Another HJ-1 Hornet prototype. In Eyerman's photos, dated 1951, another example that looks like N8170H does not wear a registration. N8120H is identified as a HJ-1 by the FAA. Was there really a HJ-1 predecessor called HH-120? Photo by: JR Eyerman / Life

Data for the helicopter on the left, which has been preserved at Fort Rucker. The medical evacuation pods seen here were too small for a stretcher, so the wounded had to be transferred by hand. The H-23A was quickly withdrawn from Korea. Photo from: Hiller

Marked 'YHJ-1', this is the prototype of the YH-32 Hornet, but not the original HJ-1 Hornet model as seen in photo 677702. Testing of the extremely noisy ramjets terrified the neighbourhoods surrounding the Hiller factory. Photo from: Vertical Flight Society

Built as a UH-12D in 1959. Converterted to four-seat UH-12E4 'Flying Station Wagon' with a stretched fuselage. The East Palo Alto factory site can be recognized from our overview photo. This helicopter had a mishap during an agricultural flight in California in 1985. Reg cancelled in 2017. Photo from: Wright State University

The first Hiller in the US Navy. Trials led to an order for another 16 HTE-1 training helicopters. Priced at $20,000 a Hiller was a bit cheaper than a Bell 47. Photo from: National Museum of the US Navy

One of the early civil prototypes of the Hiller HJ-1 Hornet ramjet-powered helicopter, flown by Stanley Hiller, with bow tie, and Prince Bernhard of the Netherlands. By the standards of early helicopter marketing they are not even overdressed. Bernhard was rated by his RAF instructors as an exceptional, but overconfident pilot. Photo from: Nationaal Archief (Netherlands)

Early Hiller helicopters at the factory, with Stanley Hiller's original HillerCopter in the front. Third is UH-4 Commuter NX66276 and sixth is NX68940, the prototype of the UH-12 / Hiller 360 as seen in the rear and overhead. As you can see, UH stood for United Helicopters, a name dropped in 1948. Confusingly, the US Army designation of the UH-12 was H-23. That type was the company's only real sales success. Digital technology has now taken over this area - Facebook Building 57 was built right on this spot, which is actually in Menlo Park. Photo from: Hiller