6. What rank or position does Hornblower hold at the beginning of this episode?
From Quiz A&E's "Hornblower" - "The Fireship"
Answer: 
acting lieutenant
On an 18th century British Man-O-War, the midshipmen were considered "officers-in-training".  When one showed enough promise that he might be considered for promotion to lieutenant, he first served as an "acting" lieutenant for a time, to show his mettle and determine his readiness for the lieutenant's exam.  
To those that feel they got this wrong because of the British pronunciation of "leftenant", please be aware: Regardless of its pronunciation, the word is still spelled "lieutenant".  This has to do with the actual meaning of the word.  It is from the French, lieu, meaning a place or location, and tenant, meaning one who holds.  In other words, a lieutenant is one who holds a position or territory under someone else's authority... he is acting in place (or in lieu) of his commander.