The Focke-Wulf Fw 191, developed for the Luftwaffe's Bomber B program to replace the Ju 88, represents a classic case where excessive technical ambition led to project failure. Despite featuring advanced innovations including a fully pressurized cabin, remote-controlled defensive armament, and an automated dive recovery system, the aircraft was plagued by critical issues: the experimental Jumo 222 engines had a service life of only 30 hours and regularly caught fire, while the electrical system required 172,000 man-hours to install and was prone to constant failures. The development timeline stretched far beyond expectations, with the first prototype flying in March 1941 but the third prototype never taking flight due to persistent technical problems. The German Air Ministry ultimately canceled the project in June 1942, redirecting resources to the Ju 288 bomber, demonstrating that even technically sophisticated aircraft designs can fail when development complexity exceeds practical production capabilities.
Focke-Wulf Fw 191: Why Germany's Most Advanced Bomber FailedAñadido:
Starting in 1939, Focke-Wulf took on an ambitious project, a clean sheet design for a new high-speed bomber called the FW 191.
Born out of the German government's sweeping bomber B program, its main goal was straightforward but critical. It was intended to eventually replace the Ju 88 medium bomber.
The Ju 88 was the backbone of the Luftwaffe at the time, but it would soon need a more capable successor.
Of course, Focke-Wulf wasn't alone in this endeavor.
A fierce competition unfolded laid out by the Reich Air Ministry or RLM, Junkers entered the fray with the Ju 288, which was widely considered the frontrunner at the time.
Dornier also joined the race with their Do 317. However, Focke-Wulf's leadership managed to successfully pitch their concept, convincing the RLM that their design had serious potential. As a result, the project was officially approved and the company was awarded a development contract for the FW 191, putting them right alongside their rivals at Junkers. By late 1940, the engineering team at Focke-Wulf dove into the detailed structural design.
The design team was headed by chief engineer Kosel. They envisioned the FW 191 as a powerful four-seat high-speed bomber.
Its main selling point was its versatility. It was capable of both precision level bombing and dive bombing.
To achieve this, the airframe was equipped with specialized aerodynamic dive brakes. The aircraft was also slated for use in long-range reconnaissance.
According to calculations, it was projected to have a range of roughly 3,500 km or 2,200 mi on a single tank.
This was possible even with a maximum takeoff weight pushing 20,000 kg or 44,000 lb.
Visually, the heavily glazed greenhouse style nose of the aircraft drew comparisons to the American Boeing B-29 Superfortress and Messerschmitt's own long-range Me 264.
Ultimately, the FW 191 design looked so promising that it became a serious threat to the front-running Ju 288. But every aircraft developed for the bomber B program shared a common Achilles' heel, their power plants.
For both Junkers and Focke-Wulf, engines became the biggest challenge.
Originally, these bombers were supposed to be fitted with the brand new 24-cylinder liquid-cooled Jumo 222 engines.
The problem was that these power plants were nowhere near for mass production.
Without reliable mass-produced Jumo 222s, the future of both the Ju 288 and the FW 191 hung by a thread.
Focke-Wulf was banking heavily on these specific engines, which promised an impressive 2,000 horsepower each.
Just to be safe, however, the engineering team came up with a contingency plan. They looked into installing two slightly weaker but far more reliable 12-cylinder Daimler Benz DB 603 engines.
When the first prototypes were finally assembled, it turned out that the Jumo 222 engines were still unavailable for flight testing.
Because of this, both companies were forced to compromise, temporarily fitting their test aircraft with weaker BMW 801 radial engines. Interestingly, Focke-Wulf engineers had been closely eyeing the new Daimler Benz DB 603 engines since early 1940.
They originally planned to use them for their FW 190 fighter.
In response to their inquiries, Daimler Benz leadership sent back glowing reports, claiming the DB 603 was already proving to be a massive success.
It was only slightly larger than the previous DB 601 model, but boasted an exceptional power-to-weight ratio. Based on these specs, the Focke-Wulf team decided to seriously explore adapting the DB 603 for their other airframes. In February 1940, Focke-Wulf's leadership received some bad news.
The first small batches of the highly anticipated Jumo 222 engines wouldn't be available until the following year.
Faced with this delay, the company initially decided to use BMW 801 engines as a stopgap measure.
But after crunching the numbers, the engineering team found a surprising alternative.
It turned out that an FW 191 bomber powered by DB 603 engines would perform almost as well as the idealized version equipped with the Jumo 222s.
This opened up a viable path forward for the aircraft. In September 1940, an initial plan for outfitting the new prototypes was laid out.
The first 10 FW 191 airframes would be divided into three batches to test different power plants.
The plan was to install BMW 801A engines on the first few aircraft, fit counter-rotating Jumo 222s on the next batch, and finally use DB 603A engines for the final group of prototypes.
When they pitched this proposal to General Wolfram Lucht, he immediately shot it down.
The reason was purely pragmatic. There were no plans to mass produce the DB 603 at the time.
Setting up an entirely new assembly line would inevitably disrupt the output of other aircraft engines desperately needed on the front lines. Focke-Wulf's engineers, however, wouldn't take no for an answer.
They presented the military with detailed performance charts for the aircraft.
After reviewing the numbers, General Lucht reversed his decision, admitting that the DB 603 looked far more promising than the alternatives.
Furthermore, Focke-Wulf representatives highlighted another key point.
Committing to the DB 603 right out of the gate would accelerate the bomber's development by at least a full year.
Even so, from a purely technical standpoint, the DB 603 still wasn't the ultimate solution in its power class.
In a rather baffling move, military leadership used this exact reasoning to repeatedly cancel flight tests for four highly promising prototypes equipped with these engines. Earlier in the spring of 1940, Focke-Wulf had drafted a comprehensive technical report detailing the FW 191's design.
The baseline aircraft was conceived as a high-speed bomber capable of precision strikes in both level flight and steep dives. They also planned to develop a four-seat long-range reconnaissance variant based on the same airframe. This recon version would carry a suite of specialized aerial cameras housed within the fuselage.
These payloads were modular, allowing ground crews to easily swap configurations depending on the mission profile.
To maximize bombing accuracy, engineers integrated an automatic dive recovery system.
The system worked like this. At the start of a dive, trim tabs on the elevators locked into a preset position.
The moment the payload was released, the automatic system smoothly pulled the aircraft out of the dive and back into level flight.
Meanwhile, an electromechanical limiter ensured that pullout G-forces on the crew would never exceed a safe limit of 3.5 Gs under any circumstances. All four crew members were seated in a single spacious pressurized cabin.
The nose section was almost entirely glazed with custom curved Plexiglas panels, functioning as a stepless cockpit that gave the pilots fantastic visibility.
To keep the canopy from icing up at high altitudes, they used double-pane glazing with an insulating layer of air in between.
Right behind the crew stations was a solid pressure bulkhead featuring an airtight entry hatch.
Interestingly, the only way the crew could board the aircraft or bail out in an emergency was by climbing up through the open bomb bay and into this hatch.
The entire cabin section was secured to the center fuselage using just four heavy-duty bolts. In the upper half of the center fuselage, engineers placed the self-sealing fuel tanks with the bomb bay sitting directly beneath them.
The fuel layout depended on which engines were used. For the version powered by Jumo 222 engines, aviation fuel went into five protected tanks inside the fuselage, each holding 1,000 L.
But if the bomber was fitted with DB 603 engines, this was reduced to four 1,000 L tanks.
To extend the flight range, they installed two additional tanks in the inner wing sections, each holding roughly 600 L.
The bomb bay itself featured two large doors spanning the entire belly of the aircraft.
The absolute maximum payload this bomber could carry was 2,000 kg or about 4,400 lb.
The bay's versatile design allowed ground crews to flexibly mix and match bomb configurations to fit whatever combat mission they were flying. Inside the FW 191's bomb bay, three bomb racks were mounted in tandem.
The engineers came up with a highly unusual and clever method for winching the bombs into place using a pulley system integrated directly into the tail gear strut.
If the main fuselage bay wasn't big enough, this bomber could also carry additional ordnance stored in auxiliary bays within the inner wing sections.
As for the main landing gear, the struts retracted rearward into the engine nacelles with the wheels pivoting 90° to lie flat.
At the rear, the bomber featured a classic twin tail configuration, which gave it some much-needed stability in flight. The FW 191 featured a high-mounted wing with a complex but highly effective design.
It consisted of the inner wing sections, the engine nacelles, and trapezoidal outer wing panels.
The designers paid special attention to specialized split flaps positioned along the trailing edge of the wing.
By adding an extra panel to seal the structural gaps, the engineers aimed for optimal aerodynamic efficiency.
They wanted to minimize drag as much as possible while massively boosting lift.
On top of that, these flaps were designed to double as dive brakes. When deployed in this mode, the mechanism split them in opposite directions. The upper surfaces hinged upward while the lower surfaces dropped downward. The engine nacelle design was quite versatile, built to accommodate either the powerful Jumo 222 or the DB 603 engines.
Because the engine mounts and cowlings were standardized, the power plants could be easily swapped out with minimal modification.
To protect against attacks from the rear, twin MG 81 machine guns were mounted in the back of the engine nacelles.
What's really fascinating is that all the defensive armament on the FW 191 was entirely electrically powered and remotely controlled, a highly advanced setup for the time.
The aft section of the cockpit was also armed with a pair of MG 81s. A powered gun turret sat on top of the fuselage while a matching turret was mounted right under the belly.
That lower turret could be fitted with either MG 81 machine guns or a heavier MG 151 auto cannon. The dimensions of this bomber were impressive. It had a wingspan of 25 m or 82 ft, a length of over 18 m or 60 ft, and stood almost 5 m or 16 ft tall.
Its maximum takeoff weight reached nearly 20,000 kg or 44,000 lb.
Powered by the Jumo 222 engines at a typical combat weight of about 15,400 kg or 34,000 lb, the FW 191 was designed for speed. It could hit 620 km/h or 385 mph at an altitude of 6,300 m or 20,800 ft.
The alternative setup with the DB 603 engines was a bit slower, topping out at 584 km/h or 363 mph at 6,000 m or 19,700 ft. The service ceiling was identical for both versions, reaching over 9,700 m or 31,800 ft.
The economical cruise speed was 550 km/h or 342 mph and 480 km/h, which is 298 mph with the DB 603s.
At these speeds, it had an impressive range of over 3,600 km or 2,230 mi. By mid-1941, the ambitious program to build and test the FW 191 prototypes was in full swing.
The initial scope of the project was massive. As early as June, Focke-Wulf put together a detailed report on the initial concept, followed quickly by a decision to build a batch of 10 prototypes for an extensive test program.
The plan called for the first, second, and fourth prototypes to fly with BMW 801 engines, while the remaining airframes would be used to test the brand new Jumo 222 engines.
On top of that, the factory was already assigning serial numbers for the upcoming pre-production and main production series, and preparing a master prototype for mass manufacturing.
Sticking to a tight schedule, the first FW 191 prototype was supposed to be completely flight ready by March 18th, 1941, with the first production models expected by the summer of 1942.
The initial flight tests of the first aircraft went exactly to plan with no major surprises. However, wartime realities soon disrupted those plans.
Due to a severe shortage of the new Jumo 222 engines, the engineering team had to hastily install BMW 801 engines on the first two test aircraft.
Because of this exact same bottleneck, the fourth prototype ended up getting those engines as well, which was problematic, as this fourth aircraft was the one engineers needed for the final and most crucial tests of the onboard armament. The FW 191 made its maiden flight on March 18th, 1941.
At the controls was Kurt Tank, a veteran test pilot for Focke-Wulf, who served as the lead test pilot for the entire flight program.
Prior to this, he had already flown the maiden flights of several iconic aircraft, including the FW 187, the FW 189, and the FW 200 long-range bomber.
However, with the FW 191, it was the first time he was tasked with more than just flying the aircraft. He was also managing the entire testing process from top to bottom.
The engineering team was banking on quick results, but their plan deadlines ultimately proved to be far too optimistic. In reality, the development and testing process for this aircraft dragged on much longer than expected.
Because the bomber was packed with innovative technology, a host of unpredictable issues and teething problems were largely inevitable.
The biggest headache for the designers was constant glitches in the complex onboard electrical system.
Along with this, the landing flaps regularly took damage during landings.
Due to constant design tweaks, the second prototype wasn't ready until early December 1941, and it didn't make its maiden flight until January 8th, 1942. Even though the team at Focke-Wulf was still pushing hard on the FW 191 project, the overall situation was starting to deteriorate.
By mid-1942, the German Air Ministry decided to slash the order for test airframes down to just 12.
On top of that, the earlier contract for an initial production run of 30 bombers was completely canceled.
The future of series production for the aircraft was suddenly in serious doubt, forcing the developers to urgently rethink their entire flight test strategy. In June 1942, they completely rewrote the test program to adapt to the strict new requirements of the ministry, as well as schedule changes and relocated test facilities.
Up to this point, the first two prototypes had been conducting their shakedown flights at the Hamburg-Wenzendorf airfield.
During that time, the first prototype managed to log 21 flights, while the second had made about nine.
Meanwhile, back at the factory, they were already wrapping up assembly on the next batch of prototypes. In May 1942, the second prototype was shipped off to the Rechlin military test facility for its next round of evaluations.
The aircraft sustained some minor damage during a landing, but this actually gave ground crews a chance to not only repair it, but also install the new, more powerful Jumo 222 engines.
The company's plans were still quite ambitious. Once the third prototype was finished, they intended to build a full test series of aircraft, but reality set in. A few unfinished airframes had to be cannibalized for spare parts just to keep the existing planes airworthy.
They even set aside certain airframes strictly for grueling ground tests to check structural vibration, with the engineers carefully logging the results in classified reports. The engineers paid special attention to those brand new Jumo 222 engines, which were supposed to become the standard power plants for the new prototypes.
Their biggest weakness was an incredibly short service life, maxing out at only about 30 hours of reliable running time.
The manufacturer, Junkers, openly warned about a major issue. If run at high power settings in flight, these power plants would fail regularly.
This meant test pilots had to be extremely careful.
By the spring of 1942, they had the third prototype prepped for testing.
They took things very slowly at first, initially just running one of its engines at idle for half an hour while the bomber sat parked on the ramp.
Meanwhile, the engineering team was already waiting on a delivery of upgraded pre-production Jumo 222 engines for the next batch of aircraft. During internal meetings, Focke-Wulf management made a decision to dedicate one of the new test aircraft to stress test specific systems, including the hydraulics, the landing flaps, and the lattice-style dive brakes.
But here's the really interesting part.
On that very same aircraft, they started testing a cutting-edge cockpit setup equipped with ejection seats.
Originally, they only planned to use the system for static ground testing, but eventually, they took the risk of trying it out in actual flight conditions. That turned out to be a massive leap forward, greatly advancing the development of crew escape systems for military pilots.
Up to this point, a major headache for the FW 191 developers had been the constant failures in the electrical system.
The entire problem boiled down to the infamous Mikel plugs or Mikelstecker in German.
To finally fix this mess, engineers decided to scrap them on an upcoming prototype, opting instead for standard terminal blocks.
The idea was to make the wiring continuous and unbroken, eliminating unnecessary intermediate connections and removing the plugs that constantly failed. To give you an idea of just how massive this problem was, consider the installation time.
Installing the electrical system on one of the first prototypes took a staggering 172,000 man-hours, accounting for a massive 60% of the total time spent building the airplane.
Initially, Focke-Wulf management decided to completely rework the wiring on all subsequent airframes.
This meant ripping out all the old harnesses and running entirely new ones with a completely different layout. On some of the aircraft, they planned to run unshielded wiring, while later versions would be fully shielded.
All of this required an extra 10,000 hours of painstaking labor.
They aimed to finish work on these prototypes between late August 1942 and early 1943.
But with these delays, some airframes would be less than half complete, forcing the company to make a tough call to stick to the schedule at all costs.
As a result, engineers had to compromise. On one batch of test airframes, they simply swapped out the old Mikel plugs in the most critical areas, replacing them with an updated and more reliable version.
Meanwhile, on another group of prototypes, they took the radical route anyway, completely removing the problematic connectors and using reliable terminal blocks and continuous hardwired connections in their place.
A similar upgrade was in store for the last of the planned prototypes, but a new complication popped up.
This airframe was supposed to feature a pressurized crew compartment, meaning all the electrical pass-throughs required perfect sealing.
Meanwhile, even by the summer of 1942, one of the first assembled prototypes still couldn't get off the ground, stuck going through endless ground tests.
Despite all these hurdles, management had approved a highly ambitious and tight schedule that spring.
According to the plan from the summer straight through to the end of 1942, the company was supposed to roll out a whole batch of new experimental bombers that would undergo full flight testing month by month. To somehow meet these strict deadlines, the development team had to improvise. For example, instead of the intended Jumo 222 engines, they urgently fitted one of the airframes with V12 Jumo 213 engines.
What is more, starting in mid-1942, they decided to completely restructure the test program for the FW 191.
The primary focus shifted to testing individual components and assemblies for a completely new, more promising project, the FW 391. For instance, they tested new landing gear doors on one of the available airframes, while simultaneously evaluating a completely redesigned tail section featuring a new trim system and additional control surfaces on another.
However, late June 1942 became the turning point for the fate of this high-speed bomber.
That was when a crucial meeting took place at the RLM, which finally put an end to their ambitions.
Officials made a harsh decision, completely halting all work on the Jumo 222 powered FW 191 project.
The exact same fate befell its four-engine sibling, the FW 491.
From that moment on, the entire massive program was reduced to simply finishing the experimental prototypes that were already on the assembly line. Instead, government officials handed the engineering team an entirely new set of top priorities.
Starting in the summer of 1942, the company's main focus shifted to developing high-altitude fighters based on the famous FW 190.
On top of that, designers were tasked with working on two FW 187 prototypes.
These were supposed to act as flying test beds for a new variant, the FW 187C, which was being developed as a direct competitor to another well-known heavy fighter, the Me 210. Following that pivotal meeting, the engineers only conducted the most essential testing on the FW 191.
On Focke-Wulf's list of priorities, this ambitious program took a backseat to more pressing projects.
The design team set some strict new deadlines. The third prototype had to be fully flight ready by late August 1942.
The sixth aircraft was scheduled for mid-September and the seventh around October.
As for the rest of the prototypes, they decided not to set any test dates at all.
By the fall, the program had to be revised yet again. Construction on most of the other planned prototypes was completely frozen, and the assembly of a few more aircraft was shelved indefinitely. Meanwhile, in early August, the first FW 191 prototype made its maiden flight fitted with asymmetric rudders.
According to test pilot Melhorn, this design choice proved quite effective, making handling the heavy aircraft much easier during critical engine-out situations.
The sheer scale of the problems Focke-Wulf was grappling with on a daily basis is perfectly illustrated by the prep work for the third prototype's first flight.
Thanks to endless delays and technical hiccups, it finally managed to get off the ground on August 12th, 1942.
Initially, this aircraft was fitted with the new experimental Jumo 222 engines, but they were constantly breaking down.
Just a month later, the engineers had to pull them and ship them back to the factory. During test stand runs, these engines generated critically high coolant pressure, and the heat dissipation system was woefully inadequate.
The old Windhoff radiators couldn't handle the stress and kept bursting, so they had to be hastily swapped out for more reliable ones made by SKF.
Because of all these failures, along with issues with the valves and flaps, the flight schedule had to be pushed back yet again.
The only silver lining for the mechanics was that this time around, there were no issues with the infamous Meischal plugs.
By then, they had already been replaced with upgraded versions that operated reliably and caused hardly any trouble.
Once all the technical gremlins were supposedly ironed out, the third FW 191 prototype was finally prepped for flight, but the streak of bad luck continued. While braking, an oil line sprang a leak, causing the right engine to suddenly catch fire, and things only got worse from there.
In mid-September, while scrambling during an air raid siren, the ground crew was rushing to tow the aircraft out of the hangar and accidentally damaged the vertical stabilizer and rudder.
A few days later, they had the aircraft patched up again, but during the very next round of testing, the valve locking system failed, resulting in a collapsed landing gear strut attached to the inner wing section.
The mechanics rushed to install a new part, but right after they did, a short circuit sparked in the electrical wiring.
The aircraft was practically falling apart right before their eyes. During yet another takeoff attempt, the right-hand Jumo 222 engine blew a piston ring.
>> [music] >> The engine instantly caught fire, engulfing part of the airframe in flames. The damage to the third prototype was extensive.
Because of this, Focke-Wulf decided against returning it to airworthy condition, planning instead to use the troubled aircraft strictly as a ground test bed.
But that idea quickly fell through when both experimental engines soon failed completely.
Professor Kurt Tank personally gave the order not to waste any new spare engines on it. It was an unceremonious end. The FW 191 V3 prototype never took to the skies again. The other aircraft weren't having much luck, either.
During routine ground runs on the V6 prototype, steam suddenly began pouring from the engines.
In the process, nearly 45 L of coolant boiled out of the system.
It became readily apparent that the engine cooling system was severely inadequate and operating right at its absolute limit.
Its performance was only considered acceptable at high altitudes. As a result, engineers had to treat the V6 with extreme caution, doing everything they could to avoid a catastrophic engine overheat before it even got off the ground. Focke-Wulf engineers had high hopes for a new set of propeller blades originally developed for the Ju 288 bomber.
Calculations showed that these props should boost engine cooling efficiency on the FW 191 by nearly 18%.
With these major upgrades in the works, only two prototypes were allocated for further flight testing, the V6 and V7.
But the schedule kept slipping.
Initially, the plan was to have the V6 ready to fly by early October and the V7 by mid-November.
Reality had other plans, though. Chief test pilot Hans Sander didn't manage to get the V6 airborne for its maiden flight until December 17th, 1942.
Earlier versions of the bomber suffered from chronic electrical issues. In fact, the electrical system that actuated the landing flaps and, frankly, the entire electrical setup on the first two prototypes was incredibly unstable and prone to failure.
So, the designers made a radical choice for the V6 prototype. They completely ditched the finicky electric motors.
For the first time, they installed much more reliable hydraulic actuators to deploy the flaps.
The upgrades didn't stop at the hydraulics. The V6 also received the finalized tail design intended for all production aircraft.
Engineers implemented an advanced dual balancing system for the vertical and horizontal control surfaces, a complex setup that included an auxiliary directional control system developed by Meltzer.
On top of that, to run a full suite of tests, the aircraft was fitted with state-of-the-art radio equipment.
Meanwhile, prototype V7 finally joined the test program. The main goal for this airframe was to test the manually operated defensive armament in real-world conditions.
Additionally, the aircraft was fitted with a modernized, heavily improved set of bomb bay doors. The flight schedule also included ambitious tests for new engines designed to be fitted with a specialized dual propeller spinner.
However, in the spring of 1943, the entire FW 191 flight test program came to a sudden halt.
The German Air Ministry ultimately threw its weight behind a competitor, the Ju 288 bomber.
Grand plans to build 60 pre-production aircraft were permanently scrapped, and series production of other variants was completely off the table.
Strict orders came down. Scrap all existing test aircraft, including the earliest prototypes that were still airworthy.
Management ordered that all valuable instruments and equipment be stripped and sent to the aviation research facility in Göttingen.
Interestingly, the fate of the more advanced V6 and V7 prototypes remained somewhat of a mystery.
At the time, the V6 was fully flight ready, and the V7 was nearly 90% complete. Initially, the Air Ministry considered it critical to finish testing the powerful Jumo 222 engines, which is exactly why they still planned to finish building the V7. However, the realities of the war forced a change in plans, and the aircraft was never completed. In the end, the V6 prototype was the only airframe in the entire FW 191 program to fully test the Jumo 222 engines.
Focke-Wulf kept using the V6 for their own internal factory trials right up until the end of 1943.
The aircraft was truly cutting edge featuring a full suite of the latest communication and navigation gear, reliable hydraulic landing flaps and dive brakes, and an enlarged vertical stabilizer for better handling.
But the most interesting detail was its unique jettisonable crew capsule.
Salvaged from another unfinished prototype, it had already proven effective during rigorous ground testing.
Much like their main competitor, the Ju 288, designers seriously considered equipping the Fw 191 with coupled engines from Daimler-Benz.
There was even a proposal to fit one of the upcoming prototypes with the massive DB 606 coupled engines, and it is highly likely these power plants would have eventually made their way onto other test airframes in the series as well.
But by then, too much time had been lost.
Focke-Wulf management had largely abandoned the ambitious plans to get the early Fw 191 variants into series production.
As the project slowly wound down, these grand ideas remained purely theoretical.
Still, Focke-Wulf engineers hadn't given up hope of getting their ambitious bomber into production. As early as August 1941, initial technical studies proposed a radical change in approach.
Instead of using two powerful Jumo 222 engines, which were facing massive development delays, they decided to mount four less powerful but more reliable engines.
The designers evaluated various options including the DB 605 and DB 601, but after careful analysis, they ultimately went with the proven Jumo 211. On August 28th, 1941, management was presented with an updated Fw 191 design now powered by four Jumo 211F engines.
The main advantage was that these engines were already in full-scale production, meaning that pushing the new bomber into production would be a much safer bet with far less technical risk.
However, this choice came with serious drawbacks. Because of the switch from two engines to four, the maximum takeoff weight of the aircraft jumped to over 25,000 kg or 55,500 lb compared to the earlier Jumo 222 version, which weighed in at around 23,500 kg or 51,800 lb.
On top of that, engineers had to sacrifice fuel capacity in the outer wing tanks. Capacity dropped sharply from 2,700 L down to just 1,500 L.
Naturally, naturally, this took a huge toll on combat performance with the maximum range falling from over 5,100 km or 3,200 mi down to around 3,700 km or 2,300 mi.
Furthermore, transitioning to a four-engine layout introduced a dangerous new problem for the flight crews.
In the twin-engine configuration, the aircraft could at least maintain level flight if one engine failed. However, with the four-engine setup, losing both engines on the same wing made it virtually impossible to keep the plane in the air.
Designers needed to prevent a catastrophic loss of control in an asymmetric thrust situation and maintain directional stability.
To do this, they would have had to either lengthen the fuselage or drastically enlarge the vertical stabilizer.
There was also an urgent need to increase the total wing area to 75 square meters or 807 square feet.
Despite these hurdles, the revised production schedule required Focke-Wulf to complete two four-engine Fw 191 prototypes by the fall of 1943.
By May of the following year, however, the entire Fw 191 development program underwent another round of major revisions.
Due to the sheer scope of these modifications, the revamped project was initially given a completely new designation, the Fw 391.
Shortly after, at the personal request of State Secretary of Aviation Erhard Milch, the aircraft was officially redesignated as the Fw 491.
This new iteration of the bomber was significantly simplified. The designers decided to completely scrap the complex pressurized cockpit. Additionally, the innovative but highly unreliable electrical systems for the landing gear, flaps, and bomb bay doors were replaced with traditional proven hydraulic mechanisms.
At the same time, the military finally abandoned the requirement for this heavy bomber to perform steep diving attacks, which significantly reduced structural stress on the airframe. Company management immediately reported these simplifications to the Reich Air Ministry, the primary customer of the project.
Focke-Wulf representatives presented the ministry with an ambitious proposal.
They would build eight fully functional flying prototypes along with one static airframe dedicated strictly to rigorous ground-based structural testing.
They promised to fast-track the assembly of two aircraft from this pre-production batch to kick off the flight test program as quickly as possible. For these initial prototypes, they planned to use readily available Jumo 211F engines originally allocated for Ju 252 transports. By midsummer 1942, Focke-Wulf had finalized the technical documentation for the new four-engine Fw 491.
Company management offered a highly practical solution since the delivery of the high-power engines for the twin-engine variant had been officially canceled. They proposed converting the unfinished prototypes already sitting on the factory floor.
The plan was to equip each of them with four Jumo 211J engines.
To save precious time and streamline the manufacturing process, they carried over most of the parts and structural components from its predecessor, the Fw 191. The major drawback was that the new four-engine power plant proved to be excessively heavy weighing nearly 2,000 kg or 4,400 lb more than the original twin-Jumo 222 setup.
Just to get the new bomber off the ground and keep it within strict maximum takeoff weight limits, engineers were forced to reduce the capacity of the fuel tanks yet again.
Consequently, the basic takeoff weight of the aircraft sat at around 23,200 kg or 51,150 lb.
Its estimated range with a standard fuel load dropped to just 3,050 km or roughly 1,900 mi.
Even in a maximum overload configuration, the bomber could only cover about 3,700 km or 2,300 mi, seriously calling its future viability as a strategic bomber into question. To speed up the development process as much as possible, Focke-Wulf engineers took a proven route. They completely copied the engine installation from the well-known Ju 88.
They planned to store all the fuel inside the fuselage. To do this, they designed a setup with five flexible fuel bladders, each holding roughly 1,000 L of aviation fuel.
They also decided to increase the wingspan of the upgraded Fw 491 bomber from 25 to 26 m or 82 to 85 ft.
As a result, its total wing area grew from 70 square meters to 75 square meters or 753 to 807 square feet.
From an engineering standpoint, these design changes were a huge success.
Building a single wing for the Fw 491 now took only a third of the time it took to assemble one for the earlier Fw 191 model, a massive advantage for mass production under wartime conditions. For defense, the new aircraft was slated to receive heavy armament. The designers planned to set up several firing positions equipped with cannons and machine guns.
These included the MG 151 and the HD 151/2 turrets covering all angles of the bomber.
This would allow the crew to reliably fend off enemy fighter attacks from any direction.
It is highly likely that Luftwaffe command viewed the Fw 491 as a true replacement for the aging Fw 200.
By that time, the flight characteristics of the Fw 200 were becoming outdated and no longer met the demands of modern air combat.
But none of these ambitious plans ever materialized. On June 30th, 1942, the German Aviation Ministry issued an official order completely halting the development of the four-engine variant of the Fw 191.
Ultimately, this promising project remained nothing more than an interesting concept on the blueprints and a topic of theoretical discussion.
Not a single prototype of this aircraft was ever built.
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