03/31/2012. Remarks by Johan Visschedijk: "First flown in 1963, the Riley Executive 400 was a remanufactured de Havilland D.H.104 Dove light transport with turbocharged fuel injected engines and airframe modifications. By mid-1964 two conversions had been made by Riley Aeronautics of Fort Lauderdale, Florida, USA, when it was announced that McAlpine Aviation of Luton Airport, Bedfordshire, England, had been appointed sole servicing and conversion engineers for all territories outside North and South America for the Riley Dove conversions. The first McAlpine conversion to Riley Executive 400 standard was completed by mid-1965.

The Riley Executive 400 conversion was available from Riley and McAlpine in six stages, any one of which could be taken on its own if the customer did not want a complete conversion:

1. 2. 3. 4. 5. 6.

Re-engining with two 400 hp Lycoming IO-720 eight-cylinder horizontally-opposed air-cooled engines, each fitted with two Riley Turbo 300 turbo-superchargers and driving a Hartzell three-blade propeller. New sweptback vertical tail surfaces and a "fatigue-free" steel spar capped wing were included in this stage of the conversion, which contributed 90% of the overall speed increase and 90% of the weight decrease of 800 lb (363 kg) offered by the conversion. Remanufacture of the flight deck to include one-piece instrument panel and improvements in field of vision. Flush riveting of entire wing from leading edge back to rear spar and epoxy coating of leading edge. Replacement of existing cabin door by air-stair door. Complete cabin re-styling, with improved sound-proofing and installation of fully-reclining individual chairs. Removal of all existing paint and refinishing with epoxy resin paints to customer's specification.

The pictured aircraft was built as a D.H.104 Dove Mk.2 and registered in France as F-BGOA on May 17, 1952. In the mid-1960s it was converted to a Riley Executive 400, although still registered as a D.H.104. On December 13, 1983 the aircraft was deregistered as "sold abroad", however, it never left France, but was used as an instructional at the Sodetag Training School at Toussus-le-Noble."