Learn Dutch: Het vertrek is vertraagd, dus de piloot wacht. - The departure is delayed, so the pilot waits.

Dus (so) is a coordinating conjunction, just like en, maar, of, and want. It joins two main clauses together without changing the word order. If you had used an adverb like daarom (therefore), you would need inversion: daarom wacht de piloot.

How would you rewrite this sentence using pas als to mean "Only if the departure is delayed, does the pilot wait"?

You would say: Pas als het vertrek vertraagd is, wacht de piloot. Because pas als fronts the entire conditional clause, the main clause that follows it must use inversion, placing the verb (wacht) before the subject (de piloot).

In is vertraagd, is this the present perfect tense or the passive voice?

It functions mostly as a state passive, where the past participle vertraagd acts like an adjective describing the condition of the departure. The verb vertragen means "to delay." When something is currently in a delayed state, Dutch uses is vertraagd. If you wanted to say an airline has delayed the departure (active voice), you would use heeft vertraagd.

The noun vertrek means departure. How do I use its verb form correctly?