The MC-4 prototype flying near the McCulloch Motors plant during a test flight. Photo courtesy of CW Bayer, who wrote the online book Flying Without Instruction about his father Al's work as a test pilot.

The prototype MC-4 at the McCulloch Motors factory on West Century Boulevard, adjacent to LAX. The MC-4 by Drago Jovanovich was based on his earlier JOV-3. The MC-4A and MC-4C were slightly larger with tailfins added. Photo, believed taken in the summer of 1951, courtesy of CW Bayer, who wrote the online book Flying Without Instruction about his father Al's work as a test pilot.

The first of two XHUM-1 helicopters evaluated by the US Navy in 1952 but not accepted for service use.

Entered service with the US Navy in June 1953, retired in August 1955. Transferred to Pima in October 1974.

This is one of two XHUM-1 delivered to the Navy in June 1953 for evaluation as the tandem-rotor was an extremely new concept. This important piece of aviation history was restored to this immaculate display standard by the Yanks Air Museum between 2007-2011.

The McCulloch MC-4 tandom-rotor helicopter was evaluated by the US Army as the YH-30 and the Navy as XHUM-1. It was found to be underpowered so no orders were forthcoming, nevertheless, an interesting piece of aviation history to be seen at the super Pima Air & Space Museum.

One of two XHUM-1 tandem rotor helicopters built for US Navy evaluation. It was a development of the smaller Jovanovich JOV-3 designed by Drago Jovanovich at the Helicopter Engineering and Research Corporation in 1948. The Pima Air & Space Museum has since move it inside for display.