View source for Engineering:Raab-Katzenstein KL.1 Schwalbe

{{Short description|German two-seat biplane}}
<!-- This article is a part of Wikipedia:WikiProject Aircraft. Please see Wikipedia:WikiProject Aircraft/page content for recommended layout. -->
{|{{Infobox aircraft begin
 | name=KL.1 Schwalbe 
 | image=File:GerhardFieselerD1212.jpg
 | caption=KL.1C Schwalbe with pilot [[Biography:Gerhard Fieseler|Gerhard Fieseler]]
}}{{Infobox aircraft type
 | type=Sport and aerobatic aircraft
 | national origin={{wipe|Germany}}
 | manufacturer=Raab-Katzenstein-Flugzeugwerke GmbH
 | designer=
 | first flight=16 January 1926
 | introduced=
 | retired=
 | status=
 | primary user=
 | more users= <!--Limited to three in total; separate using <br /> -->
 | produced= <!--years in production-->
 | number built=c.50
 | program cost= <!--Total program cost-->
 | unit cost= <!--Incremental or flyaway cost for military or retail price for commercial aircraft-->
 | developed from=Dietrich-Gobiet DP.XI 
 | variants with their own articles=
}}
|}

The '''Raab-Katzenstein KL.1 Schwalbe''' (Swallow) was a German two-seat biplane produced in the 1920s. About fifty were built and the type became well known as an aerobatic aircraft, performing at many displays in the hands of pilots like [[Biography:Gerhard Fieseler|Gerhard Fieseler]].

==Design and development==

In November 1925 test pilot Antonius Raab and engineer Katzenstein formed the Kassel-based company that bears their name. They had previously worked at Dietrich Flugzeugwerke, a company which ran into financial problems in 1925. Their first design, known initially as the KL.1 Schwalbe, was a development of the Dietrich-Gobiet DP.XI. Later, in a rationalisation of the company's naming system, it became the '''RK.1 Schwalbe'''.<ref name=Lailes1/><ref name=Russ/>

The Schwalbe was a [[Engineering:Biplane#Bays|single bay biplane]] with thick sections, unequal span wooden wings which were built around twin [[Engineering:Spar (aeronautics)|spars]] and fabric covered. The wings had marked [[Engineering:Biplane#stagger|stagger]] and were braced between the spars with forward leaning, steel tube, N-form interplane struts. The lower wing was attached directly to the lower fuselage, from which the inner upper wing was braced with an outward leaning pair of parallel struts to the spars and held over the upper fuselage by a pair of inverted V-struts, one on each side, to the forward spar alone. The wings were straight-tapered in plan, with only a slight sweep on the [[Engineering:Leading edge|leading edge]], out to rounded tips. They also tapered in thickness. The Schwalbe had ailerons on both wings, externally connected with vertical rods. The upper ailerons had large balances to serve both surfaces.<ref name=Lailes1/>

The Schwalbe's rectangular section fuselage had a steel tube structure and was fabric covered.  The first examples, designated KL.IA, were powered by a {{convert|80|hp|kW|abbr=on|order=flip}} Siemens-Halske Sh 11 seven cylinder radial engine, partially enclosed by a dural [[Engineering:Aircraft fairing#engine cowling|cowling]] which left the cylinders projecting for cooling. Its fuel tank was within the upper wing and the oil tank behind a [[Engineering:Firewall (engine)|firewall]].<ref name=Lailes1/> Two later versions of the Schwalbe, designated KL.1B and KL.IC, were powered by a {{convert|110|hp|kW|abbr=on|order=flip}} Siemens-Halske Sh 12 nine cylinder radial.<ref name=Russ/> The forward open [[Engineering:Cockpit|cockpit]] was under the wing but it was flown solo from the rear cockpit which was over the [[Engineering:Trailing edge|trailing edge]] of the lower wing and behind that of the upper wing, where there was a cut-out to increase the pilot's field of view.<ref name=Lailes1/>

A large, almost triangular tailplane was mounted on top of the fuselage and carried generous, curved and balanced elevators. Its fin was small but the [[Engineering:Rudder|rudder]] large and balanced, reaching down to the keel and working in an elevator cut-out.<ref name=Lailes1/>

The Schwalbe had fixed, conventional landing gear, with its mainwheels on a split axle sprung by rubber cords to V-struts from the lower fuselage and stabilized centrally by a transverse V-strut. There was a short, steel tailskid.<ref name=Lailes1/>

==Operational history==

Piloted by Raab, the Schwalbe first flew on 16 January 1926.<ref name=Russ/> Numbers built are uncertain but have been estimated at forty-two<ref name=Russ/> or about fifty-eight.<ref name=histav/> Engines apart, the unknown differences between the variants were small enough to allow several airframes to have been IAs, IBs and ICs over their lifetime.<ref name=histav/>

Several well known pilots used them as aerobatic aircraft, including [[Biography:Gerhard Fieseler|Gerhard Fieseler]] who was regarded as the best and most innovative aerobatic pilot of his day.<ref name=Flight3/> In September 1927 he claimed a world duration record for inverted flight in his Schwalbe KL.IC. at a Zurich meeting,<ref name=Flight1/> then bettered it later in the month with a fifteen minute flight.<ref name=Flight2/> He gave aerobatic demonstrations in his Schwalbe during 1927-8 at several other European meetings including Blackpool<ref name=Flight4/> and Waalhaven.<ref name=Flight5/>

One Schwalbe was on display at the 1928 [[Place:Berlin|Berlin]] International Aero Show.<ref name=Flight6/>

==Variants==
[[File:RaKaFabrikate.jpg|thumb|Company catalogue advertising the KL.IA variant]]

;KL.IA: Original design with {{convert|80|hp|kW|abbr=on|order=flip}} Siemens-Halske Sh 11 engine.

;KL.IB: More powerful {{convert|110|hp|kW|abbr=on|order=flip}} Siemens-Halske Sh 12.

;KL.IC: Siemens-Halske Sh 12.

;Schwalbe II: Version of KL.IC built in Greece by AEKKEA-RAAB, which was established in 1935.

;Pintsch Schwalbe II: derivative by Pintsch

;Rheinische FR-2 Schwalbe
:Derivative by ''Flugzeugbau Rheinische''

==Specifications (KL. 1A) ==
[[File:Raab-Katzenstein_RK_1a_Schwalbe_3-view_L'Air_January_1,1927.png|thumb|Raab-Katzenstein RK 1a Schwalbe 3-view drawing from L'Air January 1, 1927]]
{{Aircraft specs
|ref=Les Ailes, September 1927<ref name=Lailes1/>
|prime units?=met
<!--
        General characteristics
-->
|genhide=

|crew=One
|capacity=one passenger
|length m=6.50
|length note=
|upper span m=8
|upper span note=
|lower span m=7
|lower span note=
|height m=2.60
|height note=
|wing area sqm=17
|wing area note=
|aspect ratio=<!-- sailplanes -->
|airfoil=
|empty weight kg=470
|empty weight note=
|gross weight kg=710
|gross weight note=
|max takeoff weight kg=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity={{convert|100|L|Impgal USgal|abbr=on}}
|more general=
<!--
        Powerplant
-->
|eng1 number=1
|eng1 name=Siemens-Halske Sh 11
|eng1 type=7-cylinder radial
|eng1 hp=80
|eng1 note=nominal
|more power=

|prop blade number=2
|prop name=wooden
|prop dia m=<!-- propeller aircraft -->
|prop dia ft=<!-- propeller aircraft -->
|prop dia in=<!-- propeller aircraft -->
|prop dia note=

<!--
        Performance
-->
|perfhide=

|max speed kmh=152
|max speed note=
|cruise speed kmh=140
|stall speed kmh=70
|stall speed note=minimum speed
|never exceed speed kmh=
|never exceed speed mph=
|never exceed speed kts=
|never exceed speed note=
|minimum control speed kmh=
|minimum control speed mph=
|minimum control speed kts=
|minimum control speed note=
|range km=500
|range note=
|endurance=<!-- if range unknown -->
|ceiling m=3500
|ceiling note=
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|glide ratio=<!-- sailplanes -->
|climb rate ms=
|climb rate ftmin=
|climb rate note=
|time to altitude=9 min to {{convert|1000|m|ft|abbr=on}}
|sink rate ms=<!-- sailplanes -->
|sink rate ftmin=<!-- sailplanes -->
|sink rate note=
|lift to drag=
|wing loading kg/m2=
|wing loading lb/sqft=
|wing loading note=
|fuel consumption kg/km=
|fuel consumption lb/mi=
|power/mass=
|thrust/weight=

|more performance=

}}

==References==
{{reflist|2|refs=

<ref name=Lailes1>{{cite journal |last=Serryer |first=J |date=29 September 1927|title=L'avion Raab-Katzenstein|journal=Les Ailes|issue=328 |pages=3–4|url=http://gallica.bnf.fr/ark:/12148/bpt6k6568360v/f3 }}</ref>

<ref name=Flight1>{{cite journal |date=1 September 1927 |title=Picture caption|journal= Flight|volume=XIX |issue=35 |pages=310 |url= https://www.flightglobal.com/pdfarchive/view/1927/1927%20-%200664.html  }}</ref>

<ref name=Flight2>{{cite journal |date=29 September 1927 |title=Upside down records|journal= Flight|volume=XIX |issue=39 |pages=688 |url= https://www.flightglobal.com/pdfarchive/view/1927/1927%20-%200766.html }}</ref>

<ref name=Flight3>{{cite journal |date=19 April 1928 |title=Picture caption|journal= Flight|volume=XX |issue=16 |pages=272 |url= https://www.flightglobal.com/pdfarchive/view/1928/1928%20-%200300.html }}</ref>

<ref name=Flight4>{{cite journal |date=12 July 1928 |title=Picture caption -AIR PAGEANT|journal= Flight|volume=XX |issue=26 |pages=272 |url= 
https://www.flightglobal.com/pdfarchive/view/1928/1928%20-%200643.html }}</ref>

<ref name=Flight5>{{cite journal |date=26 July 1928 |title=Picture caption - FLYING AT WAALHAVEN|journal= Flight|volume=XX |issue=26 |pages=647 |url= 
https://www.flightglobal.com/pdfarchive/view/1928/1928%20-%200703.html}}</ref>

<ref name=Flight6>{{cite journal |date=11 October 1928 |title=The Berlin International Aero Show|journal= Flight|volume=XX |issue=41 |pages=865 |url= https://www.flightglobal.com/pdfarchive/view/1928/1928%20-%200935.html }}</ref>

<ref name=Russ>{{cite web |url=http://www.airwar.ru/enc/other1/rk1.html|title=RK.1 Schwalbe|accessdate=10 June 2017}}</ref>

<ref name=histav>{{cite web |url=http://histaviation.com/rk_kl1_production.html|title=	German aviation 1919-195-45 |accessdate=10 June 2017}}</ref>}}

==Bibliography==
* Gerdessen, Frederik. "Estonian Air Power 1918 – 1945". ''Air Enthusiast'', No. 18, April – July 1982. pp.&nbsp;61–76. {{ISSN|0143-5450}}.


[[Category:Aerobatic aircraft]]
[[Category:Single-engined tractor aircraft]]
[[Category:Biplanes]]

{{Sourceattribution|Raab-Katzenstein KL.1 Schwalbe}}