both the tail unit and jet pipe. The fuel system had one large tank in the middle-fuselage and two in the wingtips; a single-point pressure-fuelling system is located on the starboard side of the aircraft to provide a total refuelling time of around five minutes. The rear of each wing had flaps, and ailerons with a trim surface; each wing had 22 ribs and two spars. Wing fences were added mid-wing to increase the lift characteristics. Accordingly, the MB-326 was readily capable of performing relatively slow speed take-off and landing while retaining an excellent rate of climb.''Flight International'' 20 September 1961, pp. 493–494.

The MB-326 was outfitted with a tandem cockpit configuration, this arrangement had been chosen to result in a slimmer and more aerodynamically efficient fuselage in comparison to the more usual side-by-side arrangement. It was covered by a bubble canopy for excellent external visibility; it featured a windscreen anti-icing system powered by the engine compressor using bleed air. The cockpit was also pressurised, enabling the MB-326 to conduct high altitude flight. The ability to fly at higher altitudes was favourable for multiple purposes, including during the execution of aerobatic and navigational training, as well as improving fuel efficiency for long distance flights.''Flight International'' 20 September 1961, p. 494. The onboard systems were typically pre-manufactured units which were easy both to access and to remove; several elements were also intentionally interchangeable. The exterior of the aircraft was covered by a total of 80 inspection panels and doors; in-situ engine inspection could be performed via a pair of large access panels set above and below the engine bay while another pair of doors allow access to the intake duct's interior for the inspection of the first-stage compressor rotor blades.

Operational history

Italy

The MB-326 was one of the last Italian aircraft to hold the distinction of breaking multiple world records. Perhaps the most notable of these occurred during August 1961, when pilot Guido Carestiano set the C1D group 1 category altitude record of 15,489 meters. The record-breaking flights also provided publicity for the MB-326. In particular, one pilot, Massimo Ralli, was responsible for the establishment of several different records while flying the type:
* 8 February 1966, climbing records: 2 min 2 sec to 3,000 m, 3 min 56 sec to 6,000 m, 6 min 39 sec to 9,000 m, and 12,000 m in 10 min 53 sec.
* 18 March 1966, 15,690 m altitude record in horizontal flight, and 17,315 m with a launched climb.
* 18 July 1966, endurance record, with 970 km
* 2 August 1966, speed record over a 3 km straight: 871 km/h
* December 1966: speed of 880.586 km/h over 15–25 km, 831.007 km/h over 100 km, 777.667 km/h over 500 km, and another endurance record at 777.557 km

These high-profile successes functioned as objective statements of the capable performance of the MB-326 and established the type as being one of the best aircraft amongst its contemporaries in its category. Another pilot Riccardo Peracchi, who was employed by for AMI, frequently demonstrated the manoeuvrability and controllability of the aircraft at airshows for a number of years. While Peracchi displayed the MB-326's agility, Ralli concentrated on exploring its cutting-edge performance; meanwhile, early customers of the aircraft were typically reporting their satisfaction with the type to Macchi.

The first production MB-326s, following a relatively protracted development cycle, were first delivered to the Lecce- Galatina school of the AMI's 214° Group, these were temporarily fielded at Brindisi, Apulia. On 22 March 1962, the MB-326 formally entered squadron service with 43° Flyer course. The type was soon used to replace the aging North American T-6 Texan; typically, within the space of 130 hours, pilots would be as prepared to graduate as they would have been after receiving 210 hours training in the older T-6.''Flight International'' 20 September 1961, pp. 492–493.

As a training solution, the MB-326 was considerably costlier but was met with enthusiasm amongst students; additionally, when used in combination with the Fiat G.91T advanced trainer, it enabled the enactment of an "entirely-jet" training course for AMI pilots, and moreover these were domestically designed and produced aircraft. According to aerospace publication Flight International, during the early 1960s, the AMI's flight training programme was heavily influenced by the impending entry into service of the Lockheed F-104G Starfighter.

As well as being amongst the first customers to procure the aircraft, the AMI would be amongst the final customers of the later-built models of the MB-326 as well. The service ordered a batch of 12 MB-326E, comprising six MB-326 updated to MB-326G, and six newly produced (MM.54384/389). They had provisions for armament, but the engine was the Viper 11 Mk 200 and not the Viper 20 Mk 540. In Italian service, the MB-326 was replaced by the MB-339 between 1981 and 1984, acting after that as fast linkage aircraft, replacing the old T-33s that were slightly faster. Unusually, the MB-326 did not see service with the Frecce Tricolori aerobatic team, who kept their faster G.91PANs (they were later replaced by MB-339s).

In addition to its AMI service, the MB-326 was also employed in a civilian capacity within Italy. National flag carrier Alitalia placed an order for four trainer-configured aircraft, designated as the "D" version; these were expressly demilitarized and equipped with specialised instrumentation in order to train the airliner's pilots in preparation for the arrival of the new generation of jetliners that were being procured by the airliner.

Neither the "A" and "C" models of the MB-326 would ever be realized. The "A" variant had been intended to be operated as a light attack aircraft, armed with a pair of 7.62 mm machine guns which were to be installed upon the aircraft's nose. While none were originally built, a number of MB-326s were later referred to by the "A" designation, however, this was meant to indicate that these had been provisioned with a Marconi-built AD-370 automatic direction finder (ADF). The "C" version was envisioned as being provisioned with a nose-mounted North American Search And Ranging Radar (NASARR) unit and other electronic equipment in order to be used for the training of AMI F-104 pilots,''Flight International'' 20 September 1961, p. 493. however, this variant only appeared as a mock-up.

Australia

The Royal Australian Air Force (RAAF) used the MB-326H as a jet trainer. A total of 97 were ordered: 12 were delivered by Macchi, 18 assembled from kits in Australia, and another 67 were built by the Commonwealth Aircraft Corporation and Hawker Aircraft with the designation CA-30. They were essentially similar to the MB-326G but with improved avionics. The RAAF's aerobatic team, The Roulettes, flew the MB-326H from December 1970 until 1989. RAAF pilot training until 1975 consisted of 60 hours pre-selection on CAC Winjeels (from 1975 onwards the PAC CT/4 Airtrainer, aka Plastic Parrot), 150 hours medium and another 75 hours advanced training on MB-326H, before finally progressing to the Mirage IIIOD.

Although widely liked for its excellent handling and well-suited to its task, the service career of the MB-326 was cut short because of structural fatigue problems. The Australian fleet, for example, had a life of type extension program in the 1980s and were then re-winged in the early 1990s after a fatigue-related crash. Even so, the MB-326 was supplemented by new Pilatus PC-9 trainers to reduce flying hours, and the last examples had been withdrawn by 2001 when they were replaced by the Hawk 127.

Brazil

Brazil was the main customer for the MB-326, in 1970 ordering two prototypes and 166 MB-326GCs, called the AT-26 ''Xavante''. It was produced under license by Embraer with a further six for Togo and 10 for Paraguay.

The aircraft was important also for two developments: from the MB.326K the MB.326L was produced, this was the direct ancestor of the Aermacchi MB.339. With license-building in Brazil, the MB.326 opened the field to further collaborations, leading to the AMX. Neither the MB.339 nor the AMX were as successful as the MB.326, but this machine was capable of further steps in technology and commerce.

South Africa

South Africa obtained a license to produce the MB-326M (similar to the 'G' model), as the ''Impala'' Mk I in 1964 with production starting in 1966.Potgieter, Herman and Willem Steenkamp. ''Aircraft of the South African Air Force.'' London: Jane's, 1981, First edition 1980. . It received 40 Italian-built aircraft followed by about 125 built locally by the Atlas Aircraft Corporation,''The Illustrated Encyclopedia of Aircraft,'' Issue 1, 1981, p. 20. using them both as trainers and in an armed configuration. Seven examples of the MB-326K were also bought as light attack aircraft, with a further 15 assembled from kits,''The Illustrated Encyclopedia of Aircraft,'' Issue 2, 1981, p. 34. while around 78 were license-produced and known as the ''Impala'' Mk II. Licence production of the single seat version began in 1974. The Impala Mk II, locally manufactured and equipped with French armament, was also advanced with a South African ECM suite.

The South African Defence Force employed Impalas during campaigns against the People's Armed Forces for the Liberation of Angola (FAPLA) and Cuban expeditionary troops in Angola between 1975 and 1989. Impala pilots typically flew at 550–650 km/h at a height of 15 m to avoid Angolan air defences. Over the course of the South African Border War, one was downed by an SA-7; another returned with an unexploded missile in its exhaust.

The aircraft had many advantages over expensive supersonic jets. Although slower, it could operate from relatively primitive airfields and strike swiftly. The South African Air Force (SAAF) used up to 6 x 120 kg or 4 x 250 kg bombs. The main armament consisted of 68 mm SNEB rocket-launchers (four x 6 or two x 18), and two 30 mm autocannon (with 300 rounds). These cannons were the real bonus for the Impala Mk II, helping to give a superior performance compared to earlier two-seat versions. The latter could also carry a pair of 30 mm DEFA guns in under-wing pods. However, dual capability as trainer-attackers was better appreciated, as was the availability of six hard points and so dual-seat versions were far more common. Six squadrons were equipped with the Impala Mk II in the SAAF during the 1970s and 1980s. Prior to Operation Moduler, most Impalas were withdrawn from their operating bases in South-West Africa, leaving the work to Mirage IIIs and Blackburn Buccaneers.Fenili 1990

Impala Mk IIs were also opportunistically used as interceptors. In several encounters in 1985 with Mi-8 and Mi-24 helicopters, they shot down a total of six. This happened during a crucial phase of the ground war, when Angolan and Cuban troops were checked in an offensive against UNITA bases. This ended in disaster for the Angolan/Cuban alliance when their supplies were cut off by UNITA and the SAAF and front line troops ran out of ammunition. Helicopters were being used to supply the besieged troops and the SAAF cut off this link. Two Mi-24s were shot down in the first encounter while escorting Mi-17s. The MiG-21s that escorted them flew too high to react in time. Two days later the Impala Mk IIs struck again, downing two Mi-24s and two Mi-17s. Attacks on unsuspecting helicopters were carried out with only two guns per aircraft. The single seat Impala Mk IIs were also sometimes armed with Matra R550 Magic air-to-air missiles for self-defence. The Impala Mk II operated at extreme ranges and had to fly very low, climbing only when helicopters were seen at medium altitude. After each attack they returned to low level to avoid interception by enemy MiGs.

The Silver Falcons, the SAAF aerobatic team, were equipped before with Impala Mk Is.

The flying school for Impalas was Flying Training School at Langebaanweg while operational squadrons were 4, 5, 6, 7 and 8 Squadrons, with 85 Combat Flying School