| Type | Single seat glider | |
| Dimensions | Length 5,32 m, height 1,85 m, span 11,6 m, wing area 16 m2, aspect ratio 8,4, root chord 1,8 m | |
| Weights | Empty 80 kg, max. flying weight 176 kg, wing load 11 kg/m2 | |
| Performance | Max. glide ratio 16, min. sink 0,8 m/sec. | |
| Type | Werk.Nr | Registration | History | |
| Gö 449 | ||||
To continue the gliding research of the Academic Flying Group of the Technical University of Hanover, which had begun with the Vampyrs, the griffin was constructed by Dipl.-Ing. Hentzen and Martens, again in consultation with Prof. Dr.-Ing. A. Prüll and Dipl.-Ing. H. Dorner. The construction was also again taken over by the Hanoverian Waggonfabrik. The aim was to significantly reduce weight with a smaller wingspan in order to obtain a manoeuvrable machine. Particular emphasis was placed on low air resistance. The cantilevered monoplane therefore has particularly sleek shapes. The wing was again made in three parts; however, the middle section, which is only 1.30 m wide, is firmly attached to the fuselage as a canopy. The 5.15 long, trapezoidal surfaces adjoin, so that the span is 11.60 m. The greatest depth of the surfaces is 1.80 m, the depth at the ends of the wings 1 m. The load-bearing area is therefore 15 sqm. On the canopy, the profile is 28 cm high; it then tapers evenly. The construction of the wing was again single-spar in conjunction with a torsion-resistant plywood nose. The spar is designed as a normal lattice girder with a plywood web. The pressure belts and the rods, which
are particularly stressed during landing, are reinforced. The spar spacing is 40 cm, but lightened auxiliary ribs are arranged at the front of the profile to ensure that the profile is properly maintained. New paths have been taken in lateral control. The plywood tube, which together with the spar absorbs the torsional forces, terminates about halfway through the starting surfaces. The end of the wing is therefore no longer torsion-resistant. Through a duralumin tube running parallel to the spar, which is firmly connected to it at the end of the spar, the torsional forces are absorbed in this surface piece. At the same time, it is possible to twist the tube and thus twist the wing ends. This lateral control proved to be extraordinarily effective. The last angles of the wing ends are provided with duralumin sheet metal on the underside to prevent damage to the covering fabric when the aircraft is positioned after landing. The connection of the surfaces with the canopy is done like in the vampire. The connection of the outer head tubes is made by a jaw clutch, which secures itself and allows a flawless transmission of power. The fuselage is spindle-shaped and. as far as the accommodation of the Fuehrer permits. The leader's head lies in a section of the canopy, otherwise the guide is completely enclosed in the fuselage.
The fuselage frames sit firmly in four weakly dimensioned spars, as the absorption and transmission of the forces takes place exclusively through the wood skin. The wing spar is organically connected to the main frame. An auxiliary spar of the canopy also transfers the forces to a strong fuselage frame. Steel belts radiating from the spars ensure that power is transmitted according to each load case. The take-off and landing gear consists of only two roller balls lying one behind the other. The undamped elevator with a capacity of 1.8 square meters is operated by a bumper, the rudder connected to a keel fin by cable pulls in the usual way. The keel area has 0.6 square meters, the rudder 0.5 square meters.
In the Rhön Competition in 1922 and 1923, numerous flights, including one of 45 minutes, were carried out by Martens, Hentzen and Koch, but the aircraft did not prove to be on a par with the Vampire. Despite the more favorable aerodynamic formation, this is due to the unfavorable shape of the surface and the worse aspect ratio on the one hand, and the complete encapsulation of the guide on the other, which makes it difficult for it to feel the air flow.
are particularly stressed during landing, are reinforced. The spar spacing is 40 cm, but lightened auxiliary ribs are arranged at the front of the profile to ensure that the profile is properly maintained. New paths have been taken in lateral control. The plywood tube, which together with the spar absorbs the torsional forces, terminates about halfway through the starting surfaces. The end of the wing is therefore no longer torsion-resistant. Through a duralumin tube running parallel to the spar, which is firmly connected to it at the end of the spar, the torsional forces are absorbed in this surface piece. At the same time, it is possible to twist the tube and thus twist the wing ends. This lateral control proved to be extraordinarily effective. The last angles of the wing ends are provided with duralumin sheet metal on the underside to prevent damage to the covering fabric when the aircraft is positioned after landing. The connection of the surfaces with the canopy is done like in the vampire. The connection of the outer head tubes is made by a jaw clutch, which secures itself and allows a flawless transmission of power. The fuselage is spindle-shaped and. as far as the accommodation of the Fuehrer permits. The leader's head lies in a section of the canopy, otherwise the guide is completely enclosed in the fuselage.
The fuselage frames sit firmly in four weakly dimensioned spars, as the absorption and transmission of the forces takes place exclusively through the wood skin. The wing spar is organically connected to the main frame. An auxiliary spar of the canopy also transfers the forces to a strong fuselage frame. Steel belts radiating from the spars ensure that power is transmitted according to each load case. The take-off and landing gear consists of only two roller balls lying one behind the other. The undamped elevator with a capacity of 1.8 square meters is operated by a bumper, the rudder connected to a keel fin by cable pulls in the usual way. The keel area has 0.6 square meters, the rudder 0.5 square meters.
In the Rhön Competition in 1922 and 1923, numerous flights, including one of 45 minutes, were carried out by Martens, Hentzen and Koch, but the aircraft did not prove to be on a par with the Vampire. Despite the more favorable aerodynamic formation, this is due to the unfavorable shape of the surface and the worse aspect ratio on the one hand, and the complete encapsulation of the guide on the other, which makes it difficult for it to feel the air flow.
THE ELEGANT BIRD "Greif"
With their "Vampyr," the Hanoverians had already paved the way for the high-performance glider in 1921. With the aerodynamically perfected further development, the "Greif," they wanted to remain at the forefront! What can still send shivers down the spines of visitors in the gleaming sand sea of the Gobi Desert are the frequent fossil remains of Protoceratops. These bleached bones of a dinosaur genus with a parrot-like beak and the large neck frill that so strongly resembles the beginnings of wings were often found standing upright in sandstorms. bthe terror of the sky- then. For that nomadic people of the pre-Christian century, the animal remained a monster to be feared more than the inhospitable nature of the desert. Eagle's head, dagger-like talons, lion's body and wings. It guarded the gold of the mountains: the griffin. Greeks who traded with the Scythians carried the myth westward. But the further it spread from its original source, the more it became entrenched in the myth. When the griffin was removed, it became the ancient Near Eastern mythical creature that eventually attained sanctity, becoming Apollo's companion in Greek mythology.
Heraldry ultimately transformed it in the treasure guardian, became a symbol of wisdom and attentiveness. This aspect, in turn, likely prompted two Harvard students in 1922 to name their innovative new glider simply and majestically Griffin. Meanwhile, the students of the Aeronautical Society at the University of Aachen, under their professor Theodore von Karman, had attracted attention. The Black Devil and the improved Blue Mouse, created by his assistant Wolfgang Klemperer, excelled at the first Rhön competitions in 1920 and 1921. The cantilever low-wing monoplanes with their thick wing profiles were superior to all competitors designed according to conventional principles.
That changed on the third-to-last day of the 1921 competition. The students of the Technical University of Hanover appeared with their Vampyr, a high-wing monoplane, which also had a thick airfoil. But it wasn't just the unusual luster of the large quantities of cleanly processed plywood with its impressively impregnated grain that made this construction so extraordinary, but its overall appearance. All those involved, with their forward-looking vision, sensed: The searching and experimenting had come to an end – here, for the first time, was the fundamental design for the glider of the future. And so it was. The idea originated with Prof. Dr. Arthur Pröll (1876-1957), holder of the Chair of Aeronautical Engineering at the Technical University of Hanover. To have it developed further, he explained his basic ideas to his assistant, the later Professor Georg Madelung (1889-1972). And he then... The register of his knowledge and professional experience. Prof. Dr. Wilhelm Hoff - during the First World War Head of the aircraft department of the DVL (German Research Institute for Aviation) and from 1921 its overall director - in a report written immediately following the Rhön competition of 1921 by the WGL (Scientific Society for Aviation), he champions the
creators: "...carefully selected a wing cross-section. which proved extremely favorable for the sinking speed. The wings are not only stiff but also robustly constructed in an exemplary, expert manner, because they are designed so that a main spar, which is torsionally rigid through its connection with the spar edge, supports the ribs." Hoff also mentions the previously unusual robustness of the construction during an accident.
In fact, Madelung's decision for a thick airfoil stemmed from his work at Junkers in Dessau, and for the first-ever implemented idea of a single-spar wing, he drew inspiration from
a technical treatise, the publication of which was already 25 years in the past. For the design work, Madelung relied on students from the university. firstly, the former leader of a fighter squadron and Pour le Mérite recipient Walter Blume (1896-1964), who was responsible for the wing center section, and Arthur Martens—one of the subsequent fathers of the Greif—in whose legacy "...carefully selected a wing cross section.which proved extremely favorable for the sinking speed. The wings are not only stiff but also robustly constructed in an exemplary, expert manner, because they are designed so that a main spar, which is torsionally rigid through its connection with the spar edge, supports the ribs."
Hoff also mentions the previously unusual robustness of the construction during an accident. In fact, Madelung's decision for a thick airfoil stemmed from his work at Junkers in Dessau, and for the first-ever implemented idea of a single-spar wing, he drew inspiration from a technical treatise, the publication of which was already 25 years in the past.
For the design work, Madelung relied on students from the university. firstly, the former leader of a fighter squadron and Pour le Mérite recipient Walter Blume (1896-1964), who was responsible for the wing center section, and Arthur Martens—one of the subsequent fathers of the Greif—in whose legacy
But the goal was set higher. Martens and Hentzen decided to jointly develop an avant-garde new design based on the established foundation as their diploma thesis. Both were 24 years old at this time and trained military pilots. Arthur Martens (1897-1937), the son of a farmer from the Fallingbostel district, remained involved in gliding even after his studies. He achieved international success, including setting a distance record of 12 kilometers at the 4th Rhön Gliding Competition. In 1924, he made the first Alpine gliding flight in Asiago, Italy, with a 21.2-km flight from Monte Mazze to Deville. In 1925, he was a successful participant in the Crimea Gliding Competition. On the Wasser-
kuppe he founded the Martens Gliding School, which, after one year of existence, was transferred to the Rhön-Rossitter Gesellschaft. Moreover He subsequently designed a whole series of successful glider designs.
From the winter of 1925/26, he took up a position as head of the metal propeller department at the Heddernheim Copper Works (Frankfurt am Main), a position he held until his tragic death. On November 16, 1937, a Belgian airliner crashed into a chimney during a rough approach to Ostend and broke apart. All the occupants perished. Arthur Martens was among them. He was a guest of the Hereditary Grand Duke of Hesse and his family, returning from a wedding in London. Fritz Heinrich Hentzen(1897-1978) enrolled at the Technical University in December 1918 to study large and diesel engines. Unlike Martens, he found gliding only temporarily interesting. Sant. He then designed light aircraft together with Blume before in 1934 - after an interlude at Fokker - he went to the Bavarian Aircraft Works (BFW) as production director. During the war, he became head of the production group for series production at Messerschmitt-Werke. After the war, he took on tasks for India and Egypt on behalf of Messerschmitt.
During the design of the Hannover H1 Vampyr, a model one-tenth the size was examined by the Göttingen Model Research Institute for Aerodynamics (MVA), which was renamed the Göttingen Aerodynamic Research Institute (AVA) shortly afterwards. The measurements were taken on a model with the square fuselage that was ultimately used for cost reasons, but also on a version with an oval fuselage cross-section, which was naturally significantly larger.better results. Martens and Hentzen chose this round fuselage for their new design, which bore the designation Hannover H2 and the name Greifer- But they did not choose the fuselage as it had been measured, namely with a tapered small attachment behind the pilot's head, which carried the wing. This neck in particular became a successful feature of their Darmstadt competitors (TH Darmstadt) a short time later in their so-called "Darmstadt School". Martens and Hentzen aimed for frontal drag reduction at all costs. The fuselage cross-section was cast to fit the body and measured very precisely. Only the head was to protrude, for which a cutout was provided in the central wing nose. Otherwise, the structure was similar to that of the Vampyr.
With their "Vampyr," the Hanoverians had already paved the way for the high-performance glider in 1921. With the aerodynamically perfected further development, the "Greif," they wanted to remain at the forefront! What can still send shivers down the spines of visitors in the gleaming sand sea of the Gobi Desert are the frequent fossil remains of Protoceratops. These bleached bones of a dinosaur genus with a parrot-like beak and the large neck frill that so strongly resembles the beginnings of wings were often found standing upright in sandstorms. bthe terror of the sky- then. For that nomadic people of the pre-Christian century, the animal remained a monster to be feared more than the inhospitable nature of the desert. Eagle's head, dagger-like talons, lion's body and wings. It guarded the gold of the mountains: the griffin. Greeks who traded with the Scythians carried the myth westward. But the further it spread from its original source, the more it became entrenched in the myth. When the griffin was removed, it became the ancient Near Eastern mythical creature that eventually attained sanctity, becoming Apollo's companion in Greek mythology.
Heraldry ultimately transformed it in the treasure guardian, became a symbol of wisdom and attentiveness. This aspect, in turn, likely prompted two Harvard students in 1922 to name their innovative new glider simply and majestically Griffin. Meanwhile, the students of the Aeronautical Society at the University of Aachen, under their professor Theodore von Karman, had attracted attention. The Black Devil and the improved Blue Mouse, created by his assistant Wolfgang Klemperer, excelled at the first Rhön competitions in 1920 and 1921. The cantilever low-wing monoplanes with their thick wing profiles were superior to all competitors designed according to conventional principles.
That changed on the third-to-last day of the 1921 competition. The students of the Technical University of Hanover appeared with their Vampyr, a high-wing monoplane, which also had a thick airfoil. But it wasn't just the unusual luster of the large quantities of cleanly processed plywood with its impressively impregnated grain that made this construction so extraordinary, but its overall appearance. All those involved, with their forward-looking vision, sensed: The searching and experimenting had come to an end – here, for the first time, was the fundamental design for the glider of the future. And so it was. The idea originated with Prof. Dr. Arthur Pröll (1876-1957), holder of the Chair of Aeronautical Engineering at the Technical University of Hanover. To have it developed further, he explained his basic ideas to his assistant, the later Professor Georg Madelung (1889-1972). And he then... The register of his knowledge and professional experience. Prof. Dr. Wilhelm Hoff - during the First World War Head of the aircraft department of the DVL (German Research Institute for Aviation) and from 1921 its overall director - in a report written immediately following the Rhön competition of 1921 by the WGL (Scientific Society for Aviation), he champions the
creators: "...carefully selected a wing cross-section. which proved extremely favorable for the sinking speed. The wings are not only stiff but also robustly constructed in an exemplary, expert manner, because they are designed so that a main spar, which is torsionally rigid through its connection with the spar edge, supports the ribs." Hoff also mentions the previously unusual robustness of the construction during an accident.
In fact, Madelung's decision for a thick airfoil stemmed from his work at Junkers in Dessau, and for the first-ever implemented idea of a single-spar wing, he drew inspiration from
a technical treatise, the publication of which was already 25 years in the past. For the design work, Madelung relied on students from the university. firstly, the former leader of a fighter squadron and Pour le Mérite recipient Walter Blume (1896-1964), who was responsible for the wing center section, and Arthur Martens—one of the subsequent fathers of the Greif—in whose legacy "...carefully selected a wing cross section.which proved extremely favorable for the sinking speed. The wings are not only stiff but also robustly constructed in an exemplary, expert manner, because they are designed so that a main spar, which is torsionally rigid through its connection with the spar edge, supports the ribs."
Hoff also mentions the previously unusual robustness of the construction during an accident. In fact, Madelung's decision for a thick airfoil stemmed from his work at Junkers in Dessau, and for the first-ever implemented idea of a single-spar wing, he drew inspiration from a technical treatise, the publication of which was already 25 years in the past.
For the design work, Madelung relied on students from the university. firstly, the former leader of a fighter squadron and Pour le Mérite recipient Walter Blume (1896-1964), who was responsible for the wing center section, and Arthur Martens—one of the subsequent fathers of the Greif—in whose legacy
But the goal was set higher. Martens and Hentzen decided to jointly develop an avant-garde new design based on the established foundation as their diploma thesis. Both were 24 years old at this time and trained military pilots. Arthur Martens (1897-1937), the son of a farmer from the Fallingbostel district, remained involved in gliding even after his studies. He achieved international success, including setting a distance record of 12 kilometers at the 4th Rhön Gliding Competition. In 1924, he made the first Alpine gliding flight in Asiago, Italy, with a 21.2-km flight from Monte Mazze to Deville. In 1925, he was a successful participant in the Crimea Gliding Competition. On the Wasser-
kuppe he founded the Martens Gliding School, which, after one year of existence, was transferred to the Rhön-Rossitter Gesellschaft. Moreover He subsequently designed a whole series of successful glider designs.
From the winter of 1925/26, he took up a position as head of the metal propeller department at the Heddernheim Copper Works (Frankfurt am Main), a position he held until his tragic death. On November 16, 1937, a Belgian airliner crashed into a chimney during a rough approach to Ostend and broke apart. All the occupants perished. Arthur Martens was among them. He was a guest of the Hereditary Grand Duke of Hesse and his family, returning from a wedding in London. Fritz Heinrich Hentzen(1897-1978) enrolled at the Technical University in December 1918 to study large and diesel engines. Unlike Martens, he found gliding only temporarily interesting. Sant. He then designed light aircraft together with Blume before in 1934 - after an interlude at Fokker - he went to the Bavarian Aircraft Works (BFW) as production director. During the war, he became head of the production group for series production at Messerschmitt-Werke. After the war, he took on tasks for India and Egypt on behalf of Messerschmitt.
During the design of the Hannover H1 Vampyr, a model one-tenth the size was examined by the Göttingen Model Research Institute for Aerodynamics (MVA), which was renamed the Göttingen Aerodynamic Research Institute (AVA) shortly afterwards. The measurements were taken on a model with the square fuselage that was ultimately used for cost reasons, but also on a version with an oval fuselage cross-section, which was naturally significantly larger.better results. Martens and Hentzen chose this round fuselage for their new design, which bore the designation Hannover H2 and the name Greifer- But they did not choose the fuselage as it had been measured, namely with a tapered small attachment behind the pilot's head, which carried the wing. This neck in particular became a successful feature of their Darmstadt competitors (TH Darmstadt) a short time later in their so-called "Darmstadt School". Martens and Hentzen aimed for frontal drag reduction at all costs. The fuselage cross-section was cast to fit the body and measured very precisely. Only the head was to protrude, for which a cutout was provided in the central wing nose. Otherwise, the structure was similar to that of the Vampyr.
A similar airfoil had also been chosen, which, however, had a significantly lower curvature on the underside as its main difference. Since the flights in 1921 had shown that the ailerons of the Vampyr were insufficiently effective, the wing had been rebuilt with a complicated and elaborate kinematic system for wing warping. Wing warping was planned for the Greif from the outset – for which a simple, elegant solution was provided by a duralumin tube. had been found. The new model was also built at HAWA, because only their trained specialists could create such a delicate yet stable structure. While the Vampyr weighed 120 kg empty, the Greif now weighed only 80 kg.
For the 3rd Rhön Competition, the Greif and Vampyr, accompanied by their designers, were transported by rail to the Rhön region. On August 16, 1922, the two designs from Hanover were ready for flight on the slope. Hentzen was the first to take off in the Vampyr. He stayed in the air for 101 seconds, covered a distance of 990 meters, and thus fulfilled the requirements for his glider license.ID. A quarter of an hour later, Martens took off with the Greif, pulled by three men at each end of the launch rope and with the help of two more assistants at the wingtips, for the maiden flight. The flight lasted 87 seconds and covered a distance of 830 meters. This fulfilled the requirements for the aircraft certification.
Since the aircraft had proven to be nose-heavy, lead plates were installed in the tail. With this, Martens went to the launch site again in the late afternoon. He was able to stay airborne for 9 minutes and 40 seconds. It also became apparent with this very well-thought-out new design that many more test flights were needed. were to eliminate all the minor flaws. But one thing could already be said: The Greif glides exceptionally well in updrafts! Hans Rolshoven, a keen observer, describes his impressions of these first short flights: "Martens takes off in the Greif, he climbs wonderfully high, and glides strongly upwards in the updraft to the west, but when turning he loses a great deal of altitude and lands smoothly on the Eube." This enthusiasm is hardly comprehensible from today's perspective, but back then it was an absolute sensation to see a motorless aircraft rise above the altitude of the launch point. Hentzen and Martens flew the Vampyr on the following days. and Greif reciprocally. But even for such gliders, the price of 100,000 marks, which the German aircraft industry had set in the spring of that year for a motorless flight, still seemed unattainable. It was supposed to last 40 minutes between two points 150 meters apart and be concluded with a final glide of five kilometers. Martens tries it. On August 18, he takes off despite the wind fluctuating between 6 and 8 m/s. He manages to stay in the air for over an hour, landing 9,500 meters away. The next day, Hentzen even manages two hours.
While on August 24, 1922, Hentzen was completing one loop after another in the Vampyr for a three-hour flight, Martens tried to do the same in the Greif. But after just 26 minutes, he had to land again. It was quite obvious: the younger and more modern Greif was inferior to the Vampyr. But why? Once again, the AVA in Göttingen was consulted. They measured a model of the Greif, also at a scale of 1:10. And lo and behold – the wing cutout was the culprit. Because cutouts in the wings could often significantly improve the occupants' visibility, they had been examined for their detrimental effects. It had been found that cutouts on the trailing edge only resulted in a slightly increased profile drag was generated.
However, with cutouts in the leading edge, the airflow in the center section breaks away prematurely, causing an enormous increase in induced drag.
The Greif was nevertheless flown, even though it never distinguished itself in terms of performance. For the 1923 Rhön competition, it was registered by the Aeronautical Science Group at the Technical University of Hanover. It bore the number 68 and had a modified horizontal stabilizer, the rudder of which had been moved further back to increase the moment arm and fitted with a damping surface. For the 1924 Rhön competition, the Aeronautical Research Institute of the Technical University of Hanover was the applicant. It participated under registration number 15.
The end of the Greif came shortly thereafter. Among other groups, the Hanoverians had also been invited to participate in the Zugspitze competition starting in the last days of January 1925. The aircraft started from Kochel- mountain. to glide into the valley. Upon landing in Garmisch, it crashed into an obstacle. A foundation, however, enabled the construction of a new aircraft before the competition in Rossitten. Thus, practically from the wreckage of the Greif, the Hanover H8 Phoenix proudly rose.
Technical Description
Wings: Three-section; center section rectangular, outer sections trapezoidal with a 0-degree swept angle (root depth 1.80 meters, tail depth 0.95 meters). The center section, completely covered with plywood, has a main spar at approximately 1/3 of the chord and an additional auxiliary spar behind it. It is connected to the fuselage by an organic connection with the fuselage frames and additionally by steel bands that radiate from the spars into the fuselage skin. The main spar is designed as a lattice girder with a plywood web. It has reinforced compression straps for the stresses during landing. The plywood ribs have glued-on rods. The root area of the outer wing sections is formed as a torsionally rigid tube from the leading edge spar to the main spar, extending to slightly over half the wingspan. For the remainder up to the wingtips, twistability was deliberately sought to enable steering around the longitudinal axis through its twisting. The torsional forces are absorbed here by a duralumin rib. The wing is mounted on a tube that runs parallel to the spar, is firmly connected to it at the spar end, and twists cause the twisting. The outer wings are connected to the center wing at three points (upper and lower spar caps of the main spar and leading edge spar) via fittings with self-locking spring bolts. These allow for quick assembly. The aileron control tubes are quickly connected by a self-locking claw coupling. The entire wing weighs only 34 kg.
Fuselage: Elliptical cross-section. Structure consisting of bulkheads and four stringers, completely covered with plywood skinning that absorbs almost all forces. Fuselage width 0.55 meters with the smallest possible cross-section to fully accommodate the pilot's body, except for the head.which has a cutout in the wing
nose. Fuselage mass 46 kg.
Tailplane: Wooden construction with fabric covering. Horizontal stabilizer undamped, but relieved of load. Area 1.8 sq m. Operated via control stick by pushrod. Rudder (0.5 sq m) damped by fin (0.6 sq m), operated by cables. Tailplane mass 6.4 kg.
Landing gear: Two leather rollers, mounted one behind the other in the fuselage bottom.
Paintwork: White fabric covering, cellulose-coated except for the wing
valves. Plywood skinning impregnated with clear varnish.
Lettering - "Greif-" on the fuselage nose and (small) "Hanno-" on the tail - in white.
For the 3rd Rhön Competition, the Greif and Vampyr, accompanied by their designers, were transported by rail to the Rhön region. On August 16, 1922, the two designs from Hanover were ready for flight on the slope. Hentzen was the first to take off in the Vampyr. He stayed in the air for 101 seconds, covered a distance of 990 meters, and thus fulfilled the requirements for his glider license.ID. A quarter of an hour later, Martens took off with the Greif, pulled by three men at each end of the launch rope and with the help of two more assistants at the wingtips, for the maiden flight. The flight lasted 87 seconds and covered a distance of 830 meters. This fulfilled the requirements for the aircraft certification.
Since the aircraft had proven to be nose-heavy, lead plates were installed in the tail. With this, Martens went to the launch site again in the late afternoon. He was able to stay airborne for 9 minutes and 40 seconds. It also became apparent with this very well-thought-out new design that many more test flights were needed. were to eliminate all the minor flaws. But one thing could already be said: The Greif glides exceptionally well in updrafts! Hans Rolshoven, a keen observer, describes his impressions of these first short flights: "Martens takes off in the Greif, he climbs wonderfully high, and glides strongly upwards in the updraft to the west, but when turning he loses a great deal of altitude and lands smoothly on the Eube." This enthusiasm is hardly comprehensible from today's perspective, but back then it was an absolute sensation to see a motorless aircraft rise above the altitude of the launch point. Hentzen and Martens flew the Vampyr on the following days. and Greif reciprocally. But even for such gliders, the price of 100,000 marks, which the German aircraft industry had set in the spring of that year for a motorless flight, still seemed unattainable. It was supposed to last 40 minutes between two points 150 meters apart and be concluded with a final glide of five kilometers. Martens tries it. On August 18, he takes off despite the wind fluctuating between 6 and 8 m/s. He manages to stay in the air for over an hour, landing 9,500 meters away. The next day, Hentzen even manages two hours.
While on August 24, 1922, Hentzen was completing one loop after another in the Vampyr for a three-hour flight, Martens tried to do the same in the Greif. But after just 26 minutes, he had to land again. It was quite obvious: the younger and more modern Greif was inferior to the Vampyr. But why? Once again, the AVA in Göttingen was consulted. They measured a model of the Greif, also at a scale of 1:10. And lo and behold – the wing cutout was the culprit. Because cutouts in the wings could often significantly improve the occupants' visibility, they had been examined for their detrimental effects. It had been found that cutouts on the trailing edge only resulted in a slightly increased profile drag was generated.
However, with cutouts in the leading edge, the airflow in the center section breaks away prematurely, causing an enormous increase in induced drag.
The Greif was nevertheless flown, even though it never distinguished itself in terms of performance. For the 1923 Rhön competition, it was registered by the Aeronautical Science Group at the Technical University of Hanover. It bore the number 68 and had a modified horizontal stabilizer, the rudder of which had been moved further back to increase the moment arm and fitted with a damping surface. For the 1924 Rhön competition, the Aeronautical Research Institute of the Technical University of Hanover was the applicant. It participated under registration number 15.
The end of the Greif came shortly thereafter. Among other groups, the Hanoverians had also been invited to participate in the Zugspitze competition starting in the last days of January 1925. The aircraft started from Kochel- mountain. to glide into the valley. Upon landing in Garmisch, it crashed into an obstacle. A foundation, however, enabled the construction of a new aircraft before the competition in Rossitten. Thus, practically from the wreckage of the Greif, the Hanover H8 Phoenix proudly rose.
Technical Description
Wings: Three-section; center section rectangular, outer sections trapezoidal with a 0-degree swept angle (root depth 1.80 meters, tail depth 0.95 meters). The center section, completely covered with plywood, has a main spar at approximately 1/3 of the chord and an additional auxiliary spar behind it. It is connected to the fuselage by an organic connection with the fuselage frames and additionally by steel bands that radiate from the spars into the fuselage skin. The main spar is designed as a lattice girder with a plywood web. It has reinforced compression straps for the stresses during landing. The plywood ribs have glued-on rods. The root area of the outer wing sections is formed as a torsionally rigid tube from the leading edge spar to the main spar, extending to slightly over half the wingspan. For the remainder up to the wingtips, twistability was deliberately sought to enable steering around the longitudinal axis through its twisting. The torsional forces are absorbed here by a duralumin rib. The wing is mounted on a tube that runs parallel to the spar, is firmly connected to it at the spar end, and twists cause the twisting. The outer wings are connected to the center wing at three points (upper and lower spar caps of the main spar and leading edge spar) via fittings with self-locking spring bolts. These allow for quick assembly. The aileron control tubes are quickly connected by a self-locking claw coupling. The entire wing weighs only 34 kg.
Fuselage: Elliptical cross-section. Structure consisting of bulkheads and four stringers, completely covered with plywood skinning that absorbs almost all forces. Fuselage width 0.55 meters with the smallest possible cross-section to fully accommodate the pilot's body, except for the head.which has a cutout in the wing
nose. Fuselage mass 46 kg.
Tailplane: Wooden construction with fabric covering. Horizontal stabilizer undamped, but relieved of load. Area 1.8 sq m. Operated via control stick by pushrod. Rudder (0.5 sq m) damped by fin (0.6 sq m), operated by cables. Tailplane mass 6.4 kg.
Landing gear: Two leather rollers, mounted one behind the other in the fuselage bottom.
Paintwork: White fabric covering, cellulose-coated except for the wing
valves. Plywood skinning impregnated with clear varnish.
Lettering - "Greif-" on the fuselage nose and (small) "Hanno-" on the tail - in white.
