Who is the last person to sign out an a/c saying its acceptable to fly
An experienced Aicraft Ground Engineer (AGE) of SNCO status, who would have carried out a visual inspection of the aircraft as far as is practical (ie he will not open access panels to simply have a look, unless it is officially part of his checks, or if he finds good reason to do so). Other tradesmen will have checked inside the compartments and signed for their safety and access panel security.
Have I got this right, a pilot can refuse to fly an a/c if he thinks it's unsafe and no-one can say he has too. Is that right, the pilot has the final say ?
If the AGE has certified the aircaft as fit to fly, the captain must find evidence to the contrary if he doesn't want to accept it. In order to reject the aircraft, on an engineering basis, he must enter a new defect in the maintenance book. In anticipation of your next question, no, a captain cannot reject an acceptable deferred fault, without substantiating his decision to his commanders. He might be able to convince them that he is right but, if nothing has changed since the certification, its doubtful. We don't work on the principle of, "I want that one".
A example at the heart of this discussion would be: The AGE does his final checks and signs the aircraft as fit to fly. The captain then sees a fuel leak from a charted position and does not believe it is acceptable and wishes to reject the aircraft on that basis. He must either enter that leak in the documents as a new fault and await ground engineering examination to certify it as acceptable or not or, without doing any paperwork, he can (bravely) take his crew away and explain his actions to his Sqn Cdr. Although captains do have the final say, they are still part of a structured organisation and they have to answer for their decisions when they do not go with the plan.
Occasionally, a captain might discover that the aircraft, which is serviceable, does not have the role equipment he needs to carry out his duty, so he can reject it on that basis. Also, if a captain is taking a aircraft away from main base on a deployment with minimal engineering support and the extant acceptable fault(s) are too great for remote ops from home base, he can reject it. These kinds of decisions are usually made well before he is due to go to the aircraft.