This is the 9846th most frequent Russian word.
авиационного
"Авиационного" means "aviation" or "related to aviation."
In this sentence, 'авиационного' is an adjective describing the engineer, specifying a field of expertise: aviation.
Авиационного инженера попросили разработать новый тип самолёта.
The aviation engineer was asked to develop a new type of aircraft.
Here, 'авиационного' qualifies the type of equipment, indicating its relation to aviation.
В музее представлены модели авиационного оборудования.
The museum features models of aviation equipment.
'Авиационного' in this sentence specifies the type of fuel being discussed, relating it to its use in aviation.