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AC-21 Powered Sailplane

In April 2007, Advanced Design Alliance personnel were invited by Aeros Ltd., Ukraine, and its partners to participate in development of AC-21 ultralight powered sailplane project.


L/D Ratio (expected) 27
Min Sink Rate (expected), m/s 0.6
Stall Speed, VS0 (expected), km/h 47-52
Max Structural Speed Vd, km/h 168
Engine Make / HP Hirth F33 / 28HP
Climb rate (expected) 2.5
Occupants 1
Length, m 6.6
Height, m 2.15
Wing Span, m 13.36
Wing Area, sqm 13.45
Primary Structures Materials Carbon & Glass Fiber Composites
MTOW, kg 264
Empty weight incl. rescue system (expected), kg 144
Pilot Weight, kg 60-110


ADA people developed following sub-projects:

• collection of  design and manufacturing information from one of former Aeros partners;

• structural modifications to implement the newly designed bigger fuselage and the power plant;

• loads definition per German LTF-UL requirements;

• reinforcement of  the structure to meet LTF-UL load requirements;

• replacing aluminum ribs with newly designed ones of carbon fiber composites;

• design and development of appropriate tooling, i. e. molds, jigs and fixtures;

• manufacturing structural components for static load tests;

• load test jigs preparation;

• load tests;

  • • manufacturing setup;
  • • AC-21 prototype manufacturing ;
  • • the first flight test.

After the first flight test made in November 2009, ADA personnel participation in the project ended with a share of the project earned.

By now, Advanced Design Alliance has in its possession a set of design, test and manufacturing information that would allow, with an appropriate guide, reproduction and further development of the glider. The set includes as follows:

  • • a list of materials;
  • • design and manufacturing drawings;
  • • CAD files;
  • • manufacturing specs and photos;
  • • load calculations;
  • • load test reports;
  • • flight test reports

and comprises 8 disks of DVD-5 format available for review by a potential buyer.