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AS90 Braveheart 155mm - Self Propelled Howitzer

First delivered to the British Army in 1993, the AS90 self-propelled guns equip 5 field regiments, replacing the Abbot and M109. AS90 is equipped with a 155mm gun which fires the NATO L15 unassisted projectile out to a range of 24.7 kms. When firing the L15A1/A2 shell, or a further development of this shell, using MCS at a maximum range of not less than 30,000m was achieved.

A contract for the final development and production of extended range barrels and a new Modular Charge System for the AS90 self-propelled gun was placed with Marconi Electronic Systems in May 1999. This program was intended to extend the range and increase the effectiveness of AS90, and would have provided a significantly enhanced artillery capability for the British Army.

BAE systems were awarded a contract to upgrade 96 of the AS90 to a 52-calibre Length gun to increase its unassisted range to 30 km and with long-range ERA ammunition to 40km. The project was cancelled by the British Army due to technical problems with the ammunition. It is assumed that the turret was modified to take the extra weight from the increase length of the main gun, changes to the breach and ammunition stowage, hence the name Braveheart turret.

Fitted with autonomous navigation and gun laying system (AGLS), AS90 can work independently of external sighting references. the onboard navigation system combined with the automatic gunlaying and burst rates of fire enable the AS90 to come into action, fire 18 rounds and move off again in less than 5 minutes. Central to the system is an inertial Dynamic Reference Unit (DRU). All main turret functions are controlled by a Turret Control Computer (TCC).

In trials, two AS90 guns were able to deliver a total payload of 261kg on to a single target in less than ten seconds. An automated loading system enables the gun to fire with a burst rate of three rounds in fewer than ten seconds, an intense rate of six rounds a minute for three minutes and a sustained rate of two rounds a minute. The gun is equipped with a recoil and hydrogas suspension system, which allows the turret to traverse and fire through a full 360.

The AS90 was procured as a replacement for the Abbot self-propelled gun. Vickers Ship building Engineering, which was bought out by BAE Systems Land Systems in 1999, originally developed it in 1981. The 1981 project built a prototype 155mm turret designated the GBT 155. A new 155mm self-propelled artillery system project was started, and designated the AS-90, which stands for Artillery System for the 1990s. Two prototypes were built in 1986 and entered in the British Armys Abbot Replacement Competition. In 1989 the AS90 was chosen as the British Armys new Artillery System and an order was made to Vickers for 179 AS90's at the cost of 300 million pounds.

The requirement specified that the new gun platform has stretch potential, specifically that extended range be achievable without major modification, except to the barrel. No assessment work was carried out prior to Main Gate approval in September 1993.

The AS90 155mm howitzer had an original in-service date of August 1992, and the actual ISD is November 1993. An estimated over-cost of 33 million in a competitive contract is also illuminating. The AS90 self-propelled gun, a four-year in-Service reliability warranty was inserted in the contract and has been invoked to remedy shortfalls in reliability against the contract specification.

The Department used the Defence Evaluation and Research Agency to conduct range and accuracy tests, and also tests of the strength and design of the barrel. These tests were carried out in controlled conditions. Broader tests of the vehicle and firing under real conditions were also conducted during User Trials on Salisbury Plain. These included tests of mobility, navigation, communication, stowage, towing, safety, night driving and live firing. Over 80 rounds were fired by detachments wearing protective clothing against nuclear, biological and chemical threats. These trials, largely successfully completed, gave a good picture of the equipments likely real world performance, and formed the basis for the equipments acceptance off-contract.

In addition to these tests, there was also a subsequent In-Service Reliability Demonstration that comprised 11,200 rounds fired from an eight gun battery of AS90s, and 6,000 km of running on road and across country. These tests were equivalent to 80 Battlefield Days, as specified in the contract. The Demonstration was also completed satisfactorily, with a few minor problems revealed which have since been rectified.

The AS90 is fitted with a 155mm, 39-calibre gun barrel. Extended Range Ordnance/Modular Charge System (ERO/MCS) was a program to upgrade the AS90 self-propelled Howitzer. The program comprised two elements; ERO, a longer, 52 Calibre barrel and MCS, a Modular Charge System. When integrated into the AS90 gun platform the upgrade significantly increases range, giving improved lethality and survivability, together with operational and logistic benefits, especially reduced charge wastage.

Approval for development and production of ERO and initial production of the Unimodular Propelling Charge System (UPCS) was given in September 1993. Following technical difficulties with UPCS, the Equipment Approvals Committee approved development of the alternate MCS in July 1995.

In 1995 an invitation to tender was issued to Vickers Shipbuilding and Engineering Ltd. for the development and production of a 52 calibre ordnance for AS90. Under this plan, this was to lead to the first howitzers being covered to extended range ordnance before the end of the decade. Trials with a prototype 52 calibre barrel firing inert L17 rounds have resulted in some cases of "engraving" of the projectile when it has been fired at the maximum range. This was being addressed as part of the risk reduction work already in hand by the Defence Evaluation and Research Agency and industry.

Technical difficulties were encountered with barrel wear and durability and consequently, a risk reduction contract was placed with the AS90 Design Authority to examine the durability of both chromium plated and steel barrels and to select an MCS supplier. The program was re-approved in 1998 and the Prime Contract for the supply of ERO and an initial quantity of MCS was placed with Royal Ordnance Defence (BAE SYSTEMS) in May 1999. The contract sustained about 50 jobs with Marconi at Barrow-in-Furness and at the Royal Ordnance factory in Nottingham, which was to manufacture the extended range barrels. The Modular Charge System was supplied by Somchem of South Africa. The total value of the contract with Marconi was around 75 million.

The gun was subject to a User trial prior to acceptance off-contract, to ensure that the guns performance matched the Staff Requirement. The one major shortfall in meeting the requirement concerned the durability of the 39-calibre barrel. The Staff Requirement (which was accurately reflected in the contract) stipulated a barrel life of 2,500 Equivalent Full Charge firings using full calibre rounds. This figure had been derived as a direct read-across from preceding systems, and the Department assumed that, by using existing barrel technology, the required AS90 barrel life could be achieved.

However, the advent of more energetic propellants in the interim had acted to increase barrel wear. When the gun was tested under severe conditions during the user trial, only half the number of Equivalent Full Charge firings required were achieved. However, the gun was still accepted since the User assessed barrel durability as acceptable in the prevailing operational environment.

In the AS90, rather than provide each gun with a second barrel to allow a capability of meeting 2,500 Equivalent Full Charges, the imminence of an Extended Range Ordnance programme across most of the fleet, whereby 52-calibre barrels were procured to replace the existing 39-calibre barrels, allowed a trade-off to take place. The 39-calibre barrels were made redundant as a result of the Extended Range Ordnance program and they will be re-allocated as replacement barrels for those guns which are not being upgraded. As a result of this experience, the Department learned a lot about barrel characteristics which should help to ensure that future designs will quantify requirements more accurately.

In 2010 trials to look at firing American Excalibur 155m precision guided shells from the British Armys AS90 selfpropelled howitzer were successful. At the same time the US Modular Artillery Charge System (MACS) was also trialled in AS90 under an interoperability arrangement. The trials in Arizona were supported by elements of Artillery Systems and Indirect Fire Precision Attack teams at DE&S, the Royal Artillery Trials and Development Unit (RATDU) with scientific support by BAE Systems, Qinetiq and the US Department of Defense.

Initial trial observations showed that of the six Excalibur rounds fired, all impacted between one and three meters from their targets. Excalibur was in use with coalition forces, providing a 155mm precision capability to operations while UK Fire Support Teams had already used Canadian Excalibur in support of UK operations.

The now out of service M107 (green and white bag) charges had been replaced by MACS as the inservice charge system for US 155mm indirect fire systems. M107 was the UK operational reserve charge and limited clearance was sought to employ the new system as a reserve to be used only in extreme circumstances. Further trials were planned with the German modular charge system, to verify the benefits of a modular system and scope alternatives if any future UK requirement was to be set.

By 2018 BAE Systems Land UK was developing a new 155 mm extended range (ER) high-explosive (HE) projectile will have a range of more than 40 km when fired from a 155 mm/52 calibre ordnance or over 30 km when fired from a 155 mm/39 calibre ordnance as currently fitted to the BAE Systems Land UK AS90 self-propelled (SP) artillery system.

The 50,000th simulated round was fired from an AS90 Turret Trainer in early 2018, signalling savings of approximately 125 million to the Ministry of Defence. The trainer, based at Tidworth Garrison in Wiltshire, was first introduced in 2005 to train the commander, gunner and loader of an AS90 - a self-propelled 155mm Howitzer gun. It is designed to allow gun crews to practice their routine firing drills, turret operating procedures and crew duties without the expense of live firing and offers the immersion and realism of firing, with a reduced safety risk and a highly reduced cost. Based on a real AS90 turret, the trainer uses an electro-mechanical system to fully replicate a complete firing cycle. This includes the weight and size of the artillery rounds and the noise and turret movement on firing. Since the trainer was introduced more than 8,500 soldiers have used the equipment. This experience enhances their safety for when they progress to live firing and allows them to focus on more advanced training scenarios.

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Page last modified: 21-02-2019 18:44:17 ZULU