CAC CA-11 Woomera

After the first tests of the initial CA-4 Woomera on 19th September 1941, it was seen that the fuel tanks weren't reliable, and its wooden structure was seen as a vulnerability to anti-air fire (something not certainly completely true as proved by the Mosquito). Engines were considered too weak and it was decided to replace them with two 14-cylinder Pratt & Whitney R-1830-S3C3-G manufactured locally under license by DAP (Department of Aircraft Production), the tail section was completely redesigned, and engine nacelles were more streamlined, keeping the characteristic nacelles guns, a lengthened canopy and a revised rear-gunner's station.
 It wasn't until June 1944 that this version went airborne, powered by Pratt & Whitney R-2000 Twin wasp engines rated each of them at 1300hp of power and a crew of three. Reported maximum speed was 282mph (454km/h) with a range of 2225 miles (3581 Km). Service ceiling was 23500ft (7163m) with a rate-of-climb of 2090ft (637m) per minute. Main armament was slighlty revised from the CA-4 and included two 0.303in calibre Browning machine guns and two 20mm Hispano Mk.II cannons in the nose. The four-gun remote controlled turret barbettes with two 0.303in were kept and it had provision for bomb and torpedo ordnance to be mounted under the wings or in the engine nacelles as they had bomb-bays.
The CA-11 prototype was delivered to the RAAF in November 1944, but, at that time, surplus aircraft both from the USA and the United Kingdom were largely available for the RAAF negating therefore the need for a locally built aircraft in that role. The original government contract of 105 aircrafts was reduced to 20 and eventually cancelled, finishing with the project. The roles that would've been fullfiled by the Woomera were undertaken by the North American P-51 Mustang which could fullfil many roles, the Bristol Beaufort (some of them locally built by DAP) or the Lockheed Ventura.
Some sources claim that it was the second prototype that crashed and not the first one, and they even claim that, in March 1945 the second prototype took part in a reconnaissance version together with some Australian Consolidated Liberator GR Mk.VIII at the northern shore of Australia and it was written off in September 1945 just after the surrender of Japan.
Apparently the only prototype was scrapped in late 1945.

Sources:
1. https://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=848
2. http://www.avionslegendaires.net/avion-militaire/commonwealth-ca-4-ca-11-woomera/ (translated)
3. http://forum.worldofwarplanes.com/index.php?/topic/1291-ca-11-woomera-bomber-cac-ca-4ca-11/
4. https://en.wikipedia.org/wiki/CAC_Woomera
5. https://www.airforce.gov.au/sites/g/files/net3736/f/minisite/static/1469/RAAFmuseum/research/aircraft/series2/A23.htm

CAC Ca-4 Woomera

Due to the incoming war, in early 1939 the Australian Government ordered large numbers of Bristol Beaufighters to be produced in railway workshops bypassing that way the local aircraft company, the Commonwealth Aircraft Corporation CAC.
CAC which was under the direction of Sir Lawrence Wackett began to work on his own design, hoping to outperform the Beaufighter serving both as a dive and torpedo bomber. In order to keep the weight low, Wacket dispensed with traditional self-sealing fuel tanks and opted to make wing cavities liquid-tight in order to serve as fuel storage. Initially, Australian Government wasn't interested in the design, however, in mid-1940, when Australia was cut-off from the supply of British-made components needed for the Beaufort, due to the need of maximization of British aircraft production during the Battle of Britain during mid 1940, the Australian Government ordered a prototype of the CAC design, even before the Royal Australian Air Force had expressed their opinion about the type.
The prototype flew for the first time on 19th September 1941. It was a low-wing, twin-engined, multi-role bomber with a crew of three. It was armed with four 0.303in machine-guns mounted in the nose and two remote-controlled twin machine-guns barbettes mounted at the rear of the engine nacelles. It could carry either 500lb (250Kg) bombs, 250lb (110Kg) or two torpedoes. In the case of the bombs, they were stored in a compartment placed in the nacelles.
It was originally powered by two Pratt & Whitney Twin Wasp R-1830-S3C3-G radial engines yielding each of them 1200hp of power. Unfortunately, the novel fuel tanks weren't reliable and on 15th January 1943 the CAC Ca-4 prototype was destroyed in a mid-air explosion, probably due to a fuel leak and killing two of the three crewmen near Kilmore, in Victoria. The wreckage was recovered and used for components.
Due to the Japanese entry into the World War II, the RAAF accepted the design even before it was tested and placed an order for 105 examples on 8th March 1942, however the loss of the first prototype the programme was delayed.

Sources:
1. https://en.wikipedia.org/wiki/CAC_Woomera
2. https://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=848

Armstrong Whitworth A.W.166

This project started, like other Armstrong Whitworth aircrafts, as a research airplane on mach speeds.

Made out of light alloys, Armstrong Whitworth stated that a steel wing would be lighter due to the substantial loss in effective depth of the spar box when using a very thick light alloy flanges.
As it was designed the airplane would only reach Mach 1,5 at sea level unless it was made entirely of steel. Armstrong Whitworth preferred to base it's proposals on the more familiar design and fabrication of light alloy to reduce riveting and stiffening, but steel was chosen in the parts of the all-moving tail for stiffness.

The specification ER.134T required a top speed about twice of the current fighter prototypes with a wing around half the present thickness/chord ratio. Armstrong Whitworth's 4% needed moving surfaces on both leading and trailing edges and the high wing loading was considered to be an advantage in obtaining very high speed at moderate altitude, but, on the downhill, it also meant that a standard low maneouvrability had to be accepted.
The wing was originally drawn tapered 10º on both edges. A later proposal made the inner wing straight but the outer one swept 55º. It would've been powered by two Armstrong Siddeley Sapphire Sa.7 engines mounted in underslung mid-wing nacelles with two position nozzles and variable centerbody intakes, with reheat providing 25% static thrust augmentation.
The AW.166 was going to have a bicycle undercarriage with the wheels folding into the engine nacelles and a 900gl (4091liters) fuel tank would've been placed in the fuselage. That amount of fuel was considered more than enough by the company.
The aircraft would've reached Mach 2 between 10973 and 15240m high for the required 10 minutes.
Armstrong Whitworth considered Mach 2 at sea level to be easy to achieve apart from cockpit cooling and conversion to all steel and, in spite of the difficulties meeting the ER.134T specification, Armstrong Whitworth was satisified as it seemed that this design would achieve speeds of Mach 2 and beyond with barely any difficulty.

A small unrequested brochure was presented for an AW.166 for Australia, powered by two Armstrong Siddeley Sapphire Sa.10,equipped with an Ai.18 collision course interception radar, a fatter nose and unspecified wing tip missiles (most probably the Firestreak or the Red Top).

Sources:
1. Midland Publishing - British Secret Projects - Fighters since 1950