First flown in January 1942, the R-4 holds the honour of being the world's first helicopter to go into production and the first to see combat, despite being difficult to fly and suffering from excessive vibration. This one (of 131 built) was obtained from the University of Illinois in 1967

The R-4 became the world's first production helicopter and the USAAF's first service helicopter. This R-4B on display at the National Museum of the USAF was donated to the museum by the University of Illinois in 1967.