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The type and production certificates have since changed hands at least a half-dozen times. The “Rangemas- ter” version was put into limited pro- duction in the 1960’s. It replaced the sliding canopy with a solid roof/door arrangement and added enough fuel ca- pacity to boast a bladder-busting, 1,800- mile range. Less than 200 were built. Multiple upgrade and modification programs have been popular, creating many subsequent model designations. Myriad engine types, aerodynamic
in CA, where Roger Keeney jokingly suggested adding an engine to it. Jokes aside, the idea ruminated in both their minds. Daubenberger soon handed his Navion over to Acme, who enlisted the help of multiple NAA aerodynami- cists and engineers who’d worked on the original NAvion design, as well as some ex-Douglas engineers. Their local contact at the Civil Aviation Authority (CAA; predecessor to the FAA) assured them (in writing) that if they could complete the engineering and design
clean-ups, and modernization mods have been approved, as well. Navions continue to be revered by owners and supported by both an active type club and the current Type Certificate own- ers in Minnesota.
Acme’s X-Plane
The most common complaint of early Navion owners was the relatively low power, given its bulk. Even Ryan’s final production model, the “Super 260,” was not considered to be a powerhouse. They were big, roomy, rugged, stable and reliable. Yet, they were not speed- sters nor stellar climbers. Nonethe- less, many owners loved their flying qualities and contemplated solutions to improve performance.
One owner was businessman Chuck Daubenberger, who had amassed a post- war aircraft collection. His Navion was a favorite, but he was dissatisfied with its lack of redundancy, as he frequently f lew over mountainous regions. He took the aircraft to Acme Aircraft Co.
work to build and test it, it could be made legal via Major Repair/Modifica- tion Forms (337s).
Used 125hp Lycoming O-290 engines and cowlings were installed. A crude nose bowl was hand-formed. Vertically mounted, a spare horizontal stabilizer and elevator were used to replace the original vertical stabilizer and rudder in order to increase their area for mar- keting purposes (in spite of engineer- ing’s insistence that the original area was sufficient for engine-out direction- al control). The prototype was referred to as the X-16, and, of course, all sorts of minor changes and adjustments were made throughout the testing program. After about a year’s work, in Nov. 1952, the team achieved certification, and the aircraft was renamed the D-16 (being Daubenberger’s 16th aircraft).
In short order, higher-ups in the CAA got wind of the project and the fact that it had been certified via only Form 337s. They informed Acme that the certification was not valid, in spite of
The huge area of the rudder on the Twin Navion, combined with the ample trim tab, proves very effective in contending with engine-out operations.
the 2,000+ engineering drawings that Acme had submitted detailing their modifications. Acme and Daubengerger quickly prevailed, as their program and paperwork complied with the rules that existed at the time. However, the CAA learned a lesson, which soon led to the creation of the Supplemental Type Certificate (STC) process for ap- proving major modifications to certi- fied aircraft.
A second Navion was converted to a D-16 by Acme for Jack Riley, an entre- preneur and highly successful aircraft salesman, who purchased the rights to the design. Riley’s aircraft had 135hp O-290 engines. He soon purchased the original D-16, as well, and had it fit- ted with 150hp, O-320 engines. Slow production began at Riley’s facility in Florida in early 1953.
Production Twin Navions
Within months, demand was higher than Riley could meet, and the Texas Engineering & Manufacturing Co. (TEMCO) was sold exclusive rights to manufacture the D-16, marketed as the “Riley Twin.” Sixty D-16s were produced by late 1954. At that point, TEMCO introduced the D-16A, which
July 2024 / TWIN & TURBINE • 9