FRANGIBLE ESCAPE CANOPY SYSTEMS

(fig. 2-13). Since air pressure applied to this fitting bypasses the system regulator, the air source must be controlled to less than 20 psi to avoid rupturing the seal. NOTE: Some aircraft are equipped with canopy rain seals that protect the cabin area. In aircraft so equipped, the canopy seal does NOT have to be inflated for the cabin to be protected. Rain seals do not maintain cockpit pressurization. Troubleshooting Troubleshooting charts similar to the one in table 2-1 are found in most aircraft MIMs. The troubleshooting chart is provided as an aid in determining the cause, isolation procedure, and remedy for the more common malfunctions within the canopy seal system. When a mal- function is suspected, always ensure that the proper controls have been activated to provide operating potential to the unit to be inspected. Removal and Installation Procedures The MIM provides the instructions and visual aids necessary to remove and install the various components of the canopy seal system. In addition to instructions, information such as disposition of defective parts, tools and equipment requirements, and quality assurance instructions is provided. When removing a unit from the air- craft, always ensure that proper measures are taken to prevent the entry of dirt and foreign material into ports and ducts that have been opened to accommodate removal. FRANGIBLE ESCAPE CANOPY SYSTEMS Learning Objective: Recognize the purpose and operation of a frangible escape system. A frangible escape system is an explosively operated system that cuts an exit through the canopy directly over the head of each occupant. The S-3A canopy removal system is an example of this type system, and it employs shielded mild detonating cord (SMDC) in lieu of hot gas and flexible linear shaped charge (FLSC) in lieu of actuators found in other hot gas explosive systems. Normal entry and exit of the S-3A aircraft is through an entrance hatch vice a canopy, as in other ejection seat type of aircraft. Therefore, the S-3A canopy removal system is used primarily for emergency ground egress and water rescue. Normal seat ejection is through the canopy glass for the front seats and through the hatch glass for the rear seats. In both cases, exit is made without benefit of having the glass removed or cut because the seats are equipped with glass crashers. Breaker plates are installed on each canopy and hatch to assist the seat during ejection. A brief description of the frangible escape canopy system components is provided in the following paragraphs. EXTERNAL CANOPY AND HATCH JETTISON INITIATOR Two external jettison initiators are installed inside access doors, one on each side of the aircraft just below and forward of each windshield Figure 2-13.—Ground inflation of the canopy seal system. 2-16