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they called the “Riley ‘55.” The A-model incorporated a welcomed horsepower boost to 340 via two 170hp Lycoming O-340s and full-feathering, constant- speed props. Other improvements included a 250-pound gross weight increase (to 3,600 lbs.) and optional tip tanks. Fuselage tanks were exchanged for nacelle tanks. The Riley ‘55 carried an impressive 144.5 gallons in wing center-section, nacelle, and tip tanks. The CAA convinced Riley to re-certify the D-16A under a new type certifi- cate due to the sweeping changes.
Production ceased in late 1957 after 45 D-16As had been produced. Several prior conversions were later upgraded to D-16A configuration. Including pro- totypes, 107 Navion airframes even- tually became Acme/Riley/TEMCO Twin Navions.
Another twin-engine Navion con- version program was certified, as well, though its details surpass the scope of this article. Known as the Camair 480 and 480C, the timeline follows very closely behind that of the Acme/Riley story. But, the Camair was a very dif-
ferent animal, with 240hp Continental O-470 engines, many fiberglass com- ponents, a newly designed tail, and a much higher gross weight. It was, of course, faster but was even further be- hind the market trends than TEMCO/ Riley was. Costing 50% more than a TEMCO/Riley conversion, Camairs struggled for sales. Only 33 were built (between 3 different manufacturers and spread out over a decade-plus timeframe).
In the end, the Twin Navion num- bers stayed low, not because they weren’t wonderful airplanes but be- cause they simply cost too much. Com- petition was fierce, with Piper selling its PA-23 Apache for the same price as a TEMCO/Riley ‘55 conversion (which, of course, required the buyer to also supply a Navion airframe to start the process). Cessna’s 310 and Beechcraft’s BE-95 Travel Air filled any remaining voids in the light-twin market, also selling well below the all-in price of a TEMCO/Riley or Camair converted Twin Navion.
Unique Among the Rare
A flying Twin Navion of any vari- ety has become exceeding rare today. After all, these machines were built as Navions in the 1940s or early 1950s. With the exception of a few Camairs, conversions were all completed in the 1950s. So, only about 140 Navions were
The panel of prototype D-16A Twin Navion, N108N. While many upgrades have been completed over the years, owner Troy Welch says that a second Garmin G5 and full engine monitoring are on his project list.
While the power quadrant of the D-16A Twin The pilot-side yoke of the Twin Navion. TEMCO produced the aircraft for Riley Navion appears busy, it is very well organized. in Texas after Riley’s facility in Florida could not meet demand. Initially, as the
10 • TWIN & TURBINE / July 2024
Twin-Riley (D-16), then as the Riley-55 (D-16A).