Armament of the Iowa class battleship

Armament of the Iowa class battleship

The armament of the engaged the Imperial Japanese Navy battlecruiser "Kirishima" at a range of convert|18500|yd|m|-2 at night.cite book | last = Mindell | first = David | title = Between Human and Machine | publisher = Johns Hopkins | date = 2002 | location = Baltimore | pages = pp. 262–263 | id = ISBN 0-8018-8057-2 ] The engagement left "Kirishima" in flames, and she was ultimately scuttled by her crew.cite paper | author = A. Ben Clymer | title = The Mechanical Analog Computers of Hannibal Ford and William Newell | publisher = IEEE Annals of the History of Computing | date = Vol. 15 No. 2, 1993 | url = | format = pdf | accessdate = 2006-08-26] This gave the United States Navy a major advantage in World War II, as the Japanese did not develop radar or automated fire control to the level of the US Navy and were at a significant disadvantage.

The Parallax Correctors are needed because the turrets are located hundreds of feet from the director. There is one for each turret, and each has the turret/director distance manually set in. They automatically received Relative Target Bearing (bearing from own ship's bow), and Target Range. They corrected the bearing order for each turret so that all rounds fired in a salvo converged on the same point.

The Fire Control Switchboard configured the battery. With it, the Gunnery Officer could mix and match the three turrets to the two GFCSs. He could have the turrets all controlled by the forward system, all controlled by the aft system, or split the battery to shoot at two targets.

The assistant Gunnery Officers and Fire Control Technicians operated the equipment, talked to the turrets and ship's command by sound-powered telephone, and watched the Rangekeeper's dials and system status indicators for problems. If a problem arose, they could correct the problem, or reconfigure the system to mitigate its effect.

Turret Fire Control Systems

Turrets 2 & 3 had optical rangefinders (the side boxes on the turret's right and left rear corners). If in a surface action, the GFCSs were damaged, or the cable carrying the bearing and elevation order signals to the turret was cut, the Turret Officer could turn a rotary switch to put his turret in local control. Then, he could continue the action using the fire control equipment in the turret.


The large caliber guns were designed to fire two different 16 inch shells: An armor piercing round for anti-ship and anti-structure work and a high explosive round designed for use against unarmored targets and shore bombardment.

The Mk. 8 APC (Armor-Piercing, Capped) shell weighs 2,700 lb (1225 kg) and was designed to penetrate the hardened steel armor carried by foreign battleships. At 20,000 yards (18 km) the Mk. 8 could penetrate 20 inches (500 mm) of steel armor plate.William H. Garzke and Robert O. Dulin, Jr. "Battleships: United States Battleships 1935–1992"] At the same range, the Mk. 8 could penetrate 21 feet (6.4 m) of reinforced concrete. For unarmored targets and shore bombardment, the 1,900 lb (862 kg) Mk. 13 HC (High-Capacity—referring to the large bursting charge) shell was available. The Mk. 13 shell would create a crater 50 feet (15 m) wide and 20 feet (6 m) deep upon impact and detonation, and could defoliate trees 400 yards (360 m) from the point of impact.

The final type of ammunition developed for the "Iowa" class were "Katie" shells. These shells were born from the concept of nuclear deterrence that had begun to shape the United States armed forces as the Cold War began. To compete with the Air Force and the Army, which had developed nuclear bombs and nuclear shells for use on the battlefield, the United States Navy began a top-secret program to develop Mk. 23 nuclear naval shells with an estimated yield of 15 to 20 kilotons. These shells were designed to be launched from the best seaborne artillery platform available, which at the time were the four ships of the "Iowa" class. The shells entered development around 1953, and were reportedly ready by 1956; however, it is not known whether they were ever actually deployed on the "Iowa"-class battleships because the United States Navy does not confirm or deny the presence of nuclear weapons aboard its ships. In 1991 the U.S. unilaterally withdrew its nuclear artillery shells from service, and Russia responded in kind in 1992. The U.S. removed around 1,300 nuclear shells from Europe and reportedly dismantled its last shells by 2003.

econdary battery

The secondary battery was a dual purpose weapon system; it was designed to defend the ship from either surface or airborne threats. The original secondary battery consisted of 10 Mark 28, Mod 2 twin gun mounts,cite web |url=|title=Navy Weapons|accessdate=2007-08-07 ] and four Mark 37 Gun Fire Control Systems. At first, this battery's effectiveness against aircraft diminished as planes became faster, but this changed toward the end of World War II through a combination of an upgrade to the Mk37 System and the development of the VT (Variable Time) proximity fuze. In preparation for the reactivations in the 1960s and 1980s, the battery was updated to the latest gun and fire control system modifications. In the 1968 upgrade to the USS New Jersey for service off Vietnam, three Mark 56 Gun Fire Control Systems were installed. Two on either side just forward of the aft stack, and one between the aft mast and the aft Mk 38 Director tower. cite book | last = Terzibaschitsch | first = Stefan | coauthors = Heinz O. Vetters, Richard Cox | others = Siegfried Beyer | title = Battleships of the U.S. Navy in World War II | origyear = 1977 | publisher = Bonanza Books | location = New York, New York | isbn = 0-517-23451-3 | pages = 147–153 ] This increased New Jersey's anti-aircraft capability, because the Mk 56 system could track and shoot at faster planes. In the 1980s modernization, the Mk 56 GFCS's and four mounts were removed to make room for missiles, leaving the Secondary battery with four Mk 37 GFCS's and six twin mounts on all the Iowa class. By the time of the Gulf War the secondary battery was largely relegated to shore bombardment and littoral defense. Since each battleship carried a small detachment of Marines aboard, the Marines would man one of the 5 in gun mounts.Citation | last =Wass | first =Becki | author-link = | publication-date =November 1984 | date = | year =1984 | title =Iowa gets new Marine Guard Chief | periodical =All Hands | series = | publication-place =Alexandria, VA | place = | publisher =United States Navy | volume = | issue =813 | pages =27 | url = | issn = | doi = | oclc = | accessdate =2008-06-25]

Mark 28, Mod 2 Mounts

, electric-hydraulic drives for bearing and elevation, optical sights, automatic fuze setter, automatic sight setter, and an upper handling room. Each armored twin mount weighed convert|170635|lb|abbr=on. The mount had a crew of 13, not including the ammunition movers in the upper handling room and magazines, drawn from the sailors and Marines serving aboard the ship.

Mark 12 Gun Assembly

, ("pictured") each round was delivered to the guns in two pieces. Each gun, in this twin mount, had its own projectile hoist and powder case hoist from the upper handling room. The electric-hydraulic projectile hoist would deliver projectile next to the projectile-man with the nose down and waist high. The electric-hydraulic powder case hoist poked the case through a powder scuttle in the gun room's deck just next to the powder man's feet. At the load command, the powder man would slip a primer protector off the end of the powder case, extract the case from the scuttle, and lift it into the gun's rammer tray. Meanwhile, the projectile man would pull a projectile out of the hoist, and place it in the rammer tray in front of the powder case. Then, as he turned to get the next projectile out of the hoist, the projectile man would pull down on the rammer lever. This caused the power rammer to ram the projectile and powder case into the chamber. As the powder case cleared the top of the breech block, the block would rise to seal the chamber. The gun was ready to fire. The case combination primer in the base of the powder case could be fire either electrically or by percussion. Electrically was the preferred method because the electrical firing circuit could be energized by firing keys down in plot when firing salvos at surface targets, or up in the director when firing at air targets. Percussion firing could be executed by the Pointer (man controlling elevation) by pushing a foot treadle. When the gun fired, the recoil’s rearward motion returned the rammer lever to the up position, and the rammer would drive back to the rear of the rammer tray. During counter-recoil, the breech block was automatically lowered and the spent powder case was ejected from the chamber. When the gun returned to battery, a blast of compressed air was sent down the bore to clean it out. The gun was ready to be reloaded.

Electric-Hydraulic Drives

The electric-hydraulic drives powered the mount's motion. The three modes of drive operation were automatic, local, and manual. In automatic, the drives would follow the bearing and elevation orders of the fire control system. In local, the drives would follow the motion of the trainer's and pointer's hand wheels. (This is similar to power steering on a car.) Manual was direct gear linkage from the hand wheels to move the mount with no power assist.


The periscopic sights (the boxes on the side of the mount) allowed the trainer and pointer to see the target from inside the armored enclosure. Each sight had movable prisms that allowed its line of sight to be moved relative to the barrel's bore axis. These prisms could be controlled by the fire control system when the mount was in Automatic, or by the mount’s sight setter operator when the mount was in Local. Local control was not the preferred combat method, but it could be used if the fire control systems were damaged. The mount captain was trained in aiming and correcting the fall of shot.

Upper Handling room

The upper handling room was just below the visible part of the mount. It was armoredcite book |title =NAVAL ORDNANCE AND GUNNERY, VOLUME 1, NAVAL ORDNANCE, NAVPERS 10797-A|publisher =U.S. Navy, Bureau of Naval Personnel|date =1957 edition|location =Washington 25, D.C.] and reinforced to support the weight of the mount. A person standing in the upper handling room could look up and see the bottom of the gun mount inside the training circle on which the mount rotated. Hanging from the mount, and rotating with it, was the equipment used to pass ammunition up to the mount. This included the lower ends of the projectile and powder case hoists. In the center of the room there was a vertical tube that also turned with the mount. This tube enclosed the electrical power and control cables going up to the mount. Around the perimeter of the upper handling room were the ready service ammunition racks welded to the bulkheads. Close by, either in a corner of the handling room or in an adjoining compartment was the upper end of an ammunition hoist from the magazine. The responsibility of the men stationed in the upper handling room was to shuttle 30 to 40 projectiles and 30 to 40 powder cases per minute from the ready service racks to the hoists while avoiding the equipment rotating with the mount. During quiet spells, they would replenish the ready service racks with ammunition from the magazines.

Mark 37 Gun Fire Control System

The Mark 37 Gun Fire Control Systems (GFCS) was the primary Fire Control System for the Secondary Battery. There were four Mk37 GFCSs on board; one forward above the navigation bridge, two amidships on either side of the forward stack, and one aft between the aft Mk38 Director and Turret three. The major components of the Mk 37 GFCS were the Mk 37 Director, and the equipment in the plotting room.

Mark 37 Director

The function of the Mark 37 Director ("pictured") was to track the present position of the target in bearing, elevation, and range. To do this, it had optical sights (the rectangular widows on the front), an optical rangefinder (the tubes sticking out each side), and Fire Control Radar antennas. On the MK 37 Director pictured, the rectangular antenna is for the Mark 12 FC radar, and the parabolic antenna on the left is for the Mk 22 FC radar. They were part of an upgrade to improve tracking of aircraft. The Director Officer also had a Slew Sight that he could use to quickly point the director towards a new target.

Plotting Room

The Secondary Battery Plotting Rooms were down below the waterline and inside the armor belt. They contained four complete sets of fire control equipment needed to aim and shoot at four targets. Each set included a Mark 1A computer, a Mark 6 Stable Element, FC Radar controls and displays, Parallax correctors, a switchboard, and people to operate it all.

eliminated the need to use the fuze time calculation and its possible error. This greatly increased the odds of destroying an air target.

The function of the Mk 6 Stable Element ("pictured") in this fire control system is the same as the function of the Mk 41 Stable Vertical in the main battery system above. It is a vertical seeking gyroscope that supplies the system with a stable up direction on a rolling and pitching ship. In surface mode, it replaces the director’s elevation signal. It also has the surface mode firing keys.

The Fire-control radar used on the Mk 37 GFCS has evolved. In the 1930’s, the Mk 37 Director did not have a radar antenna. Then c1940, the rectangular Mk 4 Fire-control radar antenna was mounted on top. Soon aircraft flew faster, and in c1944 to increase speed and accuracy the Mk 4 was replaced by a combination of the Mk 12 (rectangular antenna) and Mk 22 (parabolic antenna) radars. ("pictured") Finally, the circular SPG 25 antenna was mounted on top as seen in the USS Wisconsin photo at the top of this article. (Look at the Mk 37 Director just above the bridge.)

Anti-aircraft batteries

Since they were designed to escort the U.S. fleet of fast attack aircraft carriers the "Iowa"-class battleships were all intended to carry a fearsome array of anti-aircraft guns to protect U.S. aircraft carriers from Japanese fighters and dive bombers. This array included up to 20 quad 40 mm mounts and 49 single 20 mm mounts. In the 1968 USS New Jersey re-activation for service off Vietnam, the 20 mm and 40 mm batteries were removed. In the 1980s re-activation, all the ships with 20 mm and 40 mm batteries had them removed, and four Phalanx CIWS mounts were added to all.

Oerlikon 20 mm anti-aircraft guns

The Oerlikon 20 mm anti-aircraft gun was one of the most heavily produced anti-aircraft guns of the Second World War; The US alone manufactured a total of 124,735 of these guns. When activated in 1941 these guns replaced the 0.50"/90 (12.7 mm) M2 Browning MG on a one-for-one basis. The Oerlikon 20 mm AA gun remained the primary anti-aircraft weapon of the United States Navy until the introduction of the 40 mm Bofors AA gun in 1943.cite web |url= |title=United States of America 20 mm/70 (0.79") Marks 2, 3 & 4 |accessdate=2007-02-25 |year=2006 |month=September |author=DiGiulian, Tony |publisher =]

These guns are air-cooled and use a gas blow-back recoil system. Unlike other automatic guns employed during World War II the barrel of the 20 mm Oerlikon gun does not recoil, the breechblock is never locked against the breech and is actually moving forward when the gun fires. This weapon lacks a counter-recoil brake, as the force of the counter-recoil is checked by the explosion of the next round of ammunition.


Bofors 40 mm anti-aircraft guns

Arguably the best light anti-aircraft weapon of World War II,cite web |url= |title=United States of America 40 mm/56 (1.57") Mark 1, Mark 2 and M1 |accessdate=2007-02-25 |year=2006 |month=November |author=DiGiulian, Tony |publisher =] the Bofors 40 mm anti-aircraft gun was used on almost every major warship in the U.S. and UK fleet during World War II from about 1943 to 1945. Although a descendant of German and Swedish designs, the Bofors mounts used by the United States Navy during World War II had been heavily "Americanized" to bring the guns up to the standards placed on them by the US Navy. This resulted in a guns system set to English standards (now known as the Standard System) with interchangeable ammunition, which simplified the logistics situation for World War II. When coupled with electric-hydraulic drives for greater speed and the Mark 51 Director ("pictured") for improved accuracy, the Bofors 40 mm gun became a fearsome adversary, accounting for roughly half of all Japanese aircraft shot down between 1 October 1944 and 1 February 1945.

When the "Iowa"-class battleships were launched in 1943 and 1944 they carried twenty quad Bofors 40 mm gun mounts, which they used for defense against enemy aircraft. These heavy guns were also employed in the protection of allied aircraft carriers operating in the Pacific Theater of World War II. These guns remained on the battleships "Iowa, Missouri," and "Wisconsin" from the time they were commissioned until they were reactivated for service in the 1980s. [USS "New Jersey" had her 40 mm guns removed in 1968 when she was called into action for the Vietnam War. - [ Dictionary of American Naval Fighting Ships - New Jersey] Retrieved March 30, 2007] As each battleship arrived for modernization during the early and mid 1980s the Bofors mounts that remained aboard were removed due in large part to the ineffectiveness of such manually aimed weapons against modern day jet fighters and enemy missiles. The replacement for the Bofors guns was the US Navy's Phalanx Close-in weapon system (CIWS).

Phalanx CIWS

During their modernization in the 1980s, each "Iowa"-class battleship was equipped with four of the United States Navy's Phalanx CIWS mounts, two which sat just behind the bridge and two which were next to the after ship's funnel. USS|Iowa|BB-61|2, USS|New Jersey|BB-62|2, and USS|Missouri|BB-63|2 were equipped with the Block 0 version of the Phalanx, while USS|Wisconsin|BB-64|2 received the first operational Block 1 version in 1988.cite web |url= |title=United States of America 20 mm Phalanx Close-in Weapon System (CIWS) |author=DiGiulian, Tony |date = September 7 2006 | publisher = | accessdate=2007-03-14]

Developed as the final line of defense (terminal defense or point defense) against anti-ship missiles, the Phalanx Close in Weapon System (CIWS, pronounced "see-whiz") is the anti-aircraft/anti-missile gun currently in use in the United States Navy. Due to their distinctive shape, they have been nicknamed "R2D2s", in reference to the droid R2-D2 from the Star Wars universe. [cite web | url= |title=Defense Tech: R2-D2 vs Mortar Rounds |author=Christian Lowe |accessdate=2007-03-21 |publisher=Defense Tech] Designed in the early 1970s by General Dynamics, and currently produced by Raytheon, the Phalanx CIWS mount utilizes a 20 mm M61 Vulcan gatling gun to destroy enemy missiles and aircraft that manage to escape anti-missile and anti-aircraft missiles fired from friendly ships.cite web |url= |title=MK 15 Phalanx Close-In Weapons System (CIWS) |accessdate=2007-03-14 |publisher=Global Security]

The Phalanx guns work by using a search radar and a tracking radar to follow targets that come within 1 to convert|1.5|nmi|km|1. When a target comes within this range the CIWS mount physically moves to track the target while simultaneously evaluating the target against several preset criteria to determine the next course of action. Depending on whether the target criteria are met, the Phalanx mount may automatically engage the incoming target if it is judged to be hostile in nature, or the system may recommend that the Phalanx operator engage a target.

Phalanx CIWS mounts were used by "Missouri" and "Wisconsin" during the 1991 Gulf War; "Wisconsin" alone fired 5,200 20 mm Phalanx CIWS rounds.cite web | title = The USS Wisconsin (BB-64) Ship's History | url = |publisher= USS Wisconsin Association |accessdate=2006-11-26] "Missouri" also received Phalanx fire during a "friendly fire" incident in which the "Perry"-class guided missile frigate USS|Jarrett|FFG-33|6 mistook chaff fired off by "Missouri" for a legitimate target and shot at "Missouri". Rounds from this attack struck the ship in the bulkhead above the famed "surrender deck" and bounced off the armor, one round penetrated the forward funnel and passed completely through it, and another round penetrated a bulkhead and embedded in an interior passageway of the ship.cite web |url= |title=TAB H -- Friendly-fire Incidents |accessdate=2007-02-25 |last=Rostker |first=Bernard |year=2000 |month=December |format=html |work=Depleted Uranium in the Gulf (II) |publisher=United States Department of Defense]


During the modernization in the 1980s, three important weapons were added to the "Iowa"-class battleships. The first was the CIWS anti-aircraft/anti-missile system discussed above. The other two were missiles for use against both land and sea targets. At one point the NATO Sea Sparrow was to be installed on the reactivated battleships; however, it was determined that the system could not withstand the over-pressure effects when firing the main battery. [Statement by Admiral Rowden in the "Department of Defense Appropriations for Fiscal Year 1982".]

Tomahawk land attack missile

The BGM-109 Tomahawk Land Attack Missile (TLAM) was first introduced in the 1970s, and entered service with the United States in 1983. Designed as a long-range, all-weather, subsonic cruise missile, the Tomahawk is capable of reaching targets at a much greater range than the convert|16|in|mm|0|sing=on guns on the "Iowa"-class ships. When added to the battleships in the 1980s the Tomahawk became the longest-ranged weapon carried by the battleships. [The maximum range for the Tomahawk Land Attack Missile is 675 nautical miles (nm), the maximum range for the Harpoon is 85 nm, ( [ Iowa Class: Missile Battery.], Retrieved on 2007-03-25) and the maximum range for the convert|16|in|mm|0|sing=on guns is 24 nautical miles (nm).( [ USS Missouri (BB-63)FAQ.], Retrieved on 2007-03-25)]

Owing to the original 1938 design of the battleships, the Tomahawk missiles could not be fitted to the "Iowa"-class unless the battleships were physically rebuilt in such a way as to accommodate the missile mounts that would be needed to store and launch the Tomahawks. This realization prompted the removal of the anti-aircraft guns previously installed on the "Iowas" and the removal of four of each of the battleships ten 5"/38 DP mounts. The mid and aft end of the battleships were then rebuilt to accommodate the missile magazines. This resulted in the construction of two separate platforms, one located between the first and second funnel and one located behind the second funnel, to which MK-143 Armored Box Launcher (ABL) canisters could be attached. Each Armored Box Launcher carries four missiles, and each of the battleships were outfitted with eight canisters, enabling the "Iowa"-class to carry and fire a total of 32 Tomahawk missiles.cite web | title = BB-61 IOWA-class (Specifications) | url = |publisher=Federation of American Scientists |accessdate=2006-11-26]

The type of Tomahawk carried by the battleships varies, as there are three basic configurations for the Tomahawk: the Anti-Ship Missile (TASM); the Land-Attack Missile-Conventional (TLAM-C); and the Land-Attack Missile-Nuclear (TLAM-N). Each version is similar in appearance and uses the same airframe body and launcher.cite web |url= |title=Iowa Class: Missile Battery | accessdate=2007-03-06 |publisher=Iowa class preservation society] The conventional Tomahawk missile can carry a convert|1000|lb|abbr=on explosive warhead or submunitions which use the missile body to reach their destination. The nuclear variant carries a 200 kt W80 nuclear warhead.cite web |url= |title=BGM-109 Tomahawk |accessdate=2007-03-18 |author=Federation of American Scientists]

The TLAM can be equipped with an inertial and terrain contour matching (TERCOM) radar guidance package to find and destroy its target. The TERCOM radar uses a stored map reference to compare with the actual terrain to determine the missile's position. If necessary, a course correction is then made to place the missile on course to the target. Terminal guidance in the target area is provided by the optical Digital Scene Matching Area Correlation (DSMAC) system, which compares a stored image of target with the actual target image.

The firing weight of the Tomahawk is convert|2650|lb|abbr=on plus a convert|550|lb|abbr=on booster. It has a cruising speed of 0.5 Mach and an attack speed of 0.75 Mach. The anti-ship version of the Tomahawk has an operating range of 250 nautical miles (nm) and a maximum range of 470 nm, while the conventional land attack missile version has a maximum range of 675 nm and TLAM-N has maximum range of 1,500 nm.

During the 1991 Gulf War, USS "Missouri" and USS "Wisconsin" used ABL launchers to fire Tomahawk missiles at Iraqi targets during Operation Desert Storm. "Wisconsin" served as the Tomahawk Land Attack Missile (TLAM) strike commander for the Persian Gulf, directing the sequence of launches that marked the opening of Operation Desert Storm and firing a total of 24 of her own TLAMs during the first two days of the campaign.cite web|title = V: "Thunder And Lightning"- The War With Iraq (Subsection:The War At Sea) |work= The United States Navy in "Desert Shield" / "Desert Storm"| url = |publisher= United States Navy |accessdate=2006-11-26]

Harpoon anti-ship missile

For protection against enemy ships, the "Iowa" class is outfitted with the Harpoon Weapons System. The system consists of four Mk 141 "shock-hardened" quad cell launchers designed to carry and fire the McDonnell Douglas RGM-84 Harpoon anti-ship missile. Each Harpoon is placed in one of four Mk 141 launchers located alongside the aft stack; eight per side, in two pods of four. The weight of the Harpoon at firing is convert|1530|lb|abbr=on, which includes a booster weighing about convert|362|lb|abbr=on. The cruising speed is 0.87 Mach and the maximum range is 64 nautical miles (nm) in Range and Bearing Launch mode and 85 nm in Bearing Only Launch mode.

When an "Iowa" class battleship fires a Harpoon Missile, a booster propels the missile away from the ship; after approximately convert|5|mi|km|0, the booster drops away. After the booster is discarded a turbojet engine ignites and propels the missile to the target. The stabilizing and actuator fins which help guide the missile to its target are stored folded in the canister and spring into position after launching. These fins direct the missile to the target through inputs from the AN/SWG-1 Harpoon Fire Control System.

The battleships carry and use the RGM/UGM-84 variants of the Harpoon Missile, which are designed to be fired by surface ships. The version uses a solid-fueled rocket booster in an A/B44G-2 or -3 booster section, which is discarded after burn-out. The maximum range is around 140 km (75 nautical miles).cite web |url= | title= Boeing (McDonnell-Douglas) AGM/RGM/UGM-84 Harpoon | accessdate=2007-03-06 |last=Parsch |first=Andreas | publisher = Encyclopedia Astronautica BLOG!]

After launch, the missile is guided towards the target location as determined by the ship by a three-axis Attitude Reference Assembly (ATA) in an AN/DSQ-44 guidance section. The ATA is less accurate than a full-fledged inertial system, but good enough for Harpoon's range. For stabilization and control, the AGM-84A has four fixed cruciform wings (3x BSU-42/B, 1x BSU-43/B) and four movable BSU-44/B tail fins. The missile flies at a low cruise altitude and at a predetermined distance from the expected target position, its AN/DSQ-28 J-band active radar seeker in the nose is activated to acquire and lock on the target. The radar switch-on distance can be set to lower or higher values, the former requiring a more precisely-known target location but reducing the risk to be fooled by enemy Electronic Counter Measures (ECM).

An alternative launch mode is called Bearing-Only Launch (BOL). In this mode, the missile is launched in the general direction of the target, and its radar activated from the beginning to scan for the target in a +/- 45° sector in front of the flight path. Once a target has been located and the seeker locked the xGM-84A missile climbs rapidly to about 1800 m before diving on the target in what is known as a "pop-up maneuver". The 221 kg (488 lb) WDU-18/B penetrating blast-fragmentation warhead (in the WAU-3(V) /B warhead section) is triggered by a time-delayed impact fuse. When no target can be acquired after radar activation, the Harpoon will self-destruct.


Further reading

* [ Firing Procedure for the 16"/50 (40.6 cm) Mark 7]
* [ Operating Instructions for Five Inch, 38 Caliber, Gun Crews]

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