CAD MAINTENANCE POLICY
Learning Objective: Identify CAD maintenance policy to include SMDC and FCDC maintenance and inspection re-quirements and safety precautions.
CAD maintenance policy prohibits un-authorized maintenance or adjustment to a CAD at any of the three levels of maintenance: organizational, intermediate, or depot. Author-ized maintenance actions are limited to removal, inspection, and replacement unless specifically detailed in the aircraft MIM or by a technical directive.
CADS and items of equipment in ejection systems are for one-time use only. They are never to be refurbished or used again after firing. This is equally true of functional equipment, rigid lines, plumbing lines, and hoses. Ejection seats and escape system components that have been used in an ejection or fired, regardless of apparent condition, are prohibited from reuse and must be disposed of as directed by OPNAVINST 4790.2, OPNAVINST 3750.6, and the applicable CAD and rocket manual. Because of the extreme stress and strain to the ejection seats and escape system components during ejection, they cannot be reused. This stress could reduce the structural or mechanical reliability of these items. In the case of an inadvertent firing of a cartridge or CAD, all contaminated ballistic lines and devices must be replaced because of the corrosive nature of the explosive. The service life of wire-braid, teflon-lined hoses installed in ballistic applications is the same as that of the aircraft in which it is installed, unless it is used. A hose is considered to be used if the device to which it is attached is fired, either intentionally or accidentally. If this occurs, the hose and related fittings must be replaced. Before you install a hose or fitting (line, T, elbow, etc.), make sure that it is not contaminated by hydraulic fluid, oil, or a similar type of contaminant. All hoses in the escape system must be inspected for accidental damage at every phased inspection, upon seat removal, after removal of any part of the escape system, and for disconnection of any hose. When CADs are not installed in an aircraft, the inlet and outlet ports must be sealed with protective closures to prevent the entrance of moisture and foreign matter. For shipping purposes, the safety pins and protective closures provided with the replacement CAD must be returned with the replaced CAD to ensure it is in a safe condition during handling and storage. During ejection system maintenance actions, all disconnected CADs and associated ballistic lines must be protected with flexible plastic plugs that conform to MIL-C-5501/ l0A and flexible plastic caps that conform to MIL-C-5501/ l1. NAV-AIR 11-100-1.1 provides information relating to these caps and plugs.
SMDC AND FCDC MAINTENANCE AND INSPECTION REQUIREMENTS The major components of an SMDC assembly are the stainless steel tubing (SST), outer and inner ferrules, a silicone rubber seal, a 0.004-inch thick SST booster cup, an explosive booster charge, and a sheathed explosive detonating cord. A sectioned drawing of a standard SMDC/ FCDC tip assembly is shown in figure 2-19. The SMDC assemblies used in the canopy and hatch severance system are similar in design and construction except for the length and bend configuration of the stainless steel tubing and silver sheathed explosive detonating cord.
Figure 2-19.- Standard SMDC/ FCDC tip assembly.
To properly inspect SMDCs and FCDCs, you should adhere to the following requirements and precautions:
1. Ensure ground safety devices required during maintenance are correctly installed.
2. To prevent damage to the SMDC and FCDC booster tips, you should use extreme caution during removal and installation. All open connections must be capped with protective covers to prevent damage to SMDC and FCDC booster tips and contamination of open fittings.
3. Inspect each SMDC and FCDC assembly fitting nut for deformation, flattening, or wrench cutting. 4. There must be no corrosion, cracks, discoloration, flatness, gouges, holes, improper bends, kinks, sharp dents, splits, swelling, or wrinkles in an SMDC or FCDC assembly.
5. Smooth dents or slight depressions in SMDC or FCDC assemblies, tubing, or hoses are permitted if they do not exceed specified damage limits (fig. 2-20). If the limits are exceeded, the SMDC or FCDC assembly must be replaced.
Figure 2-20.- SMDC damage limits.
6. SMDC and FCDC assemblies that do not pass inspection must be replaced. Repair of SMDC tubing is not permitted.
7. Proper clamp spacing (fig. 2-21) must be maintained to prevent damage to SMDCs due to vibration. Improper clamp spacing may result in failure of the SMDC.