Single-engine, high-wing monoplane liaison and air reconnaissance aircraft developed by the US aeronautical company Stinson Aircraft Corporation in the early 1940s.

The Sentinel, constructed using conventional mixed media techniques in tubes, wood and canvas, was equipped with fixed leading-edge flaps and slats.

He was enlisted by the Air Force in late 1947. He was used for anti-malarial treatments in Sardinia, and for liaison duties with almost all commands and operational units. 

Over the course of twenty years, several transformations were made, making it suitable for different needs.

The MUSAM in Vigna di Valle (RM) exhibits one example.