Month: September 2012

By me

Author’s note: while not a new topic per se, the Bf.108 has turned out to be quite a popular item on this blog, with my previous post rising to an all time high viewcount. In view of that – and my “temporary”, two-year-old promise to finally sort out the post’s missing images – I’d decided I might refresh it, and post it in a format consistent with the new look of this site 🙂 .

When the first Bf.109s faced their German rivals in mock dogfights in the mid 30s, few observers – in any country – were left in doubt about the capability and raw potential of Messerschmitt’s first fighter design. International flying competitions during the run-up to WW 2 had only confirmed these impressions – but it would take the type’s impressive (though in later years somewhat diluted) wartime service record to finally remove all doubt. Lasting more than a decade in one form or another, the type’s all-up production run had encompassed more than 35,000 examples, spanning everything from the prewar lightweight Bf.109B Berthas to the post-war Merlin-engined Hispano Buchons.

A very advanced design by contemporary standards, the Bf.109 was not actually ground breaking per se; when all was said and done, it had not really introduced anything new or revolutionary into world of interwar fighter design. Rather, what it did – and did brilliantly – was to combine all the cutting edge technologies available at the time into a single aircraft: the monoplane configuration with its high wing loading; the powerful liquid-cooled V engine and its variable pitch prop; fully retractable hydraulically-actuated landing gear; the enclosed cockpit…

Other design features – which soon became the type’s hallmarks – had also included automatic leading edge slats and an innovative construction technique that had made the aircraft extremely light by the fighter standards of the day. The latter had also made the 109 simple and cheap to build, quick and easy to service – and especially tough, durable and reliable under actual combat conditions (though the rigors of the Soviet campaign would put its mettle fully to the test). And while the big engines and retractable landing gear and the monoplane configuration could easily be traced to some of the eminent fighter aircraft of the era, the above features were inherited from a decidedly more peaceful source – the lowly Bf.108 tourer 🙂 .

When I grow up I want to be a fighter!

The aircraft that would eventually lend its technical solutions – not to mention most of its airframe – to the Bf.109 had started out in life as the four-seat* M.37 tourer prototype of 1934. Designed by the young Willy Messerschmitt, Bayerische Flugzeugwerke‘s chief designer, the M.37 was conceived primarily to compete in the 4th Challenge de Tourisme Internationale being held the same year. This interesting – and I’m sure sorely missed – general avation competition was intended to promote and spur the development of light touring aircraft, and had included such competition categories as “Short Takeoff”, “Short Landing”, “Fuel Consumption”, “Minimum Speed”, “Maximum Speed” and “Technical Trial”. Topped by an (at the time) grueling and arduous 9,500 km rally across the diverse spaces and climates of Europe and North Africa (stopping also in Zagreb 🙂 ), this competition was intended – much like the 24 Hours of Le Mans in the automotive world – to weed out inferior designs and encourage quality solutions for future touring aircraft.

* though designed as four-seaters, the M.37 and the early Bf.108 were actually flown as two-seaters, with the rear seats permanently removed to provide some storage space. With virtually all pre-series production versions having been used for competitions and proving flights, this gave impression that they were designed outright just for two…

Based in part on Messerschmitt’s previous M.29 tourer – designed in a similar manner for the 1933 competition, but never taking part due to a spate of crashes – and the M.35 aerobatic trainer prototype, the M.37 was a sleek and elegant all-metal, stressed-skin low-wing monoplane, sporting retractable main gear, an enclosed (and heated) cockpit, full-span flaps – with roll control provided by roll spoilers (in 1934!) – and a variable pitch prop… all of which had immediately made it stand out like a sore thumb in the wood & fabric biplane crowd of the time 🙂 . This brazen level of unorthodoxy had continued under the skin as well, with the wing being built around only one spar – a design that was made to work thanks primarily to Messerschmitt’s extensive glider building experience gained during the restrictions of the Versailles Treaty. The innovative mechanical leading edge slats could be extended manually to improve the airflow over the wing’s outer sections – which were likely to stall first – reducing the stall speed to just 61 km/h (33 knots). This in turn helped to significantly shorten the aircraft’s take off roll – not to STOL levels, but not far above either – and dramatically increased low-speed maneuverability, handling at high Angles of Attack, and behavior in, during and after a stall.

* of note here is the oft-confused and misinterpreted designation. Popularized by the 109, the “Bf” prefix stood for the initials of “Bayerische Flugzeugwerke” (itself often shortened to BFW); however, when the company was renamed to “Messerschmitt Flugzeugwerke” in 1938, all subsequent designs were given the new “Me” prefix. The designs that had been produced before the name change had retained their original prefixes through the war – so there never was an “Me-108” as is claimed by some Internet sources.

However, despite the praise and the design’s undoubted qualities, one feature of the 108 had never really sat well with some of the test pilots: the roll spoilers. With the full length of the wing’s trailing edge taken up by the flaps – which increased the wing area by a significant 8% when fully extended – there was no space for traditional ailerons; roll control was instead provided by roll spoilers located on the wing upper surface, whose extension would create a difference in lift along the span of the wing. For example, if you had wanted to roll left, the spoilers on the left side would extend, dumping lift on that part of the wing. The wing’s ride side would now be producing more lift, which would roll the aircraft left around its center of gravity in the same manner as the ordinary aileron. This was fine in theory – and is today still used to provide additional roll control on a number of civil and military designs – but back in the 30s it was viewed with suspicion and more than its fair share of antagonism. This came to a head when test pilot von Dungern was killed while testing the spoilers, presumably somewhere near the edge of the envelope.

With the RLM’s well documented dislike of Willy Messerschmitt threatening to ground the Bf.108 – like it had the M.29 a year before – there was no other option but to revert to a conventional aileron arrangement. “Conventional” though should be taken with a grain of salt when Willy is concerned, because the resulting arrangement had still managed to raise an equal number of eyebrows… 🙂

In this form the aircraft became known as the Bf.108A, the designation under which it would be entered in the competition. Sadly, its beautiful handling and avantgarde features did not really help its case there, with the far lighter, nimbler and simpler wooden biplanes wiping the floor with it for most of the competition…

However, the 108 did eventually notch up several notable wins, all of which would eventually steer its development into the aircraft we know today. The top three aircraft in the “Fuel Consumption” category for example were all 108s – with the winner registering an impressive 10 kg (14 l) / 100 km. This figure – nowadays exceeded even by a basic SUV – was made even more impressive by the fact that the 108A was not powered by a small, frugal, fuel-sipping engine, but a 220 HP Hirth HM 8U inverted V8 (a proper GA engine 😀 ). Its power and torque had also helped in the “Maximum Speed” event, where the 108s again took the whole podium, with the slowest – at 283 km/h (153 knots) – being 30 km/h (16 knots) faster than the next contender. The trans-European rally was less of a success though, with the 108’s best result posted by Theo Osterkamp, who placed fifth. However, this poor showing was more due to the scoring system – and external influences such weather and poor navigation – than any faults with the aircraft themselves. Points were awarded based on total average speed, BOTH moving and stationary; this had meant that a fast aircraft grounded by weather for extended periods would score less points than a slow aircraft that had managed to evade the worst of it and continue flying. When everything fell in place though, the 108s had regularly posted the fastest average flying speeds – including on the legs to and from Zagreb 🙂 .

In the end, when the tally was done, the 108s had placed 5th, 6th and 10th out of a grand total of 19 contenders. But more importantly, their demonstrated low fuel consumption, high cruise speeds and beautiful handling – not to mention a leather upholstered and heated cockpit! – had immediately lent them well to cross-country touring. A clean, aerodynamic airframe, able to zip along on comparatively little power – sounds much like the Lancairs and Cirruses of today, doesn’t it? 🙂

This did not slip past the cash-strapped BFW, where Messerschmitt had decided to capitalize on the type’s competition success by adapting it for series production. To this end, a batch of pre-production Bf.108B-0 models was made (though they were still commonly known as the Bf.108A), with each successive aircraft representing a slight step toward a definitive production standard.

By 1935, these aircraft had already started making a name for themselves – some quite literally 🙂 . Well established as the fastest tourers in the sky, one example was chosen by famous German aviatrix Elly Beinhorn for her record breaking flight from Berlin to Constantinopole (now Istanbul, Turkey) and back. Her little Bf.108B-0 had more than lived up to its Taifun nickname when it took just 13 and a half hours to do the 3,470 km trip, flying along at an average ground speed of 257 km/h (139 knots) – a respectable result even by today’s standards.

This very convincing – and, at a time when the nation was hungry for records, very public – success had immediately opened the floodgates, and the 108’s already significant popularity skyrocketed overnight. As was the case with its showing at the 4th CdTI, this had not gone unnoticed at BFW, where Willy Messerschmitt increased efforts to finalize the Bf.108B-0 into a definite, production, high performance cross-country tourer. The end result was the Bf.108B-1, now adopting Taifun into its official name 🙂 .

While there was nothing really wrong with the original A series (and the early B-0s) performance-wise, they did have several features that were judged to be unfit for a production version. The whole idea behind the B-1 was to make the aircraft more production- and consumer-friendly, so the first item to go was the original’s powerplant. The expensive and hard-to-come-by VDM three-blade variable-pitch propeller was replaced by a simpler and cheaper two-blade fixed-pitch prop (although Messerschmitt’s own P7 variable-pitch unit was offered as an option), while the HM 8U engine was swapped for the more readily available Argus Ar 10C inverted V8, producing 240 HP. The wing was a bit dulled down as well by a reversion to a fully conventional aileron and flap arrangement – but had compensated for it by gaining a folding mechanism that allowed it to be tucked close to the fuselage for easier transport by road and rail.

Additional minor changes included the removal of the upper tailplane bracing mentioned previously, the replacement of the next-to-useless tailskid with a non-retractable, freely castoring tailwheel, and the shortening of the glazed canopy over the rear seats.

In this shape and form, the aircraft had continued to participate in international competitions, rallies and fairs (and, most notably, the 1936 Summer Olympics in Berlin) – but now under the increasingly ominous banner of Nazi propaganda. Indeed, soon after its initial competition successes, the fast-growing Luftwaffe had started eying the 108 as a liaison and communications aircraft to replace the obsolete, lumbering biplanes then being used.

However, the 108’s biggest contribution to the Wehrmarcht’s war effort was as the basis and jumping-off point for the impressive Bf.109 – a fact that in itself further underscores the essential quality of the Taifun’s design. In a fantastic display of lateral thinking, in 1934 Messerschmitt had simply taken the plans for the 108A and modified the design into a single-seater with a narrower fuselage, a big V12 up front – a “right way up” Rolls-Royce Kestrel on the first prototype (oh, the irony 😀 ) – and some firepower in the slightly modified wings (which too had reverted to a conventional aileron/flap arrangement). Apart from other smaller changes needed to fit all of this together, the rest of the new aircraft was a straight 108 🙂 .

While the wildly differing roles of these two aircraft may have raised some eyebrows – not to mention questions about Willy Messerschmitt’s command of his senses – the 108 was actually an amazingly suitable base for the 109. The Taifun’s advanced construction meant that the 109 could be light and maneuverable – as was demonstrated on more than one occasion over the next decade – and its relatively low part count meant it was simple to maintain and repair in the field with whatever facilities were on hand. Lacking complicated construction components also meant that it was very tolerant of combat damage, and the low number of critical design points made disabling it with a “lucky shot” quite the enterprise. At the same time, the clean airframe sliced through the air with relative ease, meaning the 109 could do with relatively little power and a smaller, more economical engine – quite a welcome feature given its notoriously short range and pitiful combat radius.

Achtung… Messerschmitt?

But an interesting and varied operational history was not just the prevue of the 109. Having had the (mis)fortune of being the most advanced light aircraft in the world during a period of significant – and often rapid – political changes, the Taifun had naturally accumulated its fair share of odd operators. Apart from the “usual” Axis users such as Bulgaria, Romania and Japan, there were also a few unexpected ones like China – and the Royal Yugoslav Air Force. The dozen or so B-1s acquired in 1939 were part of a larger batch of aircraft that had also included 60 Bf.109Es and quantities of spare parts – all paid for not with actual money, but in strategic materials such as iron, copper, aluminum and coal… materials abundant in the Kingdom of Yugoslavia, but scarce and badly needed for the military buildup in Germany.

And while the 108s would go on to lead rather uneventful lives in training and liaison roles, the 109s would pretty soon enter the history books 🙂 . The most potent fighter aircraft fielded by the Royal Yugoslav AF at the time of the German invasion in 1941, these machines would go down in history as the only 109s to ever face other 109s in outright combat, clashing violently during the spirited – but ultimately futile and short-lived – defense of Belgrade.

Next on the scale of the improbable was – the US military 🙂 . While it was quite common for the USAAF to fly and evaluate captured Axis aircraft, the single Bf.108B-1 it had operated had never even left Germany – and was actually peacefully bought, rather than forcefully captured. Designated the XC-44, this interesting aircraft had been based in Berlin and used as a high-speed staff transport by the US Military Air Attache up until 1941, when it was repossessed by the German government following the United States’ declaration of war against Germany and its allies.

Equally improbable – and, if anything, even more interesting – were the four Bf.108B-1s brought into the UK before the war. Bought on the “open market” just like the XC-44, but operated by civilian users, these examples were quickly impounded and pressed into RAF service at the start of hostilities, becoming the Messerschmitt Aldon. Used – like contemporary Luftwaffe examples – in the communications role, they were capable of comfortably outrunning every liaison type in the UK – though their shared family tree with the Bf.109 had often caused identification problems among defending fighters…*

* for those wondering how could the 108 be so easily mistaken for the obviously different 109: the first of the Griffon-engined Spitfires, the Mk XIIs, had been delivered with clipped wingtips intended to improve roll rates and increase maximum speeds at lower altitudes – a feature already well known at the time, and seen on virtually all Spitfires marks since the Mk V. On the ground, the Spit’s famous elliptical wing planfom was still very much obvious; up in the air however, things were somewhat different. On their first few sorties, only the mark’s new-found speed advantage had kept it safe from the attentions of patrolling Hawker Typhoons, which had mistaken their long noses and cut-off wings for those of attacking 109s…

The postwar period too saw its share of unusual operators, including Czechoslovakia (where the type was known as the K-70), Poland and even the Soviet Union, all of which had flown examples captured during the final days of the war. Another interesting operator – well known now for their very colorful 108s – was Spain, which had acquired several batches of the type during the Spanish Civil War and Franco’s subsequent ascension to power.

For the full photo history of the 108’s civil and military service around the world, you can visit the excellent pages below, a gold mine of fantastic information from which I’ve linked many of the photos above 🙂 .

• Pictorial overview of the Bf.108 @ Aeronet Aviacion, Part 1
• Pictorial overview of the Bf.108 @ Aeronet Aviacion, Part 2
• Pictorial overview of the Bf.108 @ Aeronet Aviacion, Part 3

Western promises

Unlike its armed cousin though, the 108 did not go through new versions like pairs of socks. Apart from the B series, there was only one major production version, the D; equally, experimental and test versions were also few in number. However, what the latter lacked in quantity, they’d definitely made up in quality… 🙂

By far the most normal – and sensible – of these was the Bf.108C-1, an ungainly 1936 modification that had seen a B-1 airframe refitted with a Siemens Sh 14A-7 seven cylinder radial. Coupled with its increased frontal area and drag, the engine’s rather pitiful 160 HP – 80 HP, or 33%, less than the type’s standard Argus Ar 10 – made for some appalling performance, which saw the aircraft remain a one-of. However, while this version seems to be an unnecessary step backwards, there appears to have been some method in Messerschmitt’s madness after all. While there’s little concrete technical info available on the mark, the C-1 was most likely an insurance policy for the event that Ar 10 production became disrupted or sidetracked to other more important projects – a policy not unlike that later employed by Avro with the Bristol Hercules-engined Lancaster B II.

At the other end of the spectrum was a stillborn version that some sources also label as a C-1 – which, given the German aeronautical industry’s policy of reusing designations of failed models, was entirely possible. Diametrically opposed to the Siemens-engined version, this C-1 was to have been a high-speed model, fitted with a Hirth HM512 inverted V12 that would have developed an astounding 400 HP on takeoff! 🙂 Ground testing in 1938 though had quickly revealed that noticeable airframe vibration and buffeting was to be expected above 325 km/h, which would progressively become so severe that it could even tear the airframe apart. Given the scope of engineering changes that would be needed to make this version work – and the impending shift of the German military industry into high gear – meant the project was quietly dropped…

That the only way was up was quite literally demonstrated in 1939 by a specially-modified high-altitude Bf.108B-1 (lacking a special designation), built to capture the world altitude record for its class. Fitted with a supercharged Hirth HM508 inverted V8 producing 270 HP – and also providing air to pressurize the cabin – this aircraft had reached an impressive 9,125 m (29,930 ft) in the hands of Hirth’s managing director, Herman Illg.

Series production models were however less interesting – and had pretty soon started suffering from an acute case of Skyhawk-itis 😀 . If you took ten C172s of the same model and same production year and lined them all up, you’d be able to spot – with very little effort – at least one difference or unique feature on each aircraft… a different landing light here, a static port moved to there, a panel layout tweaked just so… and so on. As production ramped up, the Bf.108 became no different, with options and features freely flowing between versions. This had made sorting them by model a bit difficult and vague; however, after roving the Internet far and wide, I think I’d managed to hit the nail on the head in general terms:

• B-1: the already-described base model
• B-2: generally very similar, but with the wing fold system removed and the variable pitch P7 prop – offered as an option on the B-1 – fitted as standard. This version could easily be recognized by its thinner prop blades and slightly different propeller hub
• D-1: debuting in 1941, this was the first model produced outright for military use, and had featured a modified vertical stabilizer, improved fuel feed system, more powerful electrics, a windscreen wiper and a new constant speed prop, being turned by an Ar 10R engine of the same power output as the C (of note here is that “variable pitch” and “constant speed” propellers are not the same thing. A constant speed propeller – standard today – automatically varies the pitch of its blades to maintain the same RPM regardless of throttle setting; the variable pitch prop however was fully manual, with the pitch having to be readjusted with every change of throttle or airspeed. The 108’s variable pitch prop was operated by a large circular handle in the middle of the panel – known among the type’s pilots as the “coffee grinder” – and had added quite a bit to the crew’s workload)

The D-1 would also signal the last of German Bf.108 production before the whole works were transferred to France at the beginning of 1942. In a bid to free up domestic production capacity for badly needed Bf.109s, the B-2 and D-1 were allotted to the factory of the Société Nationale de Constructions Aéronautique du Nord – SNCAN, or simply Nord – just outside Paris, where they would remain until the end of the war in France – with interesting consequences.

Following the country’s liberation in the summer of 1944, SNCAN – having produced just 170 aircraft out of the type’s total production run of about 880 – found itself with a significant number of uncompleted airframes and engines. Deciding it would be a waste to just throw them all away – and desperate to gain a foothold in the country’s recovering economy – the top brass elected to restart production of the 108 in the guise of the Nord Pingouin (what a demotion – from an impressive meteorological phenomenon to a cute polar animal 😀 ). The first model, the 1000 Pingouin, was virtually identical to the Bf.108B-2, save for the reintroduction of the B-1’s folding wings and the refitting of the D-1’s improved vertical stabilizer.

Once these stocks had been exhausted, it was a relatively straightforward matter to re-manufacture the airframes from the original plans, the WW 2 production tooling having already been set up and waiting. However, the engines had proved to be a bigger challenge, having been produced in – and imported from – Germany during the war. The only way around this was to use a local engine of similar power; but the only unit available was the Renault 6Q family of six cylinder inverted inlines, a powerplant considerably longer than the compact Ar 10. But having no realistic alternative, SNCAN went ahead with the redesign, creating the long-nose 1001 Pingouin I. Powered by the 233 HP 6Q-11, this model was quickly followed by the 1002 Pingouin II, which upgraded to the slightly more powerful 240 HP 6Q-10 – and which would eventually become the most common of all the Pingouins.

These would eventually number at 286, bringing the 108’s overall total to a tad over 1,100 aircraft. However, I was unable to confirm with absolute certainty when French production had actually ceased – but given the type’s low rate of production, I’d guesstimate the aircraft had disappeared from the production lines during the early 50s.

Note: some of the surviving aircraft have since been retrofitted with standard Lycoming and Continental engines, and have shorter, broader and more oval cowlings. For the sake of simplicity, I decided only to represent the original Renault-powered models here.

A (third) leg to stand on

However, the end of the Pingouin was not the end of France’s 108 connection 🙂 . Back in 1943, SNCAN – under prompting and guidance from Messerschmitt – had started working on an experimental tricycle version of the Bf.108B-2, which would have been known as the Me-208 (since this version was conceived after the creation of the Messerschmitt Flugzeugbau, it was allocated the Me prefix). Two prototypes were built during the last days of the occupation of France, but only one would actually survive to its end, later to become known as the Nord 1100 Noralpha. As in the case of the 108, SNCAN had decided to see the design though to the end – having already done 90% of the work – and market it under its own name. The result was the 6Q-10 engined 1101 Noralpha (known in French military service as the Nord Ramier, or “dove”), whose production ran to the 205 mark.

Much like the 108, the Noralpha did not see much in the way of different versions, but had compensated for it by a history of use as an engine testbed 🙂 . The first (rather conservative) iteration was the planned, but never built, 1102 Noralpha II, which would have been powered by the 6Q-11 seen on the Pingouin I. This version was followed by the slightly more successful 1104 – which had actually made it to the prototype stage, but no further – powered by a Spanish Potez 6Dba engine of the same configuration and power output as the 6Q-10.

However, the ultimate expression of power – and arguably of the entire 108 line – came in the form of two 1959 SFERMA-Nord 1110 Nord-Astazous. A project of the equally long-named Société Française d’Entretien et de Réparation de Matériel Aéronautique – SFERMA, a company formed in 1949 for the purpose of repairing and overhauling civil and military aircraft – the 1110s were conceived as testbeds for the in-development Turbomeca Astazou turboprop. The first example started out in life as the 150th 1101 Ramier produced, and was initially fitted with the 467 HP Astazou I. A bit later in the program, this aircraft – along with an additional 1101 – was re-equipped with the more powerful 550 HP Astazou II, as well as a host of other modifications including shorter span wings with cut off wingtips and vertical tail surfaces of increased size (to provide more stability at higher speeds).

Like the Me-208 though, only one of these amazing aircraft would actually survive to fly another day once the Astazou test program came to an end. Owned and operated by the Association Antilope under the reg F-AZNR, the above pictured example is still airworthy and beautifully maintained, happily plying the airshow circuit in France on a regular basis 🙂 .

The wind that keeps on blowing

While the type’s prime – in any version – had passed a long time ago, its status as one of the preeminent touring aircraft of the 30s had naturally had an effect on its current status of a desirable WW 2-era warbird 🙂 . Most estimates suggest that somewhere between 25 and 30 Taifuns and Nords are still airworthy today – a number of which are, unsurprisingly, operated in Germany. Aside from Messerschmitt’s own historic flight – the previously mentioned Messerschmitt Stiftung, part of the EADS consortium – another famous 108 operator is Lufthansa’s vintage aircraft division, the Lufthansa Stiftung. Possibly the best known of all surviving 108s, the company’s silver B-1 – registered D-EBEI – also shows that there’s still some mischevous spirit left in one of the world’s most serious companies; for a Taifun named Elly Beinhorn was just too good an opportunity to pass up 😀 .

D-EBEI gallery @ Airliners.net

For photos of other flying – and museum – examples, some of which are too good to cram in here, you can visit these galleries at Airliners.net, which I’d sorted by type 🙂 :

• Bf.108 & Pingouin gallery
• Noralpha gallery

Bf.108 Specifications & Performance

Version overview

Since keeping track of all the 108 versions can be a handful – and was quite a frustration for me as I was writing (and rewriting) this 🙂 – I’ve decided it would be prudent to sum them all up in one place, along with a few of their distinguishing features:

Sources

• Aeronet Aviacion (previously linked)
• Airliners.net
• Aviation Ancienne (in French)
• Axis Aircraft of World War II book, David Mondey
• EADS History (previous iteration of the page)
• NZ Warbirds