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, 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.

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 USA 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.

SA227 Series

• 291 Metro III
  • 273 SA227-AC (11 to US Armed Forces as C-26As)
  • 18 SA227-BC (3 to US Armed Forces as C-26Bs)
• 43 SA227-AT
  • 21 Merlin IVC
  • 22 Expediter
• 115 Metro 23
  • 5 SA227 CC
  • 110 SA227-DC (37 to U.S. Armed Forces as C-26Bs)

Military

• Fairchild C-26 Metroliner - version for the US Armed Forces

• TP88 - Metro III (two aircraft) delivered to the Swedish Air Force for use as a VIP transports. The first was delivered in 1984, and this was replaced by the second (TP88B) in 1986 and remained in use until 1993. A third dubbed TP88C, was acquired in 1987 and was used for Erieye/FS-890 AEW trials.

Source: Wikipedia