SI VIS PACEM, PARA BELLUM: Lo Stridsvagn 103, o Strv-103, o Carro S

Lo Stridsvagn 103, o Strv-103, o Carro S, è stato un carro armato svedese di produzione nazionale, realizzato dalla Bofors AB, i cui primi esemplari di serie apparvero in servizio nell'esercito svedese nel corso del 1966. Costruito in 300 esemplari, il modello Strv 103 fu più volte aggiornato nel corso degli anni, venendo poi ritirato definitivamente dal servizio nel corso del 1997, sostituito dallo Stridsvagn 122 (Strv 122).

Storia

Dopo la fine della seconda guerra mondiale l'esercito svedese era equipaggiato solo con carri armati leggeri, che costituivano la massa d'urto dell'arma corazzata. Per ovviare a questo fatto venne autorizzato l'acquisto di 300 carri medi di provenienza britannica Centurion Mk.3 con consegne immediate, e successivamente avviato lo sviluppo di un carro pesante di produzione nazionale denominato KRV, armato con un cannone ad anima liscia da 150 mm. Alla realizzazione del progetto di tale carro contribuirono la AB Landsverk per lo scafo, la Volvo per il propulsore, e la Bofors per l'armamento. Nel 1956 l'ingegnere Sven Berge direttore del Kungliga Arméförvaltningen propose un modello di carro armato alternativo al pesante KRV, allora in fase di pieno sviluppo, denominato in codice Carro S. Tale progetto introduceva una nuova concezione del carro armato da combattimento, che prevedeva l'installazione del cannone nello scafo invece che nella torretta. Nel 1958 la società Bofors AB ricevette un contratto per lo sviluppo del nuovo carro, di cui si dovevano realizzare due prototipi, e contemporaneamente venne interrotto lo sviluppo del pesante KRV. I due prototipi furono realizzati nel 1961, ma già nel 1960 lo Stato maggiore dell'esercito aveva ordinato la costruzione di 10 esemplari di preserie dello Stridsvagn 103, ancora prima di conoscere i risultati delle prove operative. Il costo di sviluppo del carro risultò inferiore ai 9 milioni di sterline, e i primi 10 esemplari furono completati nel 1966. La produzione continuò fino al 1971 con la realizzazione di 300 esemplari.

Descrizione tecnica

Il carro si presentava privo della torretta, di dimensioni molto contenute, armato un pezzo L74 da 105/62 mm, derivato dall'L7 britannico, montato fisso nello scafo, senza alcun tipo di brandeggio. Questo avveniva puntando tutto il carro e facendo ricorso a un sistema di sospensioni idropneumatico che consentiva all'armamento/scafo una elevazione di +12° e una depressione di -10°. Il carro non poteva sparare in movimento, e per il tiro le sospensioni venivano bloccate e sia il pilota che il capocarro potevano manovrarle per il puntamento. Il terzo membro dell'equipaggio era l'operatore radio, che poteva fungere anche da secondo pilota durante la marcia indietro. Il funzionamento del pezzo era completamente automatico, con clips di colpi che, una volta esaurite, venivano scaricate fuori dal mezzo. Anche i bossoli venivano espulsi automaticamente. La cadenza di tiro era pari a quindici colpi al minuto, con una dotazione standard di cinquanta colpi, situati nella parte posteriore dello scafo. Il munizionamento poteva comprendere 25 granate APDS, 20 granate HEAT e 5 fumogene. Una mitragliatrice KSP-58 da 7,62 mm era installata sulla cupola del capocarro, mentre ulteriori due mitragliatrici KSP-58 da 7,62 mm erano posizionate sul lato sinistro dello scafo. Il munizionamento disponibile per le mitragliatrici era pari a 2.750 colpi. Sulla parte superiore del carro eranpo posizionati due lanciatori Lyran per l'illuminazione notturna del bersaglio. Tutti i carri erano dotati di una lama apripista per scavare posizioni difensive.

Il propulsore policarburante a pistoni contrapposti Rolls-Royce K60, erogante la potenza di 243 CV (179 kW) a 3.750 giri/minuto, la turbina a gas Boeing 502 da 300 CV (223 kW) e la trasmissione erano posizionati nella parte anteriore dello scafo, e fungevano da ulteriore protezione per l'equipaggio. Il motore diesel viene utilizzato per la marcia ordinaria, la turbina a gas per gli spunti di potenza quando il mezzo era in movimento sul terreno vario. Un dispositivo di galleggiamento consentiva al mezzo di muoversi in acqua ad una velocità di 6 km/h, e il carro diveniva completamente anfibio con una preparazione di 25 minuti, con capacità di guadare un corso d'acqua profondo 1,5 m. La capacità carburante era pari a 960 litri. Il carro poteva superare una trincea larga 2,3 m, e un gradino alto 0,90 m.

Impiego operativo

Al suo apparire in servizio il Carro S, o Strv 103, suscitò subito un notevole interesse per la sua bassissima sagoma, propria dei cacciacarri che non degli MBT, un ottimo cannone, ma emersero anche delle limitazioni, in particolare in alcune circostanze, come nel caso di scontri in aree ristrette dovendo, per brandeggiare il cannone, muovere tutto il carro. Il modello Stridsvagn 103 fu realizzato in 300 esemplari tra il 1967 e il 1971, venendo progressivamente aggiornato, passando dalle versioni A e B al definitivo modello C. In particolare, lo Strv 103B fu equipaggiato con uno schermo impermeabile che consentiva di guadare i corsi d’acqua con una preparazione di 25 minuti. La versione Strv 103C vide la sostituzione del propulsore diesel Rolls-Royce K60 con un Detroit Diesel 6V da 290 hp, l'adozione di un cambio automatico e di un telemetro laser al posto del precedente sistema di stima della distanza. Il cannone da 105/62 mm, uno dei più potenti cannoni di questo calibro in servizio all’epoca, era caratterizzato da una elevata cadenza di tiro che consentiva di impegnare in successione numerosi bersagli, grazie al sistema di caricamento automatico.

Il programma di aggiornamento allo standard Stridsvagn 103D, avviato nei primi anni novanta del XX secolo venne abbandonato, in favore dell’adozione del più potente carro Stridsvagn 122 (Strv 122), dotato di cannone da 120 mm. Il modello Strv 103 fu ufficialmente ritirato dal servizio entro la fine del 1997, e nell’ultimo anno gli esemplari di Strv 103 furono usati per l’addestramento per gli equipaggi destinati ad operare sui carri armati. Il prototipo Strv 103D è oggi esposto al Museo di mezzi corazzati di Axvall, insieme ad alcuni carri 103C.

Versioni:

Stridsvagn 103A - prima versione di serie equipaggiata con propulsore Rolls-Royce K60 da 243 CV (179 kW), e turbina a gas Boeing 502 da 300 CV (179 kW),
Stridsvagn 103B - poiché il peso del carro armato Strv 103 era aumentato rispetto aqgli esemplari di preserie, il modello base 103 si rivelò sottopotenziato. Venne quindi introdotta, dopo la produzione dei primi 80 esemplari di serie, una versione più potente della stessa turbina a gas, prodotta dalla Caterpillar 553 da 497 CV (336 kW). I primi 80 carri (designati retroattivamente Strv 103A) furono subito portati allo standard B. Le nuove regolazioni della sospensione idro-pneumatica portarono l’elevazione massima da -10/+12 gradi, a -11/+16 gradi.
Stridsvagn 103C - nel 1986 fu avviato un programma di aggiornamento per dotare tutti i veicoli di un migliore sistema di controllo antincendio. Inoltre ogni Strv 103 fu equipaggiato con una lama apripista, ed inoltre, tra il 1987-1988 fu avviato un ulteriore programma di ammodernamento che prevedeva la sostituzione del motore Rolls-Royce K60 con un Diesel Detroit 6V-53T da 295 CV (216 kW), l’installazione di corazze reattive posizionate lungo i lati dello scafo e di un telemetro laser. Il peso massimo saliva a 42,5 tonnellate.
Stridsvagn 103D - verso la metà degli anni novanta del XX secolo le forze armate svedesi stavano considerando un nuovo aggiornamento per il carro Strv 103, che venne designato Strv 103D. Le principali modifiche riguardarono l'installazione di computer per il controllo del fuoco, di visori termici sia per l'artigliere che per il comandante, e di un intensificatore di luce passivi per il conducente. Inoltre furono apportate alcune modifiche minori al sistema di sospensione e al propulsore. Ne venne realizzato un prototipo che fu testato anche sotto controllo remoto.

Utilizzatori:

Svezia.

ENGLISH

The Stridsvagn 103 (Strv 103), also known as the S-Tank, is a Swedish post-World War II main battle tank, designed and manufactured in Sweden. It was developed in the 1950s and was the first main battle tank to use a turbine engine and the only mass-produced tank since World War II to dispense with a turret. It has an unconventional design: it is turretless with a fixed gun traversed by engaging the tracks and elevated by adjusting the hull suspension. The result was a very low-profile design with an emphasis on survivability and heightened crew protection level. Strv 103s formed a major portion of the Swedish armoured forces from the 1960s to the 1990s, when, along with the Centurions, it was replaced by the Stridsvagn 121 and the Stridsvagn 122, variants of the Leopard 2. While turretless armoured fighting vehicles are usually classified as assault guns or tank destroyers, despite its unique gun laying process the Strv 103 is considered a tank since its designated combat role matched those of other tanks within contemporary Swedish doctrine.

History

In the mid-1950s, the Royal Swedish Army Materiel Administration (Kungliga Arméförvaltningens Tygavdelning) put out a contract tender for next generation tank design to replace their Centurions. A consortium of Landsverk, Volvo and Bofors responded with a suggestion to revive an earlier domestic heavy tank design, known under the codename KRV, fitted with a 155 mm smoothbore gun in an oscillating turret. However, this was deemed too expensive in comparison to the alternatives: A (Anglo-American), which was to purchase a 50-ton tank with high protection and mediocre mobility from either the UK or US. Alternative T (Tysk-Fransk /German-French) was a 30-ton tank with low protection and good mobility. Then, in 1956, Sven Berge of the Swedish Arms Administration proposed Alternativ S, a domestic alternative (S standing for Swedish).

Development

Studies of casualty reports from World War II and the Korean War revealed that the risk of being hit in combat was strongly related to height, with more than half of tank losses being the result of the turret being penetrated. Berge therefore concluded that any new design should be as low as possible. The radical solution was to eliminate the turret, which would also dispose of a vulnerable target area and make the tank much lighter. In terms of absolute height, the final design (see below) did not give the Strv 103 any significant advantage over its most likely opponent, the T-62. The latter was just sightly taller with 2.20 m (7 ft 3 in) in height with its turret versus the 2.14 m (7 ft 0 in) of the Strv 103. On the other hand, the Swedish Centurions towered over both with their 2.94 m (9 ft 8 in) – 3.01 m (9 ft 11 in) in height. However, the T-62 paid for its low profile with an extremely cramped interior and lack of gun depression. Tanks are often deployed in hull-down firing positions, either behind dug entrenchments or using the crest of a hill, in order to reduce the exposure of the vehicle to enemy fire. In this firing position, the level of exposure is determined by the distance between the bottom of the gun barrel to the top of the turret or vehicle, and the angle to which the vehicle is able to depress the gun barrel. Since the Strv 103 orients the entire tank to depress and elevate the barrel, in a hull down position it has very little apparent height and subsequent visual profile to the enemy. It could also lower the hull a further 13 centimetres (5.1 in) by adjusting the suspension.

Familiar with both the French Char B's precision transmission, the exceptional turning performance of the short tracked assault guns and the combat performance of the German StuG and Jagdpanzer series inspired Berge's design to solve the aiming problem through the use of a fully automated transmission and suspension system, which precisely turned and tilted the tank under the gunner's control. The gun itself would be fixed to the hull. This made it impossible to use a stabilised gun. As a result, the tank could not accurately move and fire at the same time, but the Swedish experience with Centurions suggested that, in order for tanks to reach acceptable accuracy, they would need to come to a halt anyway, and wrongly estimated that no breakthrough in stabilisation technology was likely within the foreseeable future.

Other features of the tank were also quite radical. The rifled gun, a Bofors 105 mm L74 with a barrel length of 62 calibres, was able to use the same ammunition as the British Royal Ordnance L7, and would be equipped with an autoloader allowing a rate of fire of one round every third second, also allowing the crew to be reduced to two; a gunner/driver and the commander (most designs of the era used a crew of four), with a single person being able to handle all functions of the tank from his ordinary position due to duplicate controls. This would of course only be used in emergencies, as the workload would be overwhelming, but apart from providing redundancy it also allowed the crew to shift tasks between them as situation required. The concept went through practical tests, that quickly revealed that a two-man crew would not be self-sufficient when considering the many tasks not directly related to handling the tank: in particular, routine maintenance, bivouacking, track-changes and reloading in field. While the last issue could have been solved by adding staff to the ammunition crews, it was decided that a third crew-member was needed. To enhance combat effectiveness, the third man was to be assigned as a rear driver/radio operator, facing the rear of the tank and equipped with a complete setup for driving. This allowed the tank to be driven backwards at the same speed as forwards, keeping its frontal armour pointed at the enemy, while relieving the commander of routine radio duty. The commander and gunner/driver both had the same set of sights and controls to fire the gun and drive the tank.

The tank was uniquely powered by two different kind of engines, a 240 horsepower (180 kW) Rolls-Royce K60 opposed-piston diesel for slow cruising and manoeuvring the tank in aiming, and a 300 horsepower (220 kW) Boeing 502 turbine for additional power when travelling at higher speed or in severe terrain; the same layout that later gave the naval configuration called CODAG (Combined Diesel And Gas), even if many ships had instead the simpler CODOG (COmbined Diesel Or Gas) thanks to the difference between the diesel and turbine power (see, as example, many frigate built for the NATO navies, like Maestrale and Bremen classes). The turbine was quickly found to be underpowered, and was replaced by a Caterpillar turbine delivering 490 horsepower (370 kW) after no more than 70 tanks had been produced, and retrofitted to all previous vehicles. This was the first use of a turbine engine in a production tank; the Soviet T-80 and US M1 Abrams would later be built with gas turbines for main propulsion. The concept was interesting enough that Bofors was asked to build a prototype of the suspension/drive train, which they completed successfully.

The Strv 103 was fully amphibious. A flotation screen could be erected around the upper hull in about 20 minutes, and the tracks would drive the tank at about 6 kilometres per hour (3.7 mph) in water.

One tank in each platoon was fitted with a dozer blade under the front hull, which was from outside the tank manually dropped and locked into working position with pins and support strutters. The blade allowed it to do simple engineering task, like digging fire pits for the platoon, filling trenches for ease of passage and so forth. Once the task was completed, the blade was again manually returned to the position under the front hull and locked in place. Upon the introduction of the 103C model all tanks had a bulldozer blade fitted, both to speed up operations and for the increased protection of the lower hull.

Service

In preparation for the defence plan of 1958 (Försvarsbeslut 1958 (FB58)) in the Riksdagen (Swedish parliament), the procurement set Alternativ S against the two foreign alternatives Alternativ A and Alternativ T. While the domestic alternative was going to be more expensive, the defence committee report recommended "S" when weighing in the symbolic value of a domestic tank for a neutral country as well as the spin-off effects on Swedish industrial competence.

Riksdagen made the formal decision regarding FB58 on 4 February 1958, and a follow-on contract called for two production prototypes, which were completed in 1961. By this point, the army was so satisfied with the design that an initial pre-production order for 10 was placed in 1960.

With minor changes, the Alternativ S was adopted as the Stridsvagn 103 ("103" from being the third tank with a 10 cm calibre gun accepted into Swedish service). Full production started in 1967 and ended in 1971 with 290 delivered. The changes included a new gyro-stabilised commander's cupola armed with a 7.62mm KSP 58 machine gun, and upgraded frontal armour. A unique grid could be mounted at the front to help defeat HEAT rounds; however, it was kept secret for many years and was to be fitted only in the event of war.

Despite its design the Strv 103 was intended for offensive operations. The armoured brigades of the Swedish army, which operated the Strv 103, were designated anfallsbrigader (assault brigades) and tasked with launching counter-offensives on enemy beachheads and airborne landings. The stated Swedish armoured doctrine contemporary to the tank describes an aggressive approach to armoured warfare, even in defensive situations. The design of the Strv 103, with its low profile, was based on protection rather than defensive battlefield behaviour.

In 1980, the Swedish army requested all tanks in the inventory to be scrapped and replaced with Stridsvagn 2000. In 1982, the Riksdag decided for severe reduction of the military budget in Försvarsbeslutet 1982, and decided the tank-fleet should go through a REMO (Renovation and modification) to at least somewhat bring them up to standard while within the economic frames imposed.

Performance

The Stridsvagn 103 never saw combat and so its design remains unproven. However, for its intended role in the 1960s, it had numerous advantages. In 1967, Norway carried out a two-week comparative observation test with the Leopard 1 and found that, with closed hatches, the 103 spotted more targets and fired faster than the Leopard while the situation was reversed when operating with hatches open. In April to September 1968, two 103s were tested at the British armour school in Bovington, which reported that "the turretless concept of the "S"-tank holds considerable advantage over turreted tanks". In 1973, the BAOR tested the 103. British crewmen received six weeks training and the vehicles were serviced by Swedish engineers. Over nine days of manoeuvres alongside the Chieftain tank, availability never fell under 90% and the final report stated, "It has not been possible to prove any disadvantage in the "S" inability to fire on the move." In 1975, two 103s were tested at the American armour center at Fort Knox. The trial demonstrated that the 103 fired more accurately than the M60A1E3, but on an average 0.5 seconds more slowly.

In comparison with the Centurion, the shorter track of strv 103 meant it performed worse on soft ground (mud and snow), the trench taking and vertical obstacle capabilities were also significantly lower: where the Centurion climbed a 100 cm wall, the 103 barely was able to climb an 80 cm wall. On hard terrain, the 103 on the other hand was far more manoeuvrable.

Versions:

Stridsvagn 103B - As the weight of the Strv 103 had increased compared to the pre-production tanks, the 103 turned out to be under-powered. Hence, a more powerful version of the same gas turbine, manufactured by Caterpillar, was introduced after the first production run of 80 tanks. The early version tanks (retroactively designated Strv 103A) were soon upgraded to B-standard. Adjustments to the hydro-pneumatic suspension increased elevation range from −10 through +12 degrees, to −11 through +16 degrees.
Stridsvagn 103C - An upgrade programme was started in 1986 to fit all vehicles with improved fire control systems. Also, each Strv 103 was fitted with a dozer blade, rather than just one per platoon. A further upgrade in 1987/88 replaced the Rolls-Royce engine with a newer 290 horsepower (220 kW) Detroit Diesel with additional fuel cans placed along the sides to function as applique armour, and added a new laser rangefinder.
Stridsvagn 103D - In the mid-1990s, as the Swedish Armed Forces were looking for a new main battle tank, one Strv 103C was upgraded into the Strv 103D. The major changes were the installation of fire-control computer, thermal viewers for both the gunner and the commander, allowing the crew to fight at night-time and in bad weather conditions, and the installation of passive light enhancers for driving. Some minor changes to the suspension system and engine were also made.

There was some consideration of adding both reactive and/or appliqué armour in the early 1990s, but, in the end, the Strv 103 was instead phased out of Swedish service in favour of the Stridsvagn 122 (Strv 122), which entered service in 1997 (the last year that the Strv 103 was used to train tank crews).

This prototype was used during the trials for the new main battle tank system for the Swedish Armed Forces alongside all the other tanks tested. For a few years this prototype was even tested under remote control. The sole Strv 103D is today on display at the Axvall armor museum, together with some 103C models. They are all still in running order.

Tanks on display

The following exhibitions possess an S-tank on display: