The Swaeringen Metroliner is a small two-engine regional turboprop airliner, seating up to 19 passengers. It is a further development of the Swearingen Merlin corporate aircraft and after a slow start, it became very popular among commuter airlines.
Swaeringen Aircraft, founded by Ed Swaeringen, started developing the SA226-TC Metroliner during the late 1960s and the first flight took place on 26 August 1969. Actually, the aircraft was a further development of the earlier Merlin I and Merlin II pressurised business aircraft. The Merlin I was a mix of a completely new fuselage, the wing of the Beechcraft Queen Air and the undercarriage of the Beechcraft Twin Bonanza. The Metro commuter airliner - a stretched version of the Merlin - also got a new wing, a new nose, a new landing gear and a revised empennage including a cruciform horizontal tail cone. The FAA awarded the certificate of airworthiness for the Metro in June 1970 and for the corporate version Merlin IV in September 1970.
However, because of financial trouble, Swearingen didn't have the money to put the aircraft in series production and the company even went bankrupt. Partner Fairchild was already producing wings and engine nacelles at that time and instead of resigning to unpaid bills, it took 90 per cent control of Swearingen. Now production could start and in March 1973 the first aircraft entered service with Commuter Airlines, soon followed by Air Wisconsin.
The Metroliner has a rather narrow fuselage in which passengers sit two-abreast (1+1). Its main competitors were the Beechcraft 1900, also with two-abreast seating, and the three-abreast British Aerospace Jetstream 31. The Metro features two turboprop engines placed upside down on a low wing. The Garrett TPE331-3UW turboprops usually drive three-bladed propellers, although some operators installed four-bladed ones. Passengers board the aircraft via a door fitted with airstairs behind the cockpit. There is a large luggage and cargo compartment behind the passenger cabin and a small one in the nose.
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Metro II & III
An improved version is the Metro II, which was being produced from 1975. The Metro II got larger, squared-oval windows instead of the round windows of Metro I. It also has an optional provision for a small rocket engine in the tail cone to deliver extra thrust for take-off from hot and high airports. The equivalent executive aircraft became the Merlin IVA. The Metro IIA is certified for higher weights and the Expediter is a cargo version.
In 1981, Swaeringen started production of the Metro III, with higher weights, a larger wingspan, more powerful engines and improved propellers. This resulted in extra range and less noise. The corporate version was the Merlin IVC. The Metro IIIA was a variant with Pratt & Whitney Canada PT6As turboprops and even more wing span, but no aircraft of this version were delivered.
The next Metro model was the 23 (certified to FAR Part 23) with higher take-off weight, more powerful engines and renewed systems. The improvements were first introduced on the military version, the C-26. Swaeringen also offered the Merlin 23 and Expediter 23.
The aircraft manufacturer studied several further versions. The Metro V was an intended version with a longer and higher fuselage to allow 'stand-up' headroom in the cabin, like Beechcraft introduced on the 1900D, but this version was never built. The Metro 25 had more seats instead of the rear cargo compartment and the cargo door was deleted. The aircraft carried baggage in a belly pod. A demonstrator flew in this configuration in 1989 but it was not sold. Never built was a projected jet-version, the Metro 25J, with two TFE731 tubofans in over-wing nacelles.
Production ended in 1998 after 703 Metro, Expediter and Merlin IV aircraft had left the factory. In 2018, over 200 are still in airline service.
Metro III Specifications
Wingspan: 17.37 m (57 ft 0 in). Length: 18.09 m (59 ft 4 in). Height: 5.08 m (16 ft 8 in).
Empty weight: 3,963 kg (8,737 lb). Max. take-off weight: 6,577 - 7,257 kg (14,500-16,000 lb).
Accommodation: 19 passengers. Range: 2,131 km (1,150 nm). Cruise speed: 515 km/h - 278 kts).
Engines: two Garrett AiResearch TPE-331 turboprops 1,100 shp (820 kW).