The SV.5 was Stampe et Vertongen's response to a 1933 requirement by the Belgian Air Force for a two-seat training biplane with aerobatic capabilities.^[1] Jean Stampe directed designer George Ivanow to update the company's RSV.22 to meet the new specifications, but the resulting design was an entirely new aircraft with only a superficial resemblance to its predecessor.^[1] It was a conventional, single-bay biplane with staggered wings of unequal span.^[8] The pilot and instructor sat in open cockpits in tandem^[8] and the aircraft was powered by an Armstrong Siddeley Serval radial engine^[9] in the nose, enclosed in a Townend ring.^[7] The main units of the fixed undercarriage were divided and the tail was supported by a tailwheel.^[8] It could be equipped for bombing or gunnery training.^[5] Unlike earlier Stampe et Vertongen products, which had wooden structures, the SV.5 airframe was riveted together from steel tube in a method inspired by Hawker in the United Kingdom.^[1]

The prototype first flew in September 1933,^[2] and on 16 October 1934, the Belgian Air Force evaluated it against five competitors: the Avro 626, Breda Ba.25, Fairey Fox III, LACAB T-7, and the Renard R.34.^[7] A sixth competitor, the Caproni Ca.113, suffered an accident on arrival and was disqualified.^[7] The SV.5 outclassed all its rivals in the maintainability trials, and was less expensive than any of them.^[7] However, the Avro 626 was selected for political reasons.^[7]

The SV.5 nevertheless found a customer in the Latvian Air Force, which was seeking a similar aircraft.^[7] When a study mission to Belgium confirmed the type's suitability, the Latvian government negotiated the purchase of ten examples in exchange for 5,700 tonnes of wheat.^[7] These machines were slightly different from the prototype, with a NACA cowl in place of the Townend ring, a redesigned horizontal stabiliser, and simplified main undercarriage.^[7] Germany would not permit the overflight of the aircraft, so in September 1936 they were shipped disassembled to Riga, where Jean Stampe oversaw their assembly by VEF.^[6]

In the meantime, the Belgian Air Force finally placed an order for twenty SV.5s.^[6] Stampe et Vertongen delivered these between October 1936 and mid 1937.^[6]

Ivanow used the SV.5 as the basis for a family of follow-on designs with only minor variations:^[6]

SV.6

version with 260-kW (350-hp) Armstrong Siddeley Cheetah IX

SV.7

version with 378-kW (507-hp) Pratt & Whitney Wasp Junior, also with spoilers under the upper wing

SV.8

version with 180-kW (240-hp) Armstrong Siddeley Lynx IV

SV.9

SV.5 with metal, variable-pitch propeller, and upper wings moved 2 cm (1 in) rearward to improve centre of gravity

Of these, only a single SV.9 was built. This aircraft was exported to Latvia, together with a license for production by VEF. Although rumours exist that VEF built examples of the type, this cannot be confirmed.^[6]

  Belgium

• Belgian Air Force (20)^[6]

  Latvia

• Latvian Air Force (10)^[4][7]

Data from Jouhaud 1999, p.86

General characteristics

• Crew: two
• Length: 8.04 m (26 ft 4 in)
• Wingspan: 10.52 m (34 ft 6 in)
• Height: 3.04 m (10 ft 0 in)
• Wing area: 26.7 m² (287 sq ft)
• Empty weight: 890 kg (1,960 lb)
• Gross weight: 1,340 kg (2,950 lb)
• Powerplant: 1 × Armstrong Siddeley Cheetah X , 250 kW (340 hp)

Performance

• Maximum speed: 272 km/h (151 mph, 131 kn)
• Endurance: 3 hours 30 minutes
• Service ceiling: 7,150 m (23,500 ft)

• The Illustrated Encyclopedia of Aircraft. London: Aerospace Publishing.
• Gerdessen, Frederik. "Estonian Air Power 1918 – 1945". Air Enthusiast, No. 18, April – July 1982. pp. 61–76. ISSN 0143-5450.
• Jouhaud, Reginald (1999). Les Avions Stampe. Amsterdam: Wimpel.
• Taylor, Michael J. H. (1989). Jane's Encyclopedia of Aviation. London: Studio Editions.