Letov Š-28
| Letov Š-28/128/228/328/428/528 | |
|---|---|
 Letov Š-328 |
|
| Type: | Reconnaissance plane |
| Design country: | |
| Manufacturer: | |
| First flight: |
1929 |
| Number of pieces: |
470 (all variants) |
The Letov Š-28 aircraft is a single-engine, two-seat biplane that was developed as a reconnaissance aircraft . The first flight of the machine took place in July 1929. The type was manufactured in the Letov factory in Letnany near Prague in Czechoslovakia. The construction was carried out by Alois Šmolík . The landing gear was rigid and had a tail skid. The hull was a metal construction. The wings were braced and braced with an N-stem on both sides. The engine powered a two-bladed wooden propeller .
Letov Š-28
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The idea for the new machine was presented to the Czechoslovak Air Force. The latter then ordered a prototype on September 8, 1928 at a price of 326,000 crowns, with a delivery deadline of December 31, 1928. However, due to delivery problems with the Walter engine , the machine was not completed until June 1929. On August 21, 1929, it was presented to the Military Commission of the Ministry of Defense, whereupon it came to Malacky for testing purposes from August 25 to September 26, 1929. However, the military commission decided against purchasing it due to the low engine power. The machine should first be modified structurally and a more powerful motor installed. The aircraft later served in the school squadron of the 1 Air Regiment in Prague until 1934. Then she came to the school squadron of the Fliegerregiment 2 in Olomouc, which rented the Š-28 - converted to a passenger aircraft - to the "Masarykova letecká liga" (registration number: OK-LOH ). On August 7, 1938, the machine crashed and was destroyed.
Letov Š-128
The improved version was called Š-128 and equipped with a 330 kW Walter Jupiter VI. This much larger engine required reinforcements on the hull and undercarriage. The prototype of this machine took off on January 27, 1931 on its maiden flight. The tests ended on August 24, 1931. On September 5, the machine was converted to the Gnome-Rhône Mercure VII with 368 kW and the name was changed to Š-128 Mercury (code: OK-VOT ). Equipped in this way, we went on a sightseeing flight through the Baltic states, which brought an order for four machines from the Estonian state. After returning on October 16, the Jupiter VI was installed again. On November 18 and 19, 1931, the machine was presented to the Military Commission of the Ministry of Defense. Due to the results achieved at VLÚS - but also due to the poor economic situation at Letov - an order for four machines was initially put out to tender and this was later increased by twelve. The first four machines were to be delivered by November 1933, the remaining twelve by December 1934.
Letov Š-228
This version was the result of the Estonian order, which, however, required a modified Š-128, as the stability behavior in particular caused problems, which is why the track width of the landing gear increased, the tail surfaces changed and another engine - the Walter Mercury IV with 368 kW - with two-bladed Wooden propeller was installed. Designated as the Š-228E, Estonian pilots took over the four series machines in Prague from May 18 to 20, 1932. The Finns also showed interest in this type, but preferred an American Pratt & Whitney Hornet with 386 kW of power instead of the Czech Walter engine . This had meanwhile been built into the Š-228-5. This fifth machine was the Estonian prototype and was first referred to as the Š-128SM. It remained in the ČSR and subsequently served as a test vehicle under the designation Š-228-5. In 1932 the machine equipped in this way was demonstrated to Finnish buyers in Letnany, who sent an enthusiastic report home, which gave rise to hope for the delivery of twelve machines and the licensing of another 35 machines in Finland.
Letov Š-328
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According to the Finnish wishes to be able to use the machine as a light bomber, the machine was modified and equipped with a new engine, the Bristol Pegasus II M2 with 427 kW power. The first flight of the Š-328F prototype took place on June 19, 1933. However, since the Finns announced in mid-1933 that they would only keep the contract with Letov if it came to the conclusion of a delivery contract for Finnish gunpowder to the ČSR, the MNO, which had no interest in this, finally refused the export permit. That was a financial catastrophe for Letov, which is why the MNO was contacted and offered the Š-328 as a multi-purpose aircraft (observation, bomb and heavy fighter aircraft). After a long test phase of the two prototypes, the MNO ordered the first series of 62 machines (to be delivered by May 31, 1935) at the end of 1934 and had a total of 412 units of this type delivered in seven lots. In the fifth series, stronger Walter licensed buildings of the Bristol Pegasus III M2 with 544 kW were used. As early as 1935, the Š-328 was the standard reconnaissance aircraft of the Czechoslovak Air Force. When the German troops occupied the country in 1939, production continued. The machine was used by the German Air Force as a trainer. Some machines were handed over to the Slovak Air Force and Bulgaria. In addition to the above-mentioned fields of application, people tried their hand at more unusual applications: for example, the serial numbers 49 to 62 were equipped for night flights in 1935 and were to be used as "heavy night fighters", which was reflected in the designation Š-328.n. There was also the version Š-328.v (W.No. 18 to 21) equipped with short floats, which were later converted back to the wheel version and used when towing anti-aircraft targets. The Š-328s remained in active service until the end of 1944. There were eleven Š-328 that flew missions for the "Combined Squadron" during the Slovak National Uprising . There are no references in Czech documents for a delivery of six machines to Spain during the Spanish Civil War.
Letov Š-428
On September 8, 1933, this variant, which was equipped with an Avia Vr 36 engine with 478 kW, made its maiden flight as the Š-328M. Due to poor flight characteristics, interest in this type waned.
Letov Š-528
After the unsuccessful Š-428-1 (the former Š-328M), the interest of the Czechoslovak Air Force turned to the new double radial engine Gnôme-Rhône Mistral Major 14 Krsd with an output of 588 kW. Bypassing the instructions of the MNO (which had ordered the conversion of the Š-428-1 to a normal Š-328), the cell was now used to create the prototype of the Š-528-1. Completed in January 1935, the flight tests of the prototype began on February 7, 1935, which lasted until March and only now received the civilian registration number OK-VOE. To accommodate the engine, the bonnet was extended accordingly. In addition, the machine was equipped with a 3-blade metal propeller. In April 1935 the machine was presented to a Soviet military commission without being able to arouse interest. In the period from May 11th to May 30th, 1935, Major Karel Mareš undertook a commercial flight to Turkey and Bulgaria, but was unable to secure any orders. A total of only six Š-528s were made, which were first used by the Czechoslovak police air force and later by the German air force.
Military use
- Bulgarian Air Force : received 62 Š-328s from Germany after the occupation of Czechoslovakia by Germany in 1939.
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Technical specifications
| Parameter | Š-28 | Š-228 | Š-328 | Š-528 |
|---|---|---|---|---|
| span | 13.20 m | 13.71 m | ||
| length | 9.90 m | 10.36 m | 10.00 m | |
| Wing area | 40.00 m² | 39.40 m² | ||
| Empty mass | 942 kg | 1322 kg | 1680 kg | 1900 kg |
| Takeoff mass | 1585 kg | 2280 kg | 2750 kg | 3000 kg |
| Top speed | 195 km / h | 258 km / h | 328 km / h | 320 km / h |
| Cruising speed | 160 km / h | 230 km / h | 250 km / h | 250 km / h |
| Service ceiling | 5300 m | 7300 m | 7200 m | 9000 m |
| Range | 650 km | 800 km | 1280 km | 1080 km |
| Armament | k. A. | k. A. | two rigid 7.92 mm machine guns ČZ Strakonice vz.30 forward two movable 7.92 mm machine guns ČZ Strakonice vz.30 backwards on a rotating carriage Škoda Šu-31 6 × 10 kg bombs vz.37 or 6 × 20 kg bombs vz.30 / 34 on under wing suspensions or 1 × 50 kg bomb vz.31 or 1 × 100 kg bomb vz.25 / 34 under the fuselage |
|
| drive | 1 × 7-cylinder radial engine Walter Castor with 177 kW (241 PS) | 1 × 9-cylinder radial engine Bristol Mercury VII with 368 kW (500 PS) | 1 × 9-cylinder radial engine Walter Pegasus II-M2 with 467 kW (635 PS) | 1 × 14-cylinder double radial engine Gnôme-Rhône Mistral Major 14 Krsd with 588 kW (799 PS) |
See also
literature
- Jiří Vraný: Letov Š-328. 2 volumes. Jakab, Bučovice 2004–2005;
- Volume 1: Od Š-28 po Š-528. ISBN 80-239-3930-0 ;
- Volume 2: Luftwaffe, slovenské a bulharské letectvo, Slovenské národní povstání. ISBN 80-903637-0-9 .
- Ilustrovaná historie letectví. (= Triáda. 7) Naše Vojsko, Prague 1991, ISBN 80-206-0203-8 .
- William Green: War Planes of the Second World War. Volume 7: Bombers and Reconnaissance Aircraft. MacDonald, London 1967.
- William Green, Gordon Swanborough: Balkan Interlude - The Bulgarian Air Force in WWII. In: Air Enthusiast. Issue 39, May-August 1989, ISSN 0143-5450 , pp. 58-74.
- David Mondey: The Hamlyn Concise Guide to Axis Aircraft of World War II. The Warplanes of Germany, Italy and Japan during World War II. Chancellor Press, London 1996, ISBN 1-85152-966-7 .
Web links
- Letov Š-28 on vinar.cz (Czech)
- Letov Š-28 on airwar.cz (Russian)