The Hawker Hart came into RAF service in January 1930 as a two-seat light bomber. The RAF kept their Harts in squadron service until 1939. The Swedish Air Force procured three Harts from Hawker to evaluate the design as a possible reconnaissance aircraft. Also a contract concerning license-production in Sweden was signed. The three British-built aircraft arrived to the Air Force in May of 1934 and were given the designation S 7 (S = Spaning = Reconnaissance). During the evaluation, successful tests with the Harts as a dive-bomber were executed. The Harts were re-designated B 4. A further 42 Harts were purchased from three manufacturers in Sweden; twenty-one airframes from The Central Workshops of the Air Force (CVM), eighteen airframes from AJSA at Linköping and three from Götaverken, a major shipyard in Gothenburg, which just had started an aircraft department. A total of 45 aircraft were supplied to the Air Force 1934-1939.
The three original British Harts (B 4) were fitted with Bristol Mercury VII engines of 580 hp. All, except two, of the Swedish manufactured aircraft were powered with the licence-built NOHAB Mercury VIIA engine (580 hp) and designated B 4A. The remaining two Harts were provided with the Bristol Perseus XI engine (755 hp). These aircraft got the designation B 4B. All Swedish Air Force Harts were equipped with ski landing gears as an alternative to wheels. The Harts were withdrawn as combat aircraft in 1940 and later used for target towing, weather reconnaissance, liaison etc. Most of the aircraft built made short careers as dive-bombers, but made an invaluable contribution in developing the dive bombing technique, later refined with the B 5 and B 17 aircraft. The Swedish Harts were armed with one fixed and one moveable 7,9 mm machine-gun. The aircraft were able to carry four 50 kg bombs or twelve smaller bombs. Five Harts were transferred to the Swedish voluntary Wing F 19, which operated in Finland during the Winter War 1939-40. Three of them were lost during the service.
Source:
B 4 - Hawker Hart Håkans Aviation page - F19 calendar Flying Regiment 19, Finnish Air Force - Wikipedia http://www.sci.fi/~fta/flygvapenmuseum-2.htm http://www.avrosys.nu/aircraft/spaning/207s7/207S7.htm