Just a few things to consider...
Listen carefully and respond to the question being asked.
Keep your answers concise and relevant, rambling on is as bad as not answering.
Pay attention to verb tenses, you don't need to use obscure compound tenses for a 6, but you need to get the ones you do use right.
If you don't understand something, ask for a repeat. One repeat shouldn't be penalised.
When describing the picture, only state for a fact what you know to be correct, if you can't tell a 747 from a 380
call it a four engined aircraft.
Don't argue with the examiner.
You're correct in that it is mainly based on fixed wing operations, but there shouldn't be anything there that would cause problems for any competent pilot. Remember that it's a test of your Aviation English not your technical knowledge.
If you didn't take a specialist course I would suggest doing a mock test at one of the aviation schools. It's relatively cheap and will give you an idea of what's in store on the day.
I used to teach at a specialist aviation English school, and unless things have changed drastically in the last 18 months I know three of the examiners in SP. Contrary to popular belief they are not out to trap you and they don't have a quota.
Good luck