MILITARY AIRCRAFT EJECTION
Why use a canopy/transparency removal system?
When a military aircraft ejection is imminent, removing the canopy by jettison or fracturing is advisable to avoid the elevated levels of head and neck load on the aircrew member ejecting. Those higher head and neck loads can result in injury to the aircrew during ejection. Also, if choosing to go through the canopy, the canopy ‘glass’ material will be limited to either cast or stretch acrylic. Other materials like polycarbonate or laminates with acrylic and polycarbonate may increase the head and neck loads resulting in a higher potential for aircrew injury.
How is the canopy or hatch removed from the aircraft prior to the seat ejecting?
There are two main methods. The first is jettison. This is accomplished by either severing or unlocking the mechanism securing the canopy or hatch to the aircraft’s structure. Once released rocket motors or a thruster are used to move the canopy away from aircraft, creating a clear path for the ejection seat. The second method is canopy fracturing. This method is possible with canopies that are either acrylic (cast or stretched), polycarbonate (less than 0.3-inch) or acrylic/polycarbonate laminate. The canopy material is severed or fractured to open a clear escape path during seat ejection or emergency ground egress from the aircraft. This can be accomplished with Mild Detonating Cord (MDC), Flexible Linear Shaped Charge (FLSC) or Expanding Tube Assembly (XTA).
How are the seat and canopy sequenced to occur in the proper order?
Sequencing of the escape system is accomplished through a network of Explosive Transfer Lines, interconnected to ensure a specific sequence of events. Additional components, including but not limited to, Time Delay Initiators, One Way Initiators, Mechanical Pull Initiators, Seat Mode Selectors, Actuators, Pin Pullers and Gas Generators can be incorporated into system to execute a safe canopy / hatch removal and seat ejection in the proper sequence.
Is canopy fracturing better than canopy jettison?
Each has their advantages and disadvantages. The aircraft platform’s mission, configuration, flight parameters and many other factors will determine which method is best. One of the advantages of canopy fracturing is a faster sequence time with no delay waiting for the canopy to jettison.
Initial seat gas pressure (firing hot gas initiator) or upward movement (for mechanical pull initiator) starts the canopy fracturing sequence of events. Canopy jettison’s advantage is there are no pieces of the canopy material that could strike the aircrew. The canopy assembly is separated from the airframe of the aircraft and remains in one piece and seat ejection won’t occur until a defined time delay expires, ensuring the assembly is clear of the aircraft.
I have a hatch, not a canopy. Can you still provide a safe escape path for the ejection seat in my aircraft?
Yes, the method recommended for providing the escape path will depend on the specific hatch configuration. Some aircraft hatches open or close like other aircraft access panels or are secured to the structure with aircraft grade screws or bolts. In other circumstance, an area is designated to be removed to provide a clear path but is not a separate panel or hatch. This would be an area of the existing aircraft skin and hardware.
Hatch or panel assemblies can be liberated from the airframe by either severing a predetermined area with a linear cutting cord, using a thruster to move a latch to the unlock position or having an expanding tube assembly break a series of fasteners. Rocket motors or thrusters are then used to move the hatch out of harm’s way, clearing a safe ejection seat escape path.
Can you provide me the ejection seat for my aircraft?
Not the seat, but we do provide the pyrotechnics necessary for the proper initiation and functioning of the seat equipment ensuring a successful aircrew recovery. Seats are designed to take worst case into account. This is done through a series of time delays or electronic sequencing of certain events on the seat (ensuring the pilot is in the best ejection posture). Then, the seat catapult and/or rocket motors ignite to propel the seat out of the cockpit, deploy and release parachutes, aircrew and equipment, all at the correct time to land safely. These seats take into account speed and altitude and determines when and if specific pyrotechnic devices function. Pyrotechnic and energetic materials provide the millisecond initiation and response time needed to ensure the aircrew’s seat equipment activates the first time, every time.