Aircraft engine lubrication circuit and method, using a non-return pressurisation valve with two plugs

A method of lubricating an aircraft engine lubrication oil circuit, the circuit comprising:

• a non-return valve comprising a case fitted with a connector on an upstream side and an outlet on a downstream side,
• an oil supply on said upstream side of the non-return valve,
• a first valve plug and a second valve plug housed in a manner free to move in the case to open and to create a communication between the connector and the outlet, when a first overpressure threshold is reached on the upstream side for the first valve plug;
• and when a second overpressure threshold on the upstream side higher than the first threshold is reached, for the second valve plug,
• in which the outlet comprises two branches, a first branch leading to a device to be lubricated remaining open at least up to the second overpressure threshold, and a second branch,
• a switching device that opens the second branch when the second overpressure threshold is reached,
• the second branch of the outlet connected to an exterior of the circuit, the method comprising a pressure limitation of the oil circuit by means of the non-return valve by extraction of an overflow and a flow from the overflow to the device to be lubricated, wherein when an overpressure threshold is reached in the circuit, the method comprises opening of the evacuation outside the circuit and said chamber and switching of the non-return valve to direct at least most of the overflow towards the evacuation.