Sentence:  There he 'd take a compass heading , figure his air speed , and deduce that in a certain number of minutes he 'd be over the broad meadows of the Merrimack Valley where it would <WSD>be</WSD> safe to let down through the overcast and see the ground before it hit him . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)