<!-- This article is a part of Wikipedia:WikiProject Aircraft. Please see Wikipedia:WikiProject Aircraft/page content for recommended layout. --> {{Infobox aircraft | name = D-D | logo = | logo_size = | image = | alt = | caption = | long_caption = | other_names = | aircraft_type = Three/four-seat cabin monoplane | aim = | outcome = | related = | national_origin = US | manufacturer = Invincible Metal Furniture Co | design_group = | designer = Irl Beach | 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 = | first_flight = February 1929 | initiated = | in_service = | last_flight = | expected = | developed_from = | variants = | developed_into = | preservation = | fate = | predecessors = | successors = | concluded = }}
The '''Invincible D-D''' was a prototype three/four seat touring aircraft, built in the US in 1929. One example flew but development was ended by the Great Depression.
==Design and development==
The D-D<ref name=aerofiles/> was a mid-wing monoplane with a rectangular plan, blunt tipped, constant thickness wing. Canvas covered, it was built around a pair of wooden spars that continued through the fuselage with the pilot's seat between them. Dihedral was 1.25°. Constant chord ailerons filled the outer two-thirds of the trailing edge. The wings were braced with steel V-struts, individually enclosed in wooden fairings, from the two wing spars to a framework under the fuselage where their vertices were transversely joined by a horizontal steel bar.<ref name=Lailes1/>
The Invincible was designed to accept two engines of significantly different power and cost. These were the {{convert|90|hp|kW|abbr=on |order=flip}} LeBlond 90-7D, a seven-cylinder radial engine or the {{convert|170|hp|kW|abbr=on |order=flip}} Curtiss Challenger, a six-cylinder, two row radial. The Challenger-powered version could carry four, one more than that with the Leblond engine, but cost $7,800 rather than $5,500. The chosen engine was mounted in the nose with cylinders largely exposed for cooling; the mounting allowed easy interchange between the two types. Fuel tanks were in the wings.<ref name=Lailes1/>
Behind the engine the Invincible's fuselage had a steel tube, rectangular-section structure with fabric covering. The enclosed cabin had, in the four-seater, two rows of side-by-side seats, optional dual control and generous forward, side and upward glazing. Entry was via an oval port-side door.<ref name=Lailes1/>
Its tailplane, triangular in plan, was mounted on top of the fuselage and carried separate, parallel chord elevators. It was wire-braced from above and below to the rudder post of a quadrantal profile fin which carried a constant chord rudder, reaching down to the keel.<ref name=Lailes1/>
The Invincible's fixed, tailwheel landing gear had mainwheels independently mounted on cranked half-axles hinged at the centre of the fuselage underside. Their outer ends were joined to the fuselage sides by inward-leaning pneumatic shock absorber struts and to the ends of the horizontal bar of the wing struttage by short drag struts.<ref name=Lailes1/>
Its first flight was in late January-early February 1929 at Manitowoc, powered by the LeBlond engine and piloted by William Williams, with its designer, Irl Beach, as a passenger. It was scheduled to appear at the Detroit air show that April.<ref name=Aviation/> Invincible, having entered into aviation in 1928 and produced three or four different prototypes, left the industry in 1929 because of the Great Depression.<ref name=aerofiles/>
==Specifications (LeBlond engine)== {{Aircraft specs |ref=Les Ailes, July 1929<ref name=Lailes1/> |prime units?=met <!-- General characteristics --> |genhide=
|crew=One |capacity=Two passengers |length m=7.34 |length note= |span m=11.60 |height m=2.21 |height note= |wing area sqm=20.26 |wing area note= |aspect ratio=6.7 |airfoil=NACA M 15 |empty weight kg=585 |empty weight note= |gross weight kg= |gross weight lb= |gross weight note= |max takeoff weight kg= |max takeoff weight lb= |max takeoff weight note= |fuel capacity={{convert|228|L|Impgal USgal|abbr=on}} |more general= <!-- Powerplant --> |eng1 number=1 |eng1 name=LeBlond 90-7D |eng1 type=7-cylinder radial |eng1 hp=90 |eng1 note=at 1,975 rpm |power original= |more power=
|prop blade number=2 |prop name= |prop dia m=<!-- propeller aircraft --> |prop dia ft=<!-- propeller aircraft --> |prop dia in=<!-- propeller aircraft --> |prop dia note=
<!-- Performance --> |perfhide=
|max speed kmh=175 |max speed note= |cruise speed kmh=145 |cruise speed note= |stall speed kmh=59 |stall speed note= |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= |range nmi= |range note= |endurance=<!-- if range unknown --> |ceiling m= |ceiling ft= |ceiling note= |g limits=<!-- aerobatic --> |roll rate=<!-- aerobatic --> |glide ratio=<!-- sailplanes --> |climb rate ms= |climb rate ftmin= |climb rate note= |time to altitude= |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== <references>
<ref name=Aviation>{{cite journal |date=16 February 1929|title=Test Invincible cabin plane|journal=Aviation|pages=485|url=https://archive.aviationweek.com/search?QueryTerm=Invincible}}</ref>
<ref name=Lailes1>{{cite journal |date=18 July 1929|title=Le monoplan "Invincible"|journal=Les Ailes|issue=422 |pages=3|url=https://gallica.bnf.fr/ark:/12148/bpt6k6554652t/f3 }}</ref>
<ref name=aerofiles>{{cite web |url=http://www.aerofiles.com/_i.html|title=Aerofiles - Invincible |accessdate=13 September 2017}}</ref>
</references>
Category:1920s United States civil utility aircraft Category:Mid-wing aircraft Category:Single-engined tractor aircraft Category:Aircraft first flown in 1929