Arm Fire Initiators (AFIs) | PacSci EMC
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Arm Fire Initiators (AFIs).

Internal Arm Fire Initiators

PacSci EMC / Products / Arm Fire Initiators (AFIs)


Arm Fire Initiators are commonly divided into three types, Internal, External and Mechanical Pull.  They are designed to provide the output stimulus to initiate explosive transfer lines in a system.  This output stimulus can either be a single or dual event.  PacSci EMC provides several types of designed and qualified AFIs for aircraft Emergency Escape Systems (EESs) when a pilot and crew eject.  They have safety and operational features meeting a wide variety of customer requirements and environments.  These requirements also include human factors of the handles for arming and functioning AFIs in accordance with Mil-Std-1472.  PacSci EMC’s AFI’s include explosive loaded and inert designs.

The following paragraphs describe the functionality of internal and exteral AFIs as well as their typical installation into an aircraft.  Actual forces of unlocking and function of the AFIs is provided in a Table 13 that follows these descriptive paragraphs. Learn more about Mechanical Pull Initiators here.

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IAFI’s require two separate actions to be functioned.  First action is to unlock the firing mechanism.  This is accomplished by turning a handle / ring or depressing a bar / push button.  Once the firing mechanism is activated the IAFI is ‘armed’ to function.  To function the handle, it is either pulled or pushed.

Rotate to Unlock (Arm) & Pull to Function (Fire) Example

Rotate to Unlock (Arm) & Push to Function (Fire) Example

Press Button & Bar to Unlock (Arm) & Pull to Function (Fire) Examples

As the handles are pulled they translate out of the IAFI housing and concurrently compress a spring retained by a firing pin. As the handle translation approaches approximately 0.25-inch, the mechanism permits the firing pin hammer to unlock from the handle.  The compressed spring energy accelerates the firing pin or a hammer to firing pin configuration with sufficient force to be driven into and fire single or dual Percussion Primers (PPs).  In the case of explosive loaded handles the PPs are located as part of an internal transfer charge.  Output from the primers initiates a loaded shell of a prime explosive, normally Lead Azide, which in turn ignites an output detonating material, normally HNS.  Output from the HNS includes high heat and high velocity of a flyer-plate from the loaded shell that impacts an attached ETL, normally a SMDC or FCDC end fitting.  For an inert AFI, instead of an internal transfer charge the firing pin strikes the PP on the end of an attached RDCTL.  Output from the primer ignites the RDCTL’s Rapid Deflagration Material (RDM) loaded ETL tubing.

Internal Arm Fire Initiators are positioned for the aircrew to have easy access to activate them but doesn’t interfere with normal aircraft operations.  During ground maintenance safety pins are installed to prevent inadvertent activation by the ground crews.  Typical installation for an IAFI can be seen below.

EAFI’s are used by ground or rescue to initiate the CFS / TRS in order to extract crewmembers should they be incapacitated.  Different types of EAFI’s are shown below.





An EAFI also has two separate actions to fire it.  One of the major difference though is that a majority of EAFIs have a 10 to 15 foot cord / wire attached to them.  Other designs will extend the length of a handle as seen in Figure 34 above, C-17 EAFI or utilize the same exact unit for both internal and external operations like the AH-64.  The cord / wire permits the ground or rescue crew to be at a safe distance before activating the CFS / TRS.  In the case of an extended handle or same unit, the safe distance factor is accounted for by means of the installed location of the device.  When either the handle and cord / wire combination is pulled / pushed, the same sequence of events that the IAFI experience have the same set of actions to fire the unit.

EAFI’s can also be a combination of a separate cable assembly, routed to mechanical pull initiator.  As an example, the Alpha Jet and Mirage F-1 have Pull Rings & Thumb Handles located  in an outside access door and canopy frame respectively (see Figure 24).  They all have attached cables routed to a single initiator located on the aft cockpit cell for each aircraft.  This combination reduces the number of explosive devices required, reduces the volume required for mounting hardware and ensures the safety of the ground crew during an emergency function.

EAFI’s are position so that the ground and rescue crews have easy access to activate them at a safe distance.  They are normally installed from the outside through an access door / panel and into a cavity.  In many cases the method of securing the handle into this cavity may affect the cockpit as a pressure vessel and mounting provisions need to be taken into account if that’s the case.  Typical EAFI installations are shown below.




Need more information or have a specific requirement you would like us to meet?
Contact us at the link below, or for immediate assistance call 831.630.5402.

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Need more information or have a specific requirement you would like us to meet?
Contact us at the link below, or for immediate assistance call 888.995.5143.

Contact Us

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