Bartel BM-4

infobox Aircraft
name =Bartel BM-4
type =Primary trainer aircraft
manufacturer = Samolot, PWS


caption =
designer =
first flight = 20 December 1927
introduced = 1929
retired = 1939
status =
primary user = Polish Air Force
more users =
produced =1928-1932
number built =~75
unit cost =
variants with their own articles =

The Bartel BM-4 was a Polish biplane primary trainer aircraft used from 1929 to 1939 by the Polish Air Force and Polish civilian aviation, manufactured in the Samolot factory in Poznań. It was the first plane of Polish design put into production.

Design and development

The aircraft was designed by Ryszard Bartel in the Samolot factory in Poznań. It was a development of the Bartel BM-2, which did not advance beyond the prototype stage. Thanks to a lower weight than the BM-2, it could use lower-powered engines, 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 the 20th of December 1927 in Poznań. It had good handling and stability and was resistant to spinning. 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 first prototype was designated BM-4b and was fitted with 90 hp Walter Vega radial engine. The second prototype, flown on 2 April 1928, was designated BM-4d and fitted with the Polish experimental 85 hp WZ-7 radial engine, then refitted with 80 hp Le Rhône C rotary engine and redesignated BM-4a. The BM-4a became a production variant, because the Polish Air Force had a store of Le Rhône engines. 22 aircraft were ordered and built in 1928-1929. This variant had a cowled engine which made it different from all other BM-4s with radial engines.

Next several variants remained experimental. The BM-4c with a 125 hp Lorraine-Dietrich 5Pb radial engine, built as a one-off in 1928, was supposed to be used for long-distance flights to advertise the engines, but was finally used as the factory's aircraft. Three BM-4a's were converted to BM-4e of 1930 with the Polish experimental 85 hp Peterlot radial engine, the BM-4f of 1931 with the Polish experimental 120 hp Skoda G-594 Czarny Piotruś radial engine, and the BM-4g of 1931 with 100 hp de Havilland Gipsy I inline engine. The last one competed against the RWD-8 in a search for a standard trainer aircraft, but was not selected. After tests in 1932, all three were converted back with Le Rhône engines.

The second series variant became BM-4h, with 120 hp de Havilland Gipsy III or 120 hp Walter Junior 4 inline engines. Like late BM-4a's, they had a rounded tailfin and a modified undercarriage. Due to the Samolot factory's closure in 1930, the BM-4h was developed at the PWS ("Podlaska Wytwórnia Samolotów") and built there in 1932 in a series of about 50 aircraft.

Operational history

BM-4a's were used in the Polish Air Force from 1929 - in pilots' school in Bydgoszcz. 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. They only partly replaced Hanriot H.28s and were themselves replaced with the RWD-8. They had military numbers 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 in September 1939. Several were used as liaison aircraft during the campaign. None survived the war.

Variants

;BM-4a:Powered by Le Rhône C, 9 cylinder rotary engine, 80 hp nominal power.;BM-4b:Powered by Walter Vega, 5 cylinder radial engine, 90 hp take-of power, 85 hp nominal power.;BM-4c:Powered by Lorraine-Dietrich 5Pb, 5 cylinder radial engine, 125 hp take-of power, 110 hp nominal power.;BM-4d:Powered by Avia WZ-7, 7 cylinder radial engine, 85 hp take-of power, 80 hp nominal power.;BM-4e:Powered by Peterlot, 7 cylinder radial engine, 85 hp take-of power, 80 hp nominal power.;BM-4f:Powered by Skoda G-594 Czarny Piotruś, 5 cylinder radial engine, 120 hp take-of power, 100 hp nominal power.;BM-4g:Powered by de Havilland Gipsy I, 4 cylinder straight engine, 100 hp take-of power, 90 hp nominal power.;BM-4h:Powered by de Havilland Gipsy III, 4 cylinder straight engine, 120 hp nominal power or Walter Junior 4, 4 cylinder straight engine, 120 hp take-of power, 110 hp nominal power.

Operators

;flag|Afghanistan|1928
*The first prototype BM-4b was given to the king of Afghanistan Amanullah Khan during his visit to Poland in 1928.;POL
*Polish Air Force

pecifications (BM-4h)

Description

Wooden construction biplane, 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 in open cockpits, with individual windshields. Cockpits with dual controls, instructor's at rear. Fixed landing gear, with a rear skid. Two-blade wooden propeller 2.55 m diameter. Fuel tank in fuselage: 89.5 l.

aircraft specifications
plane or copter?= plane
jet or prop?= prop

ref=
crew= 2, student and instructor
capacity=
length main= 7.25 m
length alt= 23 ft 9 in
span main= 10.17 m
span alt= 33 ft 4 in
height main= 2.93 m
height alt= 9 ft 7 in
area main= 25 m²
area alt=269 ft²
airfoil=
empty weight main= 551 kg
empty weight alt=1,212 lb
loaded weight main= 800 kg
loaded weight alt=1,760 lb
useful load main= 249 kg
useful load alt= 548 lb
max takeoff weight main=
max takeoff weight alt=
more general=
engine (prop)=de Havilland Gipsy III or Walter Junior 4
type of prop= 4-cylinder air-cooled straight engine
number of props=1
power main= 90 kW
power alt= 120 hp
power original=

max speed main= 138 km/h
max speed alt= 74 knots, 86 mph
cruise speed main= 110 km/h
cruise speed alt=59 knots, 68 mph
never exceed speed main=
never exceed speed alt=
stall speed main= 57 km/h
stall speed alt=30 knots, 35 mph
range main= 275 km
range alt=149 nm, 170 mi
ceiling main= 2,100 m
ceiling alt=6,900 ft
climb rate main= 1.8 m/s
climb rate alt= 350 ft/min
loading main= 31.6 kg/m²
loading alt=6.54 lb/ft²
power/mass main=0.11 kW/kg
power/mass alt=0.068 hp/lb
more performance=
armament=
avionics=

References

*Andrzej Glass: "Polskie konstrukcje lotnicze 1893-1939" ("Polish aviation constructions 1893-1939"), WKiŁ, Warsaw 1977 (Polish language, no ISBN)

External links

* [http://www.airwar.ru/enc/other1/bm4.html Photos and drawings] at [http://www.airwar.ru Ugolok Neba site] (in Rusian)

aircontent
related=

similar aircraft=

sequence=

lists=
see also=