10/31/2008. Remarks by Johan Visschedijk: "Originally this aircraft was produced in 1947 by North American as the single-engined NA-145 Navion, NC91793 c/n NAV-4-532. Its owner, Charles "Chuck" Daubenberger of Dauby Equipment, Los Angeles, USA, initiated the conversion to a twin-engined type, engineering was done by a number of Douglas and North American engineers, while the construction was undertaken by Acme Aircraft on Torrance Airport, Lomita.

Designated X-16 the project was started in April 1951, and powered by two 140 hp Lycoming O-290-D2 four-cylinder horizontally-opposed air-cooled engines, the aircraft flew in November 1951; the following April the aircraft gained its CofA and was redesignated D-16 Twin-Navion. Ordered by Jack Riley, three more Navions were converted to Twin-Navions by Acme, before the production rights were sold to Riley in 1952.

NC91793 was sold to Riley in August 1953, and re-engined with similar but experimental 150 hp Lycoming O-320s. In February 1954 it was reregistered N22Y with a new c/n D-9, while in March it was converted to the Riley D-16 Riley Twin production standard, fitted with certified O-320s, it received yet another new c/n, TN-9. In October 1954 it was sold and has since been reregistered to 18 different owners. The aircraft is still airworthy, 61 years after its very first flight as a single-engined aircraft."

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