Method of optimizing the specific fuel consumption of a twin engine helicopter and twin engine architecture with control system for implementing it

A method for optimizing specific fuel consumption of a helicopter including two turbo-engines including a gas generator including a combustion chamber, the method comprising:

• adapting at least one of the turbo-engines to operate alone at a continuous flight speed, the other engine being then at an over-idling nil power speed adapted to switch into an acceleration mode of the gas generator of such engine through driving means compatible with an emergency restart output;
• carrying out the emergency restart, in case of a failure of at least one previous conventional restart try, through an emergency mechanical assistance to the gas generator of the over-idling turbo-engine, produced by an autonomous power and dedicated to the emergency restart;
• and
• in case of a failure in one turbo-engine being operated alone, restarting the other over-idling turbo-engine by the emergency assistance.