In the S-55, he located the passenger/cargo cabin directly under the rotor and the fuel tanks directly under the cabin, minimizing cg travel due to loading/unloading passengers/cargo and fuel burn. The engine, which had been located directly under the rotor to simplify the drive train, was moved to the nose. The cockpit, which had been in the nose, was relocated above and forward of the cabin. The Army awarded him a development contract for it on behalf of the U.S. Air Force as the YH-19. First flight was accomplished on 7 November 1949.
A military service has always been quick to adapt a successful helicopter design to its own mission requirements whenever one is generally suitable, since helicopter development generally had and has a low priority relative to other demands for funds. And so it was that the Navy, needing an ASW dipping-sonar test and evaluation helicopter until Bell's HSL ASW helicopter (see http://tommythomason.com/books/Bell-HSL/) completed development, procured the S-55 as its HO4S-1 in April 1950. The 600 hp takeoff rating of the -1's P&W R-1340 proved inadequate for the hover performance required for the dipping-sonar mission so it was replaced for HO4S-3 production with the Wright R-1300 with an 800 hp takeoff rating, although at least initially it was limited to 700 hp by the helicopter's drive system.
As a result of the delays in the development of the Bell HSL that was intended to be the Navy's operational ASW dipping-sonar helicopter, the Navy procured the HO4S-3 as a placeholder until either the Bell HSL or the backup program it had initiated with Sikosky for the HSS (now better known as the H-34) could be deployed.
The multi-tank fuel system in the belly of the fuselage allowed for an opening in the bottom of the fuselage for deployment of the sonar.
The bottom of the sonar dome could extend beyond the bottom of the fuselage when not fully retracted. (Note that this HO3S does not have a rescue hoist.)
The configuration of the sonar dome changed over time the one utilized by the HO3S looked like this.
The "ball" was flat on one side, with the antenna surface protected by a wire screen.
The cable reel was housed in the cabin. The enclosure design also changed over time so this may just be representative.
The sonar operator's station looked something like this (there may have been a second seat beside it in some cases):
He could control the depth of the sonar and determine the distance and relative bearing of a contact.
The HO3S-3 could be armed with a single Mk 43 homing torpedo that was mounted on and dropped from a variable-angle rack on the left hand side of the fuselage.
This is the best picture I have of the rack:
This is the HSS rack, which appears to be very similar (note that the forward sway brace has been "cut off" by the draftsman so as not to hide details behind it).
The addition of the 375-lb torpedo generally limited the operational use of the HO3S to hunter-killer tactics, with the three-man crew of the hunter (pilot, copilot, and sonar operator) reduced to two (pilot and "bombardier") when the torpedo was carried.
Note that the Air Force and Army H-19s were subsequently modified with a different tail boom, bigger vertical fin, and much smaller horizontal stabilizer with no anhedral.
Information on and illustrations of the Royal Canadian Navy HO3S-3 can be found here: http://jproc.ca/rrp/rrp3/ho4s3.html
A little late to the party but, thought I’d provide some insight. Yes, you’re correct that the fairing on the underside was the fuel line fairing. The sumps protruded below that. In the hundreds of photographs I’ve seen of U. S. Navy HO4S’s, I’ve never seen one equipped to drop a torpedo like their Royal Navy brethren. It took awhile before all HO4S’s and Marine HRS’s were equipped with rescue hoists which is why BuNo138513 doesn’t have one in the image. BTW, this HO4S met its fate in Northern Nevada in 1957 when it suffered engine failure and after a successful auto-rotation landing, caught fire and burned. No casualties! Finally, you are also correct that the Navy Bureau never decided to replace the straight tail boom with the 3.5 degree downward sloped boom when they became available. Poor choice as photographic evidence and accident reports show both the Navy and Marines kept chopping off tail booms. No secret as to why the follow-on H-34 was designed the way it was!
ReplyDeleteA little late to the party but, hope I can add some information. Yes, the fairing on the underside was the fuel line fairing and the sumps extended to the bottom of the fairing. It took a few years for all Navy HO4S's and Marine HRS's to be equipped with rescue hoists as depicted in the image of BuNo138513. An interesting story about it here: https://www.historynet.com/cougar-on-the-loose-a-trick-from-wwii-averts-tragedy-over-southern-california.htm
ReplyDeleteIn the hundreds of images of Navy HO4S's I've seen in my years of research, I've never seen one equipped with a torpedo like their Royal Navy brethren. Finally, it's true that the Navy Bureau never saw fit to retrofit or purchase any HRS/HO4S with the 3.5 degree downward sloping tail boom as did the Army and Air Force.