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 and aeronautical engineer, 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 tailThis and subsequent Merlin and Metro models have a trimmable horizontal stabilizer (THS) usually used on jet aircraft, one of only a small number of turboprop aircraft to have this design feature (the competing Beechcraft Model 99 being another). 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, with 4 feet and 9 inches of headroom within the passenger cabin. 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."Metro production dates." fortunecity.com. Retrieved: August 21, 2011.
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. At this point, the previously cash-strapped company was able to put the Metro into production."Fairchild to Acquire Swearingen", "World News" (online archive version). Flight International, November 11, 1971, p. 751. Retrieved: December 15, 2008.
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.The article "Final Metro Delivery" in Airways magazine Issue 64 states that Metro deliveries totalled 18. The Metro production list shows that by the end of 1974, 22 Merlins had been built. Among the changes made were larger, squared-oval windows and optionally, a small rocket-assisted take off engine in the tail cone, 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 by the requirements of the Special Federal Regulation 23 that the aircraft had been certified against.Taylor 1980, pp. 443–445 The Metro II was re-certified as the Metro IIA in 1980 with a maximum weight of and the Metro II's TPE331-3 engines replaced by -10 engines of increased power.
The followed, also initially certified in 1980 for up to , increasing to as engines and structures were upgraded. An option for up to was offered. Among external improvements to the Metro III were a 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 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 but 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"Metro IV & V", Commuter Aircraft Directory,(online archive version). Flight International, May 7, 1988, p. 47. Retrieved: December 15, 2008. 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."SA227-CC/-DC Type Certificate." FAA. Retrieved: December 15, 2008
Further development In the 1960s, Swearingen Aircraft developed a prototype SA-28T eight-seat jet aircraft with a flapless delta wing.Fricker, John. "At the NBAA Convention, Part 2 - the turboprop types", "Metroliner."Flight International, October 16, 1969, p. 595 (online archive version). Retrieved: December 15, 2008."Aeronews." Air Progress magazine, July 1969, pp. 19–20. It shared the tail and cockpit with the Merlin/Metro. The two engines were to be Garrett TFE731 turbofans then in development;"Aero Engines 1970" (online archive version). Flight International, January 1, 1970, p. 15. Retrieved: December 15, 2008. 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."Hanover review - General-aviation postscript", Flight International, May 7, 1970, p. 761 (online archive version). Retrieved: December 15, 2008. Early flights were to be undertaken with General Electric CJ610 engines fitted. Development continued after Fairchild acquired the company,"Swearingen production restarts, Air Transport: Light Commercial and Business (online archive version)." Flight International, March 2, 1972, p. 318. Retrieved: December 15. 2008. 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 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."Fairchild Dornier Metro." Forecast International.com. Retrieved: December 15, 2008. The Metro VI was shelved within months of being announced due to a lack of customer interest,"NBAA Report - Fairchild launches Metro IV and V" (online archive version). Flight International, October 17, 1987, p. 20. Retrieved: December 15, 2008. 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."Fairchild unveils new 25-seat Metro variant" (online archive version). Flight International, October 28, 1989, p. 16. Retrieved: December 15, 2008. 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 Société Minière 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."TC-343" (the Fairchild c/n of a Metro IIA formerly registered in Australia). Transport Canada Canadian civil aircraft register, online search. Retrieved: August 27, 2007. Two SA227-CCs are today registered with Canadian operator Bearskin Lake Air Service Ltd.,"Canadian civil aircraft register." Transport Canada, August 25, 2007. while another two are operating in New Zealand. caa.govt.nz. Retrieved: December 15, 2008. A fifth also flew with Bearskin Airlines, but was destroyed in a mid-air collision in 1995."Accident Report." Aviation Safety Database. Retrieved: August 26, 2007.
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."Drug Wars: Barbados Swearingen C-26 Tiger Shark." Barbados Free Press, January 29, 2007. Retrieved: August 21, 2011.