American Projectiles and Explosives - Explosive Bombs - "AN" Series (Part 3)

American Projectiles and Explosives



Explosive Bombs

"AN" Series

A.P. AN-Mk 33 (1,000-pound) and AN-Mk 1 (1,600-pound)

AN-Mk 33

Overall length: 73 inches
Body length: 58 inches
Body diameter: 12 inches
Tail length: 17 inches
Tail width: 16 inches

Filling: Explosive D, Cast TNT
Weight of filling: 140 pounds
Total weight: 1,025 pounds
Charge/weight ratio: 14%

AN-Mk 1

Overall length: 83.5 inches
Body length: 69.5 inches
Body diameter: 14 inches
Wall thickness: 1.3 inches
Tail length: 20.5 inches
Tail width: 20.6 inches

Filling: Explosive D, Cast TNT
Weight of filling: 215 pounds
Total weight: 1,590 pounds
Charge/weight ratio: 14%



Construction: The bodies are of single-piece, forged, machined construction, with pointed noses, parallel sides, and alight boat tailing.  The base plate is of the male type.  Suspension in the 1,600-pound A.P. Bomb Mk 1 design was by means of lugs welded to bands, the bands being positioned by grooves on the external bomb surface.  The newer designs, AN-Mk 1 and Mk 33, are suspended by fittings which screw into holes drilled into the bomb case and secured by bolts.  The normal box-type tail assembly is used on these bombs.


Filling: The main filling of these bombs is pressed Explosive "D" or cast TNT.  The tail fuze pocket requires use of the granular TNT Auxiliary Booster Mk 1.


Remarks: The later 1,600-pound A.P. Bombs Mk 1 Type were grooved to position the suspension band.  Older bombs had a stud which fitted into a hole in the bomb body.







325-, 350-pound Depth Mk 17 (TNT - Obsolete), Mk 17 Mod 1 (TNT), AN-Mk 17 Mod 2 (TNT), AN-Mk 44 (Torpex), AN-Mk 41 (TNT), and AN-Mk 47 (Torpex)

AN-Mk 17 Mod 2; AN-Mk 44

Overall length: 52.5 inches
Body length: 31.1 inches
Body diameter: 15 inches
Wall thickness: 0.06 inches
Tail length: 20.2 inches
Tail width: 20.6 inches

AN-Mk 41; AN-Mk 47

Overall length: 49.9 inches
Body length: 27.8 inches
Body diameter: 15 inches
Wall thickness: 0.06 inches
Tail length: 24.6 inches
Tail width: 15.4 inches


AN-Mk 17 Mod 2
Filling: TNT
Weight of filling: 224 pounds
Total weight: 325 pounds
Charge/weight ratio: 68.9%


AN-Mk 44
Filling: Torpex
Weight of filling: 249 pounds
Total weight: 350 pounds
Charge/weight ratio: 71.1%


AN-Mk 41
Filling: TNT
Weight of filling: 227 pounds
Total weight: 347 pounds
Charge/weight ratio: 65.4%


AN-Mk 47
Filling: Torpex
Weight of filling: 252 pounds
Total weight: 355 pounds
Charge/weight ratio: 70.9%

Nose construction: Depth Bombs AN-Mk 17 Mod 2 and AN-Mk 44 have round noses, and can use the flat-nose attachment; AN-Mk 41 and AN-Mk 47 are flat-nosed.


Body construction:
-AN-Mk 17 Mod 2 and AN-Mk 44: These depth bombs are made with round noses welded to a cylindrical steel tube.  There is a strengthening disc around the nose and a steel strip along the suspension lugs to reinforce the body.  The transverse fuze pocket is 11.9 inches abaft the nose.  To prevent ricochet and improve underwater trajectory, a flat-nose attachment is made for these bombs, the attachment being in the shape of a bucket which fits down over the nose and is filled with plaster of paris, increasing the weight of the bomb by 44 pounds.  The bomb case is extremely thin.

-AN-Mk 41 and AN-Mk 47: These bombs are constructed with a flat nose, there being a slight taper from the walls to the nose.  The body is in three pieces.  The sides are tubular with a transverse fuze pocket tube welded in place 15 inches abaft the nose.


Suspension: Suspension of these bombs is by the usual dual or single lugs, the lugs being welded to the bomb.  The single lug is actually somewhat different than is usually found, being in the form of a bracket rather than a lug.  Trunnions on a band are for displacement gear in dive bombing.


Tail construction: Instead of employing the box-type tail, these bombs use a drum tail.  As seen from the after end, it is circular and has four fins extending at right angles to each other.  The fins are spot-welded to a cone which fits over the after end of the bomb.  The fins are also spot-welded to the drum shroud.  The tail is bolted onto the base of the bomb.


Markings: TNT-loaded bombs have weight and Mark number stencilled in yellow; Torpex-loaded bombs have these items stencilled in blue.


Remarks: The 325-pound Depth Bomb Mk 17 is TNT-loaded but has a light tail assembly; the Mk 17 Mod 1 is the same, except that a sturdier tail assembly is used.  The AN-Mk 17 Mod 2 is similar to the Mod 1, but has a larger filling hole.

The Mk 17 is obsolete; the Mk 17 Mod 1, AN-Mk 17 Mod 2, AN-Mk 44, AN-Mk 47, and AN-Mk 41 are obsolescent.








325-, 350-pound Depth AN-Mk 53 Mod 1 (TNT),  AN-Mk 54 Mod 1 (HBX), Mk 53 (TNT), and Mk 54 (Torpex)

Overall length: 52.5 inches
Body length: 33.25 inches
Body diameter: 13.8 inches
Wall thickness: 0.06 inches
Tail length: 24.5 inches
Tail width: 13.9 inches


AN-Mk 53 Mod 1; Mk 53
Filling: TNT
Weight of filling: 225 pounds
Total weight: 330 pounds
Charge/weight ratio: 68%


Mk 54
Filling: Torpex
Weight of filling: 250 pounds
Total weight: 354 pounds
Charge/weight ratio: 70.6%


AN-Mk 54 Mod 1
Filling: HBX
Weight of filling: 250 pounds
Total weight: 354 pounds
Charge/weight ratio: 70%



Body construction: The cylindrical welded sheet-steel body has a flat nose.  A base closing plate is secured to the rear of the bomb by four bolts.  A base closing plate is secured to the rear of the bomb by four bolts.


Suspension: These bombs are suspended horizontally by two lugs seven inches on each side of the center of gravity, or by a single lug at the center of gravity and 180 degrees removed from the other lugs.  There is no external band, the bombs being strengthened internally by a band which is fitted into the bomb at the center of gravity.  Trunnions for dive bombing may be threaded to the case and internal strengthening band.


Tail construction: Welded to the tail cone are four vanes which are strengthened by interior box-type struts, and an exterior wide ring strut.  The tail cone is secured to the base closing plate by four bolts.


Markings: Olive drab overall.  "Mk 53 - 325 lb. Depth Bomb", "Mk 54 - 350 lb Depth Bomb" stencilled on the respective bomb bodies in yellow if the filling is TNT, or in blue if the filling is Torpex.


Remarks: These two bombs (identical except for filling) have been designed to replace depth bombs using athwartship fuzes, since difficulties have been encountered at times in the past with the Athwartship Fuzes AN-Mk 224 and AN-Mk 234.  The Depth Bombs Mk 53 and Mk 54 will use the Tail Hydrostatic Fuze AN-Mk 230 and a nose fuze, having no athwartship pocket.

The Depth Bombs AN-Mk 53 Mod 1 and AN-Mk 54 Mod 1 differ from the Depth Bombs Mk 53 and Mk 54 respectively in that the suspension lugs are welded on, instead of being of the screw type.  In addition, the walls of the explosive cavity of the two bombs are coated with an asphaltic composition known as Hot Melt.  The AN-Mk 54 Mod 1 is loaded with HBX rather than Torpex.

Only the modifications of the Depth Bombs Mk 53 and Mk 54 have been standardized as AN bombs.











1,000-pound Aircraft Mine AN-Mk 26 Mod 1 (Ground, Influence-Fired)

Overall length (w/ parachute pack): 68.5 inches
Overall length (w/o parachute pack): 64.5 inches

Diameter:
-Case: 18.625 inches
-Tail section: 15.75 inches
-Parachute pack: 18.5 inches

Filling: TNT
Weight of filling: 465 pounds
Total weight: 1,000 pounds
Charge/weight ratio: 46.5%
Negative buoyancy: 400 pounds

or

Filling: Torpex
 Weight of filling: 525 pounds
Total weight: 1,060 pounds
Charge/weight ratio: 49.5%
Negative buoyancy: 460 pounds


Construction: The 1,000-pound Aircraft Mine AN-Mk 26 Mod 1 consists of a cylindrical steel case welded with hemispherical nose and tapered tail section.  The tail is closed by a concave cover secured with cap screws.  A ring for mounting the parachute assembly is welded around the after end of the case.  The Tail Parachute Pack Mk 1, containing Parachute Mk 2, is fitted to the tail when the mine is installed in plane.  This parachute slows the fall of the mine through the air to lessen the shock of water impact, and is released from the case on striking water by an impact release mechanism.  Suspension is horizontal, two standard lugs being welded onto the body 14 inches apart and placed 90 degrees from the side pockets.

There is a removable British single-suspension lug 180 degrees removed.


Markings: Black overall


Remarks:
-Normal Use: As ground, magnetic induction mine.  Aircraft-laid, with parachute (release altitude - 200 feet or higher).  Laid offensively in depths of water from 16 feet to 120 feet against surface craft, and up to 500 feet against submarines.  Extender and clock starter are caused to function by hydrostatic pressure at depths of 16 feet or greater.  Clock delay runs off in 170 minutes to arm the mine.

-Use as bomb: This mine is poorly suited for use as a bomb, since accurate dropping by parachute is difficult; and if parachute is not used, the case tumbles.  Fuzes require longer air travel to arm than usual, because of the shape of the mine and the manner of fall through the air.






20-pound Frag. AN-M41, and AN-M41A1

Overall length: 19.5 inches
Body length: 11.3 inches
Body diameter: 3.6 inches
Wall thickness: 0.56 inches
Tail length: 9.26 inches
Tail width: 5.1 inches
Tail weight: 1.6 pounds

Filling: TNT
Weight of filling: 2.7 pounds
Total weight: 20.3 pounds
Charge/weight ratio: 13%



Body construction: This bomb is constructed of cast-steel nose and tail pieces, a seamless steel inner tube, and a helically-wrapped drawn steel wire wrapping around the inner tube.  The tube is threaded to hold the nose and tail sections.


Suspension: For individual suspension of this bomb, a U-shaped eyebolt of steel is welded to the body at the center of gravity for horizontal suspension, and an eyebolt is welded to the tail for vertical suspension.

The bomb may be dropped in a cluster of six bombs in the Cluster Adapter AN-M1A2 or M1, forming the Cluster AN-M1A1 or M1.  The cluster adapter is made of sheet steel, and does not use eyebolts of bombs for suspension.


Tail construction: Four rectangular sheet-steel vanes are welded to a length of one-inch cast-iron pipe which screws into the base filling plug.


Remarks: This bomb is a high-level fragmentation bomb and should be dropped from a minimum altitude of 400 feet.

The A1 modification of this bomb consists of adding a 1 and 1/2-inch shoulder around the nose to facilitate clustering with unfuzed bombs.  Heretofore, the spacers of the cluster adapter have fitted against the fuze, thereby making it requisite that the bombs be clustered and shipped with fuzes inserted.








23-pound Para-Frag. AN-M40, AN-M40A1, M72, and M72A1

Overall length: 26.7 inches
Body length: 11.3 inches
Body diameter: 3.6 inches
Wall thickness: 0.56 inches
Tail length: 13.9 inches
Tail width: 4.35 inches
Tail weight: 5.3 pounds

Filling: TNT
Weight of filling: 2.7 pounds
Total weight: 24.5 pounds
Charge/weight ratio: 11%



Body construction: These bombs are constructed of cast-steel nose and tail pieces, a seamless steel inner tube, and a helically-wrapped drawn steel wire wrapping around the inner tube.  The tube is threaded to hold the nose and tail sections.


Suspension: For individual suspension of these bombs, a U-shaped eyebolt of steel is welded to bomb at the center of gravity.

The 23-pound Para.-Frag. Bombs AN-M40 are always clustered, three of the bombs with the Cluster Adapter AN-M3 forming the Cluster AN-M4.

The 23-pound Para.-Frag. Bomb M72 is a slightly modified version of the AN-M40.  It is adapter for individual suspension and can be carried in vertical cellular racks by several types of Army planes.


Tail construction: The 23-pound Para.-Frag. Bombs AN-M40 and M72 are fitted with cylindrical sheet-steel parachute housings which have end caps at the rear end and contain a white silk parachute.  The Parachute Unit M3 is used in the Para.-Frag. Bombs AN-M40 and AN-M40A1; the Parachute Unit M4 in the Para.-Frag. Bombs M72 and M72A1.


Remarks:  The AN-M40 and M72 are low-level fragmentation bombs and should be dropped from a maximum altitude of 400 feet.


The A1 modification of these bombs consists of adding 1 and 1/2-inch shoulder around the nose of the bomb to facilitate clustering with unfuzed bombs.  Heretofore, the spacers of the cluster adapters have fitted against the fuze, thereby making it requisite that the bombs be clustered and shipped with the fuzes inserted.  Bombs with this modification are designated the 23-pound Para.-Frag. Bombs AN-M40A1 and M72A1.






Fragmentation clusters and cluster adapters



Cluster AN-M1A1, Cluster Adapter AN-M1A2: This cluster, consisting of the Cluster Adapter AN-M1A2 or M1 and six Fragmentation Bombs AN-M41, is made of sheet metal and does not use eyebolts for suspension.


Cluster AN-M1A2, Cluster Adapter AN-M1A3: With the modification of Fragmentation Bombs AN-M41 to permit fuzing in the field, the following changes are made in the Cluster Adapter AN-M1A2: (1) flat springs are substituted for the fuze lock plates; and (2) the suspension lugs are changed from a strip type to a type similar to those on G.P. bombs.  The new lugs were designed to permit suspension of the clusters in all existing types of bomb racks.  The modified cluster adapter becomes the AN-M1A3, forming, with six Fragmentation Bombs AN-M41A1, the Cluster AN-M1A2.

If the modified Cluster Adapter AN-M1A3 is used with unmodified Fragmentation Bombs is used with modified Fragmentation Bombs AN-M41; or the unmodified Cluster AN-M1A1 is used with modified Fragmentation Bombs AN-M41A1; or the unmodified Cluster Adapter AN-M1A1 is used with unmodified Fragmentation Bombs AN-M41, no change will be made in the designation of the Cluster AN-M1A1.  The bombs, in these latter cases, will be fuzed when the bombs are clustered at the loading plant.

The unmodified Fragmentation Bomb AN-M41 with Cluster Adapter AN-M1A1 is not suitable for Navy use.  The modified Adapter AN-M1A2 can be used, and the cluster is designated S1ZVL.


Cluster AN-M4, Cluster Adapter AN-M3: The cluster Adapter AN-M3 and three Fragmentation Bombs AN-M40 form the Clsuter AN-M4.


Cluster AN-M4A1, Cluster Adapter AN-M3: When Para.-Frag. Bombs AN-M40A1 are clustered, the Cluster Adapter AN-M3 is still used without any alteration in design, but the designation of the cluster is AN-M4A1.


Cluster M26, Cluster Adapter M13: The Fragmentation Bomb Cluster M26 consists of a Cluster Adapter M13 to which are secured twenty 20-pound Fragmentation Bombs AN-M41A1, in two groups of ten.  The cluster is 53 and 1/2-inches long, 14 and 11/16-inches wide, and 13 and 3/4-inches high.  The cluster adapter is a steel framework consisting of a tubular suspension bar to which the suspension lugs are fitted, steel separator plates, and two metal straps secured by release buckles.  The separator plates located before each group of the bombs are built with arming vane stops for the Nose Fuzes M110A1 used in the individual bombs.  The cluster can be adapter for either quick or delayed opening.

Quick opening is accomplished by the arming wires, which are fed through the release buckles and are withdrawn on the release of the cluster from the plane.   In delayed opening, a Mechanism Time Nose Fuze M155 (T71) or M1111A2 is screwed to the fuze adapter in the forward end of the tubular suspension bar.  When the fuze detonates at the preset delay, the explosion drives a steel slug rearward to cut the shear wires in both the forward and the after release buckles, thereby permitting the cluster to open.

Tumbling of the Cluster M26 prevents the Nose Fuze M111A2 from arming correctly, and therefore the fuze has been modified by the substitution of an anemometer-type arming vane for the standard vane.  So modified, the fuze is known as the T77.  Modification can be accomplished in the field by kits now being issued.








220-, 260-pound Frag. AN-M88 (220-lb) and AN-M81 (260-lb)

AN-M81
Overall length: 43.7 inches
Body length: 32.8 inches
Body diameter: 8 inches
Wall thickness: 1 inch
Tail length: 11 inches
Tail width: 11.5 inches
Tail weight: 4.1 pounds

Filling: Composition B
Weight of filling: 34.1 pounds
Total weight: 260 pounds
Charge/Weight ratio: 14%



AN-M88
Overall length: 43.7 inches
Body length: 32.8 inches
Body diameter: 8 inches
Wall thickness: 1.25 inches
Tail length: 11 inches
Tail width: 11.5 inches
Tail weight: 4.1 pounds

Filling: Composition B
Weight of filling: 46.9 pounds
Total weight: 216.17 pounds
Charge/Weight ratio: 21.6%


Construction: The Fragmentation Bomb AN-M88 differs from the M81 only in that it has a 0.75-inch steel coil steel coil around the body instead of the one-inch coil.  Both bombs are constructed in these two ways.  In initial production, nose and tail pieces are of cast-steel construction and screw onto a central section of seamless steel tubing.  A square helical steel spring is wound around the steel tubing.  The nose and tail pieces are partially cut through to afford greater fragmentation (this is similar to the M82, except for the provision for tail fuzes and the Auxiliary Booster M104 in the larger bombs).  The majorite of AN-M88's and M81's however, have a one-piece steel tubing, and the helical steel spring is wound around the steel tubing, for the entire length of the body.

Suspension is horizontal; two eyebolts are welded to body along the longitudinal axis of the bomb, 14 inches apart.  A third eyebolt is welded to the body at the center of gravity 180 degrees removed from the other eyebolts.  The tail is the normal box type, secured to the bomb by a locking ring.


Remarks: The initial bombs were filled with TNT; later productions are filled with Composition B with TNT surrounds.

Present production of these bombs does not include Auxiliary Booster M104, as this was found unnecessary.

Next Time: Army Experimental Types, and Introduction for Chemical, Incendiary, and Smoke Bombs

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.

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