Characteristics

The 81mm mortar is the heaviest piece of fire power that an infantry battalion has in its armoury. It is capable of a high rate of fire of 20 rounds per minute with an effective rate of fire of 10 rounds per minute. Used in conjunction with a laser range finder the 81mm mortar is capable of accurately hitting targets at over 5 kilmoetres away. The high and low trajectory available to the weapon allows the operators to hit distant as well as near targets. These factors combine to make it a highly effective weapon.

The 81mm Mortar

For the uninitiated, infantry mortaring remains a so-called 'black art'. Those 'in the know' regularly astound (or infuriate) the listener with specialised terms and arguments over seemingly unimportant eight or ten-figure grid references in the Glen of Imaal. The annual pilgrimage for the DF Mortar Competition may involve three weeks of hard work, sweat and, depending on the result, tears or beers! In this article, the Brandt 81mm Light Mortar, Long Barrel (LMLB), the premier indirect fire support weapon immediately available to the battalion commander, is examined by Capt Jerry Lane, Infantry Weapons Wing.

THE MORTAR has been an important tactical support weapon since the First World War, although its design has remained largely unchanged. Recently, modern technology has greatly impacted upon its performance, permitting integrated fire control systems, longer ranges and the development of more effective and accurate ammunition. The current medium mortar used by the Defence Forces is the Brandt MO-81-61-L, which replaced the Mk 44 in 1981.

The 81mm mortar is on issue to all infantry battalions (regular and reserve). Each battalion has a mortar platoon with three sections, and each section deploys two mortars. A principal feature of the weapon is that it is in the hands of the infantry man. It is the personal support artillery of the battalion commander, directly under his control and therefore a swift response can be made to his calls for fire.

In addition, the 81mm mortar can put down a very heavy weight of fire on an objective. In fact, each mortar is capable of delivering 90kg (200lbs) of high-explosive to a target over 5km (3 miles) away. Mortar fire is particularly lethal to dismounted infantry in the open and is also useful for neutralising 'dug-in' strong points, or forcing enemy armour to close down while still some distance away, forcing him to rely on optics, such as sights or periscopes.

The '81', as it is commonly called, may be used to suppress enemy positions until assaulting troops arrive within 250-300m of the position. The mortar fire then lifts onto enemy counter-attack and supporting positions while the assault goes in supported by the battalions direct fire weapons. Assistance to friendly forces may also be given in the form of smoke and illumination rounds.

The fire of each mortar section is controlled by the MFCs (Mortar Fire Controllers, two per section), usually of NCO rank, who are generally positioned well forward of the troops being supported, bearing in mind the planning range of 5,000m. Most MFCs will be located either with the company commander or with one of the fighting elements. By radio, the MFC informs the mortar line (the mortar position) of the exact location of the target and when firing commences he then gives corrections to bring the fall of the bombs onto the target. This requires considerable skill and is one of the tests in the DF Mortar Competition held annually in the Glen of Imaal.

In this hard-fought competition, mortar sections have to engage and neutralise four targets in a 'quick action' scenario. After initial procedures, times of eight to ten minutes are not unusual; a testament to the level of skill that now prevails in the infantry battalions. The current holders of the Defence Forces title are the team from 3 Inf Bn.

Future developments bode well for the mortar. At present, a number of ire control computers are being evaluated by the Infantry Weapons Wing. In time, these will replace the plotter on the mortar line as a means of translating the MFC's information into data for the barrels. In addition, the MFC will be issued with a similar unit as an aid to fire control. This represents a considerable leap into the future for the weapon and as such is eagerly awaited.

Technical Data