PSI - Issue 14

Manu Jain et al. / Procedia Structural Integrity 14 (2019) 184–190 Manu Jain / Structural Integrity Procedia 00 (2018) 000–000

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3.3. Field data

 Log book of operations and maintenance record  Repairs, modifications and concessions provided  Criticality of operations and requirement  Timelines available 4. Methodology of life extension

The first step in life extension of UAV is to determine the viability and cost. The full service record is reviewed and if there is any major failure or incident then it has to be thoroughly probed. The following procedure is followed:

4.1. Airframe

4.1.1. Structural integrity and stiffness This is ascertained with the help of frequency measurement by Mechanical Impulse Response test. Frequencies during life extension are compared with the base frequency. The allowable deviation limit is 5.0%. 4.1.2. Visual examination This is conducted on all critical airframe parts with the help of a magnifier. Glass magnifier and optical microscope are used for the assessment of the corrosion depth. Endoscope visual examination This is carried out for the non-accessible parts like inner wing areas, fuel tanks. This helps in detection of corrosion and damage in the areas which cannot be examined directly. Liquid dye penetration examination Liquid dye penetration examination which is one of the most popular Nondestructive Examination (NDE) methods in the industry used to examine the surface level cracks, and damages to the critical areas. This method is more economical, versatile, and easy to implement on the parts with complex shapes and requires minimal training when compared to other NDT methods. Radiography Radiography is another Nondestructive test which is carried out to examine the internal cracks of the bulk heads, spider castings and critical parts to rule out any internal cracks or damages. 4.2. Electronic/electrical items Every subsystem has a history card in which all the operations, repair and modifications are recorded. Line Replaceable Units (LRU), have to go through shake check, visual inspection, bench check, Environmental Stress Screening (ESS), followed by bench check. If any fault is noticed during any stage the following can be pursued: Repair Repair takes place when the units are not maintained or handled properly. The failure report, defect investigation and the rectification are recorded in the history card of the units. Modification Modification takes place when similar failures occur in different units (similar LRU), then the defects have to be analysed and the required rectification has to be carried out. Most of the time the modification takes place when the 4.1.3. 4.1.4. 4.1.5. 4.2.1. 4.2.2.