I was just chatting with my ANDP instructor yesterday and mentioned my concern that I should have experience with back twins before doing the ANDP course. He said that he now insists that any student wanting to do ANDP must first do the intro to tech or a side mount course before doing the ANDP. It is not a TDI requirement and as he said to me, you are paying for training not a certificate.
So my own concerns that doing the ANDP course without previous back twins experience suits both myself and my instructor. He likes the fact I am wanting to do the ITT before the ANDP.
One would hope that this would mean students would have more confidence and at least be in the right mindset of redundancy and sufficient gas.
ANDP means you're doing decompression. This by definition means there's a "soft" overhead between you and the surface; therefore you *must* have redundant gas supplies. A single cylinder, even a 15 litre, is a single source of gas and is generally quite limited in volume. A twinset or sidemount provides the redundancy and additional gas, especially in the bottom phase where the decompression gas is not available.
The other challenge of singles is what happens if someone rocks up with a recreational BCD? Is that going to be easy to clip the decompression stage?