Stampe SV-4D

The SV-4D is the most elusive member of the Stampe SV-4 family: every source consulted agrees that only a single example existed, but they disagree on exactly what it was and when it flew. Most of the material describes it as an SV-4 fitted with a seven-cylinder Mathis radial engine of 175 hp (130 kW), more powerful than the family's production engines listed in the same variant tables: the 140 hp (104 kW) Renault 4P of the SV-4A and SV-4C and the 130 hp (97 kW) de Havilland Gipsy Major of the SV-4B.

The engine's designation is not consistent. The English Wikipedia calls it a Mathis G.4R; the Dutch Wikipedia, a Mathis GR7; aviationsmilitaires.net, a Mathis 7G20; and the French Wikipedia simply says "a Mathis of 175 ch". The power output, by contrast, is the same in all of them. Nor do they fully agree on the nature of the aircraft: the English Wikipedia presents it as "one aircraft re-engined", in other words an existing airframe that received a new engine, whereas the Dutch article speaks of a single example equipped with the Mathis and the French one of an aircraft powered by it, without saying whether it left the factory in that form.

aviationsmilitaires.net adds two features that the Wikipedias do not mention. The first is that it was a single-seater: the site counts it among the one-seat versions studied from the two-seat trainer, alongside the SV-4P, a glider tug with a 300 hp (224 kW) Potez 4D-31 engine that was never built. The second is that the SV-4D flew with the Patrouille d'Étampes, the famous French display team that, according to the same site, used the Stampe from 1947. The CAEA website confirms the connection in its own words: when listing the engines the Stampe came to carry, it cites the 175 hp seven-cylinder Mathis radial "which would equip a unique SV-4D prototype for the Patrouille d'Étampes", and dates the team's Stampe era to 1947 to 1953, the period that earned the aircraft its reputation in France. Neither source explains what specific use the aircraft was put to within the team or for how long it flew with it.

Against this account, avionslegendaires.net offers a very different one. According to that site, the SV.4D dates from 1965 and was a Charles Renard project that came out of the same factory as the post-war Stampe et Renard aircraft, with a 165 metric hp (about 121 kW) Continental IO-346 engine and a reworked engine cowling, wingtips and landing gear; here too only one example was built. The two descriptions are hard to reconcile: one places the aircraft with the French team in the late 1940s and early 1950s with a Mathis radial, while the other has it appearing in the mid-1960s with a Continental. It is possible that the same suffix letter was applied to two different aircraft at different times, but the material consulted does not say so and it is not assumed here.

Several questions therefore remain open: the date of the first flight, the registration or serial number of the Mathis-engined example, who carried out the conversion and what eventually became of it. The firm fact is the one shared by all the sources: the SV-4D was a one-off, outside the Belgian and French SV-4 production series.