The first two Navions converted to a twin. The first was converted for Dauby Equipment Company, while the second was sold to Jack Riley, who also purchased the design and production rights. Jack Riley's D-16 was quickly remanufactured by the Riley Aircraft Corp. to serve as the first example of the D-16 Riley Twin.

It appears that the first three D-16s converted by Riley Aircraft did not receive a Twin Navion (or TN) serial number. Its known that the original Twin Navion conversions pre-dated the CAA's Supplimental Type Certificate (STC) process and were originally certified under Note 3 of the single Navion's Type Certificate. Because of this, all D-16s had to carry both their original single Navion and new Twin Navion data plates.

Based on research done by TwinNavion.com (both through the FAA records, and by inspecting the two surviving aircraft), its our belief that the first three D-16s built by Riley did not receive serial numbers in the TN series, but maintained those serial numbers assigned when they were single Navions.

In our search for Twin Navion photos, we've uncovered several cases where we've been unable to match the plane to its Twin Navion serial number. If you feel that you can help give any of these planes an identity, we'd very much appreciate hearing from you.

• D-16 or D-16A N55N.
• D-16 operated by BD Medical from 1953 to 1959. It was apparently mentioned in an October issue of Professional Pilot.
• D-16 N99H, last known to be in FL, USA.
• D-16 or D-16A N1447A.
• D-16 or D-16A N91979.
• PI-C553, a D-16 known to have been registered in the Philippines in 1968. Not PI-C551 (TN-12).
• Camair scrapped in the Dominican Republic.
  

• (SOLVED) Camair exported to Argentina, registration LV-???. - identified as 1-082.
• (SOLVED) D-16 that crashed in Liberia Africa. Registered EL-ABX. - identified as TTN-48.
• (SOLVED) From an article in the December 1956 issue of Flight magazine. Mention of the wreckage of a Twin Navion during a flight through the St. Gatthard Pass in the Alps. Could this be one of the Swiss Twin Navions, TTN-53 or 1-073? - identified as TTN-53.
• (SOLVED) D-16 N1776E - identified as TTN-25.
• (SOLVED) D-16 or D-16A N88W, stalled on takeoff and was written off at Grand Canyon, AZ, USA on August 21, 1965 - identified as TTN-2.
• (SOLVED) CF-TQU, a D-16 operated by Ram Air Charter Ltd. in Inuvik, NT, Canada in 1971/72 - identified as TTN-15.
• (SOLVED) N480E photo - identified as 1-051.
• (SOLVED) D-16A wing photo - identified as N113N TTN-46.
• (SOLVED) D-16A photo - identified as N714T TTN-82.
• (SOLVED) Derelict D-16 photos in Costa Rica - identified as TTN-25.
• (SOLVED) Highly polished D-16A with dark blue trim - identified as TTN-77.
• (SOLVED) D-16A in Edmonton in the mid-1950s. A higher resolution scan made it possible to read the registration - identified as TTN-58.
• (SOLVED) D-16 operated by Mathieson Chemical Corporation. This should have been one of the first D-16s built in 1953 TN-11.
• (SOLVED) D-16 photo, inflight with a yellow underside, registered N4272K - identified as TN-6.
• (SOLVED) D-16 photo, white with red and black trim - identified as TTN-35.
• (SOLVED) D-16 photo, N4229K- identified as TN-11.