1. Design

2. Specifications

3. References

The Schmeidler SN.2 was a low power, single seat aircraft designed in Germany in the 1930s to test the ability of trailing edge wing extensions to lower minimum flight speeds without a high speed drag penalty.

Design

In the 1930s there was considerable interest in extending the speed range of aircraft.^[1] Slower level flight requires either larger area wings or airfoils with higher lift coefficients, the latter achieved either with higher angles of attack or greater camber. Combinations of these approaches could be used, as by modern camber and area increasing multipart flaps. The Makhonine Mak-10^[1] was a 1931 example of pure area increase by wing extension but the 1932 Schmeidler SN.2 increased both area and camber with chord extension.^[4] It was designed and built by Werner Schmeidler and Neumann, both at the Breslau Technical College, now the Wrocław University of Technology. It was the second aircraft with area increasing wings built by them,^[4] hence the SN.2 designation, though this is not used in any of the pre-war journals cited here; nothing is known of its predecessor.

Apart from its variable wing trailing edge, the SN.2 was a conventional, single engine cantilever high wing monoplane. The straight leading edge of its wing was swept to semi-elliptical tips and the unextended trailing edge was also straight but without sweep. It had unusually short and broad slotted ailerons which reached behind the trailing edge.^[4] The fixed part of the wing had the popular, thick (15%) flat-bottomed Göttingen 387 airfoil^[7][8] with room within it for the extension, which had a right angle triangular plan and circular arc profile. When retracted, its rear edge protruded slightly out of the slot in the trailing edge of the fixed section. At its root, which was supported in a groove in the narrow, central upper fuselage, it increased the chord by about 35%; overall it added 20% to the wing area and increased the camber.^[4][7] It was controlled with a ratchet-restrained lever in the cockpit which was linked to fuselage mounted gears that engaged with racks on the moving surfaces.^[11]

The SN.2 was powered by a {{convert|45|hp|kW|abbr=on|order=flip}} BMW X five cylinder radial engine mounted with its cylinder heads projecting through a domed cowling.^[4][11] Behind the engine the fuselage was flat sided with the pilot under the wing leading edge in an enclosed single seat cabin. Aft, the central, wing bearing section behind the fixed wing trailing edge dropped away to a five sided structure with a ridged upper surface. At the rear the empennage was conventional, with a roughly semi-circular tailplane mounted on top of the fuselage, a little ahead of a similarly shaped fin. Both fixed surfaces carried broad, unbalanced control surfaces, with the rudder, which extended to the keel, operating within an elevator cut-out.^[4]

Its landing gear was of the fixed, conventional tailwheel type. Each mainwheel was mounted on a faired-in pair of V-strut pairs with a tall, inward leaning shock absorber strut from the axle to the wing root.^[4][16] Later on this was replaced by a vertical shock absorber strut to the wing underside.^[17] At the rear the tailskid was vertically sprung.^[4][16]

Flown by Wolf Hirth, the SN.2 flew for the first time on 12 January 1932 from Breslau.^[16] By March tests showed that opening the wing fully shortened take-off distance by a factor of two.^[21] In May it flew to Berlin^[22] where it was demonstrated in flight at Tempelhof.^[11] It was on static display at the DELA exhibition of sports aircraft held in Berlin for most of October 1932, registered as D-2257.^[24] It remained in action until at least 1934, when it moved to the new, all letter, civil registration scheme as D-YRON.^[25]

Specifications

|genhide=
|crew=
|capacity=
|length m=6.20
|length note=
|span m=11.40
|span note=
|height m=
|height ft=
|height in=
|height note=
|wing area sqm=12.75
|wing area note= maximum, {{convert|15.25|m2|sqft|abbr=on}}
|aspect ratio=
|airfoil=Göttingen 387^[7] (fixed part of wing)
|empty weight kg=355
|empty weight note=equipped
|gross weight kg=470
|gross weight note=
|max takeoff weight kg=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity=
|more general=

|eng1 number=1
|eng1 name=BMW X
|eng1 type=five cylinder radial
|eng1 hp=45
|eng1 note=
|more power=
|prop blade number=2
|prop name=
|prop dia m=
|prop dia ft=
|prop dia in=
|prop dia note=

|perfhide=
|max speed kmh=144
|max speed note=
|cruise speed kmh=
|cruise speed mph=
|cruise speed kts=
|cruise speed note=
|stall speed kmh=
|stall speed mph=
|stall speed kts=
|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=
|ceiling m=
|ceiling ft=
|ceiling note=
|g limits=
|roll rate=
|glide ratio=
|climb rate ms=
|climb rate ftmin=
|climb rate note=
|time to altitude=
|sink rate ms=
|sink rate ftmin=
|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=
|more performance=

• Take-off speed: {{convert|72|km/h|mph kn|abbr=on}}
• Take-off distance into wind, minimum wing extension: {{convert|100|m|ft|abbr=on}}
• Take-off distance into wind, maximum wing extension: {{convert|50|m|ft|abbr=on}}
• Landing speed: {{convert|50-60|km/h|mph kn|abbr=on}}

References

• Kelvin-Planck statement
• Kelvin-Planck statement of the second law
• Kelvin-Planck statement of the second law of thermodynamics
• Kelvin Poole
• Kelvin probe force microscopy
• Kelvin probe microscope
• Kelvin probe microscopy
• Kelvin Richards
• Kelvin (river)
• Kelvin Rivers
• Kelvin Rodriguez
• Kelvin Roy
• Kelvin Scarborough
• Kelvin sense
• Kelvin Sholar
• Kelvin Smart
• Kelvin Smith (cricketer)
• Kelvin's statement of the second law of the thermodynamics
• Kelvin Steel
• Kelvin's Theorem on Circulation
• Kelvin Tan (born 1981)
• Kelvin Tan (musician)
• Kelvin temperature
• Kelvin Teo
• Kelvin thermometer