IIB - Two 495kW (665shp) AiResearch (Garrett) TPE3311151G turboprops driving three blade constant speed propellers. IIIC - Two 670kW (900shp) Garrett TPE33110U503G turboprops driving four blade constant speed Dowty propellers.
IIB - Max cruising speed 475km/h (257kt). Initial rate of climb 2570ft/min. Service ceiling 29,000ft. Range with max fuel 2872km (1550nm). IIIC - Max cruising speed 556km/h (300kt). Initial rate of climb 2650ft/min. Range with max standard fuel at max cruising speed with six people on board 3590km (1938nm).
IIB - Empty 2926kg (6452lb), max takeoff 4540kg (10,000lb). IIIC - Empty equipped 3695kg (8150lb), max takeoff 5670kg (12,500lb).
IIB - Flightcrew of one or two, with typical main cabin seating for six in executive layout or up to eight. III - Seating in main cabin for up to 11, or eight in a corporate configuration. Merlin IV seats up to 12 passengers in main cabin in a corporate configuration.
Includes 33 Merlin IIAs, 87 Merlin IIBs, 92 Merlin III and IIIAs and 10 Merlin 300s.
Turboprop corporate transport
The Merlin series of turboprop executive transports was Swearingen's first manufacturing program, and laid the foundations for the successful Metro series of commuters.
Prior to the original Merlin II, Swearingen specialised in building conversions of existing aircraft into corporate transports. The Merlin II (or SA26T) was an example of this policy in that it is based on the Beech Queen Air and Twin Bonanza. The Merlin combined the wing of the Queen Air with the Twin Bonanza's undercarriage and an all new Swearingen designed pressurised fuselage and tail. The first Merlins were powered by two 300kW (400hp) Lycoming TIGO540s, while the Merlin IIA was powered by Pratt & Whitney Canada PT6A20 turboprops. The prototype IIA flew for the first time on April 13 1965 and 33 were built before production switched to the AiResearch TPE331 powered Merlin IIB.
The improved and slightly larger Merlin III combined the Merlin II's fuselage but stretched slightly and with a new tail; and the wings and landing gear of the Metro II airliner (described separately) and more powerful engines. The Merlin III (or SA226T) was certificated on July 27 1970. The Merlin III was followed by the Merlin 300 (by which time Fairchild had acquired the Merlin and Metro lines) which introduced aerodynamic improvements including winglets. Only 10 were built.
The Merlin IV designation applies to corporate configured versions of the Metro series of commuter airliners. The Merlin IVA designation covers the corporate versions of the original Metro II (which used a stretched Merlin II's fuselage coupled with a new wing, undercarriage and tail), the IVB is the executive equivalent of the Metro III, and the Merlin 23 is equivalent to the Metro 23.