Swearingen Merlin
Encyclopedia
The Swearingen Merlin or the Fairchild Aerospace Merlin is a pressurised, twin turboprop
business aircraft first produced by Swearingen Aircraft
, and later by Fairchild at a plant in San Antonio, Texas
.
started the developments that led to the Merlin through gradual modifications to the Beechcraft
Twin Bonanza
and Queen Air business aircraft which he dubbed Excalibur. Then hybrid aircraft was developed, with a new fuselage and vertical fin, mated to salvaged and modified (wet) Queen Air wings and horizontal tails, and Twin Bonanza landing gear. This was the SA26 Merlin, more-or-less a pressurized
Excalibur but fitted with a different model engine, the Lycoming TIGO-540
6-cylinder geared piston engine. The TIGO 540 was used despite the fact that one of the reasons the IO-720 was used in the Excalibur was that the Queen Air series' IGSO-480 and IGSO-540 engines from the same manufacturer were so troublesome. The decision was soon made to offer increased engine power, this was achieved through installing two Pratt & Whitney Canada PT6
A-20 turboprop engines, resulting in the SA26-T Merlin IIA.
(which was also derived from the Model 65 Queen Air). 36 Merlin IIA models were built before a follow-on model with Garrett AiResearch TPE-331
-1 engines called the SA26-AT Merlin IIB entered production after AiResearch was appointed as distributor for the type. The TPE-331 became the definitive engine of all subsequent production Merlins and the longer-fuselage Metros
that were to follow. The Australian Department of Civil Aviation (now the Civil Aviation Safety Authority
) took delivery of four Merlin IIBs in 1969 and operated them for almost fifteen years. The Merlin IIAs and IIBs were visually still obviously derivatives of the Queen Air; featuring as they did Queen Air tailplanes and wings with the same flat-top engine nacelles as the Excalibur Queen Airs; the airstair
in the same place and of the same general design as the Queen Air; and the nose being especially similar, it was the same general shape with access panels the same size, shape and location as those of the Queen Air.
These visual similarities ended with the next model, the SA226-T Merlin III, which was placed in production in February 1972 after 87 Merlin IIBs were built. This had new wings and engine nacelles with inverted inlet Garrett engines (this again becoming a defining feature of all subsequent production models), new landing gear with two wheels on each leg, a redesigned horizontal tail mounted on the vertical fin instead of on the fuselage as in earlier models and a redesigned longer nose with room for a baggage compartment as well as the avionics
found in the noses of Merlin II series aircraft. All of these design changes came from the Metro design, which was undergoing development in the late 1960s.
The SA226-TC Metro was more-or-less a new design, conceptually a stretch of the Merlin II (which it superficially resembled) sized to seat 22 passengers. Prototype construction of the Metro began in 1968 and first flight was on 26 August 1969. The standard engines offered were two TPE331-3UW turboprops driving three-bladed propellers. A corporate version called the SA226-AT Merlin IV was also marketed and initially sales of this version were roughly double that of the Metro. These sales were not immediately forthcoming however, as the company was financially-stretched by the development of the Metro prototype and lacked the funds to gear up for production. This situation was rectified in late 1971 when Ed Swearingen agreed to sell 90% of the company to Fairchild; the company was then renamed Swearingen Aviation Corporation.
By the end of 1972 six Merlin IVs had been built and production gradually built up alongside the concurrently-produced short-fuselage Merlin III. In 1974, the original Merlin IV and Metro models were replaced by the SA226-AT Merlin IVA and the SA226-TC Metro II after about 30 Merlin IVs and about 20 Metros had been built. Among the changes made were larger, ovalised rectangular windows replacing the circular porthole
-style windows of the early aircraft, 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. The same year the Merlin III was replaced by the SA226-T Merlin IIIA, with an extra window on the right side of the cabin and a small window aft of the airstair on each side of the fuselage. Customers for the Merlin IIIA included the Argentinian Air Force, the Argentine Army
and the Belgian Air Force
.
In January 1979 production of the Merlin IIIA ended in favour of the SA226-T(B) Merlin IIIB. The IIIB differed mainly by TPE331-10U engines of increased power driving four-bladed propellers turning in the opposite direction to those of earlier models. The SA227-TT Merlin IIIC was next, introduced concurrently with the SA227-AC Metro III (the first Metro III was Fairchild c/n AC-420 and the first Merlin IIIC was c/n TT-421, Metro and Merlin aircraft at this stage being numbered consecutively with different prefixes to denote the different types), and the SA227-AT Merlin IVC version of the Metro III followed shortly after (the first Merlin IVC was c/n AT-423). The Merlin IIIC was a redesign to incorporate structural and other changes but was visually the same as the Merlin IIIB, the redesign taking place to make the aircraft compliant with Special Federal Aviation Regulation 41 (SFAR-41). The Merlin IVC version was initially certified in 1980 at 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. Other improvements incorporated into the Merlin IVC were a 10 ft (3.05 m) increase in wing span (achieved by the simple expedient of removing the wingtips from the Metro II wing, bolting an extension to the end of each wing, and fitting a new wingtip, redesigned to reduce drag), TPE331-11U engines with redesigned "quick-access" engine cowlings and driving four-bladed propellers as on the Merlin IIIB, and other drag-reducing airframe modifications including landing gear doors that close after the gear is extended. The US Army bought a second-hand Merlin IVC and operated it as the solitary UC-26C.
Towards the end of production of the short-fuselage variants of the Merlin, optional winglet
s were offered. Ten of the last 25 SA227-TTs were built with the winglets as Merlin 300s. Production of short-fuselage Merlins ended in 1983 with the building of Merlin IIIC c/n TT-541. The last Merlin IVC (c/n AT-695B) was built in 1987 and Metro production ended in 1998.
SA26-T Merlin II
SA26-T Merlin IIA
SA26-T Merlin IIB
SA226-T Merlin III
SA226-T Merlin IIIA
SA226-T(B) Merlin IIIB
SA227-TT Merlin IIIC
SA227-TP Merlin IIID
SA227-TT Merlin 300
SA226-AT Merlin IV
SA226-AT Merlin IVA
SA227-AT Merlin IVC
South Africa
Turboprop
A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear.The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller...
business aircraft first produced by Swearingen Aircraft
Sino Swearingen Aircraft Corporation
SyberJet Aircraft, formerly Emivest Aerospace Corporation, and prior to that Sino Swearingen Aircraft Corporation SSAC, is an aircraft manufacturer. Their primary product is the Swearingen SJ30-2 small business jet...
, and later by Fairchild at a plant in San Antonio, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
.
Design and development
The Merlin was an evolution of earlier modification programmes performed by Swearingen Aircraft. Ed SwearingenEd Swearingen
Edward J. Swearingen in Lockhart, Texas is an aeronautical engineer based in San Antonio, Texas.-Life:Swearingen is notable for developing modifications from existing production aircraft such as the Piper PA-30 Twin Comanche from the Piper PA-24 Comanche single engine series, the Swearingen Merlin...
started the developments that led to the Merlin through gradual modifications to the Beechcraft
Beechcraft
Beechcraft is an American manufacturer of general aviation and military aircraft, ranging from light single engine aircraft to business jets and light military transports. Previously a division of Raytheon, it has been a brand of Hawker Beechcraft since 2006....
Twin Bonanza
Beechcraft Twin Bonanza
|-See also:-References:Twin Bonanza Association http://twinbonanza.com...
and Queen Air business aircraft which he dubbed Excalibur. Then hybrid aircraft was developed, with a new fuselage and vertical fin, mated to salvaged and modified (wet) Queen Air wings and horizontal tails, and Twin Bonanza landing gear. This was the SA26 Merlin, more-or-less a pressurized
Cabin pressurization
Cabin pressurization is the pumping of compressed air into an aircraft cabin to maintain a safe and comfortable environment for crew and passengers when flying at altitude.-Need for cabin pressurization:...
Excalibur but fitted with a different model engine, the Lycoming TIGO-540
Lycoming O-540
|-Specifications :-See also:-External links:...
6-cylinder geared piston engine. The TIGO 540 was used despite the fact that one of the reasons the IO-720 was used in the Excalibur was that the Queen Air series' IGSO-480 and IGSO-540 engines from the same manufacturer were so troublesome. The decision was soon made to offer increased engine power, this was achieved through installing two Pratt & Whitney Canada PT6
Pratt & Whitney Canada PT6
The Pratt & Whitney Canada PT6 is one of the most popular turboprop aircraft engines in history, and is produced by Pratt & Whitney Canada. The PT6 family is particularly well known for its extremely high reliability, with MTBO's on the order of 9000 hours in some models. In US military use, they...
A-20 turboprop engines, resulting in the SA26-T Merlin IIA.
Operational history
The prototype IIA took to the air for the first time on 13 April 1965, about fifteen months after the competing Beech Model 65-90 King AirBeechcraft King Air
The Beechcraft King Air family is part of a line of twin-turboprop aircraft produced by the Beech Aircraft Corporation...
(which was also derived from the Model 65 Queen Air). 36 Merlin IIA models were built before a follow-on model with Garrett AiResearch TPE-331
Garrett AiResearch TPE-331
|-See also:-External links:* * *...
-1 engines called the SA26-AT Merlin IIB entered production after AiResearch was appointed as distributor for the type. The TPE-331 became the definitive engine of all subsequent production Merlins and the longer-fuselage Metros
Fairchild Swearingen Metroliner
The Fairchild Swearingen Metroliner or the Fairchild Aerospace Metro is a 19-seat, pressurised, twin turboprop airliner first produced by Swearingen Aircraft and later by Fairchild at a plant in San Antonio, Texas, United States....
that were to follow. The Australian Department of Civil Aviation (now the Civil Aviation Safety Authority
Civil Aviation Safety Authority
The Civil Aviation Safety Authority is the Australian national aviation authority , the government statutory authority responsible for the regulation of civil aviation.-History:...
) took delivery of four Merlin IIBs in 1969 and operated them for almost fifteen years. The Merlin IIAs and IIBs were visually still obviously derivatives of the Queen Air; featuring as they did Queen Air tailplanes and wings with the same flat-top engine nacelles as the Excalibur Queen Airs; the airstair
Airstair
An airstair is a passenger staircase that is built in to an airliner — often, though not always, on the inside of a clamshell-style door. The stairs can be raised or lowered while the aircraft is on the ground, allowing passengers and ground personnel to board or depart the aircraft without the...
in the same place and of the same general design as the Queen Air; and the nose being especially similar, it was the same general shape with access panels the same size, shape and location as those of the Queen Air.
These visual similarities ended with the next model, the SA226-T Merlin III, which was placed in production in February 1972 after 87 Merlin IIBs were built. This had new wings and engine nacelles with inverted inlet Garrett engines (this again becoming a defining feature of all subsequent production models), new landing gear with two wheels on each leg, a redesigned horizontal tail mounted on the vertical fin instead of on the fuselage as in earlier models and a redesigned longer nose with room for a baggage compartment as well as the avionics
Avionics
Avionics are electronic systems used on aircraft, artificial satellites and spacecraft.Avionic systems include communications, navigation, the display and management of multiple systems and the hundreds of systems that are fitted to aircraft to meet individual roles...
found in the noses of Merlin II series aircraft. All of these design changes came from the Metro design, which was undergoing development in the late 1960s.
The SA226-TC Metro was more-or-less a new design, conceptually a stretch of the Merlin II (which it superficially resembled) sized to seat 22 passengers. Prototype construction of the Metro began in 1968 and first flight was on 26 August 1969. The standard engines offered were two TPE331-3UW turboprops driving three-bladed propellers. A corporate version called the SA226-AT Merlin IV was also marketed and initially sales of this version were roughly double that of the Metro. These sales were not immediately forthcoming however, as the company was financially-stretched by the development of the Metro prototype and lacked the funds to gear up for production. This situation was rectified in late 1971 when Ed Swearingen agreed to sell 90% of the company to Fairchild; the company was then renamed Swearingen Aviation Corporation.
By the end of 1972 six Merlin IVs had been built and production gradually built up alongside the concurrently-produced short-fuselage Merlin III. In 1974, the original Merlin IV and Metro models were replaced by the SA226-AT Merlin IVA and the SA226-TC Metro II after about 30 Merlin IVs and about 20 Metros had been built. Among the changes made were larger, ovalised rectangular windows replacing the circular porthole
Porthole
A porthole is a generally circular, window used on the hull of ships to admit light and air. Porthole is actually an abbreviated term for "port hole window"...
-style windows of the early aircraft, and optional provision for a small Rocket-Assisted Take Off
JATO
JATO is an acronym for jet-fuel assisted take off. It is a system for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets....
(RATO) rocket in the tail cone, this being offered to improve takeoff performance out of "hot & high" airfields. The same year the Merlin III was replaced by the SA226-T Merlin IIIA, with an extra window on the right side of the cabin and a small window aft of the airstair on each side of the fuselage. Customers for the Merlin IIIA included the Argentinian Air Force, the Argentine Army
Argentine Army
The Argentine Army is the land armed force branch of the Armed Forces of the Argentine Republic and the senior military service of the country.- History :...
and the Belgian Air Force
Belgian Air Force
The Air Component, formerly the Belgian Air Force, is the air arm of the Belgian Armed Forces. Originally founded in 1909, it is one of the world's first air forces, and was a pioneer in aerial combat during the First World War...
.
Towards the end of production of the short-fuselage variants of the Merlin, optional winglet
Winglet
Wingtip devices are usually intended to improve the efficiency of fixed-wing aircraft. There are several types of wingtip devices, and though they function in different manners, the intended effect is always to reduce the aircraft's drag by partial recovery of the tip vortex energy...
s were offered. Ten of the last 25 SA227-TTs were built with the winglets as Merlin 300s. Production of short-fuselage Merlins ended in 1983 with the building of Merlin IIIC c/n TT-541. The last Merlin IVC (c/n AT-695B) was built in 1987 and Metro production ended in 1998.
Civil variants
SA26 Merlin- Prototype piston-engined Merlin
SA26-T Merlin II
- Prototype re-engined with two PT6A Turboprops.
SA26-T Merlin IIA
- Production version of Merlin II with two Pratt & Whitney Canada PT6Pratt & Whitney Canada PT6The Pratt & Whitney Canada PT6 is one of the most popular turboprop aircraft engines in history, and is produced by Pratt & Whitney Canada. The PT6 family is particularly well known for its extremely high reliability, with MTBO's on the order of 9000 hours in some models. In US military use, they...
A-20 Turboprop engines.
SA26-T Merlin IIB
- Similar to Merlin IIA but with two Garrett AiResearch TPE331Garrett AiResearch TPE-331|-See also:-External links:* * *...
-1-151G Turboprop engines.
SA226-T Merlin III
- Redesign of Merlin II with new fuselage and incorporating Metro wing, landing gear and tail; two TPE331-3U-303G Turboprops.
SA226-T Merlin IIIA
- Update of Merlin III design, changes include extra windows.
SA226-T(B) Merlin IIIB
- Update of Merlin IIIA design, changes include TPE331-10U-503G engines driving 4-bladed propellers; systems changes and revised interior and air conditioning.
SA227-TT Merlin IIIC
- Redesign to meet SFAR-41 standard.
SA227-TP Merlin IIID
- Proposed IIIC variant with PT6A engines.
SA227-TT Merlin 300
- Merlin IIIC fitted with wingletWingletWingtip devices are usually intended to improve the efficiency of fixed-wing aircraft. There are several types of wingtip devices, and though they function in different manners, the intended effect is always to reduce the aircraft's drag by partial recovery of the tip vortex energy...
s
SA226-AT Merlin IV
- 21-seat corporate version of the Metro, with two TPE331-3U-303G engines.
SA226-AT Merlin IVA
- Merlin IV with minor changes, most noticeably with ovalised rectangular cabin windows instead of round windows; corporate version of Metro II.
SA227-AT Merlin IVC
- Corporate version of Metro III with increased Maximum Take-Off Weight compared to Metro III. SA227-AT also built as Expediter freighter version without cabin windows (see Fairchild Swearingen MetrolinerFairchild Swearingen MetrolinerThe Fairchild Swearingen Metroliner or the Fairchild Aerospace Metro is a 19-seat, pressurised, twin turboprop airliner first produced by Swearingen Aircraft and later by Fairchild at a plant in San Antonio, Texas, United States....
article).
Military variants
- C-26 is the designation of the United States armed forcesUnited States armed forcesThe United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...
for the Metroliner series. It was not officially named by the US Armed Forces. - UC-26C - this was a second-hand 1983-built Merlin IVC operated by the US Army for several years with the serial 89-1471.
Military operators
- Argentine Air ForceArgentine Air ForceThe Argentine Air Force is the national aviation branch of the Armed Forces of the Argentine Republic. , it had 14,606 military and 6,854 civilian staff.-History:...
- Argentine ArmyArgentine ArmyThe Argentine Army is the land armed force branch of the Armed Forces of the Argentine Republic and the senior military service of the country.- History :...
- Belgium Air Force
South Africa
- South African Air ForceSouth African Air ForceThe South African Air Force is the air force of South Africa, with headquarters in Pretoria. It is the world's second oldest independent air force, and its motto is Per Aspera Ad Astra...
- No. 21 Squadron SAAF
- Swedish Air ForceSwedish Air ForceThe Swedish Air Force is the air force branch of the Swedish Armed Forces.-History:The Swedish Air Force was created on July 1, 1926 when the aircraft units of the Army and Navy were merged. Because of the escalating international tension during the 1930s the Air Force was reorganized and expanded...
- United States ArmyUnited States ArmyThe United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...