British Explosive Ordnance
Aircraft Pyrotechnics Introduction
This chapter includes data on flame floats, marine markers, smoke floats, sea markers, and smoke generators dropped from aircraft.
Flame floats and marine markers are devices designed to give off a flame to illuminate surrounding areas of water. Generally calcium phosphide is used as the filler for flame floats. When moistened, this chemical gives off phosphine, a gas spontaneously inflammable on contact with air.
Smoke floats generate smoke by the combustion of a smoke-composition filler. The smoke so produced may be used for indicating a position, for obscurement, or for signalling. Although all smoke floats are designed primarily for use at sea, they differ from each other in construction and design according to the purpose for which the smoke is intended. There are three essential types of smoke floats in use, one fore each of the following purposes: to mark a position at sea for navigational or bombing purposes; to create a smoke screen; and to be thrown by hand from a plane or dinghy to attract attention following a forced landing.
Sea markers are designed to be dropped at sea to produce a distinctive surface patch on the water readily visible from the air in daylight for purposes of navigation or identification. Generally, aluminum powder with stearic acid is used as the filling to form a slick.
Smoke generators are designed to emit smoke, sometimes colored, upon ignition of their filling. Only one type of generator is discussed, since it is the only one intended to be dropped from aircraft in flight.
Navigation Flame Float Mk I (Obsolescent)
Overall length: 17 inches (Extended); 8 inches (Collapsed)
Body diameter: 3.7 inches
Filling: Calcium Phosphide
Filling weight: 2 pounds
Total weight: 3.2 ounces
Burning time: 5 minutes
Body diameter: 3.7 inches
Filling: Calcium Phosphide
Filling weight: 2 pounds
Total weight: 3.2 ounces
Burning time: 5 minutes
Fuzing: Non; water initiated
Color and markings: Cylinder painted red with yellow label on lid.
Description: The float consists of a cylindrical tin-plate canister with a tin-plate lid, having a central aperture, soldered over the top of the canister, and a slotted brass sealing patch soldered over the aperture. Soldered to the lid is an iron gauze tube, which extends axially nearly to the bottom of the canister, and is closed at its lower end. The annular space outside the gauze tube is filled with granular calcium phosphide. At its base the canister is closed by a cap, which fits over its outside.
The canister is surrounded by an outer fabric bag, which is considerably longer than the canister. Secured by a double row of stitching inside the outer fabric bag and above the canister, is a second fabric bag, termed the inner fabric bag. Two eyelets are located above the top of the canister in the walls of the inner and outer fabric bags at different levels. The pull-off line passes through the aperture in the leather patch at the top of the inner fabric bag and through the neck of the outer fabric bag. The aperture has a fairly snug fit on the line.
Functioning: When the flame float has been prepared for use by removing the brass sealing patch and has been dropped into the sea, water enters the canister through the aperture in its lid and passes through the eyelets. The water enters the gauze tube, through which it penetrates into the calcium phosphide filling. Phosphine is then evolved, inflating the inner fabric bag, and providing sufficient buoyancy to bring the flame float to the surface of the sea. The gas escapes from the neck of the outer fabric bag, and takes fire spontaneously on contact with the air, producing a highly luminous flame.
Remarks: The flare may be dropped from any height and gives a reasonably steady and bright flame for about five minutes. A flame continues for an additional 15 minutes, but it becomes increasingly feeble and intermittent. If the sealing patch of the canister has been removed, the flame float must be dropped or removed to a safe place for disposal.
The canister is surrounded by an outer fabric bag, which is considerably longer than the canister. Secured by a double row of stitching inside the outer fabric bag and above the canister, is a second fabric bag, termed the inner fabric bag. Two eyelets are located above the top of the canister in the walls of the inner and outer fabric bags at different levels. The pull-off line passes through the aperture in the leather patch at the top of the inner fabric bag and through the neck of the outer fabric bag. The aperture has a fairly snug fit on the line.
Functioning: When the flame float has been prepared for use by removing the brass sealing patch and has been dropped into the sea, water enters the canister through the aperture in its lid and passes through the eyelets. The water enters the gauze tube, through which it penetrates into the calcium phosphide filling. Phosphine is then evolved, inflating the inner fabric bag, and providing sufficient buoyancy to bring the flame float to the surface of the sea. The gas escapes from the neck of the outer fabric bag, and takes fire spontaneously on contact with the air, producing a highly luminous flame.
Remarks: The flare may be dropped from any height and gives a reasonably steady and bright flame for about five minutes. A flame continues for an additional 15 minutes, but it becomes increasingly feeble and intermittent. If the sealing patch of the canister has been removed, the flame float must be dropped or removed to a safe place for disposal.
Navigational Flame Float Mk II, and No.4 Mk I,
and Message Carrying Flame Float Mk I(Service)
and Message Carrying Flame Float Mk I(Service)
Overall length: 23.4 inches
Body diameter: 5.9 inches
Filling: Calcium Phosphide
Filling weight: 1.8 pounds
Total weight: 11.8 pounds
Body diameter: 5.9 inches
Filling: Calcium Phosphide
Filling weight: 1.8 pounds
Total weight: 11.8 pounds
Effective illumination: 6 minutes
Fuzing: Integral striker mechanism
Fuzing: Integral striker mechanism
Color and markings: Body, strut supports, strut, and protecting cap painted red,
tail cone painted yellow.
tail cone painted yellow.
Description: The Flame Float Mk II consists of two main parts, a body and a container. The body is a cylindrical casting, to one end of which three strut supports are riveted. A cylindrical strut is riveted to the supports. Secured to the fin by a securing wire is a punch to which is attached an instruction tag. The body is thickened at the nose end, and has an attached conical nose of thin sheet steel. A protecting cap is fitted over the nose, and a safety pin passes through holes in both the cap and nose.
The container consists of a sheet-metal cylinder, to one end of which is attached a sheet-metal tail cone. The opposite end of the container is closed by a cap. The cap is apertured and carried a correspondingly apertured spigot and a wire gauze socket on the side facing the tail cone. Passing axially along the container is a central tube, one end of which is soldered to the narrow end of the tail cone, while the other end fits into the socket. Near the tail end, the tube is closed by a sealing cup, projecting from which is a punch sleeve closed by a paper cap. On the side opposite the spigot the cap carries a diaphragm, which retains a striker. The striker is bored to receive the safety pin.
The lower part of the container is filled with granular calcium phosphide, which is held in position by a closing disc. This material surrounds the slotted portion of the central tube. Beyond the closing disc the annular space between the container and the central tube forms a sealed buoyancy chamber.
Functioning: Before the float is dropped, the punch is removed from the strut by cutting the securing wire, and the sealing cup on the punch sleeve is punctured with it. After the sealing cup has been broken, the flame float must be dropped from the aircraft immediately.
On dropping from an aircraft, impact with the water crushes the nose of the float and causes the striker to penetrate the sealing disc. At the same time the securing wires holding the container to the body are broken, and the container and tail cone are forced away from the body. The buoyancy chamber maintains the tail cone uppermost in the water. Water enters the aperture in the cap, and passes through the gauze socket and the slots in the central tube into the calcium phosphide. The phosphine generated on entry of the water passes upwards through the central tube, from which it emerges through the hole pierced by the punch through the sealing cup, and, on contact with the air, takes fire spontaneously.
Remarks: The inner body of the Navigation Flame Float No.4 Mk I is identical to the inner body of the Float Mk II.
The Message Carrying Flame Float Mk I is almost identical to the Navigational Flame Float Mk II in dimensions and construction. The essential difference is that a message container is suspended in the buoyancy chamber by a fixing wire secured to a plug, which is screwed into a bush in the tail cone. The plug is provided with a handle to facilitate its removal from the bush, and a washer on the plug insures a water-tight joint. An arrow and the words, MESSAGE HERE, are painted on the tail cone to direct attention to the message.
The container consists of a sheet-metal cylinder, to one end of which is attached a sheet-metal tail cone. The opposite end of the container is closed by a cap. The cap is apertured and carried a correspondingly apertured spigot and a wire gauze socket on the side facing the tail cone. Passing axially along the container is a central tube, one end of which is soldered to the narrow end of the tail cone, while the other end fits into the socket. Near the tail end, the tube is closed by a sealing cup, projecting from which is a punch sleeve closed by a paper cap. On the side opposite the spigot the cap carries a diaphragm, which retains a striker. The striker is bored to receive the safety pin.
The lower part of the container is filled with granular calcium phosphide, which is held in position by a closing disc. This material surrounds the slotted portion of the central tube. Beyond the closing disc the annular space between the container and the central tube forms a sealed buoyancy chamber.
Functioning: Before the float is dropped, the punch is removed from the strut by cutting the securing wire, and the sealing cup on the punch sleeve is punctured with it. After the sealing cup has been broken, the flame float must be dropped from the aircraft immediately.
On dropping from an aircraft, impact with the water crushes the nose of the float and causes the striker to penetrate the sealing disc. At the same time the securing wires holding the container to the body are broken, and the container and tail cone are forced away from the body. The buoyancy chamber maintains the tail cone uppermost in the water. Water enters the aperture in the cap, and passes through the gauze socket and the slots in the central tube into the calcium phosphide. The phosphine generated on entry of the water passes upwards through the central tube, from which it emerges through the hole pierced by the punch through the sealing cup, and, on contact with the air, takes fire spontaneously.
Remarks: The inner body of the Navigation Flame Float No.4 Mk I is identical to the inner body of the Float Mk II.
The Message Carrying Flame Float Mk I is almost identical to the Navigational Flame Float Mk II in dimensions and construction. The essential difference is that a message container is suspended in the buoyancy chamber by a fixing wire secured to a plug, which is screwed into a bush in the tail cone. The plug is provided with a handle to facilitate its removal from the bush, and a washer on the plug insures a water-tight joint. An arrow and the words, MESSAGE HERE, are painted on the tail cone to direct attention to the message.
Navigational Flame Float No.3 Mk I (Obsolescent) and No.3 Mk II (Service)
Overall length: 18.5 inches
Body diameter: 2.9 inches
Filling: Calcium magnesium phosphide
Body diameter: 2.9 inches
Filling: Calcium magnesium phosphide
Total weight: 2.5 pounds
Effective illumination: 5 minutes
Fuzing: None; water initiated
Effective illumination: 5 minutes
Fuzing: None; water initiated
Color and markings: Yellow overall
Description: The Flame Float No.3 Mk I has a cylindrical tinplate body, the after end of which has four attached tail fins. The tail end of the body is closed by a tail cover having a central hole. The neck of the tail cap is closed by a thin rupture disk to which is secured a small pillar having a ring passing through it. The forward end of the body is closed by a cast-iron nose having a central water-inlet hole. The nose is contained in a tin-plate cover, having a central hole covered by a tear-off seal to which is secured either a ring or an eyelet. Inside the body is a perforated zinc central tube surrounded by a swansdown bag containing calcium magnesium phosphide. Cotton wool is packed around the tail end of the bag, and a layer of glass wool is located between the bag and the iron wire gauze. The charcoal is provided to absorb any slight traces of gas which may be given off while the flame float is in storage. The tail end of the body comprises the buoyancy chamber of the flame float.
Functioning: Before dropping, the tear-off seal at the nose is removed. When dropped, the tail rupture disc is broken and the float rises to the surface. Water enters through the water-inlet hole in the nose, passes through the perforated zinc tube, and soaks through the flannel finger into the swansdown bag, where it reacts with the calcium magnesium phosphide to give off spontaneously inflammable phosphine. The phosphine, so generated, escapes through the broken rupture disc and takes fire on contact with fire.
Remarks: Should either of the seals be broken while in storage, the damaged flame float must be removed to a dry place where the possibility of its catching afire is an acceptable risk pending final disposal.
The Float Mk II differs from the Mk I in that a rear seal and tear-off cord are substituted for the tail rupture assembly of the Mk I. The long perforated tube of the Mk I is considerably shortened in the Mk II.
Functioning: Before dropping, the tear-off seal at the nose is removed. When dropped, the tail rupture disc is broken and the float rises to the surface. Water enters through the water-inlet hole in the nose, passes through the perforated zinc tube, and soaks through the flannel finger into the swansdown bag, where it reacts with the calcium magnesium phosphide to give off spontaneously inflammable phosphine. The phosphine, so generated, escapes through the broken rupture disc and takes fire on contact with fire.
Remarks: Should either of the seals be broken while in storage, the damaged flame float must be removed to a dry place where the possibility of its catching afire is an acceptable risk pending final disposal.
The Float Mk II differs from the Mk I in that a rear seal and tear-off cord are substituted for the tail rupture assembly of the Mk I. The long perforated tube of the Mk I is considerably shortened in the Mk II.
Marine Marker Mk I (Obsolescent)
Overall length: 26.8 inches
Body diameter: 5.8 inches
Filling: Aluminum and magnesium phosphides
Body diameter: 5.8 inches
Filling: Aluminum and magnesium phosphides
Total weight: 16 pounds
Effective illumination: 2 hours
Fuzing: None; water initiated
Effective illumination: 2 hours
Fuzing: None; water initiated
Color and markings: Body and nose red. Tail and tail cap yellow.
Description: The marker consists of a light metal body and tail, which are separated by a diaphragm. The tail is closed by a metal plate, having a tail cap connected to the main outlet tube. The forward end of the body is closed by a heavy metal plate into which are set two water-inlet valves. A tube passes from the central valve, through the filling and spring-loaded pressure plate, and almost to the diaphragm. The pilot tube extends aft from the off-centre valve to the pressure plate. The pilot outlet tube then continues to a strainer attached to the diaphragm from which the main outlet tube issues. The pressure plate retains the main filling in the forward part of the body.
Functioning: When the marker has been prepared for use and dropped into water, the water jacket fills and the scalloped disc in the main valve and the large disc in the pilot valve are forced against the ledges in the valves, thus preventing too great an ingress of water while it is submerged. Some water, however, enters the main outlet tube, passes through the pressure plate, and reacts with the calcium phosphide. This reaction evolves impure phosphine gas, which ignites spontaneously when the marker surfaces. As it surfaces, the pressure against the valves is relaxed, and the springs return the discs against the circlips, thus permitting the ingress of water though the scallops in the disc to the bottom of the inlet tube and pilot tube. The water entering the main valves passes through the inlet tube into the perforated tube, and after passing through the perforated diaphragm percolates through the flannel sheath and reacts with the main charge to give off pure phosphine, which is not spontaneously inflammable. The cap over the free end of the perforated tube prevents the water from percolating through the part of the flannel sheath above the pressure plate.
The water entering the pilot valve percolates through the flannel disc and dissolves the potassium bisulphate and the sodium nitrite. The chemicals interact and evolve gaseous oxides of nitrogen which mix with the phosphine in the strainer. The mixed gases are spontaneously inflammable in air, and, passing through the main outlet tube, ignite immediately on reaching the air. The flame thus produced continues to burn evenly for approximately two hours, during the whole of which time the gases remain spontaneously inflammable, so that even if the flame is put out by a wave, it lights up again as soon as contact with air is re-established.
Remarks: The flame is visible in daylight over a distance of at least three miles, and at night over a distance of about 20 miles. White smoke is given off with the flame. In damp atmosphere, after removal of the over-seals and press-caps, this marker evolves spontaneously inflammable phosphine, and for this reason should be prepared for use only just before it is to be launched.
Functioning: When the marker has been prepared for use and dropped into water, the water jacket fills and the scalloped disc in the main valve and the large disc in the pilot valve are forced against the ledges in the valves, thus preventing too great an ingress of water while it is submerged. Some water, however, enters the main outlet tube, passes through the pressure plate, and reacts with the calcium phosphide. This reaction evolves impure phosphine gas, which ignites spontaneously when the marker surfaces. As it surfaces, the pressure against the valves is relaxed, and the springs return the discs against the circlips, thus permitting the ingress of water though the scallops in the disc to the bottom of the inlet tube and pilot tube. The water entering the main valves passes through the inlet tube into the perforated tube, and after passing through the perforated diaphragm percolates through the flannel sheath and reacts with the main charge to give off pure phosphine, which is not spontaneously inflammable. The cap over the free end of the perforated tube prevents the water from percolating through the part of the flannel sheath above the pressure plate.
The water entering the pilot valve percolates through the flannel disc and dissolves the potassium bisulphate and the sodium nitrite. The chemicals interact and evolve gaseous oxides of nitrogen which mix with the phosphine in the strainer. The mixed gases are spontaneously inflammable in air, and, passing through the main outlet tube, ignite immediately on reaching the air. The flame thus produced continues to burn evenly for approximately two hours, during the whole of which time the gases remain spontaneously inflammable, so that even if the flame is put out by a wave, it lights up again as soon as contact with air is re-established.
Remarks: The flame is visible in daylight over a distance of at least three miles, and at night over a distance of about 20 miles. White smoke is given off with the flame. In damp atmosphere, after removal of the over-seals and press-caps, this marker evolves spontaneously inflammable phosphine, and for this reason should be prepared for use only just before it is to be launched.
Marine Marker Mk II (Service)
Overall length: 30 inches
Body diameter: 5.8 inches
Filling: Magnesium-aluminum phosphide
Body diameter: 5.8 inches
Filling: Magnesium-aluminum phosphide
Total weight: 19 pounds
Burning time: 2 hours
Fuzing: None; water initiated
Burning time: 2 hours
Fuzing: None; water initiated
Color and markings: Body and nose transit cover painted red,
tail, tail cap, and tail transit cap painted yellow.
tail, tail cap, and tail transit cap painted yellow.
Description: The marker consists of a body with a steel nose at one end, having a central hole closed by a stopper which forms part of a thin bakelite disc secured to the nose by screws. The disc is protected during transit and storage by a nose transit cover held in position by adhesive tape. The tail constitutes a buoyancy chamber, and a main outlet tube extends between the diaphragm and a tail cap at the outer end of the tail. The tail cap has a neck closed by a thin rupture disc, to which is secured a small pillar having a ring attached to it. Two locating pieces, secured to the outside of the body, are provided to locate a suspension band in position if the marker is to be carried on a Light Series Bomb Carrier.
Functioning: When it is dropped into water, the bakelite disc is broken by impact with the water; the stopper falls away and the marker rises to float on the surface. Water enters the central hole in the nose, and after passing through the gauze thimble, some of it soaks through the flannel washer, passes through the small hole in the valve body, and enters the brass tube after soaking through the flannel washer in the tube. The remainder of the water passes through the water-inlet tube, percolates through the open-mesh metallic cylinder and its flannel sheath, and enters the body of the marker. The brass cap prevents water from passing through the sheath and coming into direct contact with the calcium phosphide. The water which enters through the nose reacts with the magnesium-aluminum phosphide and gives off pure phosphine, which is not spontaneously inflammable. Some water, however, passes down the main outlet tube while the marker is submerged, and this water reacts with the calcium phosphide to produce phosphine which, in contact with the air, is spontaneously inflammable. The supply of spontaneously inflammable gas lasts only about three minutes, and the flame is thereafter maintained by the phosphine evolved from the magnesium-aluminum phosphide mixing with the gaseous oxides of nitrogen given off by the interaction of the potassium bisulphate and the sodium nitrite, which are dissolved by some of the water which enters through the nose.
Functioning: When it is dropped into water, the bakelite disc is broken by impact with the water; the stopper falls away and the marker rises to float on the surface. Water enters the central hole in the nose, and after passing through the gauze thimble, some of it soaks through the flannel washer, passes through the small hole in the valve body, and enters the brass tube after soaking through the flannel washer in the tube. The remainder of the water passes through the water-inlet tube, percolates through the open-mesh metallic cylinder and its flannel sheath, and enters the body of the marker. The brass cap prevents water from passing through the sheath and coming into direct contact with the calcium phosphide. The water which enters through the nose reacts with the magnesium-aluminum phosphide and gives off pure phosphine, which is not spontaneously inflammable. Some water, however, passes down the main outlet tube while the marker is submerged, and this water reacts with the calcium phosphide to produce phosphine which, in contact with the air, is spontaneously inflammable. The supply of spontaneously inflammable gas lasts only about three minutes, and the flame is thereafter maintained by the phosphine evolved from the magnesium-aluminum phosphide mixing with the gaseous oxides of nitrogen given off by the interaction of the potassium bisulphate and the sodium nitrite, which are dissolved by some of the water which enters through the nose.
Marine Marker Mk III (Service)
Overall length: 36.8 inches
Body diameter: 6 inches
Filling: Magnesium-aluminum phosphide
Body diameter: 6 inches
Filling: Magnesium-aluminum phosphide
Total weight: 21 pounds
Burning time: 2 hours
Fuzing: None; water initiated
Burning time: 2 hours
Fuzing: None; water initiated
Color and markings: Blue grey overall
Description: The outer casing of this marker consists of a body and a tail which are connected by a diaphragm. A heavy nose is secured to the body. The nose has a cavity to receive the time valve, and a central hole at the bottom of the cavity which is closed by a transit plug. The valve is a clockwork device which permits the marker to remain in the water for a period up to six hours before it functions. The period of delay is determined by setting the valve before the marker is released from the aircraft. The main filling consists of magnesium-aluminum phosphide, and is packed round a gauze cylinder. Inside the gauze cylinder is a quantity of fast calcium phosphide, which also extends over the top of the magnesium-aluminum phosphide. The main filling is held in place by a thin steel plate having large holes covered by brass gauze, and a large spring anchored to a spring-supporting plate, which abuts against the diaphragm connecting the tail to the body of the weapon. A layer of charcoal is provided beneath the steel plate to absorb any small quantities of phosphine gas generated by traces of moisture which may be in the body of the marking during filling, and a layer of glass wool beneath the charcoal which acts as a dust filter. The tail constitutes a buoyancy chamber, and a main outlet tube extends between the diaphragm and a tail cap at the outer end of the tail.
Functioning: After entering the water, the marker rises to the surface and floats tail uppermost, water entering the nose cavity through the two small holes in the side of the nose. At the expiration of the delay set on the time valve, the Welvic plug sealing the hole in the side of the time valve is opened and the water passes through the time valve and the central hole at the bottom of the nose cavity, into the water inlet valve in the nose. Some of the water entering the water-inlet valve soaks through the flannel washer and passes through the small hole in the inlet valve into the brass tube to react with the filling in the brass tube. The remaining water, after dissolving the soluble disc covering the nut, passes upwards through the water-inlet tube, percolates through the coarse-mesh cylinder, the flannel sheath, and the fine-mesh cylinder, and enters the body of the marker. The brass cap prevents water from passing through that portion of the sheath which is above the fine-mesh cylinder.
The water passing through the fine-mesh cylinder, together with the small quantity which passes down the main outlet tube while the marker is submerged, reacts with the calcium phosphide in the gauze cylinder and covering the top of the main filling, to produce impure phosphine, which, in contact with air, is spontaneously inflammable. This supply of gas lasts only for a few minutes, and is thereafter maintained by the pure phosphine evolved from the magnesium-aluminum phosphide mixing with the gaseous oxides of nitrogen given off by the interaction of the potassium bisulphate and the sodium nitrite, which are dissolved by the water entering the brass tube.
Remarks: When breaking the rupture disc, do not hold the head directly over the tail cap of the marker. This avoids possibly injury to the eyes which might be caused should sufficient pressure be built up in the marker to force phosphide dust particles past the glass wool filter at the top of the main filling.
Functioning: After entering the water, the marker rises to the surface and floats tail uppermost, water entering the nose cavity through the two small holes in the side of the nose. At the expiration of the delay set on the time valve, the Welvic plug sealing the hole in the side of the time valve is opened and the water passes through the time valve and the central hole at the bottom of the nose cavity, into the water inlet valve in the nose. Some of the water entering the water-inlet valve soaks through the flannel washer and passes through the small hole in the inlet valve into the brass tube to react with the filling in the brass tube. The remaining water, after dissolving the soluble disc covering the nut, passes upwards through the water-inlet tube, percolates through the coarse-mesh cylinder, the flannel sheath, and the fine-mesh cylinder, and enters the body of the marker. The brass cap prevents water from passing through that portion of the sheath which is above the fine-mesh cylinder.
The water passing through the fine-mesh cylinder, together with the small quantity which passes down the main outlet tube while the marker is submerged, reacts with the calcium phosphide in the gauze cylinder and covering the top of the main filling, to produce impure phosphine, which, in contact with air, is spontaneously inflammable. This supply of gas lasts only for a few minutes, and is thereafter maintained by the pure phosphine evolved from the magnesium-aluminum phosphide mixing with the gaseous oxides of nitrogen given off by the interaction of the potassium bisulphate and the sodium nitrite, which are dissolved by the water entering the brass tube.
Remarks: When breaking the rupture disc, do not hold the head directly over the tail cap of the marker. This avoids possibly injury to the eyes which might be caused should sufficient pressure be built up in the marker to force phosphide dust particles past the glass wool filter at the top of the main filling.
Next Time: Aircraft Pyrotechnics Part 2
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