Akaflieg Berlin B12
Encyclopedia
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The Akaflieg Berlin B12 is a high performance two-place glider aircraft
that was designed and built in Germany
. Conceived as a research vehicle, only one unit was constructed.
The shape and profiles of the new fuselage were developed at the Institut für Luftfahrzeugbau (Institute for aircraft industry) and a new two-seat fuselage was constructed using contemporary GFRP (Glass-fibre Re-inforced Plastic) techniques in a monocoque shell.
The wings are standard 'Janus B' items built using identical construction methods. The empennage originally utilised a cruciform tail
using an NACA 0009-64 aerofoil section formed with ' Rohacell'/GFRP sandwich supported by CFRP (Carbon-Fibre Re-inforced Plastic) spars. After a trailer accident during road transport in 1986, which destroyed the rear fuselage and tail-unit, a T-tail
was fitted during repairs. A thicker aerofoil section was used for the vertical tail of this revised unit, a specially developed Wortmann FX-71 L 150/30 profile.
The single retractable main undercarrriage wheel is supported on a tall leg assembly which was originally built with electric actuation, but after a field landing with a flat battery caused a wheels-up landing a manual system was fitted. A rubber tail skid, capped with hardened steel, under the rear fuselage completes the undercarriage. In the original fuselage a braking parachute, used for approach control, was housed at the extreme rear, but this feature was not carried through to the replacement tailcone during its rebuild.
. The B12 continues to fly but rarely emerges from the hangar unless the soaring weather is good.
Once the quirks and foibles of the B12 are understood it is possible to compete effectively with other contemporary two-seaters. However the expected performance gains were only partly realised and the B12 does not rank with the highest performance gliders, as was hoped. One quirk is the B12 'sigh' which can be heard in certain flight conditions, the origin of which remains a mystery. Competition flying is carried out with the call-sign CB and a handicap index of 106 is applied. The aircraft carries registration 'D-7612'.
The Akaflieg Berlin B12 is a high performance two-place glider aircraft
Glider aircraft
Glider aircraft are heavier-than-air craft that are supported in flight by the dynamic reaction of the air against their lifting surfaces, and whose free flight does not depend on an engine. Mostly these types of aircraft are intended for routine operation without engines, though engine failure can...
that was designed and built in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. Conceived as a research vehicle, only one unit was constructed.
Development
The students at Akaflieg Berlin set out to improve the performance of modern gliders by reducing drag. To improve a modern glider's performance through modifying the aerofoil sections is time consuming and very costly, so to reduce costs the group utilised production wings from a Schemp-Hirth Janus B, shortened to 18.2m (59.71 feet), allowing the students to concentrate their efforts and budget on improving the fuselage.The shape and profiles of the new fuselage were developed at the Institut für Luftfahrzeugbau (Institute for aircraft industry) and a new two-seat fuselage was constructed using contemporary GFRP (Glass-fibre Re-inforced Plastic) techniques in a monocoque shell.
Construction
Built principally from GFRP the B12 uses monocoque construction, avoiding the use of a welded steel-tube core structure, maximising the volume available for crew accommodation and payloads such as research instrumentation. The cockpit seats two in tandem under large plexiglas canopies with the instructor seat, in the rear, set at a higher level to improve his forward view.The wings are standard 'Janus B' items built using identical construction methods. The empennage originally utilised a cruciform tail
Cruciform tail
The cruciform tail is an aircraft empennage configuration which, when viewed from the aircraft's front or rear, looks much like a cross. The usual arrangement is to have the horizontal stabilizer intersect the vertical tail somewhere near the middle, and above the top of the fuselage.Often this...
using an NACA 0009-64 aerofoil section formed with ' Rohacell'/GFRP sandwich supported by CFRP (Carbon-Fibre Re-inforced Plastic) spars. After a trailer accident during road transport in 1986, which destroyed the rear fuselage and tail-unit, a T-tail
T-tail
thumb|right|Grob motor gliderA T-tail is an aircraft tail stabilizer configuration in which the horizontal surfaces are mounted to the top of the vertical stabilizer. Traditionally, the horizontal control surfaces are mounted to the fuselage at the base of the vertical stabilizer...
was fitted during repairs. A thicker aerofoil section was used for the vertical tail of this revised unit, a specially developed Wortmann FX-71 L 150/30 profile.
The single retractable main undercarrriage wheel is supported on a tall leg assembly which was originally built with electric actuation, but after a field landing with a flat battery caused a wheels-up landing a manual system was fitted. A rubber tail skid, capped with hardened steel, under the rear fuselage completes the undercarriage. In the original fuselage a braking parachute, used for approach control, was housed at the extreme rear, but this feature was not carried through to the replacement tailcone during its rebuild.
History
After the first flight of the B12 on 27 July 1977, piloted by Jürgen Ehlers Thorbeck, the B12 was used for research, cross country and competition flying until a trailer accident in 1986, whilst being transported by road, destroyed the tail section and twisted the rear fuselage. Repairs were carried out and the B12 was flying again on 1 August 1987 at the IDAFLIEG ( Interessengemeinschaft deutscher akademischer Fliegergruppen e.V. - interest group for academic flying groups) summer camp at Aalen-Elchingen, sporting a T-tail identical to that of the Akaflieg Berlin B13Akaflieg Berlin B13
- Development :Students at Akaflieg Berlin studied a high performance motor-glider with the engine in the nose and an automatically folding propeller...
. The B12 continues to fly but rarely emerges from the hangar unless the soaring weather is good.
Flying
Flying the B12 requires a certain amount of care, due to:- high nose-up seating position
- tall undercarriage, which reduces forward view at low ground roll speeds
- high-mounted wings with significant dihedral, which makes ground-handling awkward
- the ailerons are relatively ineffective
- control pressures are large, causing pilot fatigue
- rigging and takedown of the aircraft are complicated and strenuous, requiring several ground-handlers
- high weight weight causes high wing loading, reducing thermalling performance (i.e. rate of climb).
Once the quirks and foibles of the B12 are understood it is possible to compete effectively with other contemporary two-seaters. However the expected performance gains were only partly realised and the B12 does not rank with the highest performance gliders, as was hoped. One quirk is the B12 'sigh' which can be heard in certain flight conditions, the origin of which remains a mystery. Competition flying is carried out with the call-sign CB and a handicap index of 106 is applied. The aircraft carries registration 'D-7612'.
Specifications (B12)
See also
External links
- http://www.sailplanedirectory.com/PlaneDetails.cfm?PlaneID=33 Akaflieg Berlin B12
- http://www.planepictures.net/search4.cgi?srch=Akaflieg+Berlin&stype=airline&srng=2
- http://akaflieg.extern.tu-berlin.de/joomla/index2.php?option=com_content&do_pdf=1&id=25 Akaflieg Berlin
- http://www.sailplanedirectory.com/berlin.htm Sailplane Directory
- http://www.akaflieg-berlin.de Akaflieg Berlin
- http://propeller-designer.co.uk/html/wortmann_aerofoils.html Wortmann aerofoils
- http://www.worldofkrauss.com/foils/1722 Section and polars for the similar but slightly thicker NACA 0010-64
- http://www.worldofkrauss.com/foils/1876 section and polars of the similar WORTMANN FX 71-120