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apophenia:
This started out as a Naval GB concept but I don't think that carrier aircraft qualify ...

Curtiss Design 92C (XSB4C-1) 'Super Helldiver'

Even before the US Navy's new Curtiss SB2C Helldiver divebomber had entered production, the Bureau of Aeronautics (BuAer) was planning for its replacement. (That would prove prescient when the trouble-prone Helldiver did finally emerge.) Curtiss put forward two proposals as potential SB2C replacements. The first was a February 1941 submission for a heavily-revised Helldiver airframe fitted with a tricycle landing gear and an R-3350 Duplex-Cyclone engine. [1] This was the Curtiss Design 93, two prototypes of which were ordered as the XSB3C-1.

Due to its size (and poor handling qualities), the SB2C would be nicknamed 'The Beast'. Despite that, Curtiss was proposing an enlarged, 'growth variant' as its replacement. As planned, the replacement SB3C could carry a greater payload thanks to its larger and more powerful 18-cylinder engine. The key question for the BuAer was: When would that R-3350 Duplex-Cyclone engine become available? In mid-1941, Wright Aeronautical - the engine-building subsidiary of Curtiss-Wright - could not provide an answer. As a hedge, the Curtiss airframe division offered a less challenging alternative to the US Navy. This was the Curtiss Design 92C. [2]

Enter the Single-Seat Curtiss Design 92C

Submitted in March 1941, the Curtiss Design 92C was a much more straightforward adaptation of the SB2C airframe.  Retaining the lower-powered Wright R-2600-8 Twin Cyclone of the SB2C, the Design 92C abandoned the rear gunner in favour of a shorter, lighter fuselage. Although similar in appearance, little commonality with the original Helldiver fuselage remained. The forward fuselage was shortened by over 3 feet by pushing the engine bearers well back. The rear fuselage was lengthened by a foot. The result was a much better-handling machine than the SB2C as well as being faster and longer-ranged. [3]

The trade-offs were in warload. Obviously, the rear defensive guns had be given up along with the observer. But the bomb bays were also shortening. The same bomb load could be enclosed but there was no longer space for a swinging bomb crutch. It was envisioned that level bombing would be the norm. (The difficulty in aiming by the sole crew member being noted in the BuAer critique.) For diving attacks, wing racks for twin 500 lb bombs would be employed to ensure accuracy of bomb delivery. [4]

Initially, the BuAer favoured the larger Curtiss Design 93 as the XSB3C-1. Curtiss completed a full scale mock-up of this aircraft in December 1941. However, after Pearl Harbor, it became apparent that Army B-29 long-range bombers would have priority for R-3350 engines. Accordingly, the entire XSB3C-1 order was cancelled. Instead, the contract was amended to single Design 92C prototype as the US Navy's XSB4C-1. This R-2600-powered airframe was also to be capable of accepting the larger R-3350 when available to the USN in numbers. [5]

The Curtiss XSB4C-1 - Single-Seat 'Super Helldiver'

The prototype Curtiss Design 92C was built as XSB4C-1 03744 (this BuAer number taken from the cancelled second prototype XSB3C-1). This prototype had components taken directly SB2C-1 production line combined with the heavily revised fuselage structure. As a result, prototype assembly proceeded very quickly at Curtiss' Buffalo plant. As result, XSB4C-1 03744 was completed at Curtiss' Kenmore Avenue Plant in  Buffalo, NY, by early August 1942. Curtiss-Wright Chief Test Pilot, H.L. Child put the aircraft through its paces. [6] On the third test flight, the XSB4C-1's engine threw a rod and 'Skipper' Child had to make a dead-stick landing. This did not speak well of quality control at Curtiss-Wright's R-2600 production facilities. However, the forced landing demonstrated rather dramatically the XSB4C-1's improved flying characteristics as compared with 'The Beast'.

Production schemes were worked out for the SB4C-1 'Super Helldiver' at Curtiss-Wright's Columbus, OH, factory as well as licensed production as the SB2F-2 by Fairchild-Canada. However, in light of experience with pre-approving production for the troublesome SB2C, no firm orders would be placed while flight testing was still underway. In the end, the Bureau of Aeronautics had a change of heart. It was concluded that the improved performance of the XSB4C-1 did not fully compensate for the loss of a rear gunner. Nor was the US Navy convinced that restricting dive bombing attacks to wing racks alone was acceptable. Thus, the sole XSB4C-1 remained at Buffalo and was returned to Curtiss ownership. BuAer 03744 served out its days as an SB2C trials aircraft. US Army interest in the related XA-40 project had also waned. The Curtiss Design 93C was a dead project.

In late November 1943, the XSB4C-1 was testing a 1,900 hp XR-2600-20 installation. This new engine burst an oil line and caught fire on a test flight. Forty miles out from the Buffalo airfield, test pilot Herb Fisher bailed out. The flaming XSB4C-1 crashed into Lake Erie, burying itself in the mud almost 80 feet down south of Dunnville, Ontario. Herb Fisher was quickly rescued by a training launch out of USCG Station Erie. No value was placed on retrieving the XSB4C-1 and the wreck of the sole 'Super Helldiver' remains where it fell.

_______________________________________

[1] There were other revisions to the original SB2C airframe. These included a lengthened rear fuselage (to improve stability) as well as an enlarged fin/rudder and elevators. Fixed armament was to consist of 6 x .50-cal Browning wing guns (or 4 x 20 mm cannons), an increased bomb bay load, and wing hard points for 2 x 500 lb bombs.

[2] The internal Curtiss designation Design 92 had originally been applied to the XSB2C-2 Helldiver floatplane conversion. When that seaplane project was was redesignated, the 'Super Helldiver' concept inherited the Design 92 designation. It is not clear whether the 'C' suffix indicates that the final design was preceded by two interim concepts.

[3] The longer-range of the Design 92C was partly due to reduced airframe weight but was owed primarily to the optional second fuselage fuel tank. The latter nearly doubled fuel load but at the cost of c/g issues.

[4] The 1,600 lb AP Mark 1 could be carried internally but this armour-piercing bomb could no longer be dropped in diving attacks.

[5] The 2,200 hp R-3350 had a 55.78 inch diameter and a weight of 2,670 lbs. The 1,700 hp R-2600-8 had a 55 inch diameter and weighed almost 650 lbs less. The R-3350 engine installation in the Design 83E would be similar to that for the USAAF's XA-40 attack aircraft (that airframe differing mainly in lacking carrier gear and adopting twin 37 mm wing guns). An alternative future engine was the 1,900 hp R-2600-20 to be installed in the Design 93F.

[6] As a naval aviator, Lt. (USN) Henry Lloyd Child was ideally suited to lead the SB4C flight testing. In this, 'Skipper' Child was assisted by fellow Curtiss-Wright test pilots Robert Fausel and B.T. Hulse.

Jeffry Fontaine:
The lengthened fuselage really does make a difference in turning the original short and stubby Helldiver into something more aesthetically pleasing.  :smiley:

apophenia:
Thanks Jeffry  :smiley:  More on the 'Super Helldiver' theme but no real backstory this time but a bit of arm-waving is needed ...

I'm imagining a range of options for submissions to eclipse the rejected SB3C concept. Here, I've grouped some of those options onto example airframes. The basic airframe features an extended rear fuselage with twin tails for more stable handling. Options are:

1: Inverted-gull anhedral on inner wing panels
-- Benefits are a slightly deepened bomb bays and shorter/lighter main undercarriage legs

2: Improved defensive armament, remotely-controlled gun turrets option
-- General Electric Model 2CGD50URC1 dorsal and Model 2CGD50LRC1 ventral gun turrets

3: Improved defensive armament, manned gun turret option
-- Grumman Type 150SE electrically-operated dorsal turret

4: Improved offensive armament, internally-mounted torpedo
-- Bomb bay changes to accommodate proposed 12-foot torpedo

The latter option involved Curtiss' proposal that the British 18-inch aerial torpedo be modified and adopted by the US Navy as an armament option specifically for the SB5C. The British torpedo would be much shortened to fit witin the bomb bays. Shortening the torpedo body would shorten the weapon's range which meant closer-in attacks. To compensate, the basic SB5C would be armed with 20 mm Hispano cannons to suppress defensive fire from ships under attack.

If the standard SB2C wing was adopted for the SB5C, the lower bomb door sections would need to be removed for clearance. If the inverted-gull form was adopted, the increased 'head room' in the bomb bays would allow the bomb doors to be fully closed. In either case, the dive bombing 'trapese' swinging-arm would need to be removed before loading torpedos into the SB5C. The emphasis on torpedos would be Curtiss' counter-argument against the Grumman TBF doing almost anything the Helldiver could ... but better.

apophenia:
A Fury monoplane derivative is a notion that I keep returning to. This time, it will be more backstory drive ...

Sidney Camm and the Hawker 'High Speed Fury Monoplane'

In August 1933, Hawker Chief Designer Sidney Camm submitted his 'High Speed Fury Monoplane' concept to the Air Ministry for consideration. Officialdom was (unofficially) interested but there was no AM Specification for such an aircraft and, therefore, no funds allocated for such a project. As an experimental aircraft, the Air Ministry had already funded the Supermarine Type 224 monoplane fighter. But RJ Mitchell's Type 224 had displayed a disappointing maximum speed of only 228 mph.

As submitted, the 'High Speed Fury Monoplane' was powered by the same engine - an evaporatively-cooled, 600 hp Rolls-Royce Goshawk V-12. [1] Of less advanced construction than the Supermarine Type 224, the Camm design would also result in a lighter, more nimble fighter. Instead of a cranked wing with heavily-trousered landing gear, the 'High Speed Fury Monoplane' featured a simple, tapered planform and dainty, cantilevered main undercarriage legs with Dowty internally-sprung wheels. Camm was convinced that his team had designed the superior fighter. But neither the Air Ministry nor the RAF was yet convinced that this 'High Speed Fury Monoplane' represented a sufficient advance to warrant development.

In mid-October 1933, Sidney Camm presented his 'High Speed Fury Monoplane' concept to the Hawker Board of Directors. With the active support of TO Sopwith, the Board approved funding for a private venture prototype. But there were stipulations. Little of the production Fury remained in Camm's 'High Speed Fury Monoplane'. To limit development costs, the Board insisted that the actual Fury fuselage be retained. It was also suggested that the Air Ministry's preferred experimental steam-cooled Goshawk be temporarily abandoned in favour of the conventionally-cooled 640 hp Rolls Royce Kestrel VI V-12. The two engines were similarly sized but, the Board felt, the Kestrel would be more acceptable to the lucrative export market.

Faster Fury - Refining the 'High Speed Monoplane'

At its best, the troublesome Supermarine Type 224 had proven to be only 5 mph faster than the pending Fury II biplane. [2] Clearly, the Supermarine Type 224 was no yardstick. Rather, the goal must be for Hawkers to produce another world-beater. To Camm, that meant a further redesign. He would need a budget sufficient to cover a fully-retractable main undercarriage and an entirely new empennage - the objective for the latter being the elimination of all struts, bracing-wires, gaps, and other drag-inducing excrescences. The Board agree to this plan. The new Hawker 'High Speed Monoplane' would combine the basic fuselage structure and engine of the Fury II biplane with new wings and tailplane.

The refined 'High Speed Monoplane' retained the basic wing design of the August 1933 concept. The planform had more sweep on its leading edge, less on the trailing edge. However, the basic structural approach and total wing area (200 sq ft) remained unchanged. A key difference, of course, was the incorporation of bays for the new retractable Dowty undercarriage main legs. Those undercarriage legs attached to new centre-section 'stub' - as did the outer wings wing panels. The empennage was entirely new, as was a retractable tailwheel.

Those centre-section 'stubs' were also designed to allow future additions to fixed armament. An immediate armaments change was in adopting the fuselage-side armament position from the August 1934 concept. This revised gun position was designed to accommodate .303-inch machine guns - either Vickers Mk.IV or Browning - or the larger .5-inch Vickers gun. Wing hard points were to be included - outboard of the retracted main wheels - for Small Bomb Carriers or racks.

The cockpit position was as it had been for the biplane Fury. The enclosed cockpit from the August 1933 design was adopted. That sliding Perspex canopy was moved aft to match the original Fury cockpit location. Plans included the use of a reflector gun sight (although the RAF had yet to make a selection of its preferred type). New to the cockpit was a hand lever which which the pilot would manually charge the undercarriage retraction system ... although it was still to be decided whether that system would be pneumatically- or hydraulically-operated.

(To be continued ...)

_____________________________________

[1] The 9-cylinder Bristol Mercury radial was offered as an alternative engine.

[2] The Type 224 and Fury biplanes also had roughly the same wing area - 295 and 252 sq ft respectively. However, the Fury II was over 1,100 lbs lighter than the Supermarine monoplane.

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