Lazarov Laz-14

 

During the 1950s it was clear that piston-engined aircraft were a thing of the past and the jet engine was the future.

At that decade, the Bulgarian aviation industry was already been cut off and made dependant of the Soviet. Most of Bulgarian aeronautical industry was reconverted to manufacture cars, electric pumps or even bee hives.

However, in Sofia, at the State Polytechnic there was still an faculty of Aeronautical Engineering and the people working there didn't want their work, carried over for more than 30 years, to fall into oblivion so ingloriously. They think that the dismantling of the Bulgarian aeronautical industry was a gross mistake and that the government should reactivate it.

Among that people was prof. Tsvetan Lazarov, dean of the faculty of Aeronautical Engineering. The father of designs like the DAR-6, DAR-6A, DAR-9, DAR-10 , Laz-7 , Laz-7M and Laz-12 thought about the future of the Bulgarian aeronautical industry and tried to revive it in the following years. So, in order to keep pace with the technological advances of the world aeronautical industry, specially regarding trainer aircraft, he started a project for a jet-powered trainer that could be used both by air forces and even flying clubs.

The copies of the designs that survived the Cold War, labelled as Laz-14, are dated 26th June 1958, meaning that work on the project began much earlier. 

Initial sketches were clearly inspired by the Czechoslovak Aero L-29 which was designed by Karel Tomasz and Zdenek Rublich, both colleagues of Lazarov. However, unlike the L-29 which flew for the first time in 1959 and was one of the main jet trainer aircraft of the Warsaw Pact and other countries, the Laz-14 couldn't pass the design stage. 

Laz-14 was designed as a two-seater, single-engined jet trainer for primary training and pilot training support. As it was expected to be armed too, it could've also performed some sort of ground support missions.

It was going to be made entirely out of metal, with trapezoidal-shaped low-wings with two spars and a strongly developed central section. Air intakes were to be located at the roots of the wings. It was also equipped with a tricycle retractable landing gear which retracted into the fuselage. The wings were to be equipped with ailerons with axial compensations and flaps for take-off and landing. They had spindle-shaped fairings at both ends to reduce inductive drag.

The power section of the fuselage was a steel pipe truss. It was going to be equipped with a fully-glazed cockpit with two seat arranged in a tandem configuration, with the student  sitting at the front and the instructor at the rear.

Lazarov wanted the Laz-14 to be powered by the French Turbomeca Marboré engine which could yield a thrust power of 400-480 kgf and was already powering some successful trainer aircraft like the Fouga Magister or the Morane-Saulnier Ms.760 Paris. However, considering the political situation of the time, it was more likely to be powered by the Czechoslovak Motorlet M-701, which powered the aforementioned Aero L-29. Anyway, the engine was going to be placed in the centre of the fuselage to avoid the loss of thrust power in the extension tube.

Tail planes' design were traditional. Elevator and rudders had aerodynamic compensation and trim tabs were going to be controlled from the cockpit. The horizontal stabilizer was going to have the ability of deviating 3 degrees up or down to facilitate aerobatics with either one or two pilots.

According to calculations, the Laz-14 was going to be extremely light, 700 kg (1.543 lbs) empty (for comparison, the mass of an empty L-29 is 2.280 kg - 5.026 lbs). Apparently, considering the expected numbers there is little doubt that, if the aircraft had been made, it would've been successful among Bulgarian pilots, as it would've fully met the requirements of the time.

Source:

http://www.airwar.ru/enc/other/laz14.html (translated and adapted)

Lazarov Laz-9

 

Professor Tsvetan Lazarov, one of the best aircraft designers of Bulgaria, lived through difficult times. The new world order that came after World War 2 was setting up across the world and there was a war going on in the Korean Peninsula. At the same time, the Bulgarian Air Force was heavily cut and purged politically after the war, leaving it short on flight and technical staff. This situation required a large number of pilots, navigators and aircraft technicians to be trained in a short period of time. As pilots and navigators must receive comprehensive and solid combat training, the Lazarov Laz-7 was employed, much to Lazarov's dismay, as a multi-purpose heavier-than-intended aircraft that went from the initial 947 kg (2088 lbs) of the prototype to the 1145 kg (2524 lbs) of the production version, worsening flight characteristics. 

In order to express his concerns about the usage of the aircraft, Prof. Lazarov wrote a letter to the Bulgarian Air Force Command, Metalchem Industrial Association (manufacturers of the Laz-7) and other institutions involved in the manufacturing process of the Laz-7. In this letter, dated at 10th October 1950 he stated that it was unacceptable the further degradation of the flight characteristics of the Laz-7 and suggested to keep the Laz-7 for the initial basic pilot training and have a new aircraft type (namely Lazarov Laz-9) as the multi-purpose airplane to assume those roles not intended for the Laz-7. For this purpose he described the design of the Laz-9 further in the letter.

The Laz-9 was designed around the German Argus As.410 engine, which yielded up to 450 hp of power, due to the fact that many of them were left over in Bulgaria, some of them even unused. The Laz-9 was going to feature a larger, strengthened and expanded fuselage reminiscent of the Laz-7 with a metallic tail unit and trapezoidal wing with TsAGI (Moscow's Central Aerohydrodynamic Institute) designed flaps. Undercarriage was designed as retractable, similar to that of the Yakovlev Yak-9.

Thanks to the more powerful powerplant, the Laz-9 was expected to take additional equipment and even carrying heavier weapons, allowing the optimal performance of additional combat tasks. It was intended to be armed with a single 13 mm (0.5 in) machine gun mounted on the engine, plus two additional 7,92 mm (0,3 in) lighter machine guns placed in the wings. It was designed to carry a payload of up to 400 kg (882 lbs) of underwing bombs, in, either 8 x 50 kg or 4 x 100 kg configuration. 

Apparently Lazarov's letter was ignored, as the Bulgarian Communist regime had already decided to dismantle the Bulgarian aviation industry, following orders from Moscow and the project never went beyond the design stage. 

Sources:

http://www.airwar.ru/enc/other/laz9.html (translated and adapted)

Lazarov Laz-7M

 

In the previous post we wrote about the Lazarov Laz-7, however, we didn't mention that, albeit a successful aircraft (relatively speaking) it was prone to various accidents caused by a nimble crankshaft in the Walter-Minor 6-III engine.
In order to cope with that issue the Bulgarian People's Army Air Force (BPAAF), which by the time of these events had already fallen under Soviet influence, ordered the replacement of the  Walter engine with a Soviet-made M-11FR, as they were, theoretically, equally powerful, more reliable and, furthermore, they had constant-speed propeller.
Although the engineers of DSF-Lovech (manufacturers of the Lazarov) were reluctant at first, they were forced to comply with the command of a higher authority, so some engineers got permission (among them prof. Lazarov) to go to Bozhurishte airfield, where, among many others, some Soviet Yakovlev Yak-12 were stationed, to study its propulsion system. 
With that knowledge gathered, a single Laz-7 (numbered as 68) was delivered to the aircraft factory at Lovech, where the Walter engine was replaced by the M-11FR in the Laz-7. 
In this configuration, that Laz-7 was test flown by test pilot Popganchev, with unsatisfactory results as the M-11FR engine, coupled with the light fuselage of the airplane, lost force really quick. 

After this failure, the BPAAF ordered the creation of a complete new aircraft, powered by the M-11FR engine and the features of the Laz-7. For this, they were given a very short deadline; by 1952 that aircraft had to be already being mass produced (all these events took place in 1951). So engineers had no time to make a scale model nor test it in the wind tunnel.

This time, design was tasked to eng. Kiril Karlov who took the same layout of the Laz-7, installed the Soviet engine and made some alterations to the wings to make them lighter. Some further changes were also made, to the point that Karlov asked permission to name this design as ZAK-1, petition which was rejected, as the design was directly based on the Laz-7, so the designation of Laz-7M (the letter standing for "modernized") was given instead.

The first test flight of the Laz-7M, with its characteristic star-shaped nose (similar to that of the Yakovlev Yak-18) took place on 16th June 1952 with satisfactory results. This was the first of a total of 102 flight tests which took place until the next month. In July the prototype was passed on to the Bulgarian 2nd Night Light Bomber Aviation Division, stationed at the town of Stara Zagoda, to undergo military trials.

In that unit it was used both as a day and night trainer but also as a ground attack trainer, as it had the same armament the Laz-7 had. However, in order to make it lighter, most of the times it flew unarmed, as it was easier to fly. 

A total of 150 Laz-7Ms were manufactured by DFS-Lovech and were employed mainly by the BPAAF's School, the BPAAF and some flight clubs until the early 1960s.

Apparently the Polish People's Republic considered ordering 100 machines, but they opted for the Yakovlev Yak-18 instead. Egypt also was one possible customer, as they considered ordering 50 Laz-7Ms in the mid-1950s. We have included hypothetical profiles for both countries.

Some few aircraft also flew with the DOSO (a civilian volunteer organization for the protection of the Bulgarian aerial space).

Sources:

1st http://www.airwar.ru/enc/other/laz7m.html (translated)

DAR-10. The Bulgarian Snipe.

 

The DAR-10 (acronym standing for Darzhavna Aeroplanna Rabotilnitsa - State Airplane Workshop) was a Bulgarian light-bomber and reconnaissance airplane which was designed by Zvetan Lazarov in 1938 at DAR's factory in Bozhuriste, near the Bulgarian capital city, Sofia. 

The DAR-10 was a two-seat (pilot and gunner) low-wing cantilever monoplane of traditional layout. It had a fixed undercarriage with spatted main wheels. Wings were made out of wood and covered in plywood and the type had no flaps.

The fuselage, constructed of steel-tube framework and wood formers was covered in fabric and, in comparison with other aircraft of the time, wide and deep to fit the Italian Alfa-Romeo 126 RC.34 radial engine which yielded 950 hp of power, driving a three-bladed propeller.

Two prototypes were built, the first of which, named DAR-10A (the A stands for Alfa-Romeo) "Bekas" (Snipe) flew for the first time on 2nd July 1941. It was designed to be armed with two forward-firing machine guns and two additional ones placed at the end of the canopy, manned by the gunner. It had provision for a total of five 100 Kg (110 lb) underwing bombs and it was also envisioned the installation of an additional 20 mm forward-firing cannon in the forward fuselage. However, it's doubtful if the DAR-10A received any armament at all.

This first prototype crashed in October 1942. Albeit having good flight reviews, it wasn't chosen for production as the high-wing Kaproni Bulgarski KB-11 "Fazan" (Pheasant) was selected instead.

The second prototype, DAR-10F (F stands for its Fiat engine) was powered by a Fiat A74 RC.38 radial engine yielding 870 hp of power. It wasn't until March 1945 that this airplane flew for the first time. It was slightly heavier than the DAR-10A and had a top speed of 454 km/h (282 mph). Owing to a stronger construction and dive brakes, it could also perform as a dive bomber. Its armament layout was the same as the DAR-10A but in this case with two additional 20 mm forward-firing fuselage cannons mounted in the upper half of the forward fuselage, on the engine. It had also provision for one 500 kg (1.100 lb) or one 250 kg (551 lb) bombs under the fuselage and four 100 kg (110 lb) of smaller underwing bombs. 

It wasn't however selected for production as the DAR-10A was discarded in favor of the KB-11 and the German Junkers Ju.87 Stuka, and the DAR-10F arrived too late, when the World War 2 was almost over, and Bulgaria had access to Soviet aircraft such as the Ilyushin Il-2 or the Ilyushin Il-10, among others.

Sources: 

1st: https://en.wikipedia.org/wiki/DAR_10

2nd http://airwar.ru/enc/aww2/dar10.html (translated)

3rd http://airwar.ru/enc/aww2/dar10f.html (translated)

Caudron C.440 Goéland, Foreign Users Part One

 

The Caudron C.440 Goéland (French word for "seagull") and its derivatives, was a French twin-engined utility aircraft of the 1930s decade that saw service with various users abroad:

• Belgium: Caudron-Renault showcased the Goéland at Evere airfield, in Brussels on 11th March 1936. In the following June, the Belgian government signed a contract for the purchase of two C.444, powered by two Renault 6Q engines, which yielded 220 hp of power each. 
  Both aircraft were delivered to the 3eme Régiment of the Aviation Militaire (Belgian Military Aviation), based at Evere in September/October of that same year. The Goéland was intended to be used as a trainer for the fast reconnaissance and bomber aircraft the Aviation Militaire was planning to acquire. In 1938 both Goélands received civilian registrations in order to allow them to fly in foreign skies. When Germany invaded Belgium in May 1940, both machines were flown to Tours, in France, and then to Merignac airport, in Bordeaux, where they were intended to train Belgian crews before they converted to the Lioré-et-Olivier LeO.45 medium bomber. The fate of these machines is unknown, but they were most likely captured by the Germans.
• Bulgaria: Bulgaria ordered three Caudron C.444 from France back in 1936, the first of which was delivered that same year. However, as Bulgarian authorities weren't satisifed with the performance of the aircraft, the order was cancelled and the sole aircraft was returned to France. Bulgari allocated three civilian registrations for these machines, LZ-REA, LZ-REB and LZ-REC.
• Germany: The Luftwaffe was the biggest foreign user of the Goéland, with more than 750 newly-built machines plus many more captured ones when France fell. In fact, the Goéland was the most produced aircraft in French factories during the German occupation. They saw service with many Luftwaffe units as utility airplanes and crew trainers and were employed in North Africa, Western and Eastern Fronts. Some were reportedly operated by Deutsche Lufthansa too.
• Italy: A total of nine Goélands served with the Italian Regia Aeronautica (Royal Italian Air Force). They were acquired by the Italians during summer 1943 from Salon-de-Provence airfield, Southern France, and were assigned to the Scuola Volo Senza Visibilitá (Blind Fliyng School) at Cameri, North-Western Italy. After the Italian armistice all nine of them were captured by the Luftwaffe.

Sources:

1. https://en.wikipedia.org/wiki/Caudron_C.440_Goéland

2. https://www.belgian-wings.be/caudron-c-444-goeland

3. http://www.aeroflight.co.uk/waf/bulgaria/af/types/misc.htm

4. http://falkeeins.blogspot.com/2015/08/caudron-c-445-goeland-zg-1-stg-1-rs.html

5. Bancarella Aeronautica - Ali Straniere in Italia 5 - Aerei Francesi nella Regia Aeronautica

DAR-7

Back in 1930s the chief designer of the Bulgarian State Aircraft Workshop, Herman Winter, designed various fighter aircrafts, even if Bulgaria was restricted by the Versailles treaty and was forbidden to build them.
The DAR-7, which never went beyond the prototype stage, was developed in detail and we know about its existance thanks to a folder miracolously preserved from 15th January 1931 which contained every technical data of the aircraft.
It was designed as a single-bay biplane aircraft of mixed construction. The wings were made out of wood, with the panels up to the first spars made out of birch plywood and the rest covered in linen. Wingspar of both wings were identical and were connected by streamlined racks. The tailplane was made out of metal with steel-pipes structure covered with linen.
The main fuselage structure was made out of steel pipes sheathed in the bow and above to the opening of the cabin with duraluminium tin. The rest was covered in fabric, stretched on the profiling strips and transmitting a circular cross section to the main fuselage. The cockpit was slightly armoured just at the back.
It was armed with four 7,92mm machine guns two of them placed in the nose and other two in the wings. It's not clear either if the prototype had weaponry installed and if the machine guns in the wings were installed in the upper or the lower wings.
It was powered by a radial Gnome-Rhône Jupiter engine with a maximum power of 480hp which already powered the DAR-5
The aircraft was theoretically comparable in performance to other fighters of the early 1930s like the Boeing P-12, Bristol Bulldog Mk.IIA or the Polikarpov I-5. However, it's not clear if it made any test flights and obviously, it wasn't tested in combat.

Sources:
1. http://www.airwar.ru/enc/fww1/dar7.html (translated)
2. http://bulgarianww2tanks.blogspot.com/2013/12/bulgarian-tech-tree-for-game-world-of.html