Officials of the Pyongyang Municipal Aviation Club are making efforts to raise the performance of engine-propelled model airplanes for free flight.
In the past, they fixed the aerofoils of engine-propelled models. So, the planes could not fully display their abilities due to strong air resistance during flight.
In order to raise the gliding performance whereas minimizing air resistance, they remoulded the fixed foils into folding ones.
They rationally defined the number of folding foils and solved the problem of materials for such metal parts as hinges and spring hangers.
They changed cabane-type foils into carbon fiber-type ones to make full shape of wings, with the result that they could reduce the time for the engine-propelled model airplanes to reach their flying altitude and markedly increase their flight range.