Bücker built two famous biplanes that look almost identical to a casual eye, and they are constantly confused. The Bü 131 Jungmann is the two-seat primary trainer — student in the front cockpit, instructor behind. The Bü 133 Jungmeister (“young master”) is a smaller, more powerful single-seat aerobatic development of it. Because the Jungmeister has only one seat, it physically cannot carry a passenger — so every genuine “fly in a Bücker biplane” experience is, necessarily, a two-seat Jungmann.

GoAviator’s Grenchen aircraft is exactly that: a two-seat Bü 131 Jungmann built under licence in 1939 by Doflug (Dornier-Werke) at Altenrhein, Switzerland, carrying the Swiss military registration A-66 (works number 79). The passenger rides up front while the pilot flies from the rear seat. GoAviator’s own listing labels the machine a “Jungmann” — the two-seater — but writes the type number as “Bü 133,” which is simply an error: a Bü 133 Jungmeister could never take a passenger. What matters is that this is the two-seat Bü 131, the classic 1930s trainer this page is about.

The Jungmann was built around the Hirth family of inverted, air-cooled, inline four-cylinder engines. The prototype and early Bü 131A used the Hirth HM 60R of roughly 80 hp; the definitive Bü 131B adopted the larger Hirth HM 504 of about 105 hp, which gave crisper aerobatic performance. “Inverted” means the cylinders point downward from the crankcase — a layout that keeps the propeller thrust-line high and the nose slim, improving forward view and ground clearance. It is a modest, unstressed engine that runs happily on ordinary fuel, which is part of why the type is still practical to operate. Many surviving airframes — especially the Spanish CASA 1.131s — were re-engined over the years with the Spanish ENMA Tigre or with American Continental and Lycoming flat-fours, so two “identical” Jungmanns can sound and fly noticeably differently.

The Jungmann is a textbook example of 1930s light-aircraft construction. The fuselage is a welded chrome-molybdenum steel-tube truss, faired to shape with wooden formers and stringers and then covered in doped fabric. The wings are wooden two-spar structures, also fabric-covered, arranged as an equal-span single-bay biplane cell with N-struts and bracing wires. This makes the aircraft light and immensely repairable: a damaged tube can be cut out and re-welded, ribs can be rebuilt, and fabric can simply be renewed. It is that repairability — rather than any exotic material — that has kept so many Jungmanns flying for the better part of a century. The trade-off is maintenance: fabric ages, wood must be protected from moisture, and airframes need regular, skilled attention to stay airworthy.

The whole point of the Jungmann was ab-initio training — taking someone who had never flown and turning them into a pilot. Its two open cockpits sit in tandem, student in front and instructor behind, connected by a simple speaking-tube or, later, an intercom. The open layout was deliberate: it immersed the pupil in the sensations of flight and let the instructor watch head and hand movements directly. Because the aircraft was fully aerobatic yet forgiving, a syllabus could progress from straight-and-level and circuits all the way through spinning and aerobatics on the same airframe. Through the mid-1930s and into the war it was the first type flown at German flying schools, and the same qualities made it a favourite basic trainer for a dozen other air forces that bought or built it.

Few trainers were copied as widely as the Jungmann. Spain built it as the CASA 1.131 in large numbers and kept the line running into the 1960s, re-engining many with ENMA Tigre or, later, Continental engines — which is why a very large share of surviving “Jungmanns” are actually Spanish CASAs. Japan licence-built it as the Army Kokusai Ki-86 and the Navy Kyushu K9W Momiji (“maple leaf”). Suíça assembled it at Dornier/Doflug, Altenrhein, for the Swiss Air Force — the source of GoAviator’s aircraft. Czechoslovakia continued production after the war as the Aero C-4 / C-104 e Tatra T-131, and Hungary and Yugoslavia built or operated it as well. Because the variants differ in engine, equipment and detail fit, headline performance and production figures vary from source to source — treat any single total as an estimate rather than a hard fact.

Pilots who fly the Jungmann tend to run out of superlatives. The controls are light and beautifully matched, the aircraft “talks” to you through the stick, and it will loop, roll and spin cleanly on modest power while remaining forgiving of a beginner. It is slow — cruising around 170 km/h — and in an open cockpit you feel every knot of it: the slipstream on your face, the smell of the engine, the horizon tipping over the top wing. That sensory honesty, not raw performance, is the whole point, and it is precisely what a modern passenger experiences on the Grenchen flight. The lineage shows, too: the single-seat Jungmeister derived from it was a world-championship aerobatic aircraft, and the Jungmann carries the same delightful DNA in a gentler, two-seat form.

The specific aircraft MiGFlug’s partner GoAviator flies is a genuine 1939 Bü 131 Jungmann built under licence by Doflug (Dornier-Werke) at Altenrhein, Switzerland — works number 79, originally delivered to the Swiss Air Force as A-66. Switzerland operated its Doflug-built Jungmanns as primary trainers from 1936 until 1971, an extraordinary 35-year career, after which many passed straight into private and warbird hands. This machine is now a lovingly maintained warbird flown from Grenchen, with the passenger seated in the front cockpit. You can choose gentle sightseeing over the Swiss Mittelland and Jura, a full aerobatic sequence — loops, rolls, inverted flight, Immelmanns, spins — or a mix, with flights of roughly 30 or 60 minutes priced around 430–790 CHF. It is one of the only ways left to experience a pre-war Bücker biplane exactly as its first students did.

The Jungmann was the making of a company that would leave a mark on aviation far larger than its size. Carl Clemens Bücker was a First World War German naval aviator who, when post-war restrictions gutted German aircraft manufacturing, moved to Sweden and built up the firm Svenska Aero. There he honed both his engineering instincts and his eye for talent — hiring the young Swedish designer Anders J. Andersson. When Bücker returned to Germany and founded Bücker Flugzeugbau in 1932, Andersson came too, and became the creative force behind the company’s aircraft. In just a few years the pair produced the Bü 131 Jungmann, the Bü 133 Jungmeister and the Bü 181 Bestmann — a trio of trainers admired for exactly the same quality: light, honest, beautifully harmonised handling. Andersson later returned to work in Sweden, but the design philosophy he brought to Rangsdorf is why a Jungmann still feels so alive in the hands today.

The two principal German versions differ mainly in power. The original Bü 131A used the Hirth HM 60R of about 80 hp; the definitive Bü 131B fitted the larger HM 504 of roughly 105 hp, giving livelier climb and crisper aerobatics, and it was the B that was built and copied in the greatest numbers. Beyond Germany, the licence machines form a family of their own: the Spanish CASA 1.131 (often re-engined and produced into the 1960s), the Japanese Ki-86 e K9W Momiji, the Czechoslovak Aero C-4 / C-104 e Tatra T-131, and the Swiss Doflug/Dornier-built aircraft. It is easy to confuse the Jungmann with its stablemates, so it is worth being precise: the single-seat Bü 133 Jungmeister is the aerobatic champion derived from it, while the Bü 181 Bestmann is a later low-wing monoplane trainer — a different aircraft entirely. The Jungmann proper is always the two-seat biplane.

There is no meaningful “unit price” or official cost-per-flight-hour for a Bü 131. It was a 1930s military and club trainer, never sold on a modern open market, and the survivors are one-off restorations whose value depends entirely on condition, engine and provenance. In practice, running one today is the cost of a small vintage aeroplane: a modest-power engine burning ordinary avgas at a low rate, set against the real expense of maintaining a fabric-and-steel-tube airframe — recovering fabric, protecting woodwork, and keeping an ageing engine airworthy — to certified standard. Restored examples change hands for figures typical of desirable vintage biplanes rather than warbird fighters, but any precise number you see should be treated as an estimate. The clearest public price attached to the type is simply the ticket: MiGFlug’s partner GoAviator offers a passenger flight in a genuine open-cockpit Jungmann from Grenchen for roughly 430–790 CHF, depending on duration and whether you choose sightseeing or aerobatics.