Scenario: a student has a homework question which checks his ability in some basic conceptual task, like reading an instrument approach chart. He has no idea, and posts the question here, with the multiple choice answers. The question is easily identifiable as a "do my homework for me" type of question, but receives an answer from someone here who seeks to be helpful. It also attracts down-votes because there is no underlying interesting issue, just picking from a couple of radial values and DME values the ones which apply to the given task, as well as no conceptual question or described difficulty understanding why "this" answer is right and "that" answer is wrong. After receiving his answer, the OP then deletes his question, which deletes the answer.
The thread in question -- visible to users who can see closed threads
The question was on its way to being closed, with two "close" votes and three down-votes. Interestingly, the answer was even more heavily down-voted, not because it was wrong (it was very clearly correct) but (I suspect) because it was answering -- and thus encouraging -- the sort of question that isn't useful for this site.
Two basic outlooks on this:
"Let's just be helpful" I think this was the sincere intent of the user who posted the answer to the question. And this answer did "help" the OP, at least in the moment. The OP, having his answer, decided to erase evidence of his activity here, which removes any possibility of his question helping anyone else out in the future (although given the nature of the question, I think that possibility is remote).
"Don't encourage these questions by answering them" This is obviously my take on things. You get more of what you reward. If students know that they can get a quick answer to basic questions by posting them here, that's what will happen. The closing process is only effective if it happens faster than the first "let's be helpful" answer; otherwise, the creator of the throw-away account cares not what subsequently happens to his thread.
I would suggest that especially when one is dealing with questions that are simply checks of a student's understanding, as this one clearly was, answering them is not, in fact, truly helpful. The student hides the fact of his limited comprehension of the material, which matters far more than a homework grade does. The instructor doesn't know where his student needs help. None of this reaches a good end, even when the intention is merely to be helpful.
When there is a misunderstanding that can be helped by explanation, then by all means, let's share the knowledge. When the question is along the lines of, this was question, this is how I arrived at my answer, here's what the actual answer is, what did I miss, that's different.
But I'd appeal to the community that when "do my homework for me" questions are posted, the best thing we can all do, both for the student seeking an easy shortcut to his own studies, and also for the Av.SE forum, is to please refrain from answering these questions.
No good purpose is served by turning this forum into a homework answer service, nor by moving in that direction. But as long as such questions get answers before they get closed, that's what such answers encourage. Please don't do that.