PADI tech 50 no refill between dives

[boulderjohn]

The better example would be getting full trimix after being a normoxic diver. Just because you are now certified for an unlimited depth vs. 200ft doesn't mean you should just up and go to 500ft right after class, nor should your instructor take you that deep.

Both the Tec 50 class and especially the PADI trimix class go into this in some detail. They talk about the attitudes you need to have as you take your next steps after the class ends. They talk about the humility you have to display, and they emphasize patience in moving forward.

In addition to these warnings, the PADI trimix course has a section on "crush depth," which is technically the depth limit of the equipment you are using. You need to be fairly certain that your equipment will not fail because you have exceeded those limits. It also includes the depth limits of your training and experience. The two of these combined on a recent dive in France. A team was diving with scooters to about 200 meters, which is about the stated limit for those scooters. One of them imploded because of the pressure. That, of course, made it extremely negatively buoyant. Unfortunately, it was also at the crush depth of the diver's skill, because he was unable to disconnect from it before it dragged him down to his death.

 

[divezonescuba]

The student is suppose to do the dive and gas planning as part of the practical applications. It sounds like the shop/instructor did that for her and told her that was ok. I think that is the definition of a "trust me" dive. Exactly the opposite of what the course emphasizes.

We carry two sets of doubles for even the tec40 class if we do dives 3 and 4 in one trip with an appropriate surface interval. If for some reason we did not have two sets, we would take some singles to equalize the doubles up to a least a higher pressure after the first dive.

 

[DevonDiver]

part of the issues with doing those long dives at the end of class for the instructor is mandatory deco, especially lots of it come with a lot of risk. Much better to hit the depth limit and not incur mandatory deco for the skills to be done at the surface in case anything goes sideways. At a roughly 1:1 ratio of bottom time to deco time at 50m, it's better to not spend that much time at depth and rack the time up on ascent where if something goes wrong, you can make a more direct ascent to the surface

You have ample opportunity on dives #1 and #2 to develop, refine and rehearse skills.

As an example, this is how I approach teaching Tec50...

Dive #1 is shallow/confined water. It's possible to spend an extensive amount of time repeatedly drilling protocols and further raising the standard of fundamental skills. I typically spend an entire day doing this and it can be exhausting. 2-6 hours of practice time is the norm, but we take breaks to hydrate and warm up as and when needed. In nearly every case, there's a lot of valuable development that can be achieved. Quite often, my students elect to extend this phase of training over multiple days... to enable very high levels of competency to be achieved. In that case, I also add numerous skills (beyond the bare minimum syllabus) that add to their 'toolbox' and give them more options and experience for future contingencies.

Dive #2 follows on. I run this as a dress rehearsal dive. I make it as realistic as possible, whilst only the actual decompression is simulated. I have to see that the student is fully competent to plan, organize and conduct the dive, as well as dealing with reasonably foreseeable contingencies, without any input needed from me. They have to handle all the logistics and preparation. This dive has to be 'passed' before I can be reasonably confident that the diver is ready and able for actual extended range decompression diving. Typically, I will choose a low-visibility site, and the ascent will be done with either a DSMB or by visual reference on the line only (i.e. all deco in neutral buoyancy, horizontal trim maintaining team formation and positioning).

Dives #3 and #4 are check out dives. They are assessed... pass/fail...and the student has to conduct both dives, with no instructor intervention (beyond fulfilling a normal team role in-water). If I have to intervene to preserve safety in any way, the dive is a 'fail'...and not counted towards certification. Runtime is calculated by the student based on gas consumption and available back and deco gas. Twin AL80s at 3000psi/200bar are used for backgas. The student can select from AL40 or AL80 deco cylinders, again filled to 3000psi/200bar. I expect them to maximize bottom time based on the resources they have available, but with the caveat of using prudent ZHL-16C GF settings for dive planning.

I teach technical diving, not glorified bounce diving. Technical divers plan and conduct dives (at great expense) with a purpose in mind. Bottom time is important, it's why we DO these dives...and divers must be familiar with the psychological and physical pressures of having the substantial deco obligations that arise from spending meaningful time at depth.

I don't emphasis the performance of 'skills' on dives #3 and #4. Frankly, the student diver shouldn't yet be doing the dives if further practice of the skills were necessary. For me, dives #3 and #4 are about the APPLICATION and ASSESSMENT of the competencies learned previously. I don't do any contingency/emergency skills during the bottom phase... and brief this point.... because I want no confusion or hesitate should a real emergency arise at depth. It's a real dive, with real consequences... so the role-playing should be reserved for the simulated dives. The few skills mandated for the dive are conducted shallow, once all decompression has been completed.

Whilst Tec50 (Extended Range) does require basic tech skills to be raised to a higher level of consistency and accuracy... this course is, IMHO, about DOING THE DIVES. It's about drilling hard in the shallows, but then after, using the training dives to amass operational experience and the application of competencies. Sacrificing that APPLICATION in favor of a few more fruitless repetitions of skills (that should already be fluid from the shallow training) is entirely self-defeating and robs the diver of the EXPERIENCE they need to be truly competent.

Lastly, Tec50 is the prerequisite (and to an extent, preparatory) training for trimix. Doing pathetic bounce dives at this level only serves to leave the student woefully unprepared for any subsequent development they wish to pursue.

Students do this training to enable safe diving at the appropriate level.... NOT to be told they should reverse to their previous level and take weeks, months or years to progress to the level IN WHICH YOU JUST QUALIFIED THEM TO DIVE.

If there are performance flaws which provoke the instructor to doubt the student's competency to perform safely and reliably AT THE CERTIFICATION LEVEL, then they should remedy those flaws before certification is issued.

The attendance / set-duration course mentality should stay put in the world of recreational diving (actually, it should be eradicated from there also....). This abject unwillingness to run truly performance-based, training-focused, courses is the ONLY reason why a tech instructor would minimize bottom times and/or counsel students NOT to dive at the level to which they are being certified.

 

[boulderjohn]

People should not forget that Tec 50 is also the last in a sequence that starts with Tec 40 and continues through tec 45. You would not believe how many times during that sequence students have to hold deco stops, do gas switches, perform valve shutdown drills while holding position, shoot bags, etc. The last two dives of tec 50 are not a time to be learning those skills. they should not have gotten that far if they still need that practice.

 

[Kevrumbo]

You all are missing the point:

There is a fundamental and dangerous flaw not taken into account in the whole PADI Tec 40/45/50 course progression & certification to begin with: The Density of Bottom Gas Nitrox 24% to 21% for a max working ppO2 of 1.2 bar is 6 g/L and higher, with Tec 50 on Air a whopping 7.2 g/L. (Refer to article: Advanced Knowledge Series: The Gas Density Conundrum | Dive Magazine )

The point is there's no safety margin left at all for the milieu of CO2 retention problems that arise with unforeseen heavy physical activity and increased work-of-breathing at these certification depths of 40/45/50 meters on primarily non-Helium, high gas density Oxygen-Nitrogen Blends (essentially Extended Range Deep Air). And to recover at depth from CO2 retention, you need plenty of bottom gas and some minutes time to relax & regain a normal non-exertion respiratory rate -if possible- before safely aborting the dive and nominally ascending to any required deco stops.

And further compounded in this instance of two Tec 50 class dives, in which there is no provision to refill bottom gas tanks on the boat in between dives, or providing an extra set of full cylinders of bottom gas along with the same required and enough volume of contingency deco gas to cover the later subsequent dive. . . !

Hi. Just wanted to see what opinions people have. A friend is presently doing her tech 50 course. I asked her how it was going and she told me that she had just completed a short first dive to 50m with a total runtime of 26 minutes.

It seems a bit short so I asked her why and she said it was because they were on a boat with no capacity to refill so they needed to save enough backgas for their second dive which was planned to 40m.

I expressed some concern about this and she told me that they had worked out their minimum gas and so she was told it was okay.

I was wondering is this actually permissible or does she have a loose canon for an instructor

 

[Michael Guerrero]

I think it depends on what the student has done previously during the courses. Might not be a big deal if they're good to go, since you don't learn how to deco by doing bottom time. If they're just getting rushed through with a bunch of short dives, then it's not great.

 

[boulderjohn]

Here is what the instructor manual says at the beginning of the section for Dive #3:

Reminder: As you know, beginning with Training Dive One, students must demonstrate
mastery of all skills in each training dive prior to progressing to the next.
Because Dive Three is the first actual decompression dive at this level, there should
be no doubt that skills learned and practiced in the previous dives have been mastered.
Remember, you do not continue instruction into Training Dive Three with any
students who have not yet demonstrated mastery of all prior skills and learning.​

 

[Colliam7]

but there is no mention in the standards of a required bottom time.

Yes. The critical 'standards' in the Tec 50 course (and 40, and 45) are depths and performance requirements, not times. For example, did the dive take place within the minimum / maximum depth range, and did the student divers successfully meet the stipulated requirements for planning, skills performed, gear configuration, etc.? Even for courses where there are statements regarding expected duration of a dive, these are generally not considered to be standards.

From afar, in the comfort of my arm chair, where I am sitting - wearing my drysuit, of course, with my Instructor manual in my lap - I can easily conclude that someone else's dive was too short, or too long, or just right. And, as a matter of personal preference, I admit that I prefer not to conduct tec training dives where I am forced to arbitrarily limit the time based on gas availability constraints. But, there are realities that we all deal with - maybe a diver has a fixed amount of time available to complete a course; maybe weather is coming in and there is a desire to complete the dive before conditions turn ugly, maybe the only boat available on a particular can only accommodate a certain number of cylinders.

I think the better criteria for assessing the overall course is whether the student diver completed the requirements, and feels confident that they can now go forward and complete similar dives without an Instructor backstop. Just a thought.

 

[divezonescuba]

The key dive standards for tec50 dives 3 and 4 from the instructor manual appendix include:

"Decompression: Decompression dive with two decompression gasses"

A bounce dive within the depth limits would not necessarily and probably would not meet that standard. So, if you are not actually going into decompression, you are violating that standard.

 

[Colliam7]

The key dive standards for tec50 dives 3 and 4 from the instructor manual appendix include:

"Decompression: Decompression dive with two decompression gasses"

A bounce dive within the depth limits would not necessarily and probably would not meet that standard. So, if you are not actually going into decompression, you are violating that standard.

I would agree.