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LAK-12 dropping the ballast

LAK-12

The LAK - 12 is a sailplane for competition and 'just for fun' flying. The sailplane exhibits high gliding performance and excellent stability and control. It’s pleasant handling is appreciated by glider pilots in more than 20 countries. With a span of 20.42m, wing flaps and good handling qualities this glider offers excellent value for money. This sailplane has the best L/D ratio per $. The flying properties and performance of the sailplane resemble ASW-17 and Nimbus-II. The glider is finished with the trouble free white epoxy paint instead of polyester gelcoat that is prone to cracking.
The LAK - 12 is certified to JAR - 22 requirements and successfully flies in Lithuania, Latvia, Estonia, Russia, Hungary, Bulgaria, Portugal, Slovenia, Poland, Sweden, S.Africa, Iceland, Austria, England, Spain, Argentina, Australia, N. Zealand and USA. It has been used to set World gliding records.
The LAK-12 sailplane has been flight tested by the well-known American glider pilot Richard Johnson. His report in the July 1996 issue of Soaring magazine was very favourable and showed our claim of a high glide ratio to be true.

DESCRIPTION: Single seat FAI Open-Class mid wing monoplane, made of epoxy, fiberglass and carbon fiber materials.
Fiberglass monocoque fuselage reinforced with carbon fiber tapes. Spacious and crash worthy cockpit, comfortable arrangement of controls, adjustable pilot seat and rudder pedals that are adjustable in flight permit a comfortable position to be found by both tall and short pilots. The one piece forward hinged canopy can be jettisoned by a single handle. Main landing wheel is 350x150 mm in size. It is retractable and has a mechanical brake with an oil/nitrogen shock absorber, and mechanical brake that is actuated by a squeeze lever on the control stick. The tail skid has a shock absorbing mount. Tow hook for aero-tow is provided, but for the winch launch can be provided additionally according customer’s order. Both the hooks accept the TOST LN 65 towrings. VHF radio antenna is located in the vertical fin.
The two-piece wing has the Wortmann FX67-K-170 airfoil inboard and tapers to the FX67-K-150 at the tips. The wing skins are of a glass-foam-glass construction. The I-beam spar has it’s caps made of carbon fibre. Air brakes are on the upper surface only and are double plated. Carbon fibre tapes are used to reinforce the ailerons and flaps.
Water ballast tanks are in the wing leading edge, they are filled and emptied through a hole at the bottom of the fuselage. Total capacity is 190 liters.
The tailplane mounts mid way up the vertical fin. The elevators connect automatically, as do the wing flaps. An elevator trimmer is provided.

Above information quoted from the letter sent to me from Prienai on May 20, 1999
500 Hours or 5 Years LAK-12 check-up list (8 pages 385 Kb PDF document)

Wing
     Span ................................ 20.42 M
     Area ................................ 14.62 Sq. M
     Aspect Ratio ........................ 28.5
Airfoil
         Root ............................ FX67-K-170
         Tip ............................. FX67-K-150
     Root chord .......................... 0.946 M
     Tip chord ........................... 0.390 M
     Mean aerodinamic chord .............. 0.754 M
     Dihedral angle ...................... 3 deg.
     Incidence angle ..................... 2 deg.

Aileron - Non-slotted, dropping
         Length .......................... 4.5 M
Aileron Deflection (flaps 0 deg.)
     Up .................................. 23 (+/- 1) deg.
     Down ................................ 12 (+/- 1) deg.

Flaps
         Length .......................... 5.1 M
Flap Deflection
     Up (handle position "-2") ........... 7 (+/- 1) deg.
     Down (handle position "T") .......... 18 (+/- 1) deg.

Air Brake Type - Extended
         Area of Air Brakes .............. 0.24 Sq. M
Fuselage

     Length .............................. 7.23 M
     Height (cocpit) ..................... 0.81 M
     Maximum height (fin) ................ 1.92 M
     Maximum Width ....................... 0.64 M

Vertical Tail

     Height .............................. 1.6 M
     Area ................................ 1.24 Sq. M
     Airfoil ............................. FX71-L-150/30
     Rudder Deflection ................... 30 both ways (+/- 2) deg.

Horizontal Tail

     Span ................................ 3.1 M
     Area ................................ 1.395 Sq. M
     Airfoil ............................. FX71-L-150/25
Elevator Deflection
     Up .................................. 18 (+/- 1) deg.
     Down ................................ 18 (+/- 1) deg.
Weight Data and C.G. Position
     Empty Weight ........................ 360 Kg. (+/- 3.5%)
     Minimum Flying weight ............... 430 Kg.
     Maximum Flying weight (with water ballast) ... 650 Kg.
     C.G. Position of an empty sailplane . 70% (+/- 3%) m.a.c.
C.G. Position in flight, see Graphic

Water Ballast System


     Water Ballast Tank Capacity ......... 190 Liters
     Time for draining water off ......... 5.5 Min.

Flight Data

                          Without Water Ballast   With Water Ballast
     Flying Weight .................... 430 Kg.   650 Kg.
     Max. L/D .............................. 47   48
Best Range Cruise Speed (flaps 0 deg) . 95 Km/H   115 Km/H
Economy Cruise Speed (flaps 11 deg) ... 75 Km/H   92 Km/H
Minimum sink (flaps 11 deg) .......... 0.43 M/s   0.58 M/s
Stalling Speed (flaps 11 deg) ......... 65 Km/H   80 Km/H
          Lift-off Distance on a grass field
"Wilga 35A" .............................. 80 M   100 M
"AN-2" ................................... 40 M   65 M
Take-off Speed ........................ 75 Km/H   85 Km/H
          Take-off Distance
"Wilga 35A" ............................. 260 M   320 M
"AN-2" .................................. 160 M   220 M
Touch-down Speed ...................... 75 Km/H   -/-
Landing Distance on a grass ............. 255 M   -/-
Operational Limits
Maximum flight weight With Water Ballast)... 650 Kg.
Forward C.G limit .......................... 25% m.a.c.
Aft C.G. limit ............................. 42% m.a.c.
      Maximum Load Factor without water ballast:
@ flaps: 0, -4, -7 deg. .................... "+"6 "-"4
@ flaps: 5, 11, 18 deg. .................... "+"4.6 "-"3.1
@ flaps: 5, 11, 18 deg. and airbrakes extended .. "+"4.4 "-"2.3
@ flaps: 0, -4, -7 deg. and airbrakes deployed .. "+"4.4 "-"2.9
      Maximum operational G-Loading with water ballast
@ flaps: 0, -4, -7 deg. ......................... "+"5 "-"3
@ flaps: 5, 11, 18 deg. ......................... "+"3.9 "-"2.3
@ flaps: 0, -4, -7 deg. and airbrakes extended .. "+"3.7 "-"2.2
@ flaps: 5, 11, 18 deg. and airbrakes extended .. "+"2.9 "-"1.7
      Maximum Indicated Airspeed:
@ flaps: 0, -4, -7 deg. ......................... 250 Km/H
@ flaps: 5, 11, 18 deg. ......................... 175 Km/H
with airbrakes extended ......................... 250 Km/H
with landing gear extended ...................... 250 Km/H
in rough air or maneuvering speed ............... 175 Km/H
Maximum bank angle .............................. 60 deg.
STANDARD EQUIPMENT LIST OF THE LAK-12 GLIDER

    The instruments:
    • airspeed indicator LUN-1106 (Czech product)
    • altimeter BD-10 (Russia)
    • variometer BP-10 (Russia)
    • electronic variometer LAK-RE-303 (AB "Sportine aviacija" product)
    • turn/bank indicator LUN-1211 (Czech product)
    • compass KI-13 (Russia)
    • G-meter AM-10 (Russia)
    • two batteries 12V (optional)
    • barograph AD-2 (optional) (Latvian product) The price is $70

    - Front (for air-tow) and rear (near landing gear, for air and winch tow) release hooks (AB "Sportine aviacija" product). The release hooks are suitable for the TOST LN 65091 towing rings.
    - The provision for instalation of an oxygen system (optional) $450
    - Water ballast filling system
    - Wing stands (optional) $150
    - Total energy tube
    - Tail dolly
    - Canopy cover
    - All glider fabric covers (optional) $415
    - Glider documentation including the Export Certificate of Airworthiness

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