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Detectable Problems
Published in Tony Giampaolo, Gas Turbine Handbook: Principles and Practice, 2020
Foreign Object Damage (FOD) is defined as material (nuts, bolts, ice, etc.) ingested into the engine from outside the engine envelope. Domestic Object Damage (DOD) is defined as objects from any other part of the engine itself. Statistically foreign or domestic object damage accounts for 10.5% of gas turbine failures.3 Most of the impact incidents are the result of small loose parts within the engine. These parts are either left in the engine during the build or overhaul, or break loose after operation is initiated. In a relatively small number of cases, damage is the result of tools left in the inlet or the formation of ice in the inlet downstream of the filters. There have even been several cases where the inlet silencers failed and bits of silencer debris entered the engine. In any event, FOD is almost always accompanied by an increase in vibration.
Air transport safety: A basic issue for aviation insurers
Published in Hans M. Soekkha, Aviation Safety, 2020
Benito Pagnanelli, Paolo Albanese
Although these big new engines are designed to be more damage tolerant it is likely that because of the size of these engines, the passenger capacity of the 777, the long over-water flights of these aircraft and the general interest of the public at large, the manufacturers are likely to insist on closer repair tolerances and therefore less opportunity to repair damaged blades. Replacement rather than repair will lead to higher engine costs following FOD.
Impact of foreign object damage on the leading edge of TC11 titanium alloy aeroengine blade like specimen
Published in Australian Journal of Mechanical Engineering, 2023
Harish R, D. Shivalingappa, H G Hanumantharaju, Raghavendra N R
Foreign object damage (FOD) is a major concern in aero gas turbine engines. Around 50% of all component damage in jet engines accounts for fatigue failure (Cowles 1996). High cycle fatigue (HCF) is responsible for approximately half of all these failures, while low cycle fatigue (LCF) and all other modes of fatigue leads to remainder of fatigue failures in aeroengine. There is a particular HCF concern in aircraft engines which involves damage on the turbine blades by the impact of Foreign Objects (FO’s), i.e. foreign object damage. Aero gas turbine engines frequently experience the ingestion of foreign object debris ranging in size from millimetre to centimetre such as sand, gravel, concrete, rocks, broken pavement, etc resulting in foreign object damage generally along the leading edge surface of aerofoils (TRAVT- 094 2005). Impact damage of foreign object debris on the leading edge of compressor blade as shown in Figure 1. Including direct and indirect costs, failures of aeroengine components attributed to the impact of foreign object is estimated to cost the aviation industry billions of dollars per year (Hussin, Ismail, and Mustapa 2016). Foreign object damage (FOD) typically does not cause immediate catastrophic failure, but the damage can reduce the fatigue life of aero-engine components. The fatigue strength reduction due to foreign object debris impact was assumed to be associated with three prime factors: Induced residual stress field at the vicinity of impact.Formation of microcracks in crater regions.Effect of stress concentration microstructural distortion.