Ditching run time

[RJP]

. But no one is calling the coast guard if you are 3 minutes late.

Unless that "3min late" is late leaving the bottom... and your computer now tells you that you'll be 18min late getting back on the boat.

Working on a boat, I can't tell you how often I hear someone come up late saying something like "I don't know what happened. My computer was giving me 10min of deco when I went after that lobster. It only took me like five minutes to bag him, but when I looked at my computer again it was giving me 32 minutes! What a piece of crap..."

 

[PfcAJ]

Its also additive on the deeper portion of the ascent, and it gets more pronounced the deeper you are.

Take a 200' dive. Extra time spend at 120' when you really should be at 70' could mean the deco plan you're using isn't as appropriate as it could've been if you didn't dillydally through the ascent.

RT is a useful tool.

 

[Wookie]

So when I first read your post I thought you're kidding right? So now I am wondering, you're kidding right?

If I can see you on a line decoing somewhere, or I'm following your bag, I don't really care when you get to the surface (within reason). An exact to the minute schedule is something nice, but not the object of the sport.

 

[rjack321]

[


For simplicity sake, let's take deco gas, switching, etc out of the equation for a moment. (Assume a lost-gas scenario, if you will.)

　

Suppose you plan a dive to 140ft, with 24%, and a planned bottom time of 25min.　　 What are your deco obligation (stops and time) and gas requirements for that plan? (Hint: 25min at 140ft = 37min of deco time for a run time of 62min and 133cf of gas.)

Now, considering the same dive, imagine if you stay at 140ft for 5min longer than you planned - 30min instead of 25min. What are the changes to your deco obligation (stops and time) and gas requirements? (Hint: 30min at 140ft = 52min of deco time for a run time of 82min and 167cf of gas.)

Still not seeing any benefits to being "forced to stick to a strict schedule"? 　Asked another way, which would be more stressful: sticking to your planned runtime... or trying to complete a deco obligation requiring 167cf of gas on a set of double 80's that only contains 160cf of gas?

My tech instructor (who has posted above) drilled us on "schedule, schedule, schedule" which was stressful during the class, but following a rigorous runtime plan outside of a course setting actually reduces stress because you understand where the limits are and plan accordingly. 　In a non-course setting, there would only be stress if you are pushing the limits.　

If you find that having a plan - and sticking to it - is stressful, perhaps tech diving is not for you.

By the same token I have seen tech instructors sit and wait at 150ft on the way up from an aborted 210ft dive. Bottom time was <5mins (wreck wasn't there) and they had no idea how to adjust their deco schedule to match the actual deco obligation. So they sat at 150ft (their first deep stop) for 15mins to get back onto their pre-planned schedule.

"Breaking runtime" doesn't always mean the deco time gets beyond what you brought gas to accomplish.

I don't actually use (total runtime), never have. We do have a good understanding of our maximum allowable deco based on the gas we have, and strategies for completing the deco within a given time frame (typically plus/minus 10mins, sometimes more sometimes its much tighter like plus/minus a minute)

 

[DevonDiver]

...the run time forces you to stick to a strict schedule, putting stress on you during critical tasks such as gas switches.

Another perspective... the stress of following basic tech procedures on a strict schedule is a diver-originated issue. i.e. task loading versus ingrained skill

It never made sense how you're supposed to carefully check your gas and depth and do a switch at the same time you're rushing to meet the schedule planned by your run time.

1) Most dive planning software allows you define extra time, within the run-time, for completion of gas switches. Or you can manually add that (slates). This works if doing 'team switches' using formal procedure (NOTOX) once reaching the deco level.

2) Many technical divers prepare for the gas switch during the 'free-time' on ascent to the stop/gas-change. This basically re-orders the NOTOX protocol; on ascent to stop - confirm the tank/markings, deploy the regulator, turn the cylinder on, confirm team mate has prepared the right gas (trace regulator to cylinder and confirm markings).... on arrival at the stop; confirm above MOD, signal, gas-switch, examine buddy again (trace regulator to cylinder and confirm markings). That is seamless and very quick.

I teach both methods on my courses. What matters is that all critical steps are completed before you breath the regulator... and that a physical/visual confirmation of buddy/team is completed during or immediately after the switch.

Then I moved to IANTD normoxic, and my instructors did away with run time. This allowed us, in team diving, to do our gas switches sequentially, so you can check your teammates switches, and start your deco time only when everyone has switched. So you don't have to stick to an absolute run time schedule planned at the start of the dive.

There is no reason PADI courses can't be run with sequential (or team) switches. But why blow run time, when you can just anticipate your needs in dive planning?

Run-time is pretty useful... and much easier to follow than stop-times alone.

I don't really understand why your instructors would have you plan/mark a run-time, then condone breaking it as a routine. It sounds lazy to me...

It also makes more sense, for instance, if you had to spend a bit more time during a switch, to untangle a hose, or fix a buoyancy problem, which would throw off your run time for the rest of the dive.

Which makes a good argument for planning/preparing ahead... and making use of your ascent to stop, when you have nothing else to do...

So I say, why task load yourself and stress out trying to stick to a run time schedule -- to the point where rushing can compromise safety?

Task-loading and stress is a diver/skills issue, not a procedural issue. It seems like you are asking for validation to abandon a proven, tested procedure, to compensate for personal difficulties you are experiencing.

You WILL find the task-loading and stress decreases as you gain more experience and competency. Re-visit this thread after another 100 technical dives and you'll see what I mean

 

[RJP]

By the same token I have seen tech instructors sit and wait at 150ft on the way up from an aborted 210ft dive. Bottom time was <5mins (wreck wasn't there) and they had no idea how to adjust their deco schedule to match the actual deco obligation. So they sat at 150ft (their first deep stop) for 15mins to get back onto their pre-planned schedule.

"Breaking runtime" doesn't always mean the deco time gets beyond what you brought gas to accomplish.

I don't actually use (total runtime), never have. We do have a good understanding of our maximum allowable deco based on the gas we have, and strategies for completing the deco within a given time frame (typically plus/minus 10mins, sometimes more sometimes its much tighter like plus/minus a minute)

Not understanding the change to your schedule when the dive runs short is just as bad/lazy as not understanding it on the long side... albeit with less likelihood of a helicopter ride afterwards.

 

[wedivebc]

I am not getting this at all.

When I was trained and when I teach (remember the original question was about a class) we calculate a plan and a contingency, we allow time for task loading skills such as throwing a bag and gas switches and we all ascend together as a team.

What I am seeing here is more like SOSD dives with very loosely held schedules.

If we just jump in the water and swim around willy-nilly then ascend on our computers, aren't we just rec divers with extra stuff?

I think we should treat tech training as a formal event and practice precise team and time management. What you do after training is your business.

 

[RJP]

If we just jump in the water and swim around willy-nilly then ascend on our computers, aren't we just rec divers with extra stuff?

Dive until your computer starts beeping... exit water... stay out until your computer stops beeping. Repeat.

 

[Redshift]

I don't think people are saying it's ok to delay ascent or to hang around doing something when they should be going up. I think the point is that it may be difficult for a team to have exactly the same runtime, to perform all the tasks within it and to accommodate for anything that could happen and that it's not as enjoyable for some people and may not make much difference in the end.

Will every member of the team have the computer / depth gauge turning on at the same time? No. I have seen it countless times. Therefore someone on the team will have to redo the whole runtime. Will everybody swim at exactly the same pace and be at the same position? No, especially when going up a shotline. What if starting the ascent one was a bit slower, will it exceed max ascent rate to meet runtime? I wouldn't. What if sending up the smb takes a little longer? I don't think (or at least don't hope) anyone is advocating not caring about times at all, but that runtime to the minute may not be necessary when it's easy to be one minute off switching gases or one minute off sending an smb. What will the difference be in deco? And among the huge variety in deco models and different parameters are those couple of minutes any important? If a stop is at Xm are you never at X.3m?

 

[Nasser]

In the beginning when I was first learning to follow Run Times, stay within the various descent and ascent rates, and hit the gas switches on the mark I felt pretty task loaded and a little overwhelmed. But like anything, after more practice I become much more fluid and relaxed. Now I find following Run Times and doing gas switches quite easy to execute and don't even feel the need to pad my times for switches during ascents. If I so choose, the options are there with the deco software we use, but I have not found the need for that. Plenty of practice, good team communication and awareness, and feeling relaxed during the dive is the key.