The Bartel BM.4 was a Polish

biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...

primary

trainer aircraft A trainer is a class of aircraft designed specifically to facilitate flight training of pilots and aircrews. The use of a dedicated trainer aircraft with additional safety features—such as tandem flight controls, forgiving flight characteristi ...

used from 1929 to 1939 by the

Polish Air Force The Polish Air Force ( pl, Siły Powietrzne, , Air Forces) is the aerial warfare branch of the Polish Armed Forces. Until July 2004 it was officially known as ''Wojska Lotnicze i Obrony Powietrznej'' (). In 2014 it consisted of roughly 16,425 mil ...

and Polish civilian aviation, manufactured in the

Samolot Samolot (full name: Wielkopolska Wytwórnia Samolotów ''Samolot'' '' S.A.'') was the Polish aerospace manufacturer, located in Poznań and active between 1924 and 1930. It manufactured among others aircraft under the Bartel name. The name ''Sam ...

factory in

Poznań Poznań () is a city on the River Warta in west-central Poland, within the Greater Poland region. The city is an important cultural and business centre, and one of Poland's most populous regions with many regional customs such as Saint John ...

. It was the first plane of Polish design put into production.

Design and development

The aircraft was designed by

Ryszard Bartel Ryszard Bartel (22 March 1897 – 3 April 1982) was a Polish engineer, aircraft designer and aviator, one of Poland's aviation pioneers. Life and career Bartel was born in Sławniów village near Pilica. He was interested in aviation from h ...

in the

factory in Poznań. It was a development of the Bartel BM.2, which did not advance beyond the

prototype A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and Software prototyping, software programming. A prototyp ...

stage. Thanks to a lower weight than the BM.2, it could use lower-powered

engines An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...

, so its performance was actually improved. Its performance was also superior to the Hanriot H.28, used by the Poles and licence-built by Samolot. The BM.4 prototype was flown on 20 December 1927 in Poznań. It had good handling and stability and was resistant to

spinning Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...

. A distinguishing feature of all Bartels was an upper wing of a shorter span, because lower and upper wing halves were interchangeable (i.e. the lower wingspan included the width of the

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

). The first prototype was designated BM.4b and was fitted with Walter Vega

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ca ...

. The second prototype, flown on 2 April 1928, was designated BM.4d and fitted with the Polish experimental WZ-7 radial engine, then refitted with

Le Rhône 9C The Le Rhône 9C is a nine-cylinder rotary aircraft engine produced in France by '' Société des Moteurs Le Rhône'' / Gnome et Rhône. Also known as the Le Rhône 80 hp in a reference to its nominal power rating, the engine was ...

rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and i ...

and redesignated BM.4a. The BM.4a became a production variant, because the Polish Air Force had a store of Le Rhône 9C engines. 22 aircraft were ordered and built in 1928–1929 with cowled engines which made it different from all other BM.4s with radial engines. Three BM.4a's were converted to BM.4e of 1930 with the Polish experimental Peterlot radial engine, the BM.4f of 1931 with the Polish experimental

Skoda G-594 Czarny Piotruś Škoda means ''pity'' in the Czech and Slovak languages. It may also refer to: Czech brands and enterprises * Škoda Auto, automobile and previously bicycle manufacturer in Mladá Boleslav ** Škoda Motorsport, the division of Škoda Auto respons ...

radial engine, and the BM.4g of 1931 with a

de Havilland Gipsy The de Havilland Gipsy is a British air-cooled four-cylinder in-line aircraft engine designed by Frank Halford in 1927 to replace the ADC Cirrus in the de Havilland DH.60 Moth light biplane. Initially developed as an upright 5 litre (300 ...

I inline engine, which competed against the

RWD-8 The RWD 8 was a Polish parasol wing monoplane trainer aircraft produced by RWD. It was used from 1934 to 1939 by the Polish Air Force and civilian aviation. Development The RWD 8 was designed in response to a Polish Air Force requirement in 193 ...

in a search for a standard trainer aircraft, but was not selected. After tests in 1932, all three reverted to Le Rhône 9C engines. Due to the Samolot factory's closure in 1930, the BM.4h was developed at the PWS (''

Podlaska Wytwórnia Samolotów Podlaska Wytwórnia Samolotów (PWS) - ''Podlasie Aircraft Factory'' - was a Polish aerospace manufacturer between 1923 and 1939, located in Biała Podlaska. History Podlaska Wytwórnia Samolotów SA was created in 1923. The first aircraft prod ...

'') and built there in 1932 in a series of about 50 aircraft.

Description

Wooden construction

, conventional in layout. Fuselage rectangular in cross-section, plywood covered (engine section - metal covered). Rectangular two-spar wings, plywood and canvas covered. Crew of two, sitting in

tandem Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction. The original use of the term in English was in ''tandem harness'', which is used for two ...

in open

cockpit A cockpit or flight deck is the area, usually near the front of an aircraft or spacecraft, from which a Pilot in command, pilot controls the aircraft. The cockpit of an aircraft contains flight instruments on an instrument panel, and the ...

s, with individual windshields. Cockpits with dual controls, instructor's at rear. Fixed

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...

, with a rear skid.

Operational history

BM.4a's were used in the Polish Air Force from 1929 - in pilots' school in

Bydgoszcz Bydgoszcz ( , , ; german: Bromberg) is a city in northern Poland, straddling the meeting of the River Vistula with its left-bank tributary, the Brda. With a city population of 339,053 as of December 2021 and an urban agglomeration with more ...

. 6 burnt in September 1929 in the Samolot factory. BM.4h's were used in the Polish Air Force from 1932, in schools in Bydgoszcz and

Dęblin Dęblin is a town at the confluence of Vistula and Wieprz rivers, in Lublin Voivodeship, Poland. Dęblin is the part of the agglomeration with adjacent towns of Ryki and Puławy, which altogether has over 100 000 inhabitants. The population of ...

. They only partly replaced Hanriot H.28s and were themselves replaced with the

RWD 8 The RWD 8 was a Polish parasol wing monoplane trainer aircraft produced by RWD. It was used from 1934 to 1939 by the Polish Air Force and civilian aviation. Development The RWD 8 was designed in response to a Polish Air Force requirement in 193 ...

. They had military

number A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers c ...

s starting with 33. In 1936 the Polish Air Force handed over their remaining 23 BM.4h's to civilian aviation - most to regional aero clubs, some to the Ministry of Communication. They received registrations SP-BBP - BBZ and from a range SP-ARB to ARZ. Several survived until the German

invasion of Poland The invasion of Poland (1 September – 6 October 1939) was a joint attack on the Republic of Poland by Nazi Germany and the Soviet Union which marked the beginning of World War II. The German invasion began on 1 September 1939, one week aft ...

in September 1939; several were used as

liaison aircraft A liaison aircraft (also called an army cooperation aircraft) is a small, usually unarmed aircraft primarily used by military forces for artillery observation or transporting commanders and messages. The concept developed before World War II and ...

during the campaign, but none survived the war.

Variants

;BM.4a :Powered by a

9-cylinder

, nominal power. ;BM.4b :Powered by a

Walter Vega The Walter Vega was a five-cylinder, air-cooled, radial engine for aircraft use, built in Czechoslovakia in the late 1920s. Applications * Aero A.34 * ANBO V * Avia BH-11 * Couzinet 22 * Pander E85 * PWS-8 Specifications See also Refere ...

5-cylinder radial engine, take-off power, nominal power. ;BM.4c :Powered by a Lorraine-Dietrich 5Pb 5-cylinder radial engine, take-off power, 110 hp nominal power. Built as a one-off in 1928, the BM-4c was supposed to be used for long-distance flights to advertise the engines, but was finally used as a factory run-about. ;BM.4d :Powered by an Avia WZ-7 7-cylinder radial engine, 85 hp take-off power, nominal power. ;BM.4e :Powered by a Peterlot 7-cyl radial engine, take-off power, nominal power. ;BM.4f :Powered by a

5-cylinder radial engine, take-off power, nominal power. ;BM.4g :Powered by a

de Havilland Gipsy I The de Havilland Gipsy is a British air-cooled four-cylinder in-line aircraft engine designed by Frank Halford in 1927 to replace the ADC Cirrus in the de Havilland DH.60 Moth light biplane. Initially developed as an upright 5 litre (30 ...

4-cylinder in-line engine, take-off power, 90 hp nominal power. ;BM.4h :Powered by a

de Havilland Gipsy III The de Havilland Gipsy is a British air-cooled four-cylinder in-line aircraft engine designed by Frank Halford in 1927 to replace the ADC Cirrus in the de Havilland DH.60 Moth light biplane. Initially developed as an upright 5 litre (30 ...

, 4-cylinder in-line engine, nominal power, with rounded tailfin and modified

undercarriage Undercarriage is the part of a moving vehicle that is underneath the main body of the vehicle. The term originally applied to this part of a horse-drawn carriage, and usage has since broadened to include: *The landing gear of an aircraft. *The ch ...

introduced on late BM-4a aircraft. : or a Walter Junior 4, 4-cylinder in-linet engine, take-off power, nominal power.

Operators

; *

Afghan Air Force The Air Force of the Islamic Emirate of Afghanistan, also referred to as the Islamic Emirate Air Force and the Afghan Air Force, is the air force branch of the Armed Forces of the Islamic Emirate of Afghanistan. The Royal Afghan Air Force was e ...

- The first prototype BM.4b was given to the king of

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...

Amanullah Khan Ghazi Amanullah Khan (Pashto and Dari: ; 1 June 1892 – 25 April 1960) was the sovereign of Afghanistan from 1919, first as Emir and after 1926 as King, until his abdication in 1929. After the end of the Third Anglo-Afghan War in August 1919, ...

during his visit to Poland in 1928. ; *

Specifications (BM.4a)

References

Bibliography

External links

Photos and drawings

Ugolok Neba site
(in Russian) {{Bartel aircraft BM-4 Single-engined tractor aircraft Biplanes 1920s Polish civil trainer aircraft 1920s Polish military trainer aircraft Rotary-engined aircraft Aircraft first flown in 1927