Clamp Kl 35

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Clamp L35
Klemm Kl 35 in Swedish design
Type: School and sport aircraft
Design country:

German Reich NSGerman Reich (Nazi era) German Empire

Manufacturer:

Light aircraft construction Klemm

First flight:

February 1935

Production time:

1936-1943

Number of pieces:

1429

Klemm Kl 35D in the colors of the German Air Force

The Klemm Kl 35 was a training and sports aircraft developed by Leichtflugzeugbau Klemm GmbH on behalf of the Reich Ministry of Aviation (RLM) , which was the successor to the L and Kl 25 , which became famous worldwide, in the 1930s and 1940s in the classic Klemm design as a cantilever low-wing aircraft was built.

The fully aerobatic aircraft was shown for the first time in October 1935 at the International Air Show in Milan and soon found interest among many private individuals and foreign air forces, such as the Romanian and Hungarian , as well as the Swedish Flygvapnet , which alone bought 74 aircraft and called them Sk 15 used for training. At least five of them were float planes . However, there was no license building abroad.

Career

The aircraft was designed in 1934 on behalf of the Reich Aviation Ministry (RLM), with Friedrich Fecher responsible for the design. The so-called mixed construction was used , whereby steel was used for the fuselage, wood for the wings and tail units and only a little light metal for the cladding. It was the construction that was most valued at the RLM at that time because of the general material situation.

The machine first appeared in the aircraft development program on February 1, 1935. In it, the flight clearance at the manufacturer with March 1st and the delivery to the E -stelle (test center) Rechlin with June 1st was named as target. In reality, however, the then chief pilot from Klemm, Werner Marczinski , flew with V1, serial number (Wnr.) 959, registration D-EHXE, already in February, although the exact date is not known.

After Rechlin, the plane should have come according to schedule. But then there was a setback. Already on July 19, the V1 crashed during the test after a broken wing near Vietzen not far from Rechlin, killing both inmates, members of the E unit. Material defects came out as a not entirely satisfactory answer to the question of the cause . The further testing now had to be carried out with the V2, which the Wnr. 960 and had the registration D-ERQA. It was apparently already in Rechlin at the time of the crash, but the determination of the flight characteristics and performance, as well as the testing of the engine, apparently did not begin until the beginning of September. According to the plan, these trials should be completed by the end of March 1936.

production

The results seem to have turned out to be satisfactory, because according to delivery schedule No. 3 of July 1936, 23 aircraft were to be delivered between January and September 1937 at a rate increasing to 3 aircraft per month. It is noteworthy that Klemm also had to build 26 Fw 44s in around the same time . However, he was able to avoid that with cunning by sending the order off to his new plant in Halle. Everything speaks for the fact that the RLM was already looking for a licensee for the class 35 at that time, who was then found in Gerhard Fieseler . In its Kassel plant, in addition to its storks , which are just going into series production , He 72 and Fw 58 C were also built.

The order for the Kl 35 in delivery schedule No. 4 of October 1, 1936 already included 119 aircraft to be built by Klemm and 105 by Fieseler. On September 1st (LP 6) the production numbers were increased again, for Klemm now to 229, including 57 Kl 35 A with HM 60 R , of which the last 12 had to be delivered by the end of the following month. The number of aircraft to be built by Fieseler, all of the B version, was now 142, of which the first four were to be ready for acceptance in January 1938. From March onwards, both Klemm and Fieseler had to deliver 10 pieces per month. On August 15, 1938, the order to Klemm was increased to 313 pieces, 40 of which were already finished. Fieseler had also delivered 21 of the 142 Kl 35 B units that had been ordered. For this, the company had specified the serial numbers from 4001 to 4199. The first of these was given to the Kl 35 B aircraft with the registration D-ENBH. Because this amount of serial numbers was not enough in the end, it was continued, starting with 4500 or 4501, obviously until 4665. At that time, the RLM had to pay an amount of RM 17,500 for each machine delivered.

The fact that the production of the Kl 35 was further increased, but now already in the D version with a standard three-legged landing gear, is evident from the delivery plan no.10 of January 24, 1939. Therein the number of aircraft already delivered is given as 332, albeit without an indication of their origin, while the planning goes up to a total of 1386, which should have been reached in March 1942. That this number, but also the date, remained mere theory, was one of the reasons. a. the Bücker Bü 181 , which was to make its maiden flight a month after the planning was published.

With the end of production at Fieseler in November 1939, after 365 pieces, the RLM had found a new licensee for the production of the Kl 35 D in the Czech company Zlín , a subsidiary of the Bata shoe company . This company was supposed to build 323 aircraft by August 1942, so that by the final cessation of all production in May 1943 all three companies involved would have built a total of 1341 Kl 35s for the Luftwaffe. The order for Zlín seems to have been cut by 39 aircraft in favor of the new Bü 181 production, so that the end result is the number of 1302 aircraft built for the Air Force, as shown in the aircraft program 223/1 from 15 August 1943. In addition, however, there are aircraft built for private and export purposes, for which no figures have yet been released. Almost 700, to get to the total of around 2000 found in the literature, it could never have been.

production

The Klemm 35 was built in series by Klemm, Fieseler (GFW) and Zlín.

Construction numbers of the Klemm Kl 35:

Manufacturer 1935 1936 1937 1938 1939 1940 1941 1942 1943 total
Clamp 3 17th 53 201 186 174 74 6th 21st 735
GFW       90 92 182 1     365
Zlín           54 175 100   329
TOTAL 3 17th 53 291 278 410 250 106 21st 1429

In the RLM order, seven aircraft were delivered as pilot series, 57 with the HM 60 engine (A series) and 1302 with the HM 504 engine (B and D series), a total of 1366 Kl 35. The rest are private sales and the two prototypes.

Exports

Some of the exports are taken from the RLM series. Production since August 1942 was intended exclusively for export.

Exports of the Klemm Kl 35:

country 1936 1937 1938 1939 1940 1941 1942 1943 total
Norway 1               1
Sweden 1     8th 57 30th     96
Denmark     1           1
Hungary 2       1 1   2 6th
Slovakia           10 15th   25th
Romania 6th   12 6th   11 14th 19th 68
Lithuania     1 2         3
TOTAL 10 0 14th 16 58 52 29 21st 200

Deliveries to Sweden consisted of 22 civil aircraft and 74 aircraft (delivered in 1940 and 1941) for the Swedish Air Force. Klemm had built 13 serial numbers for the civil domestic market (1062–1063, 1068, 1141, 1143–1144, 1235–1236, 1239, 1506, 1523, 1580, 1660). Norway received the W.-Nr. 1142 LN-EAV, Denmark W.-No. 1521 OY-DYO, Lithuania the W.-Nr. 1522, 1573–1574, Romania the W.-Nr. 1030, 1060-1061, 1064-1067, 1145, 1231-1234, 1237-1238, 1503-1505, 1507, 1518-1519, 1560-1564. For Hungary only the W.-No. 1028 noted.

description

View into the rear cockpit of a Kl ​​35

The new design differed in many respects from the previous sample, Kl 25. In place of the previous pure wood construction of the fuselage, a welded tubular steel framework with a rectangular cross-section was created, which was brought into an oval shape with the help of shaping strips made of wood, whereby the semicircular back panel could be removed for maintenance purposes after loosening a few screws . In the fuselage there were two open seats, one behind the other, of which the rear one was adjustable in height during the flight, while the front one could only be adjusted in three different positions on the ground. A permanent cover for the two seats was available on request. Control sticks (the front one was removable) and pedals were available on both seats, but the mechanical wheel brakes could only be operated from the rear seat. The instrumentation was also a bit more extensive at the back. The wing center section was firmly welded to the fuselage structure in a slightly negative V-position , creating the characteristic kink of the structure. In the left part there was a lockable luggage compartment, in the right a fuel tank.

landing gear

The aircraft elegant looking had, at least in the embodiments A and B, a solid, clad Einbeinfahrwerk with muted Dowty - spring legs of EC Bad Cannstatt. The abrasive spur was rubber-sprung. The monopod landing gear on later aircraft was exchangeable for a simple and more robust three-legged landing gear with EC suspension, which was then used as standard in the D version. Conversely, the latter could also be changed back to the one-leg shape. Also float or snow runners could be used.

Structure and tail unit

The supporting structure was made entirely of wood in two spars , the front part was planked with plywood , otherwise covered with fabric. Four socket pins each connected the outer wings to the center piece. The latter could be entered thanks to stronger plywood.

The simple wooden tail unit was planked with plywood, the horizontal stabilizer supported by a strut to the lower fuselage chord. All oars were made of wood and covered with fabric. There were adjustable trim tabs on both halves of the elevator , while the rudder and ailerons had bow edges . The trim could be operated from both seats. Elevators and ailerons were mass balanced and operated by bumpers, while cables were used for the rudder. There were no landing flaps.

drive

Hirth HM-504 in Swedish class 35 D SE-BPU

The Hirth HM 60  R was still used as the engine in version A , while HM 504 A 2 was installed in all later versions . The entire engine cowling was connected to the engine and swung with it. It could easily be removed. The two engine mounts on the left and right were identical and therefore interchangeable. The engine was suspended in rubber swing bearings. It could be started with a hand crank attached to the side wall of the driver's seat. The fuselage fuel tank with 31 liters as a drop tank was installed between the fire frame and the front seat, while the main tank with 60 liters was located in the right wing center section. A separate lubricant reservoir was not necessary as the entire supply of 4.25 l was in the engine. A number of the aircraft delivered to Sweden had a second 60-liter fuel tank installed instead of the luggage compartment.

further explanation

It is noticeable that version Kl 35 B is immediately followed by D, so the letter C is missing. There was an airplane, if only for a short time, that bore this name. What was special about it was that, instead of the tubular steel hull, it had a hull made entirely of wood in the so-called partial shell construction developed by Hanns Klemm . Because of this fundamentally different structure, the aircraft was soon renamed Kl 106 and further developed under this name. Finally there was also an E version, which differed in the use of the HM 500 motor instead of the HM 504. For this, the RLM had already issued an order for 102 pieces on November 1, 1940 (LP18), which was then withdrawn, probably also because of the ongoing series of the Bü 181. Nevertheless, an aircraft with this designation and the registration D-EGJK is available at the Travemünde test site from July 1941. As early as 1937, Travemünde was involved in the testing and approval of an aircraft class 35 A W (W for water), which was delivered to Norway equipped with floats as Wnr 1183 with the registration LN-EAV .

Sporting successes

Klemm Kl 35 D D-EHKO (year of construction 1940, picture from 2005)

Many pilots took part in competitions with Kl 35. During the flight to Germany in 1937, the Taxis / Voy crew won the individual ranking with their Class 35 A. A little later, four aircraft were to be found in the ranking list of the international rally for sport and touring aircraft in 1937 in Dübendorf. 7th place went to the Hungarian von Buzay and 12th place for the Swede Simonsson, who had already finished fourth in the international star flight to the Summer Olympics in Rangsdorf a year earlier . The German Sachsenberg landed in 14th place and the chief pilot of Klemm, Hellmut Kalkstein, in 24th place . It was noteworthy, however, that two other aircraft from the Klemm company, namely two Swiss class 25 aircraft, occupied ranks 2 and 3. Two other Kl 35s, with the Germans Dempewolf and Thomsen at the wheel, took part in the international competition that was running at the same time.

During the flight to Germany in 1938, the units A1, A2 and A3, each consisting of three aircraft, flew with Class 35 B. The first of these was led by Friedrich Christiansen , the corps leader of the NSFK . The other two came from the RLM. A total of 8 of the participating associations were equipped with Kl 35.

With a specially prepared machine ( HM 506 with 160 HP / 125 kW) and floats (code: D-ERLQ), Hellmut Kalkstein set five world records over Lake Constance on September 11 and 12, 1938 Set up class sea light aircraft with engines up to 6.5 liters displacement. One-seat over 100 and over 1000 km with 228.7 and 227.7 km / h, as well as 7000 m altitude and two-seater (together with Karl Voy , who would later become his successor) over 100 km with also 227.7 km / h and 5600 m altitude. On October 18, a single-seat altitude record followed with a height of 8,350 m.

post war period

None of the Air Force Kl 35s seem to have survived. If some aircraft can still be found in museums or even still fly today, this is due to the fact that the Swedish Flygvapnet sold its Kl 35 to private individuals and aviation clubs during the war and after the access from Bü 181. A number of them found their way to Germany from 1955 on. After their re-registration, some took part in the Germany flights and other flight events. One aircraft was particularly noticeable. It was that of the well-known stunt pilot Liesel Bach , in which she had also had an HM 506 installed and with which she took part in many a flight day. It is exhibited today in the German Museum of Technology in Berlin .

Technical specifications

Parameter Kl 35 D
crew 1
Passengers 1
length 7.35 m
span 10.40 m
height 2.05 m
Wing area 15.20 m²
Wing extension 7.1
Empty mass 520 kg
Max. Takeoff mass 780 kg
Cruising speed 198 km / h (with monopod undercarriage)
Top speed 208 km / h (with monopod undercarriage)
Nosedive 340 km / h
Service ceiling 4600 m
Range 600 km
Engines a hanging, air-cooled 4-cylinder in- line engine
Hirth HM 504 A2 with 105 PS (77 kW)

swell

  • Karlheinz Kens: Hanns Klemm - pioneer of wooden aircraft construction. In: Flieger Revue Extra, No. 9
  • RLM documents such as aircraft development programs, aircraft delivery schedules, and C-office programs
  • Setup and operating instructions for class 35 D, edition III / July 1940
  • Class 35 B and D operating instructions-Fl, edition March 1943 (L.Dv.T 2035 B and D / Fl)

See also

Web links

Commons : Klemm Kl 35  - Collection of images, videos and audio files

Individual evidence

  1. ^ Federal Archives / Military Archives Freiburg, RL 3: Production programs and takeovers by the Air Force; Monthly production 1931 to 1940
  2. ^ Rolf Nagel, Thorsten Bauer: Kassel and the aviation industry since 1923 , Melsungen undated, p. 232
  3. ^ USSB Bombing Survey Report
  4. ^ Federal Archives / Military Archives Freiburg, RL 3: Export of aircraft to friendly and allied countries 1936 to 1942 ; Various annual statements for export
  5. ^ Andersson, Lennart: Svenskt Militärflyg. Propellerepoken, Karlshamn 1992; Flyhistorisk Revy 30. Svenskt Civilregister 1, Stockholm 1983
  6. ^ Federal Archives / Military Archives Freiburg, holdings RL 3: Overview of construction numbers for Klemm up to 1940