Composite Failure Index
Surface Model

Home Projects AC-21 Powered Sailplane

In April 2007 personnel of ADA were invited by Aeros and its partners to participate in 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's people developed the following sub-projects:

  • take design and manufacturing information from one of the former partners of Aeros;
  • revise the structure along the updates from Aeros, taking into account newly designed fuselage and power plant;
  • loads definition per German LTF-UL requirements;

Pressure distribution on lifting surfaces

  • reinforce the structure to meet LTF-UL;
  • replace aluminum ribs with newly designed ones of carbon fiber composites;
  • design and develop appropriate tooling, i. e. molds, jigs and fixtures;


  • manufacture structural components for static load tests;
  • prepare load test jigs and perform load tests;

                                         D-Spar Load Test                                                                                    Fuselage Load Test

VIDEO: D-Spar Load Test

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


VIDEO: AC-21 Maiden Flight

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

By now ADA has in its possession a set of design, test and manufacturing information that would allow, with an appropriate guide, reproduction and development of the glider.

A set of documentation developed by now for AC-21 project includes as follows:

  • a list of materials;
  • design and manufacturing drawings;
  • 3D models;
  • manufacturing specs and photos;
  • load calculations;
  • load test reports;
  • flight test reports.


The set is located on 8 disks of DVD-5 format.