Unfortunately, OFBSLF and Ghengis are quite off base in the walkway analogy, and roofus perpetuates it in his post.
The Engineer in the helicopter case is not an engineer, he is a mechanic, authorized to follow repair guidelines and fix aircraft. He can change the oil. He can use nuts and bolts to change a part. He can conduct authorized repairs using maintenance procedures and common aerospace techniques.
He is not educated or trained as a true professional Engineer, and is not capable of originating or approving a design in any sense. He is not paid to originate a new design or repair technique, he cannot change the maintenance manual that a professional engineer wrote.
It is unfortunate that British usage of "engineer" blurs this important destinction. Most of the world uses a different title for mechanic than for engineer, to avoid this error. British usage stems from the fact that the terms were in use before the profession of engineer was differentiated, and before engineering schools were created.