Transmission lubricating structure of helicopter

A transmission lubricating structure of a helicopter,

• the transmission lubricating structure comprising:
• a main tank in which lubricating oil is stored;
• an auxiliary tank in which the lubricating oil is stored;
• a common line arranged lower than the auxiliary tank and supplied with the lubricating oil from the main tank or the auxiliary tank;
• a main line through which the lubricating oil in the main tank is introduced to the common line;
• an auxiliary line through which the lubricating oil in the auxiliary tank is introduced to the common line;
• a common nozzle provided downstream of the common line and configured to discharge the lubricating oil, supplied from the common line, to a transmission;
• a pump configured to supply the lubricating oil by pressure from the main tank to the common line;
• a relay valve arranged lower than the auxiliary tank and higher than the common nozzle and provided upstream of the common line;
• a supply line through which the lubricating oil in the main line is introduced to the auxiliary tank;
• and
• a resistance orifice that is provided at the supply line, and always fluidically connects the main line to the auxiliary tank;
• wherein
• the relay valve is configured to:
• block the auxiliary line when the pump is operating;
• and
• open the auxiliary line by the own weight of the lubricating oil in the auxiliary tank and by decrease in hydraulic pressure applied from the pump to the relay valve to make the common line communicate with the auxiliary tank when the pump is in stop state.