Cranwell CLA.3

{{Use dmy dates|date=March 2018}} {{Use British English|date=March 2018}} {{Infobox aircraft | name = CLA.3 | logo = | logo_size = | image = Cranwell C.L.A.3 Les Ailes January 28,1926.jpg | alt = | caption = | long_caption = | other_names = | aircraft_type = Racing aircraft | aim = | outcome = | related = | national_origin = United Kingdom | manufacturer = The Cranwell Light Aeroplane club | design_group = | designer = Nicholas Comper | builder = | issuer = | status = | owners = | primary_user = | more_users = | service = | major_applications = | proposals = | prototypes = | number_built = 1 | construction_number = | civil_registration = | military_serial = | radio_code = | requirement = | aircraft_carried = | flights = | total_hours = | total_distance = | construction_date = | introduction = | retired = 1929 | first_flight = mid- July 1925 | initiated = | in_service = | last_flight = | expected = | developed_from = | variants = | developed_into = | preservation = | fate = | predecessors = | successors = | concluded = }} The '''Cranwell CLA.3''' was a parasol winged single-engined, single-seat British aircraft built to compete in the Lympne air races of 1925. It was designed and built by an amateur group drawn from staff and pupils at the RAF College Cranwell. Though it won one prize and set a Class record, only one CLA.3 was made.

==Design and development== The Cranwell Light Aeroplane (CLA) club was formed in 1923 by staff and students at the RAF College Cranwell. The students came from No.4 Apprentices Wing and one of their lecturers, Flt-Lt Nicholas Comper became chief designer of the three aircraft produced by the club as well as one, the CLA.1 that was not completed.<ref>{{Harvnb|Ord-Hume|2000|pages=310–2}}</ref> Their first finished aircraft, the CLA.2 won a £300 prize at the Lympne trials in 1924, but was a rather slow biplane, and Comper decided to design something much quicker for the 1925 Lympne event. The result was the CLA.3, a single-engined parasol winged single seater.<ref name="FlightA">[http://www.flightglobal.com/pdfarchive/view/1925/1925%20-%200484.html ''Flight'' 30 July 1925 p.484-7]</ref><ref name="AJJ">{{Harvnb|Jackson|1973|pages=296}}</ref><ref name="OrdH">{{Harvnb|Ord-Hume|2000|pages=311–2}}</ref>

The wings of the CLA.3 were straight and had constant chord apart from at the rounded tips.<ref name="FlightA"/> The airfoil section used, the Eiffel 371<ref>Although Gustave Eiffel is best known for his large engineering structures, principally the Eiffel tower and the armature of the Statue of Liberty, he did important work in aerodynamics from 1909 onwards (Anderson 1997, pp.268-282), using his own, large wind tunnels to establish the pressure distributions over aerodynamic surfaces</ref> was something of a novelty, a thick wing with a quite flat bottom.<ref name="FlightA"/> The wings were built on two I-section spruce spars and fabric covered everywhere apart from at the leading edge, where thin aluminium was used.<ref name="FlightA"/> Differential ailerons were fitted;<ref name="FlightA"/> initially the gap between aileron and wing was filled with narrow rubber flaps, but later they were removed as they added weight and made lateral control heavy.<ref name="OrdH"/> The wings were held about 7 in (180 mm) above the fuselage, parasol fashion, by two steel lift struts on each side which ran from a common point on the lower longeron of the fuselage to the front and rear spars at mid-span.<ref name="FlightA"/> Three vertical steel cabane struts on each side joined the centre section to the upper longerons.<ref name="FlightA"/>

The rear part of the fuselage was a Warren girder based on four longerons, tapering towards the tail. The fuselage cross section was kept to a minimum to reduce drag and to this end the pilot sat on the cockpit floor.<ref name="FlightA"/> There were concerns about ease of escape from this position under the rear wing spar,<ref name="FlightA"/> but it was after all, a racing machine. In front of him the structure was wire braced, the longerons converging to become overhung engine bearers.<ref name="FlightA"/> The 32 hp (24 kW) Bristol Cherub II engine was mounted on a plate with a fireproof bulkhead, within a long, smooth aluminium cowling blended into the spinner of the two-bladed propeller. The Cherub's cylinder heads were exposed for cooling. A rounded decking, built up with stringers in the usual way, topped the fuselage from propeller to stern and contained the 4.5 imp gal tank immediately in front of the cockpit, high enough above the engine to allow it to be gravity fed.<ref name="FlightA"/> The overall fin plus rudder shape was not unlike the de Havilland form, though the rudder was not balanced. The tailplane had a straight leading edge inboard, then curved; it could be adjusted in incidence on the ground but not in the air.<ref name="FlightA"/> Its elevators were unbalanced and divided to allow rudder movement. The undercarriage was a simple single axle design using rubber shock absorbers, with the main legs attached to the lower longerons at the same points as the lift struts and braced to the most forward fuselage frame.<ref name="FlightA"/> It was completed with a tail skid.

Nick Comper took the CLA.3 for its first flight in mid-July 1925.<ref name="OrdH"/> The only significant later modification exchanged the geared Cherub II for a direct drive 36 hp (27 kW) Cherub III, fitted with a metal propeller.<ref name="OrdH"/>

==Operational history==

Comper was still getting to know the CLA.3 when he flew it at the Royal Aero Club (RAC) race meeting Lympne in August 1925.<ref name="FlightB">[http://www.flightglobal.com/pdfarchive/view/1925/1925%20-%200505.html ''Flight'' 6 August 1925 p.505-6]</ref> It was the only new aircraft there.<ref name="FlightA"/> Several of the races were handicaps and did not reward the CLA.3, but it did win the Single-Seater Light 'Plane Scratch Speed Race and the accompanying £50 prize, albeit against only three other competitors.<ref name="FlightB"/> There was also a series of competitions to establish records in the light aeroplane Class, defined by the RAC as those with an engine weight of less than 170 lb (77 kg).<ref name="FlightB"/> The CLA.3 was the fastest out of a field of nine over 3 km, at a speed of 139.89 km/h. (86.9 mph). The same group of aircraft competed over 50 km, and here the CLA.3 came a close second at 135.5 km.h. (84.25 mph).<ref name="FlightB"/> In 1926, fitted with the Cherub III it flew in the King's Cup Race, but engine failure forced it out.<ref name="AJJ"/><ref name="OrdH"/> The sole CLA.3 was scrapped in 1929.<ref name="AJJ"/><ref name="OrdH"/>

==Specifications== thumb|Cranwell C.L.A.3 3-view drawing from Les Ailes January 28,1926 {{Aircraft specs |ref=''Flight'' 30 July 1925 p.484-7<ref name="FlightA"/> |prime units?=imp   |genhide= |crew=1 |capacity= |length m= |length ft=18 |length in=6.5 |length note= |span m= |span ft=21 |span in=0 |span note= |upper span m= |upper span ft= |upper span in= |upper span note= |mid span m= |mid span ft= |mid span in= |mid span note= |lower span m= |lower span ft= |lower span in= |lower span note= |swept m= |swept ft= |swept in= |swept note= |dia m= |dia ft= |dia in= |dia note= |width m= |width ft= |width in= |width note= |height m= |height ft=6 |height in=10 |height note=<ref name="OrdH"/> |wing area sqm= |wing area sqft=70 |wing area note= |swept area sqm= |swept area sqft= |swept area note= |volume m3= |volume ft3= |volume note= |aspect ratio= |airfoil=Eiffel 371 |empty weight kg= |empty weight lb=325 |empty weight note= |gross weight kg= |gross weight lb=530 |gross weight note= |max takeoff weight kg= |max takeoff weight lb= |max takeoff weight note= |lift kg= |lift lb= |lift note= |more general=  |eng1 number=1 |eng1 name=Bristol Cherub II |eng1 type=flat twin piston |eng1 kw= |eng1 hp=32 |eng1 kn= |eng1 lbf= |eng1 note= |power original= |thrust original= |eng1 kn-ab= |eng1 lbf-ab= |eng2 number= |eng2 name= |eng2 type= |eng2 kw= |eng2 hp= |eng2 kn= |eng2 lbf= |eng2 note= |eng2 kn-ab= |eng2 lbf-ab= |eng3 number= |eng3 name= |eng3 type= |eng3 kw= |eng3 hp= |eng3 kn= |eng3 lbf= |eng3 note= |eng3 kn-ab= |eng3 lbf-ab= |more power= |prop blade number= |prop name= |prop dia m= |prop dia ft= |prop dia in= |prop dia note= |rot number= |rot dia m= |rot dia ft= |rot dia in= |rot area sqm= |rot area sqft= |rot area note=  |perfhide= |max speed kmh= |max speed mph=100 |max speed kts= |max speed note=estimated |max speed mach= |cruise speed kmh= |cruise speed mph=88 |cruise speed kts= |cruise speed note=<ref name="OrdH"/> |stall speed kmh= |stall speed mph=48 |stall speed kts= |stall speed note=<ref name="OrdH"/> |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= |range miles=175 |range nmi= |range note=<ref name="OrdH"/> |combat range km= |combat range miles= |combat range nmi= |combat range note= |ferry range km= |ferry range miles= |ferry range nmi= |ferry range note= |endurance= |ceiling m= |ceiling ft= |ceiling note= |g limits= |roll rate= |glide ratio= |climb rate ms= |climb rate ftmin= |climb rate note= |sink rate ms= |sink rate ftmin= |sink rate note= |lift to drag= |wing loading kg/m2= |wing loading lb/sqft= |wing loading note= |disk loading kg/m2= |disk loading lb/sqft= |disk loading note= |more performance=  |armament= |guns= |bombs= |rockets= |missiles= |hardpoints= |hardpoint capacity= |hardpoint rockets= |hardpoint missiles= |hardpoint bombs= |hardpoint other= |avionics= }}  {{aircontent  |see also= |related= |similar aircraft= |lists= }}

==References==

===Notes and citations=== {{reflist}}

===Cited sources=== {{refbegin}} *{{cite book |title= A History of Aerodynamics|last=Anderson|first=John D. Jnr.| year=1997|publisher=Cambridge University House |location=Cambridge |isbn=0-521-66955-3}} *{{cite book |title= British Civil Aircraft 1919-72|last=Jackson|first=A.J.| year=1973|volume= 2|publisher=Putnam Publishing |location=London |isbn=0-85177-813-5}} *{{cite book |title= British Light Aeroplanes|last=Ord-Hume|first=Arthur W.J.G.J.| year=2000|publisher=GMS Enterprises |location=Peterborough |isbn=978-1-870384-76-6}} {{refend}}  {{Comper aircraft}}

Category:1920s British sport aircraft Category:Aircraft first flown in 1925 Category:Parasol-wing aircraft Category:Single-engined tractor aircraft