View source for Swearingen Merlin

{{Short description|Type of Aircraft}}
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{{Infobox aircraft
 |name= Merlin
 |image= File:C-FAMF 1977 Swearingen SA226-T C-N T274 (6445535163).jpg
 |caption= The Merlin is a low-wing, twin turboprop light [[utility aircraft]] with [[retractable gear]]
 |type= [[business aircraft]]
 |manufacturer= [[Sino Swearingen Aircraft Corporation|Swearingen]] <br/>[[Fairchild Aircraft]]
 |designer= Ed Swearingen <br/>John T. Jennings
 |first_flight=13 April 1965
 |introduction=
 |retired=
 |status=  Out of production, in service
 |primary_user=
 |produced= 1965-1998
 |number_built=
 |developed_from = 
 |developed_into = [[Fairchild Swearingen Metroliner]] <br/>[[C-26 Metroliner]]
}}

The '''Swearingen Merlin''' or the '''Fairchild Aerospace Merlin''' is a pressurized, twin [[turboprop]] business aircraft first produced by [[Sino Swearingen Aircraft Corporation|Swearingen Aircraft]], and later by [[Fairchild Aircraft|Fairchild]] at a plant in [[San Antonio]], [[Texas]].

==Development==

The Merlin was an evolution of earlier modification programs performed by Swearingen Aircraft. [[Ed Swearingen]] started the developments that led to the Merlin through gradual modifications to the [[Beechcraft Twin Bonanza]] and [[Beechcraft Queen Air|Queen Air]] business aircraft which he dubbed [[Beechcraft Queen Air#Excalibur|Excalibur]]. Then a hybrid aircraft was developed, with a new fuselage and vertical fin, mated to salvaged and modified [[Fuel tank#Aircraft|(wet)]] Queen Air wings and horizontal tails, and Twin Bonanza landing gear: the Merlin.
[[File:N20KV Swearingen SA26T Merlin 2B (7459128376).jpg|thumb|SA26T Merlin IIB]]

The prototype IIA took to the air for the first time on 13 April 1965, about fifteen months after the competing [[Beechcraft King Air|Beech Model 65-90 King Air]] (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.<ref name="FI69">Fricker, John. "At the NBAA Convention, Part 2 - the turboprop types", [http://www.flightglobal.com/pdfarchive/view/1969/1969%20-%202983.html ''Flight International'', 16 October 1969, p.595 (online archive version).] Retrieved: 15 December 2008</ref> The TPE-331 became the definitive engine of all subsequent production Merlins and the longer-fuselage [[Fairchild Swearingen Metroliner|Metros]] that were to follow.

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 (This and subsequent Merlin and Metro models have a trimmable horizontal stabilizer (THS) usually used on jet aircraft, one of only two turboprop aircraft types to have this design feature). 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.<ref>Based on production dates in the [http://meltingpot.fortunecity.com/pecan/617/propairliner.html Metro production list] {{webarchive|url=https://web.archive.org/web/20080620212124/http://meltingpot.fortunecity.com/pecan/617/propairliner.html |date=2008-06-20 }}.</ref> 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.<ref name="AW"/> 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.
[[File:SA226-AT Merlin IVA at the Royal Thai Air Force Museum.jpg|thumb|SA226-AT Merlin IVA of the Royal Thai Air Force ]]
By the end of 1972 six Merlin IVs had been built<ref>[http://meltingpot.fortunecity.com/pecan/617/propairliner.html Turboprop Production Lists Home Page] {{webarchive|url=https://web.archive.org/web/20080620212124/http://meltingpot.fortunecity.com/pecan/617/propairliner.html |date=2008-06-20 }} Metro production list accessed via this site September 3, 2007</ref> 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.<ref>The article "Final Metro Delivery" in Airways magazine Issue 64 states that Metro deliveries before the Metro II was introduced totalled 18. The Metro production list shows that by the end of 1974 22 Merlins had been built. However a photo on Airliners.net ([http://www.airliners.net/open.file/0667896/M/ here]) of the 33rd Merlin IVA built (Fairchild c/n AT-038, built in 1975), shows it to have the earlier round windows.</ref> 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 [[JATO|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]].

[[File:SA-226 F-GLPT 24oct14 LFBO.jpg|thumb|Merlin IIIA]]

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 {{convert|14,000|lb|kg}} this increasing to {{convert|14,500|lb|kg}} as engines and structures were upgraded. An option to go as high as {{convert|16,000|lb|kg}} was offered. Other improvements incorporated into the Merlin IVC were a {{convert|10|ft|m|abbr=on}} 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.<ref name="BA"/>

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.<ref name="AW">"Final Metro Delivery." Airways magazine Vol. 8, No. 4; Issue 64, June 2001, p. 32. Airways International Inc. ISSN 1074-4320.</ref>

==Design==

The '''SA26 Merlin''' is a [[Cabin pressurization|pressurized]] Excalibur fitted with a different [[Lycoming O-540|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, which was achieved through installing two [[Pratt & Whitney Canada PT6]]A-20 turboprop engines, resulting in the '''SA26-T Merlin IIA'''.

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, of the same general shape with access panels the same size, shape and location as those of the Queen Air.

==Operational history==
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.<ref>[http://www.airwaysmuseum.com/DCA%20Merlin%20index.htm Department of Civil Aviation Airways Museum Swearingen Merlin page.]</ref>

==Variants==

===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 PT6]]A-20 Turboprop engines.
;SA26-T Merlin IIB
:Similar to Merlin IIA but with two [[Garrett AiResearch TPE-331|Garrett AiResearch TPE331]]-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 [[winglet]]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 Metroliner]]).

===Military variants===
;C-26
:Designation of the [[United States armed forces]] for the Metroliner series. It was not officially named by the US Armed Forces. 
;UC-26C
:Single second-hand 1983-built Merlin IVC operated by the US Army for several years with the serial 89–1471.<ref name="BA">[http://home.att.net/~jbaugher/1989.html USAF FY1989 Serial Number list] {{Webarchive|url=https://web.archive.org/web/20071011213752/http://home.att.net/~jbaugher/1989.html |date=2007-10-11 }} retrieved 25 August 2007.</ref>
;B.L.6
:({{langx|th|บ.ล.๖}}) [[Royal Thai Armed Forces]] designation for the Merlin III and Merlin IVA.<ref name=":0">{{Cite web |title=Thai Military Aircraft Designations |url=https://designation-systems.net/non-us/thailand.html |access-date=2025-03-19 |website=designation-systems.net}}</ref>
;B.TL.6
:({{langx|th|บ.ตล.๖}}) Royal Thai Armed Forces designation for the Merlin IVC.<ref name=":0" />

==Military operators==
[[File:Swearingen SA-226T Merlin IIIA, Belgium - Air Force AN1334062.jpg|thumb|[[Belgium Air Force]]]]
;{{ARG}}
*[[Argentine Air Force]] – Two Merlin IVAs were used in the search and rescue role.<ref name="andrade12">Andrade 1982, p. 12</ref>
*[[Argentine Army]] – Five Merlin IVAs.<ref name="andrade13">Andrade 1982, p. 13</ref>
;{{BEL}}
*[[Belgium Air Force]] – Six Merlin IIAs<ref name="andrade25">Andrade 1982, p. 25</ref>
;{{flag|South Africa|1928}}
*[[South African Air Force]] – Seven Merlin IVAs<ref name="andrade198">Andrade 1982, p. 198</ref>
**[[No. 21 Squadron SAAF]]
;{{SWE}}
*[[Swedish Air Force]]{{Citation needed|date=January 2013}}
;{{THA}}
*[[Royal Thai Air Force]] – Four Merlin IVA, three equipped as survey aircraft.<ref name="andrade224">Andrade 1982, p. 224</ref>
;{{USA}}
*[[United States Army]]{{Citation needed|date=January 2013}}

==Incidents and accidents==
As of May 2021 there have been 63 documented incidents and 96 deaths involving the Merlin.<ref>{{cite web|url=https://www.baaa-acro.com/search-results?combine=merlin|title=Accident Archives|website=Bureau of Aircraft Accidents Archives|access-date=6 May 2021}}</ref> Listed below are a select few of the most notable ones.
* 1 April 1993: [[NASCAR]] champion [[Alan Kulwicki]] died in [[Alan Kulwicki plane crash|the crash]] of a Merlin III, [[aircraft registration]] ''N500AK'', near [[Blountville, Tennessee]], while on approach to the nearby [[Tri-Cities Regional Airport]]. All four people on board, including two executives of the [[Hooters]] restaurant chain, were killed. The [[National Transportation Safety Board]] (NTSB) attributed the accident to ''"Failure of the pilot to follow procedures concerning the use of the engine inlet [[Ice protection system#Engine-inlet icing|anti-ice system]] and/or continuous ignition while operating in [[icing conditions]]."''<ref>{{cite web|url=https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20001211X12077&AKey=1&RType=Final&IType=MA
|title=National Transportation Safety Board Aviation Accident Final Report|author=NTSB|date= 16 March 1994|website=app.ntsb.gov|publisher=NTSB|access-date=24 October 2017}}</ref>
* 23 April 2021: a Merlin IIIB, registration ''N59EZ'', crashed near [[Winslow, Arizona]], killing [[IndyCar]] racer and [[1979 24 Hours of Le Mans]] winner [[Bill Whittington]] and the other occupant. The accident is under investigation by the NTSB and the [[Federal Aviation Administration]].<ref>{{cite news|author=<!--Staff writer(s)/no by-line.--> |title=NCSO: 2 people dead after a plane crash near Winslow|url=https://www.abc15.com/news/region-northern-az/ncso-2-people-dead-after-a-plane-crash-near-winslow|work=KNXV-TV |agency=Associated Press|date=28 April 2021|access-date=6 May 2021}}</ref><ref>{{Cite web|last=Aviation Safety Network|title=ASN Wikibase Occurrence # 253831|url=https://aviation-safety.net/wikibase/253831|access-date=6 May 2021|website=Aviation Safety Network}}</ref>

==Specifications (Merlin IIIC, SFAR 41 certification)==
{{Aircraft specs
|ref=''Jane's All The World's Aircraft 1982–83.''<ref name="jawa82 p364-6">Taylor 1982, pp. 364–366.</ref>
|prime units?=kts
<!--
        General characteristics
-->
|genhide=

|crew=2
|capacity=up to 9 passengers
|length m=
|length ft=42
|length in=2
|span m=
|span ft=46
|span in=3
|height m=
|height ft=16
|height in=10
|wing area sqm=
|wing area sqft=277.5
|airfoil=NACA 65<sub>2</sub>A215 at root, 64<sub>2</sub>A415 at tip
|aspect ratio=7.71:1
|empty weight kg=
|empty weight lb=8150
|gross weight kg=
|max takeoff weight lb=13230
|fuel capacity={{convert|648|USgal|impgal L|abbr=on}}
<!--
        Powerplant
-->
|eng1 number=2
|eng1 name=[[Garrett AiResearch TPE-331]]-10U-503G
|eng1 type=[[turboprop]]s<ref>option for continuous [[Water injection (engines)|alcohol-water injection]] (AWI)</ref>
|eng1 kw=<!-- prop engines -->
|eng1 hp=<!-- prop engines -->
|eng1 shp=900<!-- prop engines -->

|prop blade number=4<!-- propeller aircraft -->
|prop name=Dowty Type R.321

|prop dia ft=8<!-- propeller aircraft -->
|prop dia in=10<!-- propeller aircraft -->

<!--
        Performance
-->
|perfhide=

|max speed kmh=
|max speed mph=
|max speed kts=
|cruise speed kmh=<!-- if max speed unknown -->
|cruise speed mph=<!-- if max speed unknown -->
|cruise speed kts=300
|cruise speed note=at {{convert|10000|ft|m|-1|abbr=on}} (max cruise)
|stall speed kts=92
|stall speed note=(flaps and landing gear down)
|range km=
|range miles=
|range nmi=1938
|range note=at {{convert|26000|ft|m|abbr=on}}, six occupants
|ferry range nmi=2239
|ceiling m=
|ceiling ft=27000
|climb rate ms=
|climb rate ftmin=2650
|more performance=*'''Take off run to {{convert|50|ft|m|abbr=on}}:''' {{convert|2920|ft|m|abbr=on}}
*'''Landing run from {{convert|50|ft|m|abbr=on}}:''' {{convert|2920|ft|m|abbr=on}}

|avionics=
}}

==See also==
{{Aircontent
|related=
* [[Beechcraft Queen Air]]
* [[Beechcraft Twin Bonanza]]
* [[Fairchild C-26 Metroliner]]
* [[Fairchild Swearingen Metroliner]]
|similar aircraft=
* [[Beechcraft King Air]]
* [[Cessna 425|Cessna 425 Conquest I/Corsair]] and [[Cessna 441|441 Conquest II]]
* [[Embraer EMB 121 Xingu]]
* [[Mitsubishi MU-2]]
* [[Piaggio Avanti]]
* [[Piper PA-31T Cheyenne|Piper PA-31T]] and [[Piper PA-42 Cheyenne|PA-42 Cheyenne]]
* [[Aero Commander 500|Rockwell/Gulfstream Turbo Commander]]
|lists=
* [[List of military aircraft of the United States]]
|see also=
}}

==References==
;Notes
{{reflist|2}}
;Bibliography
* Andrade, John. ''Militair 1982''. London: Aviation Press Limited, 1982. {{ISBN|0 907898 01 7}}.
* Frawley, Gerard. "Fairchild (Swearingen) Merlin". ''The International Directory of Civil Aircraft''. Canberra: Aerospace Publications Pty. Ltd., 1997. {{ISBN|1-875671-26-9}}.
* [[John W. R. Taylor|Taylor, John W. R.]] ''Jane's All The World's Aircraft 1982–83''. London: Jane's Yearbooks, 1982. {{ISBN|0-7106-0748-2}}. 
* Taylor, M. J. H. ed. ''Jane's Encyclopedia of Aviation'' Studio Editions Ltd. {{ISBN|1-85170-324-1}}

==External links==
{{commons category-inline|Swearingen Merlin}}

{{Fairchild aircraft}}
{{Thai transport aircraft designations}}
{{Thai observation aircraft designations}}

[[Category:Fairchild aircraft|Merlin]]
[[Category:Swearingen aircraft]]
[[Category:1960s United States business aircraft|C-26 Metroliner]]
[[Category:Aircraft first flown in 1965]]
[[Category:Twin-turboprop tractor aircraft]]
[[Category:Low-wing aircraft]]
[[Category:Aircraft with retractable tricycle landing gear]]