Ascend drills - how many is too many?

[Alaskan Scuba Dude]

Is this pressurized submarine escape training or do you like getting students bent?

 

[Roy_W]

I am neither an instructor nor do I wish to give any advice, what follows is simply my own opinion and personal experience.

I live in France and have done my Level 2 CMAS and will be doing my Level 3 next week in the south of France..

In French we say a "Remontée Assisté", translation = Assisted Ascent".. and it is the exercise that most divers apprehend as being a difficult exercise.

Whilst doing my Level 2 training we would do a max of 3 ascents from 20m to 6m.

In my upcoming Level 3 we will probably be doing a max of 2 ascents from 40 to 6m.
Most instructors here, will as a rule of thumb, use the 90m rule, that is to say that the total ascension distance should not pass 90m per dive/per day, Hence the max 2 ascents on level 3 and 3 on level 2.

I have done this exercise many times as it is mandatory in order to pass your level, the speed of ascent must be controlled and should remain below 15m per minute between 20m and 10m and then slow down for the next 4 metres, this is for the level 2. The hardest part is judging your speed without looking at your computer.

In level 3 training the ascent from 40m to 20m can be a little quicker due to the fact the pressure difference are less than that between 20m and 6m... ( The last 10m are definately the most fragile due to pressure drop and expansion )

Everyone in Belgium, France and Switzerland knows very well this exercise and as far as I know I have never heard about anyone getting bent, we are talking about 10 of thousands of divers that have done this training over the last x years...

Is there a difference between doing this exercise at 40m compared to 20m ,yes, very much so. We have to deal with the narcosis, the cold and the dark, in other words, the exact same conditions that we would normally be diving in. The inertia is different, we have to move slower, thinking is different, the dangers are multiplied all round. We are very much made aware of the dangers before we go down, it is an essential part of the training. Level 3 divers are essentially tech divers in respect to the fact that they can plan and do their own dives down to 40m and then down to 60m with the appropriate Dive Director authorisations. So somewhere along the line these exercises really are essential. A simple cramp at 40m can become seriously life threating..

I know that I would have much more confidence in and would very much prefer to dive with someone who knows this exercise at 40m than someone that doesn't. That's just my opinion.

As far as things going wrong, yes they do, I have been there. I was doing the exercise with another student from 40m and I was a little bit too quick in the initial take off, to be perfectly honest I think I was a little bit under the influence of Narcosis...

Anyway, we took of too quickly and the instructor saw it but was too slow in starting their own ascent along side us.. The instructor saw that we were far too fast and they too started their ascent in order to catch up with us, except the instructor forgot that they were wearing a dry suit and forgot to purge. By the time the realisation hit it was too late, the instructor popped straight to the surface... Meanwhile my narcosis had worn of and fortunately I managed to bring the other student and myself to a stop at 14m, so no damage there.. We could see the instructor so we then made the sign that we would go to the surface to find the instructor since we were in a lost diver situation..

We had barely began our ascent when the instructor came back down to us..
I can't remember exactly what we did next, we stayed for a short while at depth but I do remember when we eventually surfaced and the instructor shouted at me, "What the F*** did you think you were doing ascending at that speed", I did not accept this and shouted back , "I am the F**ng student why are you shouting at me", it was heated for a minute or two..

Eventually we were back on land and we discussed the problem, everyone was calm now.. We agreed that I had probably suffered from narcosis, we dive in lakes, so in May it is cold ( around 8°), and dark... and the instructor admitted that they too had made a mistake and that they should not have shouted at me, it was a spur of the moment emotional reaction.

The instructor told me that they had seen us shoot off , started to worry that we would pop the surface, thought they we were in a life threatening position, we were in all fact, and when they made their own ascent and realised that they too had made a mistake that 3 lives would have been taken that day..

We still talk about it to this day when we meet up...

Anyway, no one was injured and no-one got bent or ill, were we lucky, of course we were.. Could it have gone completely wrong, yes definitely. it was a major lesson for all concerned, especially the instructor.

I think that the relatively short bottom time, of only a few minutes at most is what makes the difference. We descended quickly in the beginning and almost immediately headed back up, therefore there is very little on-gassing.

As much as this exercise is probably a little contentious I still feel that it is a very important exercise.
YMMV....

 

[skippy311]

OK, some more background. I AM an instructor (albeit a fresh one - CMAS indeed), and I am asked to assist on this drill. And, clearly, I am having some concerns. I agree with @DiveProKoko that many lessons can be learned from 10m. Having said that, I also see the value of experiencing how loooong (2.5 min) a safe ascend from 25m really is. But three in one dive seems quite a lot, esp if the idea is that we need to repeat in case of 'beauty flaws'. Hence my question.

But what is the recommended max? Say we do it once, but there is room for improvement, does it make sense to do it a second time in the same dive? BTW: I am unaware of any (CMAS or otherwise) 'rule book' where it specifies that this is not 'allowed'. So any recommendation is greatly appreciated.

CMAS? I am a CMAS SCUBA diver and have never heard of such a drill.

 

[skippy311]

I am neither an instructor nor do I wish to give any advice, what follows is simply my own opinion and personal experience.

I live in France and have done my Level 2 CMAS and will be doing my Level 3 next week in the south of France..

In French we say a "Remontée Assisté", translation = Assisted Ascent".. and it is the exercise that most divers apprehend as being a difficult exercise.

Whilst doing my Level 2 training we would do a max of 3 ascents from 20m to 6m.

In my upcoming Level 3 we will probably be doing a max of 2 ascents from 40 to 6m.
Most instructors here, will as a rule of thumb, use the 90m rule, that is to say that the total ascension distance should not pass 90m per dive/per day, Hence the max 2 ascents on level 3 and 3 on level 2.

I have done this exercise many times as it is mandatory in order to pass your level, the speed of ascent must be controlled and should remain below 15m per minute between 20m and 10m and then slow down for the next 4 metres, this is for the level 2. The hardest part is judging your speed without looking at your computer.

In level 3 training the ascent from 40m to 20m can be a little quicker due to the fact the pressure difference are less than that between 20m and 6m... ( The last 10m are definately the most fragile due to pressure drop and expansion )

Everyone in Belgium, France and Switzerland knows very well this exercise and as far as I know I have never heard about anyone getting bent, we are talking about 10 of thousands of divers that have done this training over the last x years...

Is there a difference between doing this exercise at 40m compared to 20m ,yes, very much so. We have to deal with the narcosis, the cold and the dark, in other words, the exact same conditions that we would normally be diving in. The inertia is different, we have to move slower, thinking is different, the dangers are multiplied all round. We are very much made aware of the dangers before we go down, it is an essential part of the training. Level 3 divers are essentially tech divers in respect to the fact that they can plan and do their own dives down to 40m and then down to 60m with the appropriate Dive Director authorisations. So somewhere along the line these exercises really are essential. A simple cramp at 40m can become seriously life threating..

I know that I would have much more confidence in and would very much prefer to dive with someone who knows this exercise at 40m than someone that doesn't. That's just my opinion.

As far as things going wrong, yes they do, I have been there. I was doing the exercise with another student from 40m and I was a little bit too quick in the initial take off, to be perfectly honest I think I was a little bit under the influence of Narcosis...

Anyway, we took of too quickly and the instructor saw it but was too slow in starting their own ascent along side us.. The instructor saw that we were far too fast and they too started their ascent in order to catch up with us, except the instructor forgot that they were wearing a dry suit and forgot to purge. By the time the realisation hit it was too late, the instructor popped straight to the surface... Meanwhile my narcosis had worn of and fortunately I managed to bring the other student and myself to a stop at 14m, so no damage there.. We could see the instructor so we then made the sign that we would go to the surface to find the instructor since we were in a lost diver situation..

We had barely began our ascent when the instructor came back down to us..
I can't remember exactly what we did next, we stayed for a short while at depth but I do remember when we eventually surfaced and the instructor shouted at me, "What the F*** did you think you were doing ascending at that speed", I did not accept this and shouted back , "I am the F**ng student why are you shouting at me", it was heated for a minute or two..

Eventually we were back on land and we discussed the problem, everyone was calm now.. We agreed that I had probably suffered from narcosis, we dive in lakes, so in May it is cold ( around 8°), and dark... and the instructor admitted that they too had made a mistake and that they should not have shouted at me, it was a spur of the moment emotional reaction.

The instructor told me that they had seen us shoot off , started to worry that we would pop the surface, thought they we were in a life threatening position, we were in all fact, and when they made their own ascent and realised that they too had made a mistake that 3 lives would have been taken that day..

We still talk about it to this day when we meet up...

Anyway, no one was injured and no-one got bent or ill, were we lucky, of course we were.. Could it have gone completely wrong, yes definitely. it was a major lesson for all concerned, especially the instructor.

I think that the relatively short bottom time, of only a few minutes at most is what makes the difference. We descended quickly in the beginning and almost immediately headed back up, therefore there is very little on-gassing.

As much as this exercise is probably a little contentious I still feel that it is a very important exercise.
YMMV....

I am also a CMAS SCUBA diver. I would like to learn the different approaches each National Association uses in their instruction.

 

[Roy_W]

Here is a link to the CMAS Rescue Diver Standard.

https://www.cmas.org/document?sessionId=&fileId=2164&language=1

This is the section concerning the assisted ascents.

"12.9.3 Participants to be certified shall complete at least two (2) open water rescue dives/exercises under the direct supervision of a CMAS Instructor at depths between nine (9) to twenty (20) meters. All assisted ascent exercises shall be terminated at a depth of 6 meters and shall be directly supervised by the CMAS Instructor."

Since I am in France the FFESSM, the French Federation which is a CMAS affiliate, have taken things a little further and we also do this from 40m when doing 3 Star training.

I would be interested to know how others that have not been taught to do an assisted ascent have been instructed to react in this situation, especially below 20m.

 

[boulderjohn]

Here is a link to the CMAS Rescue Diver Standard.

https://www.cmas.org/document?sessionId=&fileId=2164&language=1

This is the section concerning the assisted ascents.

"12.9.3 Participants to be certified shall complete at least two (2) open water rescue dives/exercises under the direct supervision of a CMAS Instructor at depths between nine (9) to twenty (20) meters. All assisted ascent exercises shall be terminated at a depth of 6 meters and shall be directly supervised by the CMAS Instructor."

Since I am in France the FFESSM, the French Federation which is a CMAS affiliate, have taken things a little further and we also do this from 40m when doing 3 Star training.

I would be interested to know how others that have not been taught to do an assisted ascent have been instructed to react in this situation, especially below 20m.

This standard does not mention a requirement to do 3 ascents from 25 meters on a single dive. It mentions two ascents, but it does not say anything about dong them on one dive.

 

[Roy_W]

This standard does not mention a requirement to do 3 ascents from 25 meters on a single dive. It mentions two ascents, but it does not say anything about dong them on one dive.

Yes, I agree, this is merely the CMAS Standard that states that assisted ascents are part of the criteria.. As I mentioned the French Sports authority have taken it further.. I believe that this Swiss and the Belgians also adhere to the same or very similar cursus as the French.

Even here in France it's a contentious subjects, especially among the Dive Schools that do not agree with the practice.

 

[skippy311]

I don't know

 

[Bob DBF]

Unless you're including submarine escape drills where there's no descent.

You decend in the submarine, so one ascent for each decent. Although inside a sub is one atm, once in the escape trunk you are equalized to depth in a matter of seconds (the actual decent) before the outer hatch is opened and you are out and on your way up.

 

[Akimbo]

This is a sawtooth dive profile, which can increase the risk for decompression sickness.

Best regards,
DDM

Agreed, however there is a long history of doing saw-tooth profiles. Although they were freediving, instructors at US and Royal Navy submarine escape towers would do them all day, day after day for decades. Most towers were 30m/100' deep.

Commercial divers will often do sawtooth profiles for pier and platform inspections.

This is not a recommendation, only a point of reference:​

First, keep in mind that I was trained to do free ascents in my 1962 Scuba class and again in the US Navy. I have done a free ascent from the at least 120' once a year for most of my life, before Covid anyway. I do them at 60'/minute, at the start of the first dive of the day, with only a few seconds of bottom time, and only once per day. I still do them at 60'/minute because that was the standard from the 1960s when I started diving until it changed to 30'/minute in the 1990s.

As for decompression, this is not much different in terms of Nitrogen absorption than accomplished freedivers do many times/day, except at 200' or 60m/minute.

Why do I practice free ascents? It gives me the confidence that I can do it if everything goes sideways. I may get bent on a decompression dive, but that is more treatable than being drown. I have always followed this principal:

Avoid drowning, embolism, and getting bent —
in that order.​