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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 Effectiveness of life extension procedures based on the type of UAVs (Metallic structures, Composite structures etc) Lakshya life extension is carried out on completion of original prescribed life of 10 sea dunking / 10 years of storage Manu Jain et al. (2016). This is a major life extension, which is done at the base. UAV is stripped open and after thorough inspection extent of damages/corrosion is documented (Fig 1, a and b). A detailed scheme of repair and restoration is proposed Manu Jain et al.(2009). After successful completion of repair and all the base integration checks (mechanical and electrical), Lakshya is cleared for 5 flights or 2 years of storage life whichever is earlier. Once Lakshya has completed its extended life of 5 launches/2 years of extended storage, minor life extension can be taken up at the user premises Manu Jain et al. (2009-2016). Structural integrity checks, dye penetration test (Fig 2, a and b), endoscopic examination (Fig 3a), radiography (Fig 3b), rigging and electrical integration are carried out and UAV life is extended for 2 launches/6 months whichever comes first. Depending on the state of UAV minor life extension can be carried out several times. At present an average Lakshya with full life extension has completed more than 20 flights i.e double of original predicted life.

Fig. 1. Deriveting of aileron skin (b) corrosion on wing surface

Fig. 2. DP test of wing bracket (b) DP test of rear fuselage joint

Nishant is mostly made of GFRP, which does not have the consistent behavior or life prediction techniques as metallic parts. The recovery conditions of Nishant also vary frequently because change of location and terrain. Thus, life extension of Nishant cannot be done for a large number of flights or fixed duration. In case of Nishant continuous inspection of critical parts are carried out after every flight, beyond original life of 15 flights. The airframe is subjected to frequency check (Fig 4a) and dye penetration test of critical components is mandated. During the parachute landing/ recovery if airframe sustains any damage, the components/modules are to be repaired or replaced. If damaged structure is repaired then it is subjected to requisite static load of (Fig 4b) to ensure that deflections are within the permitted limits. Nishant life extension has been carried out on experimental basis and the life of UAV has been extended to two fold of the original calculated life.