Fairchild Swearingen Metroliner
The Fairchild Swearingen Metroliner (previously the Swearingen Metro and later Fairchild Aerospace Metro) is a 19-seat, pressurized, twin-turboprop airliner first produced by Swearingen Aircraft and later by Fairchild Aircraft at a plant in San Antonio, Texas. Design. The Metroliner was an evolution of the Swearingen Merlin turboprop-powered business aircraft. Ed Swearingen, a Texas fixed-base operator (FBO), started the developments that led to the Metro through gradual modifications to the Beechcraft Twin Bonanza and Queen Air business aircraft, which he dubbed Excalibur. A new fuselage (but with a similar nose) and vertical fin were  then developed, married to salvaged and rebuilt (wet) Queen Air wings and horizontal tails, and Twin Bonanza landing gear; this became the SA26 Merlin, more or less a pressurized Excalibur. Through successive models (the SA26-T Merlin IIA and SA26-AT Merlin IIB) the engines were changed to Pratt & Whitney Canada PT6, then Garrett TPE331 turboprops. These were marketed as business aircraft seating eight to ten passengers. An all-new aircraft was built and named the SA226-T Merlin III with a new nose, wings, landing gear, cruciform horizontal tail and inverted inlet Garrett engines. Ultimately a stretch of the  Merlin III was designed, sized to seat 22 passengers and called the SA226-TC Metro. Because FAA regulations limited an airliner to no more than 19 seats if no flight attendant was to be carried, the aircraft was optimized for that number of passengers. The standard engines offered were two TPE331-3UW turboprops driving three-bladed propellers. A corporate version called the SA226-AT Merlin IVA was also marketed and initially sales of this version were roughly double that of the Metro. Development. Prototype construction of the Metro began in 1968 and the first flight was on August 26, 1969 . Swearingen Aircraft encountered financial difficulties at this stage, and late in 1971 Fairchild (which was marketing the Metro and building its wings and engine nacelles), bought 90% of Swearingen and the company was renamed Swearingen Aviation Corporation. It was at this point that the previously cash-strapped company was able to put the Metro into production. In 1974, the original Metro models were replaced by the SA226-TC Metro II after about 20 Metros and about 30 Merlin IVAs had been built. Among the changes made were larger, squared-oval windows and optional provision for a small Rocket-Assisted Take  Off (RATO) rocket in the tail cone, this being offered to improve takeoff performance out of "hot & high" airfields in the event of an engine failure. The Metro and Metro II were limited to a maximum weight of 12,500 pounds (5,670 kg) in the US and countries using imperial units, and 5,700 kg in countries using SI units. When this restriction was lifted the Metro II was re-certified as the Metro IIA in 1980 with a maximum weight of 13,100 pounds (5,941 kg) and the Metro II's TPE331-3 engines replaced by -10 engines of increased power. The  SA227-AC Metro III followed, also initially certified in 1980 for up to 14,000 pounds (6,350 kg), this increasing to 14,500 pounds (6,577 kg) as engines and structures were upgraded. An option to go as high as 16,000 pounds (7,257 kg) was offered. Externally, improvements incorporated into the Metro III were a 10 ft (3.05 m) increase in wing span, four-bladed props, redesigned "quick-access" engine cowlings and numerous drag-reducing airframe modifications, including landing gear doors that closed after the gear was extended. Once again a corporate version was offered as the Merlin IVC (the model name was  chosen to align with the contemporaneous short-fuselage Merlin IIIC). A version with strengthened floors and the high gross weight option was offered as a cargo aircraft known as the Expediter. Both the Expediter and the Merlin IVC were designated the SA227-AT. Finally, due to reliability problems with Garrett engines in the second half of the 1980s, the Metro IIIA was offered with two Pratt & Whitney Canada PT6A-45R turboprops in place of the Garrett units; however none were actually delivered. A special model was the SA227-BC Metro III built for Mexican airline AeroLitoral, which took delivery of 15  of the 18 of this model that were produced. Improvements beyond the Metro III provided better systems, more power and a further increase in takeoff weight. This design effort resulted in the SA227 CC (for Commuter Category) and SA227-DC models, initially called the Metro IV then renamed Metro 23, so named as they were designed for certification under FAR Part 23 (Amendment 34) standards. A Metro 23 EF with an external pod under the lower fuselage for greater baggage capacity was also offered as well as an Expediter 23 and Merlin 23. The SA227-CC was an interim model  with TPE331-11U engines and only a handful were built. Further development. In the 1960s Swearingen Aircraft developed a prototype SA-28T eight-seat jet aircraft with a flapless delta wing. It shared the tail and cockpit with the Merlin/Metro. The two engines were to be Garrett TFE731 turbofans then in development; they were originally to be mounted on the aft fuselage, however during the course of design work their location was moved to under the high-mounted wing. Early flights were to be undertaken with General Electric CJ610 engines fitted. Development continued after Fairchild acquired the company, but  the project was shut down nine weeks from first flight. It was later cut up as scrap and the fuselage used as a Metro display at trade shows. At the 1987 Paris Air Show, Fairchild released details of proposed developments of the Metro designated the Metro V and Metro VI. These versions would have featured a longer fuselage with a taller "stand-up" cabin providing 69 in (180 cm) of interior height for passengers; a redesigned, longer wing; engines moved further out on the wing from the fuselage; a "T-tail" and various system improvements. A Merlin V corporate version  of the Metro V was also planned. The Metro V was to be fitted with the same engines as the Metro 23 and the Metro VI was to be fitted with more powerful TPE331-14 engines. The Metro VI was shelved within months of being announced due to a lack of customer interest, but Fairchild did not proceed with the Metro V either. One version that did see the light of day was the Metro 25, which featured an increased passenger capacity of 25 at the expense of the baggage space found in earlier models; the deletion of the left  rear cargo door, the addition of a passenger door on the right-hand rear fuselage, and a belly pod for baggage. A Metro III was converted as a Metro 25 demonstrator, it flew in this configuration in October 1989. Also mooted but not built was the Metro 25J, which would have been another jet-powered aircraft with TFE731s in over-wing pods. The type certificates for Metro and Merlin aircraft are currently held by M7 Aerospace. Operational history. Two of the original Metro model were delivered in 1972 to Societe Miniere de Bakwanga (MIBA) in Kinshasa, Zaire, the first customer  to put the Metro into service. The first airline to put them into service was Commuter Airlines in January 1973, followed shortly after by Air Wisconsin. At least one Metro IIA flies in Canada with Perimeter Aviation. Two SA227-CCs are today registered with Canadian operator Bearskin Lake Air Service Ltd., while another two are operating in New Zealand. A fifth also flew with Bearskin Airlines, but was destroyed in a mid-air collision in 1995. In service with Perimeter Aviation in Canada, this long-term operator of the Metro II and III made a number of modifications to suit  its use in northern and remote Canadian sites where rudimentary gravel "strips" were common. Some of the many innovative changes to the design of the Metro allowed the aircraft to fly more efficiently, as well as cutting down on the "noise factor" that was attributed to the early models. The airline installed Garrett engines with quieter and more efficient four-bladed Hartzell propellers. More recently, in 2016, 5-blade composite propellers are being installed, further enhancing performance and reducing noise levels. Their Metros are also all equipped with modern avionics suites, including the recent installation of Garmin 950 glass cockpits  and GPS satellite tracking. Many of the improvements resulting in the Metro 23 came about during work to produce the military C-26B model for the United States Air Force. A Metro III aircraft was modified for the Colombian Air Force for counternarcotics reconnaissance purposes. The Colombian National Police also operates several Metro 23 aircraft for counternarcotics reconnaissance purposes. In addition, the Peruvian Air Force operates a Metro 23 and the Trinidad and Tobago Coast Guard operates a Metro III, both similarly configured. A "Regional Security System" Metro III with a large belly radome has been seen in the Caribbean. In  civilian service the type has proved to be popular, with sales in the 19-seat airliner market rivalled only by the Beechcraft 1900. It is especially popular in Australia. Since the first example (a Merlin IVA) arrived in 1975, almost 20% of the fleet has operated there, and, as of December 2008, 61 Metros and Expediters are registered in Australia, more than all of its market rivals combined. Metro production ended in 1998; however, by this time, regional jets were in vogue and turboprop types were out of favour with airlines. At the time, several airframes remained unsold at the  factory. In 2001, the last aircraft, Metro 23 c/n DC-904B, was finally delivered to National Jet Aviation Services of Zelienople, Pennsylvania, an air charter operator. A total of 703 Metro, Expediter, Merlin IV series and C-26 series aircraft were built. In addition, 158 other SA226- and SA227-series aircraft were built as short-fuselage Merlin IIIs, IIIAs and IIIBs. Operators. In July 2019, 196 Metroliners were in airline service; airline operators with six or more aircraft were: