pete v:
the reason that i am looking for the alt air source is not only gas mismanagement but unforsceen issues such as

-ring failure at the 1 stage, free flow reg, stuck pressure gauge showing inncorrect psi, rupture of tank o-ring, bc inflator stuck in open postion, etc etc...... yes alot of these are preventable the key word is "preventable" not "eliminate" with care and maintence and we can what if this to death, but sh*& happens and thats why we call them "unforeseen circumstances" and dead is dead so a ounce of prevention is worth that pound of cure when your down under. thanks fir reading this. p
Ok,
I'm about to step into a hole here.. I know it. But here we go...
I think the exerienced divers are saying that with proper planning, and use of time tested principles of diving, the pony bottle is superflous. It's one more thing to have to manage, practice, and another failure point. So let's look at common principles of diving related to what you just said:
1. First stage o-ring failure. Use a DIN fitting. But even with a yoke, it seems that most issues I've heard of occur when the regs are pressurized on the surface, not during the dive. If you have a catastrophic failure, you should be surfacing anyway. And if you can't surface immediately (overhead restriction, mandatory deco stops, you are out of the realm of NDL recreational diving, and you should be using redundant back gas. Not a bailout bottle.
2. Free-flow regs can be breathed off of. I had to do it in openwater cert. Practice this by keeping the purge pressed and breathing. If it's a second stage issue, switch to your backup reg. This should give you enough time to track down your buddy and share air.
3. Stuck pressure guage. If you check your air every 5 minutes or so, as should be common, you'd know if it was stuck. If you've been down 50 minutes and your pressure guage still reads 2800#, you've put yourself in an awkward position. Turn the dive. do your safety stop if you can, and surface with your buddy.
4. BC inflator stuck. Disconnect it.
5. Tank O-Ring failure. This is a slow leak issue isn't it? Surface after a safety stop.
In a basic openwater dive, there is nothing that should prevent you from coming to the surface immediately if you have to. Once you drop below recreational depths, you had better keep your buddy close, and be on the same page. And if you start diving deep or go into overheads, you need to be fully redundant AND have a well trained partner.
The recurring themes I keep reading in these stories of incidents, are either diver is out there alone, buddy is unaware of problem or has "lost" their partner, diver paniced in what should be a manageable situation, or a surface problem arose and was ignored.
For most people 80cuft is 60 minutes worth of air. A 6cuft pony is 8 minutes max if things all go well. if you are in an environment where you should not be (overhead, lost buddy, lost anchor, etc.) it will be more like 4-5 minutes with your increased breathing rate. Maybe that's enough. Maybe not.
I just hate to see the bailout bottle become an excuse for not practicing safe diving habits, or worse, not working with your diving buddies as a team.