This problem is starkly illustrated by China’s ongoing difficulty in producing a high-quality indigenous jet engine.
The problem of technology mismatch, at its root, is that the thief lacks trade secrets and human capital associated with the manufacturing and assembly of a system. At the very least, this absence can make the replication of foreign systems a costly and time-consuming process, as the thief needs to develop manufacturing procedures from scratch. At worst, it can lead to seriously substandard components that reduce the capabilities and reliability of a system. Chinese efforts to reverse engineer certain Russian jet engines during the 1990s and 2000s invariably produced engines with extremely short lifespans, and without the power of their Russian counterparts . Even today, jet engines remain an obstacle for PLAAF fighter modernization, with its early 5th generation prototypes notably underpowered.
Russian engines are less powerful and shorter-lived than their Western equivalents, and Chinese copies aren’t as good as Russian originals.
Example of trade secrets…during WWII, Packard-build Merlins used indium-plated bearings to improve performance. When the Germans analyzed captured examples, they assumed the plating was an inpurity.