CA-11 Woomera: The Bizarre WWII Bomber with Bombs in Its Engines

追加: 2026-05-15

[00:00:00]In our last episode, we ended on a pretty dark note. The crash of Australia's first twin engine combat aircraft, the CA4 Wacket bomber. This crash happened on January 15th, 1943.

[00:00:14]It claimed two lives and was a massive blow. At the time, the government and the Royal Australian Air Force had set an incredibly ambitious goal. With a world war already on their doorstep, they wanted to become completely independent of foreign supply lines and build their own combat aircraft.

[00:00:30]However, reality turned out to be a bit more complicated. For a variety of reasons, development of the multi-roll CA4 stretched on far longer than anyone expected. Just think about it. Even 4 years after Australia officially entered the war, the bomber was still undergoing endless flight testing. During these test flights, engineers uncovered a string of critical flaws. These stem mostly from a simple lack of experience in designing combat aircraft. That is exactly why back in 1942, chief designer and wing commander Lawrence James Wackett decided to take drastic action.

[00:01:06]He was the man the original CA4 prototype was named after.

[00:01:11]He launched a massive effort to radically redesign the aircraft. But despite heavy backing from the government, time was not on their side.

[00:01:19]The new version of the aircraft was designated the CA11 WUra, and there was absolutely no room for error. Everyone expected it to be an instant success.

[00:01:29]Full-scale production was supposed to kick off right after factory trials wrapped up. Otherwise, there was almost no chance the aircraft would ever see frontline service. And that was not because anyone could predict exactly when World War II would end. The real problem was how fast aviation technology was moving. What counted as cutting edge in 39 was completely obsolete and totally inadequate for actual air combat just four or 5 years later. In the spring of 1942, the brass actually went ahead and signed a contract for over 100 CA11s.

[00:02:03]This aircraft was supposed to be a truly versatile warbird. It would take on the roles of a bomber, a reconnaissance platform, and even a torpedo bomber.

[00:02:13]However, construction on the second prototype was suddenly put on hold.

[00:02:17]Australian factories were completely overwhelmed with other projects. They desperately needed to finish the production runs for the CA6 Wacket trainers. They also had to keep assembling the light multi-roll CA16 wearways and start churning out the new CA12 Boomerang fighters. On top of that, the strategic situation had drastically changed. Australia was no longer the isolated country it had been in the late30s. Back then, it had to rely entirely on its own resources.

[00:02:47]Now, it was receiving massive support from its allies, and modern aircraft were pouring in from Great Britain and the United States.

[00:02:55]In 1942, highly capable American bombers like the North American B25 Mitchell and the Douglas A20 Boston began entering service with the RAAF.

[00:03:06]They were also expecting shipments of a whole range of other advanced aircraft.

[00:03:11]This included the latest single engine fighters and four engine heavy bombers.

[00:03:16]Besides that, local factories were ramping up production of bowurt bombers, gearing up to build the bow fighter and actively negotiating to acquire the legendary British Mosquito.

[00:03:26]With this flood of modern aircraft, the urgent need for their homegrown CA11 slowly faded away. It also did not help that the designers just could not nail down the final configuration of the baseline CA11A variant. This model was slated to receive much more powerful engines. It was not until mid 1944 that the second prototype of the CA11 WRA bomber designed by Lawrence James Wackett finally rolled out of the CAC factory gates at Fisherman's Bend. Right off the bat, the most obvious change was the paint job. a fresh camouflage scheme with dark green on the top and sides of the fuselage and light blue underneath.

[00:04:07]Looking closer, some major structural changes were also pretty obvious. The center wing section was noticeably wider.

[00:04:15]The wings themselves now featured increased dihedral. They swept upward more noticeably, giving the bomber better stability in the air. The tail section and the canopy were also enlarged. There was a massive boost in firepower, too. In the nose, engineers had installed two 20 millimeter cannons and 2.33 caliber machine guns. On July 7th, 1944, the CA11 prototype took to the skies for the first time. Behind the stick was veteran CAC test pilot George Robert Bour. With 200 lb of ballast loaded into the rear cockpit, the aircraft's total takeoff weight came in at 16,164 lb. That Friday around Melbourne, the weather was about the worst conditions you'd ever want for a test flight.

[00:05:01]Strong, gusty winds were blowing. The sky was completely socked in. A solid ceiling of heavy, dark clouds hung at an altitude of just about 2,000 ft. Not exactly the conditions you'd pick for a maiden flight. While taxiing out to the runway, George Robert Bour noticed a welcome improvement. The main landing gear brakes worked absolutely perfectly.

[00:05:22]This was a massive step up from the previous CA4 model. As soon as the airplane lifted off, it was clear that the rudder was light and highly responsive to the pilot's inputs. The engineers had added special cooling cowl flaps to keep the engines from overheating. These also served as a backup in case the primary control system failed. The flaps were installed all the way around the trailing edge of the engine cowlings. But once in the air, a pretty alarming issue cropped up.

[00:05:49]The oil temperature kept climbing, pushing right past red line. And this was happening even with the oil cooler shutters wide open. Actually, that whole Friday turned out to be full of nasty surprises. Right in the middle of the flight, the dome of the remote machine gun turret on the right engine NLE suddenly ripped clean off the aircraft.

[00:06:09]Almost at the exact same moment, the radio completely died, leaving the pilot cut off from the ground. The bomber started shaking violently. The throttles started creeping forward on their own without any input from the pilot.

[00:06:22]Naturally, at this point, George Robert Bour was getting seriously concerned. He made the only right call and decided to head back to base immediately. But after a short climb, the oil temperature spiked violently past red line again.

[00:06:35]This practically guaranteed an engine fire. Sure enough, smoke and a sharp acrid smell soon followed. But surprisingly, it was not coming from the engines. Instead, the smoke was filling up the cockpit itself.

[00:06:50]To keep from choking on the smoke and passing out, the pilot quickly threw open his canopy and hooked up his oxygen mask. With that done, he turned straight back toward the field. As he set up on final approach, his air speed dropped to 120 mph. Yet another problem reared its head. The bomber's handling became extremely sluggish. Just to keep the wings level, he had to push the stick all the way to the stops. This incredibly stressful flight dragged on for 35 grueling minutes. Fortunately, it ended without any further disasters.

[00:07:22]Board pulled it off and got the bomber down in one piece. The prototype was immediately towed back to the factory floor for a close inspection and urgent repairs. During the debrief, engineers figured out that the acurid smoke in the cockpit simply came from the heating system burning out. This smoke came specifically from the heaters for the cockpit itself and the forward weapons bay. Mechanics went to work on the oil cooler. They patched up the engine cowling, readjusted the ailerons, and fixed the radio. This ensured the aircraft would be ready to fly again. On July 10th, 1944, George Robert Board took the CA11 prototype up for its second flight. He logged a solid 80 minutes in the air. This time around, the tests went much better. They did not find any major defects and the airplane only experienced minor airframe vibrations. The pilot even decided to try a risky experiment. He successfully flew straight and level and he executed some complex turns with an engine shut down. Board feathered one engine and then the other. The aircraft handled the asymmetric flight with ease. Just 3 days later on July 13th, the third test flight took place. George Robert Board was flying solo once again, carrying nothing but ballast in the rear cockpit.

[00:08:38]They had some pretty demanding tests lined up for the day. The pilot had to take the aircraft down to its stall speed and put it into a steep dive.

[00:08:47]During that dive, as the airplane speed passed 250 mph, the flight control suddenly stiffened up. They felt almost like they had turned to wood. To recover, the pilot had to actively use engine thrust to help pull the aircraft out of the dive. On top of that, he ran into some serious trouble during the landing. Once the aircraft was safely back on the ground, the ground crew found the culprit. The elevator trim tab had completely failed. This explained why the airplane was not responding to the control stick. Because of this failure, the prototype had to be towed right back into the hanger for yet another round of repairs. It took 6 days before the airplane was ready for its fourth flight. However, the chief test pilot was still not happy with how the aircraft was handling. It was right during this tense phase of the program that they decided to bring in another highly experienced pilot. This was Air Force Major David Robert On July 22nd, 1944, another test flight took place. This time, the experienced pilot James Richard Bour was at the controls. To get a visual on how the airflow was behaving over the airplane in flight, the engineering team used a classic flight test method. They taped yarn toughs to the engine, the cells, and the tail section. This simple but highly effective experiment let them pinpoint exactly where the airflow was separating. As a result, the aircraft was sent right back to the hanger for further modifications.

[00:10:11]The designers noticeably lengthened the rear sections of the engine to cells.

[00:10:15]They reshaped the machine gun turret domes and completely reworked the horizontal stabilizer. This gave it a very pronounced dihedral. Along with that, they also redesigned the control linkage for the elevator trim tabs.

[00:10:28]Beyond just the technical tweaks, the airplane got a cosmetic update, too. The entire airframe was painted in a protective green camouflage scheme. By November 21st, 1944, the airplane was officially handed over to the Australian Air Force for flight performance evaluations at the Leverton base. At that point, it had already racked up 19 factory test flights. Interestingly, with the exception of just one single sordy, James Richard Board was at the controls for every flight. Meanwhile, the Commonwealth Aircraft Corporation had almost finished building the third prototype. This was meant to be the full production version of the CA11A.

[00:11:08]The main difference between this new version and its predecessors was the power plant. Engineers plan to power the aircraft with Pratt and Whitney R2000 twin wasp engines. These were rated at 1,350 horsepower each.

[00:11:24]Although direct deliveries of these engines from the United States had not started yet, licensed production was already underway in Australia.

[00:11:32]However, in September 1944, things took an unexpected turn. On the recommendation of military command, the Australian government pulled the plug on the CA11 program for good. This did not just mean sending a nearly finished prototype to the scrapyard. It also meant a complete halt to any further flight testing. In December 1945, after testing was officially concluded, the CA11 was sent to a central storage facility in Wereabby. By April 11th, 1946, official orders were issued to dismantle and scrap the aircraft. The most valuable components such as the instruments, engines, and armament were salvaged by the Air Force. Everything else, including the bare metal airframe, was written off and scrapped. But the cancellation of the CA11, did not leave its creator, Lawrence James Wackett, out of a job. He quickly moved on to a much more successful project. He traveled to the United States to iron out the technical details with North American aviation. This was for the licensed production of the legendary P-51D Mustang. Still, Wackett had not forgotten about his multi-roll brainchild, the Womera.

[00:12:44]During a meeting with Boeing representatives, he managed to pitch the remote control turret system he had originally developed for the CA11A, now proposing it for use on American B29 Superfortress bombers. We all know what those B29s went on to do. After the Second World War, CAC made a few attempts to revive the Wra platform.

[00:13:06]They tried converting it into a multi-roll trainer. However, these efforts never gained any real traction.

[00:13:12]When evaluating the theoretical combat capabilities and real world performance of the CA4 and CA11, a lot of questions remain unanswered. However, one thing is certain. Even though the program failed to reach production, the core concept was incredibly solid. In the hands of a more mature aviation industry, a design like this could have become a genuinely capable combat aircraft in far less time. From a technical standpoint, the CA4 Wacket Bomber and CA11 Womera were classic canolver monoplanes with a robust all-metal construction and retractable main landing gear. These aircraft were designed as versatile warplanes primarily intended to serve as light bombers, torpedo bombers, and aerial reconnaissance platforms. The backbone of the fuselage was a rugged tubular steel frame welded into a sturdy rectangular crosssection with a streamlined duralamin skin attached to that framework. The rounded lower section of the fuselage essentially formed a vententral gondola. That is exactly where they located the station for the third crew member. This person had to juggle three rolls at once. They served as bombardier, navigator, and gunner. This vententral tub was attached directly to the main frame. Meanwhile, the upper fuselage was skinned with smooth sheets of duralamin. Right behind the cockpit, the engineers included a dedicated compartment for an inflatable life raft. This was an absolutely crucial detail for surviving overwater.

[00:14:41]The fuselage side panels behind the crew were designed to be removable. They were built out of fabric covered plywood and mounted on wooden formers. The aircraft carried a crew of three. The pilot sat up front in what looked like a classic fighter canopy. Right behind him was the co-pilot gunner. His station featured a basic instrument panel and dual controls. These included rudder pedals and a folding control stick. This meant he could take over flying the plane if necessary, but the pilot's main job was rear defense. To do this, he operated two remote controlled turrets. These were housed in the rear of the engine cells. To aim precisely, the gunner used a reflector sight. This was pretty advanced for the time. Interestingly, on the CA4, the gunner literally had to stand on his seat facing a to fire the guns.

[00:15:32]On the later CA11, they made this a lot easier. He just had to swivel his seat around. The third crew member was stationed down in the belly. The sides of his compartment had large triangular windows. These also doubled as entry and escape hatches. When it came time to drop bombs, launch torpedoes, or fire the vententral gun, he would move down into the gondola.

[00:15:54]The pilot got into his cockpit through a sliding canopy. He used flush steps on the left side of the fuselage. You could climb in from the right side, too.

[00:16:03]However, it took a bit more effort. Up front, the pilot was protected by a massive block of armored glass 3 in thick and 10 by 13.8 in across. To get to the rear cockpit, the crew could easily use footholds. These were located on both sides of the aircraft. The designers intended for the co-pilot to take over in emergencies. For example, if the pilot was wounded, needed a break during a long patrol, or if the sperry autopilot failed. On the CA11, the co-pilot also handled the radio. He just had to spin his seat around to use it.

[00:16:36]By comparison, on the older CA4, the third crew member had to handle all the radio duties. The bottom of the fuselage featured heavyduty hard points. This is where the wing center section was attached. Back in the rear, there were hard points for mounting the impenage and the tail wheel. The wing itself featured a classic rugged cantaliever design. It did not have any external bracing. It was built around a strong twin sparse section and two outer wing panels. The center section was a single continuous piece. Its cord gradually increased from the outer edges toward the wing route. The leading edge of this center section was swept back slightly.

[00:17:14]Meanwhile, the trailing edge was completely straight. The outer wing panels, on the other hand, had a sharply swept back leading edge. They also had a nearly straight trailing edge. Here is an interesting detail. The rounded wing tips were made of wood. They could be easily removed and replaced in the field. The rest of the wing, however, was all metal. This provided maximum structural strength in combat. Near the outer ends of the wing center section, engineers mounted streamlined engine necessels which also served as the attachment points were the outer wing panels bolted on the leading edge of the wing featured handley page slots. The trailing edge was equipped with a complex flap system. There were two flap segments on each side of the fuselage.

[00:17:57]These included an inboard section and a shorter section placed between the engine and the edge of the center wing panel. Another pair of flaps sat further outboard on the wing panels near the ailerons. This elaborate system had specific settings. 17° for takeoff, 45° for landing, and a full 75° deflection to act as highly effective air brakes.

[00:18:19]Just above the flaps, designers added upper surface dive brakes that hinged upward. In a steep dive, these panels deflected 60° to keep the bomber from gaining too much air speed. Altogether, there were two pairs of these brakes on top of the wing, one pair inboard of the engines and another further outboard.

[00:18:37]This entire setup was hydraulically driven, which significantly reduced the pilot's workload. The ailerons were located on the outer wing panels. They featured a lightweight aluminum frame covered in aircraft fabric. For night landings, powerful landing lights were mounted in the leading edges of the wings. A PTO tube was also installed on the right wing. The tail section evolved during development. On the first prototype, the CA4, the tail shared the same shape as the wearway. However, on the later CA11, the overall size was reduced. The vertical stabilizer was also given a more tapered shape. The main tail components, meaning the vertical fin and the horizontal stabilizer, were all metal and rigidly mounted. But the elevators and rudder used a fabriccovered metal frame to save weight. Much like the ailerons to improve handling, the elevators were equipped with trim tabs. The rudder was aerodynamically balanced. The aircraft featured a conventional landing gear layout. It had two main gear struts under the wings and a tail wheel. The main struts were robust. Each had twin wheels fitted with heavyduty brakes.

[00:19:47]They retracted rearward into wheel wells in the lower engine NLS. Interestingly, the main wheels did not retract completely. Even when fully raised, about a third of each wheel still stuck out below the NL. This was an intentional design choice. In the event of a wheels up belly landing, the exposed tires would absorb the impact.

[00:20:06]This protected the fuselage from major damage while also allowing for a simpler NL design. The tail wheel was fixed and did not retract.

[00:20:15]Another interesting feature involved the main gear doors. They had to be split lengthwise. This was because concealed bomb bays were built directly into the necessels just after the engines. Each of these bays could carry a 250lb bomb.

[00:20:30]The heart of the aircraft was a pair of powerful Pratt and Whitney R1830 twin wasp 14cylinder air cooled radial engines. The CA4 prototype received early versions of this engine. The subsequent CA11 variant was equipped with a slightly upgraded model. On takeoff at 2,700 RPM, the CA4 engines produced a solid 1,100 horsepower each.

[00:20:56]The upgraded power plants on the CA11 cranked out up to 1,200 horsepower.

[00:21:02]However, when cruising at an altitude of around 7,500 ft at 2,250 RPM, their continuous output dropped slightly. It fell to 950 and 1,50 horsepower, respectively. By the time the aircraft reached 13,800 ft, the performance of both engine variants equalized. They steadily put out 700 horsepower each.

[00:21:26]The specs of this power plant are impressive. Each engine weighed roughly 1,466 lb. They measured about 48 in in diameter. They also had a total cylinder displacement of 1,830 cubic in. That is where the R1830 name comes from. To keep the prop RPM in check and squeeze out maximum efficiency, the designers used a reduction gear. Meanwhile, a supercharger ensured the engine maintained optimal manifold pressure at altitude. The first CA4 prototype was fitted with Curtis Electric constant speed propellers.

[00:22:02]These measured 11.5 ft in diameter. The CA11 model, on the other hand, initially flew with hydraulically actuated three blade to Havlin propellers. These were later swapped out for more reliable Hamilton standard props.

[00:22:17]Despite the change in manufacturers, the propellers retained that exact same 11.5 ft diameter. For fuel, the aircraft ran on high octane aviation gas. This was housed in dedicated tanks built deep into the wing center section. The main tanks were located on either side of the fuselage. One set held 126 gall while the others carried 119 gall. On top of that, the designers managed to squeeze in two 75gal auxiliary tanks. These were tucked right behind the engine cells.

[00:22:50]Altogether, the internal fuel system held around 639 gall. If a combat mission called for extended range, they could also carry two massive 352gal drop tanks under the wings. Now, let's talk about the armament. For the fixed forward firing weapons, the pilot aimed the aircraft using a standard reflector gun site. The early CA4 prototype was equipped with four Vicer's machine guns.

[00:23:14]These were later swapped out for more reliable Brownings. All of them were chambered in 303 caliber. But on the CA11 variant, firepower got a massive upgrade. The nose now packed two heavy 20 mm British Hispano cannons. These were positioned alongside a pair of those familiar 303 caliber Brownings. To defend the bomber from enemy fighters attacking from the rear, two remote control defensive turrets were mounted.

[00:23:42]They were placed at the aft end of the engine necess Browning machine guns.

[00:23:51]A second crew member operated this defensive system. He tracked enemy targets through his own dedicated site.

[00:23:58]There was also a third gunner covering the lower hemisphere. He operated a303 caliber Vicar's machine gun which was mounted right on the belly of the aircraft. Interestingly enough, these bombers did not have a traditional internal bomb bay in the main fuselage.

[00:24:13]Instead, the primary ordinance was carried externally on heavyduty underwing pylons. The aircraft could carry four massive 1100lb bombs. It could also carry a couple of aerial torpedoes or a mixed loadout of both.

[00:24:27]Additionally, the engine necessels themselves featured built-in bomb bays.

[00:24:31]These were capable of housing four 250lb bombs each. When flying training sorties, the crew would carry eight 25lb practice bombs under the wings.

[00:24:41]Accurately dropping all this ordinance was the job of the bombardier. He was the third crew member stationed in a dedicated vententral gondola. He looked out through the forward nose glazing.

[00:24:52]This allowed him to calculate the perfect moment to drop the payload.