Zlin Z-37 Bumblebee is a single-engine low-wing aircraft built specifically for economic purposes, specifically to apply chemicals and fertilizers from the air. Due to his extraordinary flight abilities, he was also often used to tow gliders, banners, photogrammetric activities or as a training aircraft. It is also inherently linked to several Czechoslovak films. The legendary comedy My Sweet Little Village is hard to imagine without this machine today. However, he also starred in the film musical The Blockbuster and the adventure film for children Alarm in the Clouds.
The machine was created in the late 1950s, when the Czechoslovak Republic received a mandate from the Council for Mutual Economic Assistance (RVHP) to develop and manufacture agricultural aircraft. Specifications for a brand new type of aircraft included a wide range of requirements that included, for example, the ability to start from short and untreated areas, to fly very low above ground at low speeds, or enough robustness to survive rough handling and whims of nature. In the competition in 1960, the XZ-37 project was selected for implementation, which was co-operated by LET Kunovice and Moravan Otrokovice. The prototype was factory pilot Vladimir Vlk zalétnutý 29th June 1963 and already it turned out that the machine met most of the required specifications.
During the series production, which began in 1965, the entire production process was divided between three companies. The fuselage and application equipment was in charge of Moravan Otrokovice, the wings and tails were provided by LET Kunovice and the chassis was developed and produced by Technometra Radotín. The final assembly of the aircraft took place exclusively in Kunovice. Between 1971-77 and 1983-84, the Z-37A was produced, which had even better corrosion resistance. For the training of the new pilots, the Z-37A-2 was equipped with dual control and seat-mounted seats. The special four-seat variant of the Z-37C3 (called Hyena) served for the State Air Inspection and later for AAII. In 1967, a single Z-37C was made with the Continental American six-cylinder, which was to give the aircraft the potential to penetrate the western markets. However, the performance did not work, so this version was not produced in series.
The fuselage of this aircraft is an all-metal frame covered with duralumin and partly also a silk fabric with a polyurethane coating that is highly resistant to chemicals. Under it, either a spreader or a nozzle sprayer was mounted as needed. The three-piece all-metal wing with fixed slots and large double-wing flaps ensures good maneuverability even at very low working speeds. Fuel tanks with a total capacity of 250 liters could be supplemented with another two 125 liters of baky, which were placed under the wings. However, it was not possible to pump the fuel from them in flight, so this activity on the ground had to be done manually by a mechanic.
The pilot’s cabin, located high above the nose of the airplane, offers excellent visibility even when flying in high tilt. A chemical tank with a volume of 650 liters is placed just behind the pile seat, and liquid, loose and granulated chemicals can be applied. Behind it is still an emergency seat (so-called mine), where when flying from permanent bases to a field airport sits back to the direction of flight mechanics. The unusually high and massive chassis allows not only very low landing speeds, but also a safe distance from the propeller disc to the ground. The propulsion unit consists of a modified star devítiválec Ivčenko AI-14 with new reducers redesignated the Avia M-462RF to which was then installed two-blade, hydraulically adjustable propeller V-520.
A new generation is coming
In the company LET Kunovice, they reworked the entire original concept of Čmelák and the new machine received several significant innovations. The prototype was equipped with a turboprop engine M-601 B with an output of 515 kW, which also significantly extended the entire fuselage. Other changes were the increase of the boiler volume from the original 650 to 1 000 l, winglets at the wing ends and a partial change in the shape of the tail. The flight was conducted on 6 September 1981, and soon thereafter was shown at the 10th Aviation Day with Flowers. In 1982, the development moved to n. Moravan Otrokovice, when three more prototypes were built. The first was first airborne on 12 July 1983, the second took off on 28 December of the same year, and the latter was used for breaking tests.
Serial production, which took place in Moravan Otrokovice, comprised between the years 1984-1992 a total of 50 aircraft, including prototypes and 2 pieces of the two-seat variant Z-137T2. Machines to serial number 024 marked Z-37T Agro Turbo as had installed engines M-601Z with power of 360 kW. A series of adjustments have been made since the 3rd series, such as a two-stage air intake filter, changes in agricultural application accessories, and improved aircraft flight characteristics. Beginning with serial number 030, the machines got thicker 380 kW engines and redesignated the Z-137T Agro Turbo. Interestingly, the two-seat training versions of the Z-37T-2 have behind the cockpit mounted small 400 l tank, designed for practical training.
Farmer with soul of soldier
Even though I was Bumblebee and later returned to having a chance to get into a fight, in its history for a while, and the chance to produce a multifunctional military variant. The first glimpses of this vision first appeared in 1984, when new requirements for the creation of a special purpose airplane appeared. Therefore, the first Z-37T series was selected from serial number 006, it was shown that several necessary adjustments. For reasons that disagree with the armament of other military equipment, it was primarily the reinforcement of the airframe structure. The resulting machine should have several uses. In addition to the subsonic attack warrior version, the type is designed for joining and observing, photographic radiation, or specific mine equipment. Successful verification tests of all additional equipment and fuel tanks in the area of the Otrokovice Airport were also carried out.
But the candle of hope went out too soon. Presentation of machines in front of the GDR’s general armies, in September 1985 at the military shooting range in Malacky was canceled and when all that happened for the successful commencement of production, etc. The order from the contracting authority eventually for unknown reasons. The only positive development of the Turbo version of the military version is that its current time only manifests itself when it comes to its concept of 24 years. AT-802U and later also S2R-660 as part of the Archangel BPA (Border Patrol Aircraft) project.
The fate of the prototype
At the end of the program, the machine was again put into serial condition and sold by Slov Air as Z-137T. In the 1990s, Reas Brno and Air Specialties Usti nad Orlici in 2005 were sold to Hungary, where they were sold until 2016. At that time, they managed to discover and save members of the Kunovice Museum. After announcing the restoration at SimplyFin, its members have rebuilt the original form and since 2017 it has been exhibited in the aforementioned museums.
- Z-37A C3
- Z-37T Agro Turbo
Zlín Z-37A Bumblebee
|Manufacturer||Let Kunovice-Moravan n.p. Otrokovice|
|Capacity||650 l of chemicals|
|Airplane type||Low wing|
|Engine||Avia M-462 RF|
|Engine power||232 kW|
|Wing area||23,80 m²|
|Available||4 050 m|
|Flying range||640 km|
Zlín Z-37TM Turbo Military
|Manufacturer||Let Kunovice-Moravan n.p. Otrokovice|
|Airplane type||Low wing|
|Engine||Walter M 601 Z|
|Engine power||382 kW|
|Wing area||27,06 m²|
|Available||5 500 m|
Intended equipment and accessories Z-37TM
|Conventional weapons||2 x PK3 container with three PKM machine guns|
|Capacity of bombs||
Zlínské letectví: Ilustrovaná historie 1924 - 2004. Zlín: Muzeum jihovýchodní Moravy Zlín, 2009. ISBN 978-80-87130-10-0.