Dive Physics 2

Question 1

Descent Time

Answer 1

-Total elapsed time from when the divers LEAVE the SURFACE to the time when they REACH the BOTTOM

Question 2

Max rate of Descent

Answer 2

• 75 feet per minute max

- Round to next nearest whole minute (ex. 53 fsw = 43 seconds = 1 minute)

Question 3

Bottom Time

Answer 3

(BT)

• Total elapsed time from when the divers LEAVE the SURFACE to the time they LEAVE the BOTTOM
• Round to the nearest whole minute

Question 4

Total Decompression Time

Answer 4

(TDT)

-Total elapsed time from the time the diver LEAVES the BOTTOM to the time they ARRIVE on SURFACE

Question 5

Max Ascent Rate

Answer 5

• 30 fpm
• 1 ft / 2 seconds
• Time needed to “off-gas”

Question 6

Decompression Table

Answer 6

• Structured set of decompression schedules or limits

- Organized in order of increasing bottom times and depths

Question 7

Decompression Schedules

Answer 7

• Specific decompression procedure for a combination of DEPTH and BOTTOM TIME
• Indicated as feet/minutes

Question 8

Decompression Stop

Answer 8

• Specified depth a diver must remain at for a specified time
• Eliminates inert gasses from the body
• “Lets the fizz out”

Question 9

Deepest Depth

Answer 9

-Deepest reading on depth gauge during a dive

Question 10

Max Depth

Answer 10

• Deepest depth attained after correcting depth gauge for error
• Max depth is used on decompression table

Question 11

Scuba Max Depth

Answer 11

• Max depth and deepest depth are the same

- Gauges in scuba are considered error free

Question 12

Surface-Supplied Max Depth

Answer 12

• Surface Supplied uses “pnneumofathometer” not dive gauge
• max depth is = deepest reading on pneumo gauge + pneumo correction factor
• Gauges on surface supplied not considered error free

Question 13

Unlimited / No decompression Limits

Answer 13

(No D)
-Max amount of time that can be spent at a given depth such that safe ascent can be made directly to surface with no stops

Question 14

Types of Decompression Tables

Answer 14

1) Unlimited / No D Limits
- All scuba dives should be here
2) Residual Nitrogen Timetables
- Used for “repet” dives
- RNT
3) Air Decompression Table

Question 15

Unlimited / No D Table

Answer 15

-Identifies that on dives in 20 fsw and shallower, unlimited bottom time can be achieved

Question 16

Selection of Decompression Schedule

Answer 16

• Select schedule at the EXACT or NEXT LONGER bottom time of the dive
• Deviations from established decompression procedures are not permitted except in an emergency and with the guidance and recommendation of a Undersea Medical Officer (UMO) and with the CO’s or OIC’s approval

Question 17

Should you use AIR or AIR/O2 option?

Answer 17

• All SCUBA dives are AIR dives
• Only Surface supplied dives can deliver 100% O2
• 100% O2 allows divers to off gas quicker due to lack of N2

Question 18

Table and Schedule Format; For No D Dive

Answer 18

EX. 43 fsw, BT :40

T/S_45/:46, No D, F

Question 19

Table and Schedule Format for Decompression Dive

Answer 19

EX. LS 0900, Depth 85’, BT :34

T/S_90/:35, AIR D, :04 STOP @ 20’, J

Question 20

LS

Answer 20

Left Surface

Question 21

RB

Answer 21

Reached Bottom

Question 22

LB

Answer 22

Left Bottom

Question 23

R

Answer 23

Reached Stop

Question 24

L

Answer 24

Left a Stop

Question 25

RS

Answer 25

Reached Surface

Question 26

TBT

Answer 26

Total Bottom Time

Question 27

TDT

Answer 27

Total Decompression Time

Question 28

TTD

Answer 28

Total Time of Dive

Question 29

Variations in Rate of Ascent

Answer 29

- Do not ascend faster than your SMALLEST BUBBLES - If ascending faster than 30 fpm, Stop the ascent and allow watches to catch up - Disregard delays of 1 minute or less

Question 30

Delays Deeper than 50'

Answer 30

- Round delay up to nearest whole minute and add to the BOTTOM TIME - Use new decompression schedule, based off new bottom time

Question 31

Delay Shallower than 50'

Answer 31

No D Dive -Delay is accounted for in the ASCENT TIME Decompression Dive -Delay is rounded up to the next whole minute and added to the 1st decompression stop

Question 32

Repetitive Diving Terms

Answer 32

``` Repetitive Dive (repet) -Any dive conducted while N2 is still present in the body from a previous dive Repetitive Group Designator -Ex. "K" "I" "J" -closer to "Z" more N2 in body ```

Question 33

Surface Interval

Answer 33

-Time a diver has been on surface following a dive -Begins as soon as diver surfaces -Ends as soon as descent for next dive begins RS - LS = Surface Interval

Question 34

Residual Nitrogen

Answer 34

- N2 that is still in divers tissues after surfacing from a dive

Question 35

Residual Nitrogen Time

Answer 35

(RNT) | - Time (minutes) added to the bottom time of repet dive to compensate for nitrogen still in solution in divers body

Question 36

Equivalent Single Dive Time

Answer 36

(ESDT) - Time in minutes for which a repet dive is selected - RNT + BT = ESDT

Question 37

If surface interval is less than 10 minutes what is the procedure?

Answer 37

Add bottom times together and use the decompression table for the deeper of the two dive depths

Question 38

RNT Exception Rule

Answer 38

- Occurs when surface interval (SI) between dives is short - Recalculate the RNT requirement by summing the 2 bottom times and using the deepest depth - Compare to the RNT table/schedule and choose the one with the lesser decompression obligation - AKA "Alternative Method"

Question 39

Diving at Altitude

Answer 39

Due to reduced atmospheric pressure dives at altitude require MORE decompression than identical dives at sea level

Question 40

Sea Level Equivalent Depth

Answer 40

(SLED) -Gives corrected sea level equivalent depths and equivalent depth stops for dives 10-190 fsw and for altitudes 1000-10000 ft

Question 41

NAVSEA 00C

Answer 41

Big bosses Call if there are any questions not covered "specific guidance"

Question 42

Altitude Correction Requirements

Answer 42

0-300 ft = No correction 300 - 1000 ft = Correct dives deeper than 145 1000 - 10000 ft = Correct all dives >10000 = Call NAVSEA 00C

Question 43

Flying after Diving

Answer 43

- Ascent to altitude after diving increases risk of DCS - More "fizz" is released due to lowered atmospheric pressure - Determine SI needed by taking the "highest" repet dive group designator achieved in past 24 hours - Commercial flights = 8000 ft - If flying below the altitude where a dive was conducted no SI is required