Sav wrote;
"I think it was from a fellow Rotorhead (probably 500 Fan) that I learned about the rear passenger skylights being wider on the Cayuse than on the civilian 'C' models and which begs the question .. was HSKY ex-mil? "
Here is my take on the early production versions of the Hughes 500. The first Hughes 500 built was N9000F. It appears initially to have been modified only with a new slimmer instrument panel and a civilianised interior. It had a left-hand start. Presumably, the wiring for the mini-gun was also removed. The rear doors retained the small windows of the OH-6A. After completing its first promotional tour in 1966, it returned to Culver City and got the new rear doors with the larger windows. The over-head window above the rear doors was the same size as that featured on the OH-6A.
The next ten Hughes 500 airframes built were a mixture of H369H, H369HM and H369HE and H369HS versions. The H369Hs were employed mostly for test work, with one being sold to a commercial operator. The H369HMs were military versions and these (4) went to Colombia while the others, the HE and HS, were the very first of what would become the two versions for sale commercially in the late sixties. Some of these first twelve were "soft bellies" as they lacked the necessary reinforcement on the belly to support a cargo hook. From C/N No.12 onwards, the design remained pretty much the same, with the larger rear window in the rear door and the OH-6A-style large overhead rear window.
As always with the 500 series, there are a few anomalies. At least one of the early 500s was sold with the OH-6A rear doors with the small windows. G-HSKY was No.36 built and was a H369HM. This was initially purchased by Denis De Ferranti and as reported previously, due to his sight difficulty, he needed a right-hand starter. My guess is that G-HSKY (EI-ATY) was wired up with a right-hand start collective but was completed with a civilian interior and had the wiring for the mini-gun removed! The same probably holds true for EI-AVN (G-HAUS). Both airframes were probably assigned M-data plates and when they were diverted to a civilian customer, retained their H369HM designation.
I think the first 115 (I'm not 100% sure of this figure) Hughes 500s built had the large overhead window. The rear door appears to have undergone a redesign in the early seventies and production changed to the new style door. The new style of door may have been in production before the Hughes 500C designation was adopted in promotional literature. Apologies for the thread drift.
500 Fan