Monday, 13 February 2017

British Explosive Ordnance - Aircraft Pyrotechnics Part 2

British Explosive Ordnance


Smoke Float No.1 Mks II, III, IV, and IVZ (Service)

Overall length: 22 inches
Body diameter: 6 inches
Total weight: 11.5 pounds
Burning time: 6 minutes
Color of smoke: White

Fuzing: Tail Pistol No.23

Color and markings: Body, head, and nose painted green,
tail cone vanes and strut painted yellow,
red ring 1/2-inch wide around head near nose.

Description: The Smoke Float No. 1 Mk IV comprises a cylindrical body, closed at one end by a conical head and a heavy nose.  A retarding band is secured to the body adjacent to the head.  A tail cone, carrying three vanes to support the vane ring, is secured to the opposite end of the body.  The end of the tail cone houses a pistol adapter for the tail pistol, which is locked in place by a grub screw.  Inserted in the pistol adapter is a cup, containing a cartridge base and a small quantity of flash composition, sealed with a paper disc.  A sleeve leads from the bottom of the pistol adapter into the funnel-shaped upper end of the tube, known as the container cap tube. 

The container for the smoke composition has a fusible cup inserted into the top of the smoke composition, which is filled with pressed priming composition, and a primed cambric disc through which is threaded a length of quickmatch.  The cylinder, provided with a ring of holes, surrounds the container.  The rest of the body and the tail cone comprise a buoyancy chamber.  The tail cone is provided with a sinking disc, which is scored, so that if a floating smoke float is found, the disc can be easily pierced to sink the float, the water entering the tail cone and passing into the body through the holes in the central cylinder.

Functioning: When the fuzed smoke float has been dropped from the aircraft, impact of the nose on the surface of the water causes the striker of the pistol to hit the cartridge base, and the ensuing flash ignites the flash composition.  The flash from the flash composition passes down the container cap tube and ignites the primed cambric disc and quickmatch, which ignite the primings.  The fusible cup melts, and the primings ignite the smoke composition.  Smoke rises up the container cap tube, and as the pressure increases, bursts the seal of the tail cone.  The short period between impact with the water and bursting of the seal is sufficient to enable the smoke float, after submerging, to rise to the surface, owing to its buoyancy.

Suspension: A suspension lug provided on the body permits attachment of the smoke float to a Light Series Bomb Carrier.

Remarks: In the Float No.1 Mk II, the container cap tube serves only to carry smoke from the container to the sealed hole in the tail cone.  A length of safety fuze, giving a 20-sec delay, extends between the pistol adapter and the container.  In the Float No.1 Mk III, the container cap tube also serves only to carry the smoke from the container to the sealed hole in the tail cone.  A separate flash tube guides the flash from the flash composition to the container.  The Float No.1 Mk IVZ differs from the Float Mk IV only in the nature of the smoke composition used.

Should water, especially salt water, come into contact with the smoke composition, it is liable to spontaneous combustion due to chemical action.

Smoke Float No.2 Mks I and II (Obsolete)

Overall length: 45.5 inches
Body diameter: 13 inches
Total weight: 108 pounds (empty)
Duration of burning: 8-10 minutes

Fuzing: Tail Pistol No.48

Color and markings: Green overall, red band around nose, yellow band around tail.

Description: This float consists of a cylindrical body with a rounded nose containing the smoke composition.  The nose piece is riveted to a metal band passing around the body at the joint.  The rest of the body is cylindrical and contains a central well filled with primed cambric.  At the after end of the central well is the pistol well.  The body has several internal stiffening rings.

Functioning: When the fuzed float is dropped, the striker overcomes the creep spring on water impact, and fires a detonator located below the pistol in the pistol well.  The flash is carried to the smoke composition in the nose of the float by means of the primed cambric in the central well.

Suspension: The float is suspended by means of a single lug attached near the nose.

Remarks: The Float No.2 Mk I has its forward end reduced in diameter about 1 and 1/2-inch for a distance of about one foot.


Smoke Float No.3 Mk I (Obsolescent)

Overall length: 10.1 inches
Body diameter: 6.7 inches by 4.95 inches
Filling: Calcium magnesium phosphide
Color of smoke: Red

Duration of burning: 40 seconds

Fuzing: Pull-percussion igniter

Color and markings: Upper half of body is yellow,
lower half of body is green, with red band 1/2-inch wide 2 inches from bottom.

Description: The float consists of a thin metal body at the upper end of which six smoke-emission holes, covered by a fabric seal, are located.  A wire gauze washer, held in place by an upper and lower liner, divides the body into two portions, the upper portion comprising a buoyancy chamber, and the lower portion housing a number of large and small smoke pellets disposed around a pull-percussion igniter.  The large smoke pellets are arranged in tiers.  The pellets in the upper tier are each contained in a primed cambric cylinder.  Below the wire gauze washer, a primed cambric washer rests on the upper ends of the primed pellets, and strips of primed cambric cross over the igniter.  The igniter, which is secured to the body, includes a split-headed clutch which is movable lengthwise in the igniter body.  A whipcord becket is secured to the head of the clutch and threaded through a rubber disc.  The upper end of the clutch is sprung over one end of a striker, which is spring-loaded when the clutch is pulled out.  Opposite the free end of the striker is a percussion cap, and an anvil housed in an ignited plug screwed into the igniter body.  A length of safety fuse, enclosed in a tube, terminates in a capsule filled with igniter composition.

When the float is to be used, proceed as follows: Remove the adhesive tapes securing the covers and remove both covers.  Press in the center of the press-cap to release the cap, and then remove the cap.  Pull the whipcord becket and the clutch out of the float, and immediately throw the smoke float overboard to leeward.

Functioning: When the clutch is pulled out, the striker is released and fires the percussion cap.  The flash from the cap ignites the safety fuse, which fires the igniter composition in the capsule after a delay of not less than eight seconds.  The flash from the igniter composition is conveyed by the primed cambric strips and the primed cambric washer to the pellets in the upper tier.  The smoke produced raises the pressure in the buoyancy chamber until the pressure bursts the fabric seal, and the smoke escapes to the atmosphere through the smoke-emission holes.

Remarks: This smoke float is intended for use from an emergency dinghy after a forced landing has been made, to assist search planes.

Aluminum Sea Marker Mk I (Service)

Length: 4.5 inches
Width: 3.5 inches (square)
Weight: 1 pound

Fuzing: None; impact initiated

Color and markings: Aluminum overall

Description: The marker consists of a fragile, paper-side body of square cross section, fitted with wooden end pieces, and filled with aluminum powder.  The outside is coated with aluminum paint.  The body is surrounded by a loose cardboard sheath to protect it from damage while being handled.

Functioning: When the sea marker is dropped from a plane, the cardboard sheath separates from the marker, and the latter ruptures on impact with the sea, leaving a patch of aluminum powder floating on the surface.

Remarks: This marker contains no explosive.


Aluminum Sea Marker Mk III (Service)

Overall length: 23.12 inches
Body diameter: 4.4 inches
Total weight: 10.25 pounds

Fuzing: Simple impact striker

Color and markings: Aluminum overall

Description: The sea marker consists of a cylindrical tin-plate body and tail cone containing aluminum powder, and a detonator-burster charge, which explodes when the marker is dropped on the sea.  The body has an internal strengthening band near each end.  The tail cone is soldered to the body and carries the fnis to which a circular strut is secured.  At the other end, the body is closed by a steel diaphragm.  The diaphragm has a central opening, threaded to receive a plug, which carries a detonator-burster tube.  A nose is fitted to this diaphragm and secured in position by three set screws.  Screwed into the nose is a striker guide in which slides a striker needle, secured to a striker head which projects outside the nose.  When in its operative position, a transit safety pin engages with the striker head, preventing it from moving inwards.  A second safety pin is provided in the nose.  This pin is flanged and is spring-loaded outward, but normally is held in position by a split pin to which a withdrawal wire is secured.  A securing wire is passed through the eye of the split pin, around the head of the safety pin and the nose of the marker, and through a boring in the transit safety pin.

Functioning: When the sea marker has been prepared for use and dropped on the surface of the sea, impact of the striker head with the water drives the striker needle inwards and explodes the detonator-burster charge, which disrupts the body and tail cone and scatters the aluminum powder.

Aluminum Sea Marker Mk V (Service)

Overall length: 12.5 inches (telescoped); 20 inches (extended)
Body diameter: 3 inches
Total weight: 10 pounds

Fuzing: None; impact initiated

Color and markings: Aluminum overall

Description: The sea marker body has an inner case of sheet metal, the lower end of which is pressed on to a heavy, aperture head.  The aperture in the head is sealed by a paper disc and is traversed by a pin.  A circular retaining piece is secured to the upper end of the inner case.  Inside the inner case is a fabric bag containing aluminum powder, each end of the bag being tied with thread to close it.  The thread at the lower end of the fabric bag is passed around a pin, to hold the bag in contact with the head.  An outer case slides over the inner case.  At its upper end the outer case is closed by two millboard discs, and inside its lower end a circular retaining piece is secured to provide a stop to prevent its being withdrawn completely from the inner case.  A cutter is provided immediately below the millboard discs.  The cutter is a ring secured inside the outer case and cut across in four places at about 45 degrees.  The cut ends are bent up at right angles to form four sharp projections with the outer case.

Functioning: The head is the heaviest part of the marker and consequently will strike the water first when dropped.  Impact with the surface of the water breaks the paper disc sealing the aperture in the head.  Water enters this aperture and carries the fabric bag rearwards from the head, breaking the thread which anchors it to the pin and also ejecting the millboard discs sealing the aperture at the tail end of the outer case.  As the bag passes through this aperture it strikes the sharp projecting parts of the cutter, which slit it, releasing its contents.  As a result, a slick of aluminum powder is formed on the surface of the sea.

Remarks: This marker contains no explosive.

Smoke Generator No.6 Mks I and II (Service)

Overall length: 7.13 inches
Body diameter: 2.42 inches
Total weight: 1 pound
Emission time: 2 and 1/2 minutes
Smoke Color: Orange

Fuzing: Percussion igniter

Color and markings: Light green overall

Description: The generator consists of a cylindrical metal body containing smoke composition in a metal foil cup, a quantity of priming composition, and a length of quickmatch.  When prepared for use, a percussion igniter replaces the adapter plug.  A tail unit is formed integrally with the body, and the upper end of the body is closed by a lid.  The igniter consists of an igniter body, a striker supported above the cartridge base by a shear wire, and a safety pin.  The cartridge base includes a small quantity of cap composition located between a percussion cap and an anvil.

Functioning: The safety pin is removed just before the generator is dropped.  On impact the striker moves downwards, breaks the shear wire, and fires the cap composition in the cartridge base.  The flash from the cap composition ignites the quickmatch, which, in turn, ignites the priming composition in the adapter.  The priming composition ignites the igniter composition, which then ignites the smoke composition.  The heat due to the combustion of the smoke composition loosens the metal discs covering the smoke-emission holes in the top lid, and the pressure of the smoke forces the discs off the top lid, allowing the smoke to escape to the atmosphere.

Remarks: This smoke generator is designed to be dropped from an aircraft to enable the pilot to ascertain the direction of the wind on the ground before making an emergency landing.

Next Time: Cluster Projectiles Part 1

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