Method of managing an engine failure on a multi-engined aircraft having a hybrid power plant

A method of managing an engine failure on a rotary wing aircraft, said aircraft comprising:

• a hybrid power plant having at least two fuel-burning engines, at least one electric machine, a main gearbox “MGB”, and at least one electronic engine control unit “EECU”, each EECU being connected to a respective engine, each engine being capable of delivering at least a maximum continuous power MCP rating and OEI 30″, OEI 2′, and OEI Cont power ratings, said hybrid power plant delivering total driving power WT to said MGB;
• at least one electrical energy storage means;
• and
• at least one main rotor that is driven in flight at an instantaneous speed of rotation Nr by said hybrid power plant;
• the method being characterized by:
• a checking step, in which the operation of each engine is checked during each flight by means of said EECU in order to detect a failure, if any, of at least one engine, an engine being considered as having failed when at least one other engine delivers said OEI power rating;
• a monitoring step during which a monitoring value is determined relating to at least one monitoring parameter of said aircraft and a detection threshold is determined for detecting a deficit in said total power WT, a comparison then being performed by comparing said monitoring value with said detection threshold in order to identify a risk of a deficit in said total power WT, said deficit in the total power WT appearing whenever at least one engine needs to deliver power greater than a predetermined power WP;
• and
• a control step, during which, when a failure of at least one engine is detected and said detection threshold is crossed, said electric machine is controlled to deliver auxiliary power We so that said total driving power WT from said hybrid power plant is sufficient to fly said aircraft safely, each engine that remains operational not delivering power greater than said predetermined power WP.