The Continental Tiara series are a family of air-cooled, horizontally opposed aircraft engines. Designed and built by Continental Motors/TCM, the Tiara series were commercially unsuccessful, costing the company millions of dollars.
Continental began development of the Tiara series in 1965.[1] At the time, CAE, Continental Motor's turbine engine subsidiary, had developed the T65, a small turboshaft engine which was being considered by Bell for its new Model 206 helicopter. Faced with having to fund the production tooling for the T65 in order to keep the price reasonable, or funding the Tiara series, Continental's corporate management chose to invest in the Tiaras.[1]
While the Tiara series were basically traditional boxer engines, they did have some unique features.[2] The engines had high rotational speeds, 0.5:1 gearing was used to reduce propeller speed, with the camshaft forming an extension of the propeller shaft.[2] [3] The propeller shaft featured the Hydra-Torque drive to reduce the shaft's vibrations.[2] The engines were available with four, six- and eight-cylinders. All were fuel-injected, with turbocharging being optional.
The engines' fuel consumption was high, which became a disadvantage during the 1973 oil crisis era.[1] In addition, the Tiaras' performance was not significantly improved over existing engines, making it difficult for aircraft manufacturers to justify the costs of certificating their products for the engines.[1] These problems led Continental to finally discontinue the engines in 1980.[2]
Reference: Continental, Teledyne Continental Motors, TCM (US); Rolls-Royce (UK) Part 1: Introduction and O-110 through OL-300