American Projectiles and Explosives - Explosive Bombs - Navy "MK" Series (Part 2)

American Projectiles and Explosives



Explosive Bombs

Navy "MK" Series

650-pound Depth Mk 38 (TNT) and Mk 49 (Torpex) (Obsolete)

Overall length: 58.5 inches
Body length: 36.4 inches
Body diameter: 17.7 inches
Wall thickness: 0.12 inches
Tail length: 29 inches
Tail width: 17.7 inches


Filling: TNT
Weight of filling: 425 pounds
Total weight: 634 pounds
Charge/weight ratio: 67%

or

Filling: Torpex

Weight of filling: 472 pounds
Total weight: 681 pounds
Charge/weight ratio: 69%

Body construction: The body is constructed in three pieces, the flat nose and tail pieces being welded onto the sheet-steel center tube.  The suspension lugs are reinforced with a strip of sheet steel.


Suspension: Horizontal suspension is provided by the usual two suspension lugs, with threaded holes on each side 90 degrees removed to receive the trunnion lugs for suspension from dive bombers.


Color and markings: TNT-loaded bombs have Mark numbers and weight stencilled in yellow; Torpex-loaded bombs have markings in blue.


Tail construction: Four vanes are supported by a circular strut.


Remarks: AN-Mk 219 will not arm under 2,500 feet of altitude if the flat-nose attachment is used.  An Adapter Mk 219 and an additional Auxiliary Booster Mk 1 must be used with this fuze.

Mk 221 arms with difficulty, and should not be used because of delay.

AN-M103 or AN-M103A1 will not arm with the flat-nose attachment, unless special arming vanes are used.

An extender is supplied with each bomb to permit installation of the Hydrostatic Fuze AN-Mk 224 or AN-Mk 234 in the longer athwartships tube.

Because of numerous instances in water crash landings where depth bombs fuzed with the Athwartships Fuze AN-Mk224 or AN-Mk 234 exploded, these two fuzes have been suspended from use.  As a consequence, the Depth Bombs Mk 38 and Mk 49 may be used only if a nose impact fuze is installed.

30-pound Frag. Mk 5 Mods 0-3 (Obsolete)

Overall length: 22.2 inches
Body length: 12.8 inches
Body diameter: 4.2 inches
Wall thickness: 0.57 inches
Tail length: 7 inches
Tail width: 6.5 inches
Tail weight: 2.5 pounds
Filling: Cast TNT
Weight of filling: 4.5 pounds
Total weight: 33.4 pounds
Charge/weight ratio: 13%

Body construction: Cast-steel nose and tail pieces are threaded onto a tubular steel body.  The only difference in construction is that in the Mk 5 Mods 1 and 2, 23 rings cut from seamless tubing are fitted around the tubular body, while on the Mk 5 Mod 3, a steel wire is helically wound left-handed, the adjacent surfaces of wire being parallel.


Suspension: Horizontal suspension is provided by a single eyebolt which is screwed into a ring at the center of the body.


Color and markings: Yellow overall or grey with yellow disc on the body.


Tail construction: Four sheet metal vanes are welded to the tail cone, which is secured to the base plug by a single bolt.

5-pound A.A. Mk 34 (Obsolete) and 3-pound Type C Mk 32 (Obsolete)

No picture available

Mk 34

Overall length: 15 inches
Body length: 12 inches
Body diameter: 3 inches
Wall thickness: 0.05 inches
Tail length: 3 inches
Tail width: 3 inches
Filling: TNT
Weight of filling: 1.9 pounds
Total weight: 5.5 pounds
Charge/weight ratio: 34.5%

Body construction: The reinforced steel nose and conical tail section are welded to a cylindrical steel body.


Suspension: The container Mk 3 or Mk 3 Mod 1 is used.  Its capacity is 20 Bombs Mk 34.


Color and markings: The bombs are painted grey or olive drab overall.  If grey, they will have a yellow disc on the body; if olive drab, they will have a yellow nose band.


Tail construction: Eight sheet-steel vanes are welded to a tail cone which, in turn, is welded to the body.  The vanes are welded on the cone at a ten-degree angle from the longitudinal axis.


Remarks: The 3-pound A.A. Bomb Type C (Mk XXXII) is a smaller copy of the 5-pound Bomb Mk 34.  It is no longer being used.

Bomb Container Mk 3 Mod 1

Overall length: 51.1 inches
Diameter: 13.2 inches
Capacity: 20 A.A. Bombs Mk 34

Mk 3
Weight (Unloaded): 65 pounds
Weight (Loaded): 175 pounds

Mk 3 Mod 1
Weight (Unloaded): 67 pounds
Weight (Loaded): 177 pounds

General: The containers are designed to carry 20 A.A. Bombs Mk 34, ten in the front compartment and ten in the rear.


Description: Each housing assembly contains three bomb bays running lengthwise, the outer side holding three bombs each, and the center holding four bombs; a total of ten for each assembly.  The bombs are loaded onto three ejector springs that run crosswise of the housing and are anchored on the flange on each side of the housing.  These springs eject the bombs after the door-opening mechanism unlatches the doors.  After the last bomb has left each compartment, the door-closing mechanism shuts and holds the doors closed under spring tension until the container is re-loaded.  The skin of the container is of sheet aluminum.


Operation: When the operating switch is closed, the Solenoid Mk 24 or Mk 24 Mod 1, mounted on each of the door-opening assemblies, is energized.  The solenoid unlatches the doors.  The ten bombs in the front compartment are expelled on the first closing of the operating switch, and the ten in the rear are expelled on the second closing of the switch.  The container can also be operated manually.


Remarks: The Bomb Containers Mk 3 and Mk 3 Mod 1 are identical, with exception of the suspension band, fork rests, and outside skin.

1,000-pound Aircraft Mine Mk 13 Mod 0, Magnetic Induction;
Mk 13 Mod 3, Magnetic Induction;
Mk 13 Mod 4, Magnetic Induction; and
Mk 13 Mod 5, Acoustic

Overall length: 68.75 inches

Diameter (case): 19.875 inches
Diameter (tail section): 15.25 inches
Diameter (fins on tail section): 25.5 inches

Mods 0, 3, and 4 -- TNT
Weight of filling: 640 pounds
Total weight: 1,030 pounds
Charge/Weight ratio: 62%
Negative buoyancy: 430 pounds

Mods 0, 3, and 4 -- Torpex
Weight of filling: 700 pounds
Total weight: 1,090 pounds
Charge/Weight ratio: 63.3%
Negative buoyancy: 490 pounds

Mod 5 -- TNT
Weight of filling: 640 pounds
Total weight: 1,000 pounds
Charge/Weight ratio: 64%
Negative buoyancy: N/A

Mod 5 -- Torpex
Weight of filling: 700 pounds
Total weight: 1,060 pounds
Charge/Weight ratio: 66%
Negative buoyancy: N/A

General: The Aircraft Mine Mk 13 Type is designed as a ground influence mine, laid offensively by aircraft from altitudes of 100 to 500 feet in 16 to 75 feet of water (40-100 feet for Mk 13 Mod 5) against surface craft and up to 500 feet against submarines.  The Aircraft Mines Mk 13 Mods 0, 3, and 4 are magnetic induction mines using the Search Coil Firing Mechanism M4, while the Mk 13 Mod 5 is an acoustic mine utilizing the Acoustic Firing Mechanism A3.

When the mine is dropped as a bomb, the minimum altitude of release is 1,200 feet to insure pilot safety.  Because of the shape of the mine, the standard bomb nose fuzes require longer air travel to arm.


Mine construction: The body is a cylindrical steel case with a welded hemispherical nose containing a fuze seat liner which houses an adapter ring and two Auxiliary Boosters Mk 1.  The cylindrical tail section is of a smaller diameter and is welded to the body.  The dome steel tail cover of the Mk 13 Mod 5 is modified to contain the Microphone MI-2; the rubber diaphragm microphone cover of the Mk 13 Mod 5 is stamped with the word "BRUSH".  Horizontal suspension is accomplished by either of three sets of lugs placed 45 degrees apart; each set consists of two standard lugs 14 inches apart.


Color: Black overall


Remarks: The extender and clock starter are activated by hydrostatic pressure at a depth of 16 feet or greater.  The clock delay runs off in 45 minutes to arm the mine.

The Aircraft Mine Mk 13 Mod 3 is a Mk 13 Mod 0 fitted with the Tail Parachute Pack Mk 1.

In the Mk 13 Mod 4, the extender and clock starter are modified for shallow-water planting, allowing the mine to function in ten feet of water.  In other respects, the Mk 13 Mod 4 is identical to the Mk 13 Mod 0.

Cluster Adapter Mk 3 Mod 0

General: The Cluster Adapter Mk 3 Mod 0 is used to cluster three bombs for external suspension on V.B.F.-type aircraft.  The purpose of this cluster is to increase the bomb-load capacity of fighter planes.  Five types of bombs may be used with this adapter, as outlined below:

3x 100-lb G.P. AN-M30A1 (Weight: 364 pounds)
3x 90-lb Frag. M82 (Weight: 300 pounds)
3x 220-lb Frag. AN-M88 (Weight: 688 pounds)
3x 260-lb Frag. M81 (Weight: 800 pounds)
3x 100-lb Incendiary AN-M47A2 (Weight: 340 pounds)

The adapter consists of a band incorporating a take-up bolt, a frame assembly, and a delay opening pistol assembly.


Operation: When the cluster is dropped, the arming wires are withdrawn and the pistol and tail fuze vanes are free to rotate.  After approximately 45 revolutions of the vanes, the arming screw will thread far enough out to allow the firing-pin release levers to cam in.  The firing-pin spring, acting through the firing pin on the firing-pin release levers, will cause the upper portion of the firing-pin release levers to cam in.  The lower portion of the firing-pin release levers then releases the firing pin, allowing it to move aft under action of the firing-pin spring, to strike the percussion cap of the caliber .45 blank cartridge.

Explosion of the blank cartridge expels the cartridge chamber and cartridge-chamber plug (as a unit) from the pistol cradle, pulling the two cotter pins out as they are ejected.  The cluster band clamps that were held together by the clamping action between the cartridge chamber and the pistol cradle, and are now free to open.  Through the action of the displacing springs, the three bombs are ejected from the cluster.  The bomb tail-fuze arming wires are withdrawn when the cluster falls from the plane, and the bomb nose fuzes are free to arm after being ejected from the cluster, freeing their vanes from the fuze arming safety plate.

The air-arming delay-opening pistol requires approximately 45 turns to arm, and will allow the cluster to drop approximately ten feet below the releasing aircraft before functioning.  Minimum release altitudes for these clusters are the same as those issued by the Chief of Naval Operations for bombs of the size used and fuzes installed plus twenty-five feet to allow for cluster opening.  These clusters are safe for take-offs and landings anywhere, including catapult take-offs and arrested landing.

Cluster Adapter Mk 4 Mod 0

Bombs: Two 100-pound G.P. bombs

General: The Cluster Adapter Mk 4 is a simplification of the Mk 3.  It employs only the band and pistol release device to hold the bombs together.  With the bombs clustered together, one of them is then suspended from the bomb rack by its suspension lug.  The nose-fuze vanes are held stationary by two clips which are attached to wire springs.  These springs are held between the bombs until the cluster opens, after which they are sprung free.

Cluster Adapter Mk 7 Mod 1

Bombs: Eight 20-lb Frag. Bombs, AN-M41A1

Total weight: 186 pounds

Loaded length: 46.38 inches

Width: 8.36 inches

General: This cluster, 250-pound bomb size, uses the same pistol release device to open the cluster as used on the Mk 3; otherwise the mechanism is different.  In this cluster, there is not only the release of the steel bands holding the bombs together but a spring-loaded force to push the bombs out of the cluster.

Description and operation: The frame has a front and a rear plate separated by the longitudinal members, the upper and lower rods.  The lower rod is rigid, but the upper one is free to rotate.  To this upper rod are fixed the band hooks.  When the cluster is assembled, the hooks are under torque from the tension of the band.  However, the band hooks are held stationary by a king pin swung between two supports, which supports are placed between the upper and the lower rods.  Firing of the pistol device, seated in the front plate, knocks out this king pin, allowing the upper rod and hooks to rotate, freeing the bands.

When the bands fall off, the springs on the lower rod expand and, acting through the lever arms, push outboard on all the bomb cradles, forcing the bombs away from the cluster.

The arming vanes of the nose fuzes in the fragmentation bombs are kept from turning by safety arms attached to the front plate.

The cluster is suspended by the suspension plates in the middle part of the cluster.

Next Time:"AN" Series (Part 1)