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PzH 155-1 / SP70 155mm Self Propelled Howitzer

The SP-70 (self-propelled gun for the 1970s) was a derivative development of the collaborative FH-70 155mm towed gun. According to the calculations of the late 1970s, the characteristics of the SP70 self-propelled artillery mount allowed it to attack remote enemy targets without the risk of being subjected to a retaliatory strike. In addition, high efficiency was noted when firing at short distances, including direct fire. The chassis based on the Leopard 1 tank was supposed to provide high mobility, and the aluminum armor - a sufficient level of protection, which, according to some estimates, was twice as high as the American M109 SPH. Thus, it was not excluded that prospective self-propelled guns will be able to effectively operate in conjunction with tank units, moving behind them at a short distance.

As a multi-national project, responsibility for the ordnance was British, the turret was Italian and the main body German. In Germany it was designated as "PzH 70" (Panzerhaubitze 70). The Germans went with the tried and tested Leopard tank chassis. The basic problem was no ground level door into the fighting compartment and hence all ammo had to go in through some contrivance. The problem was the tank-like design with the engine at the rear and the turret in the middle, unlike the standard self-propelled artillery design with the engine in front and the turret at the rear. A complicated ammo handling system was required to move the shells and charge bags from the ground up. By one account, this system had some twenty micro-switches in series that all needed to be in the correct position for the system to work. As each micro-switch had about a 2% chance of not correctly aligning, the overall odds of the thing working was tiny.

With a mechanical loading arm like on the SP 70 it only takes one act to load the shell from the ground pile and the mechanical system does the rest. Which therefore obviously requires less crew to match the same rate of fire. The vehicle axis is important because of the relationship with where the ground pile is located. Which is at the rear of the vehicle. So if the gun has to train 90 degrees to the left for a target of opportunity the mechanical loading arm will move away from the ground pile and now be located on the vehicles right side. This required the gunners to port the shells from the ground pile to the loading arm.

Since the introduction of the M109, 155-mm self-propelled howitzers have been an important element of NATO's artillery. During the 1960s and 1970s when doctrine did not require field artillery to match the speed of maneuver vehicles, the M109 had sufficient mobility. AirLand Battle coupled with the Abrams tank and the Bradley infantry fighting vehicle, however, necessitated introducing more mobile field artillery to furnish reliable close support. Without improved mobility the howitzer could not keep up with the maneuver forces.

The highly mobile armored vehicles of the infantry and armor require the artillery to keep pace in mobility and crew protection if it is to survive on the modern battlefield. For some time, there had been a rapidly growing concern throughout NATO over the concept of the future battlefield what will it look like, say, in the year 2000; and what was the artillery doing to move with the times? This situation was addressed by the United Kingdom and West Germany back in the 1960s and later by Italy; together the three nations jointly developed a new towed field howitzer FH70, followed by a new self-propelled howitzer SP70. A good deal of research went into this project.

In the second half of the sixties, Germany and Great Britain agreed to create a joint project for a prospective towed howitzer. The FH70 gun was supposed to have a caliber of 155 mm and a firing range of an active-rocket projectile at the level of 30 kilometers. In 1970, Italy joined the development of a prospective howitzer, which also wished to receive a modern towed artillery gun. By the mid-seventies, all work on the project was completed and since 1976, the FH70 howitzer began to enter the troops of the three countries. The new gun made it possible to significantly increase the capabilities of field artillery, but it had a number of disadvantages inherent in all towed artillery systems. Therefore, already in 1973, Germany, Great Britain and Italy began to create a new self-propelled artillery unit.

In 1973, Germany, Italy, and the United Kingdom began the collaborative development of the SP70. All three countries recognized that a significant improvement had to be made in the major indirect fire support system for the future battlefield. (Indeed, NATO and the United States participated in this exercise and drew up a Basic Military Requirement leading to the agreed operational characteristics of the 155-mm gun of the future.) Under a binding trilateral aagreement, firms from all three countries were contracted to provide the hardware to develop a weapon the SP70 to meet these characteristics. (Even though the US was unable to join the collaborative programme at that time, there is in existence a 155-mm Quadrilateral Ballistics Memorandum of Understanding between the four nations which defines the internal ballistic parameters and the 155-mm family of projectiles.)

The trilateral programme completed its Project Definition Phase in 1973 and then embarked on a long and exhaustive validation phase. The development was divided between the three nations to make maximum use of existing technologies but with the aim of retaining as far as possible a systems approach. In outline, Germany contributed the ordnance, chassis, and main engine; Italy provided the elevating mass, hull, and auxiliary power unit; and the United Kingdom was responsible for the turret, ammunition handling system, and sights.

Especially for the creation of a new SPH, designated SP70, a joint design bureau was organized on the basis of one of the West German enterprises, in which specialists from three countries were supposed to work. The new organization was called upon to carry out the overall coordination of the actions of the three countries. Other responsibilities for the project were divided among various organizations in Germany, Great Britain and Italy. So, specialists from Germany had to create a tracked chassis and a power plant, with the exception of the fuel system, an automatic loader, a gun barrel, as well as the electrical and hydraulic systems of the SPH. In the future, it was supposed to entrust Germany with the assembly of serial combat vehicles. The auxiliary power plant, the main engine fuel system, recoil devices and gun mount mechanisms were developed in Italy.

According to customer requirements, the prospective SP70 self-propelled howitzer was supposed to have dimensions that allow it to be transported by rail and a combat weight of no more than 50 tons. The requirements for the gun were about the same as in the case of the FH70 project. In order to reduce development costs and reduce the price of ready-made self-propelled guns, the military departments of the three countries demanded to unify the new combat vehicle with existing equipment. For this reason, it was decided to use the developments on the projects of the FH70 towed howitzer, the Leopard 1 tank and the Marder infantry fighting vehicle.

As a basis for the chassis of a prospective self-propelled gun, the corresponding unit of the Leopard-1 tank was chosen. The armored SPG hull had almost the same size and shape as the tank hull, but differed in the materials used. To lighten the combat vehicle and ensure the required level of protection, the SP70 self-propelled body hull was decided not to be made of steel, but of aluminum alloys. Sheets up to 50 mm thick provided the self-propelled gun with an acceptable level of protection. The frontal projection of the combat vehicle could withstand the hit of a 14.5 mm bullet, the sides and stern - from 7.62 mm bullets. The hull layout was also borrowed from the tank without major changes. A control compartment with a driver's workspace was placed in its front part. In the middle part of the hull there was a fighting compartment with a turret, and in the aft - the engine compartment.

The chassis of the SP70 self-propelled gun was made on the basis of the corresponding units of the Leopard 1 tank. It had seven road wheels on each side. All road wheels had torsion bar suspension, and the first, second, third, sixth and seventh rollers on each side were additionally equipped with hydraulic shock absorbers. In the front part of the side there was a steering wheel with a track tension system, in the stern - a driving wheel. The upper branch of the caterpillar lay on three supporting rollers.

West Germany did a splendid job on the development of the chassis and automotive aspects. The chassis is custom built by Porsche using proved Leopard tank components, but sbstantily modified. The powerful diesel engine from the firm MTU gave the gun a level of mobility as good as that of a main battle tank, but it also provides two other major advantages: there is power to spare for any weight increases caused by future product improvement; and, secondly, being understressed for most conditions of use, its reliability is excellent. As the main power plant, the new self-propelled gun was supposed to receive an 8-cylinder Daimler-Benz MB781 diesel engine with a capacity of 1000 hp. The engine was made as a single unit with a hydromechanical transmission, a cooling system, etc. In addition, the prospective SPH received an auxiliary power unit with a capacity of 35 hp. It was supposed to be used to supply power to various electrical systems with the main engine off. The power to weight ratio is better than 22 brake horsepower (bhp) per metric ton, with its turbo-charged, liquid-cooled, V8, 100-bhp diesel engine.

The SP70 has a road range of 550 kilometers and a cross-country range of 420 kilometers. Since mobility is considered so important, the SP70 is designed to wade to a depth of over seven feet it only takes pressing a switch and closing the driver's hatch, thanks in part to the equipment's effective NBC sealing.

The length of the SP70 self-propelled gun in the stowed position should not exceed 10.2 meters, width - 3.5 m, height along the roof of the turret - 2.8 m.The combat weight reached 43.5 tons. With this weight, the 1000-horsepower engine allowed her to accelerate on the highway to a speed of 68 km / h. The fuel supply was enough to overcome 420 kilometers. Thanks to the use of worked out, tested and mastered in production units of the power plant and chassis, it was possible to avoid a lot of "childhood diseases".

In the four-seat (commander, gunner and two loaders) turret of the SP70 self-propelled gun, it was proposed to install a 155-mm gun, which was a modified version of the FH70 gun. Some changes were made to the design of the towed howitzer, designed to ensure the installation of the gun in the turret of the SPH and increase its performance.

The indirect-fire periscopic sight is fitted with an electronic tilt compensator that records the tilt of the vehicle by means of sensors and converts this directly into correction signals which are automatically applied to elevation and azimuth as displayed in the layer's display unit. The eyepiece of the periscope sight is mounted in such a way that both the layer and crew chief can view in turn, thus giving the crew chief a means of checking the layer. The firing command is passed to the gun by means of data input/output units, which link the gun directly to the fire control equipment. The direct fire day/night telescope sight is sited in such a way that it can be used by either the layer or the crew chief.

The self-propelled howitzer variant was equipped with an ejector. The howitzer had a rifled barrel a little less than 39 calibers long, a two-chamber muzzle brake and a semi-automatic bolt with a wedge moving in a vertical plane. The recoil devices included two hydraulic recoil brakes and one hydropneumatic recoil device. The design of the recoil devices was made in such a way that when firing at any possible elevation angle, the recoil was the same and equaled 700 mm.

The horizontal guidance of the gun was carried out by turning the entire turret using a hydraulic drive. The crew could use hand-operated mechanisms as a backup horizontal guidance system. For vertical guidance of the gun, the SP70 turret was equipped with a hydropneumatic drive. It allowed changing the elevation angles of the barrel in the range from -25 to + 70 .

The elevating mass consists of the gun and cradle extension for both the loading system and cradle and the recoil mechanism. The mass is mounted on two trunnion roller bearings and a large saddle, which not only connects it with the turret but also blocks off the turret opening. The NBC seal is provided by a mantlet and mantlet seal. The SP70 provides full NBC collective protection for the crew with charcoal filters and a ventilation unit. The elevation system consists of a combined balance and power elevator. Like the recoil system, this is an excellent Italian contribution to the SP70. The elevation system consists of a hydraulic cylinder which provides the power for both elevation drive and corrects the out-of-balance movement of the elevating mass; i.e., should there be any deviation of the gun elevation selected after the firing of a round, a compensator re-establishes the correct elevation angle, thereby allowing a high rate of accurate fire to be achieved automatically. Conventional power traverse is fitted, and there is a manual backup for both traverse and elevation should the power fail.

The internal ballistics of the gun met the requirements of the Quadrilateral Ballistics Memorandum of Understanding; i.e., all charges may be used, and current and future 155-mm projectiles can be fired. The barrel is of autofrettage monoblock construction, fitted with a muzzle brake and fume extractor. The breech mechanism has a vertical-sliding block opening upwards; there is an opening cam which opens the breech automatically on run-out. The breech is fitted with a primer magazine which automatically ejects the spent primer and feeds in a new one.

On the outside of the gun is a shell replenishment gear with an extending arm which can be adjusted to collect a projectile at ground level or from the back of a truck. From this point onwards, the projectile is untouched by human hand; once it reaches the magazine in the turret, it is moved by the magazine hoist to its selected storage row and is then moved along the row by the action of the rigidly mounted pawls hence the title "rigid pawl magazine." This magazine holds 32 projectiles and will take any of the current M107/M549/M483 family.

To the right of the breech of the gun, the designers of the SP70 project placed the workplaces of the self-propelled gun commander, gunner and one of the loaders. The second was to the left of the gun. To increase the rate of fire, the new SPH was equipped with an original automatic loader. Directly next to the gun, it was supposed to install a receiving tray with a chambering mechanism. In the rear of the self-propelled turret, a three-row magazine for 32 shells, nine containers for propelling charges and a projectile feeder were provided. On the outside of the stern of the turret, there was to be a lifting mechanism designed to supply ammunition to the inside of the fighting compartment, including when reloading the store. The work of the automated store and the entire process of loading the howitzer was to be controlled by the first loader. Before firing, he had to manually set the projectile fuses, after which he could give a command to load the gun. At the command from the control panel, which was at the loader's disposal, the mechanisms had to put a projectile of the required type on the feeder. The feeder, in turn, moved the ammunition to the receiving tray, to the chambering mechanism. Further, the process had to be repeated with propelling charges.

German and British specialists, who developed the magazine and automatic loaders, managed to create an original mechanism capable of loading a gun at any angle of elevation of the barrel. At the same time, however, the maximum rate of fire of the self-propelled gun, according to calculations, could not exceed 6 rounds per minute. If the automation was damaged, the self-propelled guns crew could load the gun manually, but in this case the maximum rate of fire was significantly reduced. Provided for the possibility of supplying ammunition from the ground. In this case, both loaders had to be outside the fighting compartment and supply ammunition. The maximum rate of fire when manually loaded did not exceed 4 rounds per minute.

The 155-mm gun of the SP70 self-propelled artillery mount could use any projectile of the corresponding caliber, manufactured according to NATO standards. At the same time, several types of shells were to become the basis for the ammunition of prospective self-propelled guns:

  • L15A1. The main British-designed high-explosive fragmentation projectile. With a length of 788 mm, such a projectile carried over 11 kg of explosives, which ensured greater effectiveness in hitting targets in comparison with other types of ammunition of that time;
  • DM105. Smoke projectile developed in Germany. The ammunition was equipped with four capsules with a smoke-generating chemical. The capsules are ejected at an altitude of about 200 meters and, after falling, form a large cloud of smoke that persists for several minutes;
  • DM106. West German illlumination shell. The illumination block of the projectile must descend by parachute from a height of 600-800 meters. The characteristics of the applied lighting composition allow illuminating the area within a radius of 350-400 meters within one minute.

When using high-explosive fragmentation shells, the maximum firing range of the SP70 SPH reached 24 kilometers. In the future, it was supposed to introduce an active-rocket projectile into the self-propelled gun ammunition, allowing it to hit targets at ranges up to 30 km. The possibility of purchasing foreign developments was considered.

As an additional weapon, the SP70 SP70 was supposed to receive a 7.62 mm machine gun mounted above the commander's hatch. It was proposed to install two four-barreled smoke grenade launchers on the frontal sheet of the turret.

The validation phase began in 1973 and included the manufacture of five prototypes which became available in 1976 and were then subjected to a rigorous programme of travelling and firing. For instance, one of the prototypes covered 8,600 kilometers in the United Kingdom and then went on to do a further 2,400 kilometers in the cold trials in Norway. In Norway, firing was carried out at all eight charges to test the functioning of the equipment in temperatures below zero, where it was important to prove the efficient operation of the ordnance at the combination of low pressures and short recoil. Another of the five prototypes underwent hot trials in Sardinia where the equipment was given another heavy test programme of travelling, this time over rocks and dirt, with plenty of dust to make life difficult. The prototype completed 1,600 kilometers under these conditions.

During the validation phase, prototypes fired 2,300 rounds and demonstrated the high standards of accuracy and consistency which had come to be expected of its towed forerunner, the FH70 (there are 424 FH70s in the hands of troops of the three countries). The information from both travelling and firing provided a solid basis of confidence on which to proceed to the maturation phase, or Phase B in trilateral parlance. The overall concept had been shown to be soundly based, and the equipment proved itself thoroughly. Development goals were met, and the tests ended without any major failures.

Here, then, was a gun with the required range to achieve early attrition and also with a rate of fire to provide massive fire support. Mobility trials confirmed that it possessed high manoeuvre capability and that it had a similar performance to both the M1 tank and the infantry fighting vehicle, and in all had the ability to support short action manoeuvres.

By the end of the 1970s, the countries participating in the SP70 project had identified their needs. It was assumed that the serial construction of new self-propelled guns will start in 1985, and the first vehicles were to enter the troops in two years. In total, it was planned to release about 650 combat vehicles, 400 of which Germany was going to acquire. The remaining equipment was intended to be divided between Great Britain and Italy.

In 1980, five prototypes of the prospective SP70 SPH entered the test site. The chassis, in the design of which components already mastered in production, were used, did not cause almost any complaints. Its fine-tuning was completed quickly enough. Various units installed in the turret brought many problems to the designers of the three countries. Automation, designed to feed ammunition into the gun, turned out to be the most complex component of the entire artillery system. Although the problems that arose during the design phase were successfully solved, during the tests, some of them reappeared, in addition, new ones appeared.

Testing and fine-tuning of various automatic systems continued for several years. When compared to the equipment which the SP70 is to replace in the armies of the three countries, the SP70 undoubtedly had a vastly improved performance. Semi-automatic loading and fast ramming have increased the rate of fire substantially; with an unassisted firing range of 24 kilometers and a rocket-assisted projectile firing range of 30 kilometers, it meets the range requirement of the future battlefield. Automotively, the SP70's high power-to-weight ratio gives it mobility comparable to that of the modern battle tank and infantry fighting vehicles; and its improved reliability, availability, and maintainability make it now ready to meet the users' needs for the 1990s.

The US Army chartered the Division Support Weapon System (DSWS) Special Study Group in 1980 which outlined three options for acquiring an improved howitzer. The US Army could obtain improved versions of the Howitzer Extended Life Program howitzer, develop a new self-propelled 155-mm. howitzer, or adopt the self-propelled SP70 155-mm howitzer being developed jointly by the United Kingdom, Italy. and the Federal Republic of Germany. Even though none of the howitzers represented a quantum improvement in capability, each choice offered sufficient promise to warrant development. Of the three alternatives, purchasing a foreign howitzer and developing a new system were too costly. After conducting a cost and operational effectiveness analysis in April 1983, the US Army found product improvements to the M109A2/A3 to be the least expensive option, while purchasing the SP70 was the most exorbitant.

In 1985, when, according to the initial plans, it was supposed to start mass production of new self-propelled guns, Germany refused to further participate in the project. The West German military and designers considered that the project in its current form had no prospects. After several years of work, a number of shortcomings of the self-propelled gun were not eliminated, which was the reason for the corresponding reaction of German specialists. Having lost an experienced assistant, Great Britain and Italy soon froze, and then officially stopped all work on the project. When the SP70 artillery project was scrapped by the UK Government the estimated cost of United Kingdom participation in the SP70 trinational development program to date had been some 88 million. The slippage in the development program predominantly reflected design changes needed for the equipment to meet the demanding operational requirements. To date the United Kingdom's costs in real terms are just under 50 percent above the estimate made when the phase B development began around the end of 1977.

The main problem faced is the reliability of the equipment in particular in the areas of the turret and ammunition handling system. A review of the program was undertaken to determine the best way ahead. By 1986 the SP70 should enter service in the early 1990s, although a trinational review of the development program was taking place which may affect the way ahead on the programme. This is being pursued as a matter of urgency. No production orders have yet been placed.

It should be noted that the joint project was not useless. Based on the developments gained during its creation, all three participating countries have developed their own artillery systems. Germany created and adopted the PzH 2000 self-propelled guns. Development of the Panzerhaubitze 2000 self-propelled howitzer (SPH) began in 1987 after the trilateral PzH 155-1 SP 70 SPH project was suspended. The UK has been operating the AS90 self-propelled guns since the early nineties. A total of 179 self-propelled howitzers were built for the British Army. Italy, while working on the SP70 self-propelled gun, developed its own Palmaria project. The Palmaria 155 mm self-propelled howitzer was developed by Oto Melara specially for export. It evolved from the cancelled international SP70 project.

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