Question for Petrel owners - how are you using your computer?

[Michael Guerrero]

#1, cut sheets using MVPlanner, with over and under runs, Petrel in tech mode since square profiles are something of a rarity in my diving.

 

[HIGHwing]

Given the increase in computational power of PDCs over the last few years, it's hard to for me to see why it's OK to cut tables on a PC at home and transfer them to a slate or wet notes, but bad to run the same deco software on a PDC during the dive. Obviously, preplanning is still required to estimate gas consumption.

Because it's difficult to cover all the lost gas scenarios on an OC Tec dive using just the Petrel. Using Multideco, I can forecast several lost gas scenarios, click print, (print extras for my dive partners), slap those on some slates and away we go.

 

[rongoodman]

That's the nice thing about the newer computers--you can pre-plan with MultiDeco or a similar program and then run the exact same deco model in real time during the dive.

 

[Dr. Lecter]

I tend to use a modified version of option 1: I'll cut CCR and OC bailout tables on V-Planner for a dive to the deepest possible depth at the site for the maximum amount of BT I'm willing to rack up, and plan for deco/gas around that schedule…then I'll fly the stand-alone Petrel and Predator controller within the plan. If I do a somewhat shorter multilevel dive (reality 90% of the time) and they don't fail, I'll have lots of extra gas and exit the water a bit sooner. If both SWs fail, then I know I'm covered by the cut tables no matter what I've actually done.

 

[Agility]

If both SWs fail, then I know I'm covered by the cut tables no matter what I've actually done.

How do you track depth and time if both DCs fail?
Do you have an analog depth gauge and a watch as backup?

 

[Dr. Lecter]

How do you track depth and time if both DCs fail?
Do you have an analog depth gauge and a watch as backup?

Indeed I do. If my Planet Ocean decides to quit on top of both my Predator controller and my Petrel, it's probably just my time…no pun intended.

 

[clownfishsydney]

The deep decompression dives I do in Sydney are ones I have done many times before, one wreck I have done over 100 times. Therefore, I do not make a plan before the dive. I use what I know will work for each dive, the bottom time and the known approximate depth (all are square profiles give or take a few metres). I know what deco I will need to do for each dive based on my normal bottom time as well as if I extend it (given perfect conditions) or cut it short (for less than reasonable conditions). This comes from experience of diving these sites so many times.

Sure, if I was doing a dive to a site with a depth that I had not done before, then I would use either software on my PC or my computer (I have an OSTC but my wife has a Shearwater) to give me a rough idea of what I will need to do. When doing these dives I always have a backup computer that is a bit more conservative than mine.

 

[kensuf]

Tables cut for the dive plan as a backup, but use the petrel for the actual dive. I only need one petrel, but I have a watch as a backup.

 

[Nasser]

Tables cut for the dive plan as a backup, but use the petrel for the actual dive. I only need one petrel, but I have a watch as a backup.

So are you following the runtimes of the dive plan on the Petrel or following the Petrel's deco schedule entirely? I assume you're using the same deco model for both cut tables and Petrel ?

 

[victorzamora]

How do you track depth and time if both DCs fail?
Do you have an analog depth gauge and a watch as backup?

This may sound grumpy, but I swear I don't mean it to be. I've heard this sentiment from more people than you, and I truly don't get it. The sentiment I don't understand is one that two computers is less safe than one computer and a backup/bottom timer/analog depth gauge. Anyway, here goes my question:

He's diving with two highly reliable computers. He's also diving a backup to those, but can that really be expected of everybody realistically? For example, do you expect this of divers diving two bottom timers and a bunch of tables? How about redundant tables in case they lose a set? Why are analog gauges thought of as more reliable than digital? I've seen more analog gauges fail early than digital....to the point that I've been told by DMs to completely ignore the analog gauge's readings.

What I'm getting at is this: If I'm diving two Petrels, why should I be diving a bottom timer or depth gauge and watch, and why should I be diving tables? If I plan my dive for gas reserves, why should I cut tables and take them with me? Do other divers have double redundancy as is expected of a two-computer diver?