Lesson 1, Topic 1
In Progress

# Planning

In the planning of the dive we will have to consider the following parameters:

1. Maximum depth to be achieved
2. Duration of the dive
3. Calculation of autonomy
4. Underwater route
5. Arrival at the surface and exit of the water
6. Preparation of an emergency plan

# 1. MAXIMUM DEPTH To BE ACHIEVED

The establishment of a depth limit is intended to ensure a greater degree of safety bearing in mind that the Diver CMAS One Star Diver can only evolve in the medium depth space (up to 20m).

# 2. DURATION OF THE DIVE

The establishment of a maximum dive time allows us to trigger the “emergency plan” of search and recovery of divers that surpass it in a timely manner.

# 3. CALCULATION OF AUTONOMY

In Module 14 – Calculation of air consumption, we only considered the variation of the air consumption in a bottle depending on the depth of evolution of the diver. In fact, what interests us is the calculation of the “bottle autonomy” so that we know how to plan our dive according to the air we will consume.

Assuming that the Diver CMAS One Star Diver does not make decompression stops, the first safety standard to be defined is that in the calculation of the air required for the bottom time does not take into account the reserve air (50bar).

FOR DIVES UP TO 20M WITHOUT DECOMPRESSED LEVELS, WE ASSUME THAT THE RESERVE AIR IS INTENDED EXCLUSIVELY FOR RISE TO THE SURFACE

After this premise, the amount of air used by the diver from the beginning of the descent and during his stay at the bottom until he starts the ascent (Bottom Time) is considered the useful volume of air of the bottle.

Autonomy is the volume of useful (available) air contained in the bottle converted into time of use, i.e. the autonomy will be equal to the division between available air and consumption. The formula for calculating the autonomy (in minutes) of a bottle is as follows:

Autonomy =[C x (PtPr) ] / (c x Pa)

In which:

• C = bottle capacity in liters
• Pt = pressure at which the bottle is loaded
• Pr = reserve pressure (50bar)
• c = surface air consumption (25L/min)
• Pa = absolute pressure (to the depth considered)

#### Autonomy in Minutes

It is intended to make a dive at the depth of 20m, using a bottle of 12 liters, loaded at a pressure of 220bar. What will be the autonomy of the bottle for this diving profile, knowing that its surface air consumption is 25L/min.

• Pa = 3bar
• C = 12L
• Pt = 220bar
• c = 25L/min
• Pr = 50bar
##### Available Air Calculation

C x (PtPr) = 12 x (220-50) = 2040 liters

##### Calculation of Autonomy

Available air ÷ (c x Pa) = 2040 ÷ (25 x 3) = 27.2 min

From the result obtained we can conclude that we can perform the desired dive (20m) with the duration (TF) of 27 minutes.

From the analysis of the Bühlmann table we found that this dive does not require any level of decompression as defined for the CMAS One Star Diver.

#### Autonomy in Liters

It is intended to make a dive to the depth of 20m, whose duration (TF) will be 30min, using a bottle of 15 liters, loaded at a pressure of 230bar. Knowing that your surface air consumption is 25L/min, will the dive be done safely?

• Pa = 3bar
• C = 15L
• Pt = 230bar
• c = 25L/min
• Pr = 50bar
• TF = 30min
##### Available Air Calculation

C x (PtPr) = 12 x (220-50) = 2040 liters

##### Calculation of Autonomy

Available air ÷ (c x Pa) = 2040 ÷ (25 x 3) = 27.2 min

From the result obtained we can conclude that the diver has available for his return to the surface, has 1200 liters of air, in which 750 liters correspond to the reserve 50bar of a bottle of 15L (15L x 50bar),

(2700 – 2250) + 750 = 1200 litres of air,

this guarantees a safety margin that will allow you to make a direct rise to the surface or resolve an unforeseen situation.

# 4. UNDERWATER ROUTE

It depends among other factors, on the interest of divers (leisure, photography, biology, etc.), profile of the dived (avoid the reverse profiles and type yo-yo), dangerous zones, “air consumption”, possibility of the existence of alternative exits, etc.

# 5. ARRIVAL TO THE SURFACE AND WATER OUTLET

It is related to the way divers will be collected by the support vessel (anchored vessel or not) or, if it is made ashore, with the choice of the exit location.

# 6. PREPARATION OF AN EMERGENCY PLAN

All divers and support personnel have to be aware of an emergency plan.