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 characteristic ...

used from 1929 to 1939 by the

Polish Air Force The Polish Air Force () is the aerial warfare Military branch, 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 26,000 military personnel an ...

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 ''Samo ...

factory in

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

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

Design and development

The aircraft was designed by Ryszard Bartel in the

factory in Poznań. It was a development of the

Bartel BM.2 The Bartel BM 2, originally Bartel M.2 was a Polish biplane primary trainer aircraft prototype of 1926 in aviation, 1926. Design and development The aircraft was designed by Ryszard Bartel, a chief designer of Samolot factory in Poznań. It was t ...

, 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 prototype ...

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 gen ...

, 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: * Spin (physics) or particle spin, a fundamental property of elementary particles * Spin quantum number, a number which defines the value of a particle's spin * Spinning (textiles), the creation of yarn or thr ...

. 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 language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

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

radial engine The radial engine is a reciprocating engine, reciprocating type internal combustion engine, internal combustion engine configuration in which the cylinder (engine), cylinders "radiate" outward from a central crankcase like the spokes of a wheel. ...

. 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 engine, 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, t ...

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 its ...

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

, 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 ( ...

I inline engine, which competed against the

RWD-8 The RWD 8 was a Polish parasol wing monoplane trainer aircraft produced by RWD (aircraft manufacturer), RWD. It was used from 1934 to 1939 by the Polish Polish Air Force, Air Force and civilian aviation. Development The RWD 8 was designed in re ...

in a search for a standard trainer aircraft, but was not selected. After tests in 1932, all three reverted to

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; ''Podlachian Aircraft Factory'') was a Polish aerospace manufacturer between 1923 and 1939, located in Biała Podlaska. History Podlaska Wytwórnia Samolotów S.A. (corporation), SA was created in 1923. The f ...

'') 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 two or more animals, machines, or people are lined up one behind another, all facing in the same direction. ''Tandem'' can also be used more generally to refer to any group of persons or objects w ...

in open

cockpit A cockpit or flight deck is the area, on the front part of an aircraft, spacecraft, or submersible, from which a pilot controls the vehicle. The cockpit of an aircraft contains flight instruments on an instrument panel, and the controls th ...

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 taxiing, takeoff or landing. For aircraft, it is generally needed for all three of these. It was also formerly called ''alighting gear'' by some manufacturers, s ...

, with a rear skid.

Operational history

BM.4a's were used in the

from 1929 - in pilots' school in

Bydgoszcz Bydgoszcz is a city in northern Poland and the largest city in the historical region of Kuyavia. Straddling the confluence of the Vistula River and its bank (geography), left-bank tributary, the Brda (river), Brda, the strategic location of Byd ...

. 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 (geography), 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 together have over 100,000 inhabitan ...

. 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 19 ...

. They had military

number A number is a mathematical object used to count, measure, and label. The most basic 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 can ...

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, also known as the September Campaign, Polish Campaign, and Polish Defensive War of 1939 (1 September – 6 October 1939), was a joint attack on the Second Polish Republic, Republic of Poland by Nazi Germany, the Slovak R ...

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. Operation The concept developed before Worl ...

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 * Fizir AF-2 * Pander E85 * PWS-8 Specifications Se ...

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

Lorraine-Dietrich 5Pb The Lorraine 5P, also called the Lorraine 100CV, Lorraine 110CV and Lorraine 120CV, was a family of five-cylinder air-cooled radial engines designed and built in France by Lorraine-Dietrich during the 1920s and 1930s. Nominal engine powers were ...

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 Skoda G-594 Czarny Piotruś 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 (300 ...

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 (300 ...

, 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 General Command of the Air Force (, Dari: ) also referred to as the Islamic Emirate Air Force and the Afghan Air Force, is the air force branch of the Afghan Armed Forces. The Royal Afghan Air Force was established in 1921 under the reign o ...

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

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central Asia and South Asia. It is bordered by Pakistan to the Durand Line, east and south, Iran to the Afghanistan–Iran borde ...

Amanullah Khan Ghazi (warrior), Ghazi Amanullah Khan (Pashto/Dari: ; 1 June 1892 – 26 April 1960) was the head of state, sovereign of Afghanistan from 1919, first as Emirate of Afghanistan, Emir and after 1926 as Kingdom of Afghanistan, King, until his abdic ...

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