A device is disclosed for training pilots by simulating the operation of retractable landing gear in aircraft. The oil is supplied to the components via a heat exchanger in which oil and fuel are placed in direct heat exchange relationship. A nutrient solution is sprayed onto the micro-fleece cloth and the developing root mass of the plants, while controlling temperature, humidity, and carbon dioxide within the growth chamber. The string select bias interconnection may be disposed between the ground select bias interconnection and the cell bias interconnections of the bias interconnection group. The barrel is provided with lands designed to catch the sabot at the front end of the barrel in such manner that the barrel is sealed off in a gas-proof fashion by the sabot.