Pyrotechnic devices and firing mechanisms for aircraft canopy jettison

Pyrotechnic devices and firing mechanisms for aircraft canopy jettison are disclosed herein. An example firing mechanism includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a primary charge disposed in the second bore, a closure disc between the second bore and the channel, and a firing pin assembly disposed in the first bore. The firing pin assembly includes a percussion primer and a firing pin piston including a piston body, a firing pin extending from the piston body, and a piercing pin extending from the piston body. In response to a firing signal, the firing pin piston is moved toward the primary charge such that the piercing pin punctures the closure disc and the firing pin engages the percussion primer to ignite the primary charge.

FIELD OF THE DISCLOSURE

This disclosure relates generally to aircraft and, more particularly, to pyrotechnic devices and firing mechanisms for aircraft canopy jettison.

BACKGROUND

Some known aircraft include an ejection system for ejecting a seat (along with a pilot) from a cockpit of the aircraft. Prior to ejecting the seat (along with the pilot), a canopy over the cockpit is jettisoned from the aircraft so that the seat (and/or the pilot) do not collide with the canopy during ejection. The aircraft includes a thrusting/unlatching system that quickly unlatches the canopy prior to initiating the launching of the canopy from the fuselage. This thrusting/unlatching system includes one or more pyrotechnic devices that provide fast, powerful actuations.

SUMMARY

An example firing mechanism for a pyrotechnic device disclosed herein includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a primary charge disposed in the second bore, a closure disc between the second bore and the channel, and a firing pin assembly disposed in the first bore. The firing pin assembly includes a percussion primer and a firing pin piston including a piston body, a firing pin extending from the piston body, and a piercing pin extending from the piston body. In response to a firing signal, the firing pin piston is moved toward the primary charge such that the piercing pin punctures the closure disc and the firing pin engages the percussion primer to ignite the primary charge.

An example pyrotechnic device disclosed herein includes a body defining a chamber, a piston disposed in the chamber, and a firing mechanism coupled to the body. The firing mechanism is to, when triggered, generate high pressure in the chamber to move the piston. The firing mechanism includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a firing pin assembly disposed in the first bore, a primary charge disposed in the second bore, and first and second closure discs welded to the housing to hermetically seal the primary charge in the second bore.

An example aircraft disclosed herein includes a forward fuselage defining a cockpit, a canopy removably coupled to the forward fuselage over the cockpit, and a pyrotechnic device to unlatch the canopy from the forward fuselage. The pyrotechnic device includes a firing mechanism. The firing mechanism includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a primary charge disposed in the second bore, a closure disc between the second bore and the channel, a percussion primer, and a firing pin piston including a piston body, a firing pin extending from the piston body, and a piercing pin extending from the piston body. The firing pin is a first distance from the percussion primer and the piercing pin is a second distance from the closure disc. The second distance being less than the first distance.

DETAILED DESCRIPTION

Disclosed herein are example firing mechanisms and example pyrotechnic devices incorporating such example firing mechanisms. The example pyrotechnic devices and firing mechanisms disclosed can be used on an aircraft canopy jettison system, for example. The example firing mechanisms disclosed herein have longer lifespans than known firing mechanisms, which reduces costs and maintenance associated with replacing and/or servicing the firing mechanisms.

Pyrotechnic devices are used in many applications. In general, pyrotechnic devices convert a small explosive or combustive force into a working force that can be used to move one or more objects. For example, some aircraft, such as fighter planes, include an ejection system that can be triggered to eject one or more pilots from a cockpit of the aircraft. Before ejecting the pilot(s), a canopy over the cockpit is jettisoned (removed) from the cockpit according to a jettison sequence. The canopy jettison system includes one or more pyrotechnic devices (e.g., a series of pyrotechnic devices). The pyrotechnic device(s), when triggered, can be used to provide a fast, powerful burst of motion to help unlock and/or launch canopy away from the fuselage.

Example pyrotechnic devices disclosed herein include a firing mechanism. The firing mechanism includes a primary charge (e.g., propellant) and a piston or firing pin assembly that can ignite the primary charge. The primary charge, when activated (e.g., ignited), provides a high pressure burst that is used to generate motion or working power. The primary charge material tends to deteriorate when exposed to atmospheric conditions. Therefore, known firing mechanisms attempt to seal the primary charge between two discs constructed of Mica, which is brittle enough to be ruptured during the ignition process. However, these known discs still allow leak paths to the atmosphere. Therefore, known firing mechanism devices have limited lifespans (e.g., only a few years) and must be removed, discarded, and replaced periodically. This lifespan can be shortened even further because of the harsh atmospheric conditions experienced during flight.

Disclosed herein are example firing mechanisms that include welded closure discs to seal the primary charge. In particular, the closure discs, which are constructed of metal (e.g., stainless steel), are welded to the housing of the firing mechanism. This enables the primary charge to be hermetically sealed in the body of the firing mechanism, thereby preventing or substantially limiting leak paths to the primary charge. As such, the example firing mechanisms have longer lifespans than known firing mechanisms.

The example firing mechanisms disclosed herein include a firing pin piston with a piercing pin that is used to puncture one of the welded closure discs during activation. This ensures the welded closure disc is ruptured or opened. This also eliminates the need for an ignition charge, which is commonly used in known firing mechanisms between the percussion primers and the primary charge. For example, when a firing signal is received (e.g., during a canopy jettison operation), the firing pin piston is moved toward the welded closed disc such that the piercing pin engages and punctures a hole in the welded closure disc. Further, the firing pin piston includes one or more firing pins that impacts one or more percussion primers, which creates a spark or hot byproducts that ignite the primary charge. In some examples, the distance between the piercing pin and the closure disc is less than the distance between the firing pin(s) and the percussion primer(s). As such, when the firing pin piston is fired, the piercing pin punctures a hole in the welded closure disc first, and then the percussion primer(s) are activated. This ensures there is a flow path for the spark or hot byproducts from the percussion primer(s) to ignite the primary charge.

Now turning to the figures,FIG.1illustrates an example aircraft100in which the examples disclosed herein can be implemented. In the illustrated example, the aircraft100includes a fuselage102, wings104, horizontal stabilizers106, vertical stabilizers108, and engines110(e.g., jet engines). In operation, the engines110generate thrust to propel the aircraft100forward while the wings104generate lift. The wings104, the horizontal stabilizers106, and/or the vertical stabilizers108can include movable control surfaces (e.g., ailerons, flaps, elevators, rudders, etc.) to maneuver the aircraft100while thrust is provided by the engines110. In other examples, the aircraft100can include more or fewer engines and/or more or fewer flight control surfaces.

In the illustrated example, the aircraft100includes a forward fuselage112(sometimes referred to as an aircraft forebody). The forward fuselage112defines a cockpit114. One or more persons (e.g., a pilot, a passenger, etc.) can sit in the cockpit114to operate and/or otherwise travel in the aircraft100. In this example, the cockpit114holds two persons. In other examples, the cockpit114may be designed to hold only one person or more than two persons. The person(s) sit in respective seats in the cockpit114.

In the illustrated example, the aircraft100includes a canopy116disposed over the cockpit114. The canopy116is at least partially constructed of transparent glass, plastic, or other material that enables the pilot(s) and/or passenger(s) to see out of the aircraft100. The canopy116is removably coupled to the forward fuselage112over the cockpit114and can be removed from the forward fuselage112during an ejection operation or sequence. In particular, the aircraft100includes an ejection system that can be used to eject the seat(s) from the aircraft100during a critical situation. Prior to ejecting the seat(s), the example ejection system jettisons the canopy116from the forward fuselage112. The example ejection system includes one or more pyrotechnic devices to jettison the canopy116away from the forward fuselage112. In particular, the pyrotechnic device(s) provide fast, powerful actuating means to unlatch and launch the canopy116away from the forward fuselage112. For example, the ejection system can include a canopy unlatch thruster and one or more rocker motors. The unlatch thruster, when activated, actuates a series of mechanisms to unlatch the canopy116from the forward fuselage112. Then, the rocket motors propel or launch the canopy116upward. The canopy unlatch thruster and/or the rocket motor can include and/or be activated by one or more pyrotechnic devices. Therefore, the example pyrotechnic devices disclosed herein can be used to unlatch the canopy116from the forward fuselage112prior to initiating the jettisoning of the canopy116away from the forward fuselage112. Example pyrotechnic devices are disclosed in further detail here.

In the illustrated example, the aircraft100is depicted as a type of fighter jet aircraft. However, the example pyrotechnic devices and firing mechanisms disclosed herein can be implemented in any other type of vehicle, such as other fixed wing aircraft (e.g., a commercial aircraft), non-fixed wing aircraft, and/or other types of vehicles (e.g., a car, a train, etc.). Further, the example pyrotechnic devices and firing mechanisms disclosed herein can be implemented in non-vehicular applications.

FIG.2is a cross-sectional view of an example pyrotechnic device200including an example firing mechanism202constructed in accordance with teachings of this disclosure. The pyrotechnic device200can also be referred to as a gas generator pyrotechnic device. The pyrotechnic device200, when activated or triggered, is used to move a working device. For example, the pyrotechnic device200can be part of the ejection system and used to unlock and/or launch the canopy116(FIG.1).

In the illustrated example, the pyrotechnic device200includes a body204. In this example, the body204includes a first body portion206coupled to a second body portion208via a collar210(e.g., a threaded collar). The first body portion206can be considered a manifold, and the second body portion208can be considered an actuator cylinder. In other examples, the body204can include more or fewer body portions. The second body portion208of the body204defines a chamber212. In the illustrated example, the pyrotechnic device200includes a piston214disposed in the chamber212, and a stem216coupled to the piston214and extending outward from the second body portion208. The stem216can be coupled to another structure or system used to unlock and/or launch the canopy116(FIG.1).

In the illustrated example, the firing mechanism202is coupled to and disposed in the body204. In particular, in this example, the firing mechanism202is partially disposed in each of the first body portion206and the second body portion208. In the illustrated example, a washer or spacer215is disposed above the firing mechanism202in the second body portion206. The firing mechanism202is clamped between the first body portion206and the second body portion208. Additionally or alternatively, in some examples the firing mechanism202is held in the body204via welding and/or threaded fastener(s). In the illustrated example, the pyrotechnic device200includes one or more seals217(e.g., o-rings) between the body204and the firing mechanism202. The seals217prevent or limit gas or other fluid from leaking past the firing mechanism202. The first body portion206defines a passageway218to the firing mechanism202. To activate the pyrotechnic device200, a firing signal is supplied to the passageway218. The firing signal can be a pressure signal (e.g., a burst of high pressure air). The firing signal activates or triggers the firing mechanism202. The firing mechanism202ignites a charge or propellant, which provides a high pressure pulse or burst into the chamber212. This high pressure moves the piston214and, thus, the stem216. As mentioned above, the stem216can be coupled to one or more structures or systems for unlocking and/or launching the canopy116(FIG.1). Therefore, when the firing mechanism202is triggered and the piston214is moved, the canopy116is unlocked and/or launched.

FIG.3is an enlarged cross-sectional view of the firing mechanism202. The firing mechanism202includes a body or housing300(which may also be referred to as a booster housing) having a first end302and a second end304opposite the first end302. The housing300defines a first bore306extending into the first end302, a second bore308extending into the second end304, and a channel310between the first bore306and the second bore308. Therefore, the first and second bores306,308and the channel310form a passageway or channel312between extending between the first and second ends302,304. In some examples, the housing300is constructed of metal, such as stainless steel. Additionally or alternatively, the housing300can be constructed of other materials (e.g., aluminum).

In the illustrated example, the firing mechanism202includes a primary charge314(which can also be referred to as a primary propellant charge) disposed in the second bore308. In some examples, the primary charge314includes titanium hydride potassium perchlorate (THPP). In other examples, the primary charge314can include other materials, such as zirconium potassium perchlorate (ZPP). The primary charge314can be installed or inserted into the second bore308from the second end304. To prevent air from leaking into the second bore308and potentially deteriorating the primary charge314, the primary charge314is hermetically sealed in the second bore308. In the illustrated example, the firing mechanism202includes a first closure disc316coupled to the housing300between the second bore308and the channel310and a second closure disc318coupled to the second end304over the second bore308. The first and second closure discs316,318are constructed of metal, such as stainless steel. In this example, the first and second closure discs316,318are welded to the housing300. For example, the first closure disc316can be welded to an inner surface320of the housing300between the second bore308and the channel310(e.g., at a shoulder between the second bore308and the channel310) and the second closure disc318can be welded to the second end304over the second bore308. As such, the primary charge314is hermetically sealed between the first and second closure discs316,318in the second bore308. This limits and/or prevents atmospheric air from leaking into the second bore308and potentially deteriorating the primary charge314. As such, the primary charge314has a longer life span or shelf life.

In the illustrated example, the firing mechanism202includes a firing pin assembly322disposed in the first bore306. The firing pin assembly322can be installed or inserted in the first bore306from the first end302. The firing pin assembly322is used to ignite or activate the primary charge314, as disclosed in further detail herein. The firing pin assembly322includes a body or housing324having a first end326and a second end328opposite the first end326. In some examples, the housing324of the firing pin assembly322is held in the housing300via the washer215(FIG.2), which is retained by the first body portion206(FIG.2). In the illustrated example, the firing mechanism202includes a seal330between the housing324of the firing pin assembly322and the housing300of the firing mechanism202. The seal330limits or prevents air leakage between the housings300,324(before firing) and also limits or prevents leakage of combustion gasses after the primary charge314is initiated.

In the illustrated example, the firing pin assembly322includes a firing pin piston332disposed in the housing324. The firing pin piston332includes a piston body334and a piercing pin336coupled to and extending downward from the piston body334. In this example, the piercing pin336is threadably coupled to the piston body334. In some examples, this allows for easy assembly, positioning, and installation. In other examples, the piercing pin336can be coupled to the piston body334via other techniques (e.g., welding, fasteners, etc.). In still other examples, the piercing pin336and the piston body334can be formed as a single unitary part or component (e.g., a monolithic structure). In some examples, the piercing pin336is constructed of metal, such as steel. In the illustrated example, the housing324of the firing pin assembly322defines an upper channel338in the first end326. The piston body334is disposed in and moveable (e.g., slidable) up and down in the upper channel338. In the illustrated example, one or more seals340(e.g., o-rings) are disposed between the piston body334and the housing324.

In the illustrated example ofFIG.3, the housing324of the firing pin assembly322also defines a central pin channel342between the upper channel338and the second end328. The piercing pin336is disposed in and moveable (e.g., slidable) in the central pin channel342. The housing324of the firing pin assembly322defines a first lower channel344and a second lower channel346that extend between the upper channel338and the second end328. In the illustrated example, the firing pin piston332includes a first firing pin348that extends from the piston body334into the first lower channel344and a second firing pin350that extends from the piston body334into the second lower channel346. In the illustrated example, the firing pin assembly322includes a first percussion primer352disposed in the first lower channel344and a second percussion primer354disposed in the second lower channel346. The central pin channel342is parallel to and between the first and second lower channels344,346. While in this example the firing pin assembly322includes two lower channels and two percussion primers, in other examples, the firing pin assembly322may only include one lower channel and one percussion primer.

In an example firing sequence, a pressurized signal is received on the top of the firing pin piston332. This creates a force the moves the firing pin piston332downward inFIG.3toward the primary charge314. As the firing pin piston332moves downward toward the primary charge314, the piercing pin336punctures or pierces the first closure disc316. This creates a hole or opening in the first closure disc316. At the same time or after, the first and second firing pins348,350of the firing pin piston332engage or impact the first and second percussion primers352,354. The percussion primers352,354activate (e.g., burst) to emit hot byproducts and/or a spark. The hot byproducts and/or spark travels through the channel310and through the hole created in the first closure disc316to the primary charge314. The primary charge314activates (e.g., ignites) and ruptures the second closure disc318. Therefore, in response to a firing signal, the firing pin piston332is moved toward the primary charge314such that the piercing pin336punctures the first closure disc316and the first firing pin348engages the first percussion primer352to ignite the primary charge314. The high pressure ignition byproducts from the primary charge314fill the chamber212(FIG.2) of the pyrotechnic device200(FIG.2), which moves the piston214(FIG.2).

Because the piercing pin336pierces or punctures the first closure disc316to provide a path for the ignition products, the example firing mechanism202does not include an ignition charge between the percussion primers352,354and the primary charge314as seen in known firing mechanisms. Such ignition charges are not retained in their own enclosures and therefore limit the life of the firing mechanism. Therefore, in the example firing mechanism202, all propellant material in the firing mechanism202is hermetically sealed or protected by the welded enclosure. This significantly increases the life span or shelf life of the example firing mechanism202compared to known firing mechanisms. This also reduces costs and weight associated with the firing mechanism202.

In the illustrated example ofFIG.3, the firing mechanism202includes a shear pin356that extends through the housing324and the firing pin piston332. The shear pin356holds the firing pin piston332in place until a sufficient force from a pressurized firing signal is created on the firing pin piston332. This prevents the firing pin piston322from pre-maturely moving in the housing324and accidently igniting the primary charge314. When a sufficient force is created on the firing pin piston332from the pressurized firing signal, this force causes the shear pin356to break, which allows the firing pin piston332to move downward in the housing324. Therefore, the firing pin piston332has a certain surface area (e.g., on the top side) on which the pressurized firing signal operates to (1) break the shear pin356and (2) move the firing pin piston332downward with enough force to puncture the first closure disc316. In some examples, the pressurized firing signal is about at least 450 pounds-per-square-inch (psi). In other examples, the pressurized firing signal may be greater than or less than 450 psi.

In the illustrated example, the distal ends of the first and second firing pins348,350have semi-circular nubs or protrusions358,360. In some examples, this shape results in an increased impact force per unit area (by reducing the area of contact) of the firing pin piston332on the percussion primers352,354. In other examples, the distal ends of the first and second firing pins348,350may have another shape or may be flat.

In the illustrated example, the piercing pin336has a barbed tip or end362. The barbed tip362is formed by a shaft364with a conical or pointed tip366. The widest part of the conical tip366is wider than the shaft364. As such, when the conical tip366punctures the first closure disc316, the conical tip366creates an opening that is larger than the shaft364. This creates a flow path between the shaft364and the first closure disc316for the spark from the percussion primers352,354to reach the primary charge314.

As shown inFIG.3, when the firing pin piston332is in the pre-fired position, the first firing pin348is spaced from the first percussion primer352by a first distance of D1. The second firing pin350is similarly spaced from the second percussion primer354by the first distance of D1. Further, the piercing pin336(e.g., the barbed tip362of the piercing pin336) is spaced from the first closure disc316by a second distance of D2. The second distance D2is less than the first distance D1. Therefore, when the firing pin piston332is moved toward the primary charge314(e.g., downward inFIG.3), the piercing pin336engages or punctures the first closure disc316before the first and second firing pins348,350engage the percussion primers352,354. This enables the piercing pin336to puncture the first closure disc316before the percussion primers352,354are ignited. Therefore, when the percussion primers352,354are triggered, the spark can travel to the primary charge314.

FIGS.4A-4Cillustrate an example sequence of firing the firing mechanism202in the pyrotechnic device200. Each ofFIGS.4A-4Cshows a perspective cross-sectional view of the pyrotechnic device200and the firing mechanism202and an enlarged callout of the first closure disc316of the firing mechanism202.

FIG.4Ashows the firing pin piston332in the pre-fired position. The shear pin356is intact, which holds the firing pin piston332in this position until a firing signal is received. As shown in the callout ofFIG.4A, the piercing pin336is spaced apart from the first closure disc316.

As shown inFIG.4B, when a firing signal is received, the pressure in the passageway218of the first body portion206creates a force on the firing pin piston332. The force on the firing pin piston332causes the shear pin356to break. As the firing pin piston332moves downward, the barbed tip362of the piercing pin336engages the first closure disc316. This punctures a hole or opening in the first closure disc316.

As shown inFIG.4C, the firing pin piston332continues to move downward until the first and second firing pins348,350of the firing pin piston332impact the first and second percussion primers352,354. When the first and second percussion primers352,354are impacted by the first and second firing pins348,350, the first and second percussion primers352,354activate. This creates a hot spark and/or hot byproducts that travel downward to the primary charge314. As shown in the callout inFIG.4C, the barbed tip362has passed through the first closure disc316, which creates an opening400. The opening is larger than the shaft364, which forms a forms a flow path for the hot spark or byproducts. The hot spark or byproducts ignite the primary charge314. The primary charge314ruptures the second closure disc318(FIG.3), which creates a high pressure burst in the chamber of the pyrotechnic device200.

From the foregoing, it will be appreciated that example apparatus have been disclosed that improve sealing of a primary propellant charge in a firing mechanism of a pyrotechnic device. This improved sealing significantly increases the lifespan of the firing mechanism, thereby reducing costs associated with maintenance and replacement of the firing mechanism. Examples disclosed herein also provide an improved manner for puncturing a closure disc to ensure the primary charge is ignited.

Example methods, apparatus, systems, and articles of manufacture are disclosed herein. Further examples and combinations thereof include the following:

Example 1 is a firing mechanism for a pyrotechnic device. The firing mechanism comprises a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a primary charge disposed in the second bore, a closure disc between the second bore and the channel, and a firing pin assembly disposed in the first bore. The firing pin assembly includes a percussion primer and a firing pin piston including a piston body, a firing pin extending from the piston body, and a piercing pin extending from the piston body. In response to a firing signal, the firing pin piston is moved toward the primary charge such that the piercing pin punctures the closure disc and the firing pin engages the percussion primer to ignite the primary charge.

Example 2 includes the firing mechanism of Example 1, wherein the closure disc is welded to the housing.

Example 3 includes the firing mechanism of Example 2, wherein the closure disc is a first closure disc, the firing mechanism further including a second closure disc welded to the housing such that the primary charge is hermetically sealed between the first and second closure discs.

Example 4 includes the firing mechanism of any of Examples 1-3, wherein the closure disc is constructed of metal.

Example 5 includes the firing mechanism of any of Examples 1-4, wherein, when the firing pin piston is in a pre-fired position, the firing pin is a first distance from the percussion primer and the piercing pin is a second distance from the first closure disc, the second distance being less than the first distance, such that when the firing pin piston is moved toward the primary charge, the piercing pin punctures the closure disc before the firing pin engages the percussion primer.

Example 6 includes the firing mechanism of any of Examples 1-5, wherein the piercing pin has a barbed tip.

Example 7 includes the firing mechanism of any of Examples 1-6, wherein the piercing pin is threadably coupled to the piston body.

Example 8 includes the firing mechanism of any of Examples 1-7, wherein the percussion primer is a first percussion primer and the firing pin is a first firing pin. The firing pin assembly further includes a second percussion primer. The firing pin piston has a second firing pin extending from the piston body, such that when the firing pin piston is moved toward the primary charge the second firing pin engages the second percussion primer.

Example 9 includes the firing mechanism of Example 8, wherein the housing defines a first lower channel, a second lower channel, and a central pin channel. The first percussion primer is disposed in the first lower channel, the second percussion primer is disposed in the second lower channel, and the piercing pin is disposed in the central pin channel. The central pin channel is parallel to and between the first and second lower channels.

Example 10 includes the firing mechanism of any of Examples 1-9, wherein the firing mechanism does not include an ignition charge between the percussion primer and the primary charge.

Example 11 is a pyrotechnic device comprising a body defining a chamber, a piston disposed in the chamber, and a firing mechanism coupled to the body. The firing mechanism is to, when triggered, generate high pressure in the chamber to move the piston. The firing mechanism includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a firing pin assembly disposed in the first bore, a primary charge disposed in the second bore, and first and second closure discs welded to the housing to hermetically seal the primary charge in the second bore.

Example 12 includes the pyrotechnic device of Example 11, wherein the first closure disc is welded to an inner surface of the housing defining the second bore.

Example 13 includes the pyrotechnic device of Example 12, wherein the second closure disc is welded to an end of the housing over the second bore.

Example 14 includes the pyrotechnic device of any of Examples 11-13, wherein the firing pin assembly includes a firing pin piston including a piercing pin to puncture the first closure disc when the firing pin piston is moved toward the primary charge.

Example 15 includes the pyrotechnic device of Example 14, wherein the piercing pin has a barbed tip.

Example 16 includes the pyrotechnic device of Examples 14 or 15, wherein the firing pin piston includes a piston body, the piercing pin coupled to and extending from the piston body.

Example 17 includes the pyrotechnic device of Example 16, wherein the firing pin assembly includes a percussion primer, and wherein the firing pin piston includes a firing pin extending from the piston body. The firing pin is to engage the percussion primer when the firing pin piston is moved toward the primary charge.

Example 18 is an aircraft comprising a forward fuselage defining a cockpit, a canopy removably coupled to the forward fuselage over the cockpit, and a pyrotechnic device to unlatch the canopy from the forward fuselage. The pyrotechnic device includes a firing mechanism. The firing mechanism includes a housing defining a first bore, a second bore, and a channel between the first bore and the second bore, a primary charge disposed in the second bore, a closure disc between the second bore and the channel, a percussion primer, and a firing pin piston including a piston body, a firing pin extending from the piston body, and a piercing pin extending from the piston body. The firing pin is a first distance from the percussion primer and the piercing pin is a second distance from the closure disc. The second distance is less than the first distance.

Example 19 includes the aircraft of Example 18, wherein the closure disc is welded to the housing.

Example 20 includes the aircraft of Examples 18 and 19, wherein the piercing pin has a barbed tip.