Expedition/offshore dive planning.

[stevechesh]

Following on from this thread here:

Skipper only or 2 crew on offshore trips?

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Scenario:

Vessels crew: Skipper and crewmember.

Distance to nearest land: 40 odd miles

Location: Typical Uk sea diving and 10 divers in the water...

Dive is to 80 metres and return to shotline with the usual lazy shot/trapeze in place.


There is an incident and diver X needs removing to a recompression facility
having dived to 80 metres and missed XX minutes of stops (For this scenario, the amount of missed deco is irrelevant,
so let's assume symptoms are being displayed and it's serious).

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Just been doing some figures, and i reckon that you'd be looking at an absolute minimum of 1 hr (and more likely 90 minutes) to get to a chamber, and that's assuming a helicopter will be
manned,started and airborne within 5 minutes of the call.....

At least an hour is a hell of a long time to wait if you are in trouble. . . . .



So, how would you plan an expedition trip like this, and what safety procedures/guidelines would you put in place.....

[nigelH]

Originally Posted by stevechesh

At least an hour is a hell of a long time to wait if you are in trouble. . . . .

So, how would you plan an expedition trip like this, and what safety procedures/guidelines would you put in place.....

It's going to be more than an hour.

Let's max it out. The first diver down has a run away ascent as he arrives back at the bottom of the shot. By the time the skipper and his mate have recovered the him from the water the others have done their bottom time and are committed to two hours on the bar. As the skipper is talking to the CG he sees the lazy start to drift with the tide. There is no recall but the last guy is still on a deep stop.

The first obvious trick I saw on one boat was an oxygen admin set with a bullnose fitting and a huge reel of hose. (Loyal Watcher I think)

[SoggyFox]

couple of question that popped up in my mind....

How long would it take the helicopter to get to the boat?

do all the divers have to be out of the water before the helicopter can take the casualty?

would the boat have to leave the drifting shot/divers to get the casualty away?

[warmwaterdiver]

Originally Posted by SoggyFox

How long would it take the helicopter to get to the boat?

quite a while, depends how far out you are, is the helo busy already? dont assume you'll get the helo (recently they sent the lifeboat out to pick up one bent diver)

Originally Posted by SoggyFox

do all the divers have to be out of the water before the helicopter can take the casualty?

no

Originally Posted by SoggyFox

would the boat have to leave the drifting shot/divers to get the casualty away?

yes. the helo pickup is a moving (not stationary) operation

[SoggyFox]

so if the helicopter had to pick up the casualty the boat would be leaving the divers who're still in the water decoing, is this the done thing?

how long would the boat be away from the divers and would there be anyway for the boat to mark the divers etc for other shipping to see or be aware they are there apart from the bouys on the trapeze?

[warmwaterdiver]

Originally Posted by SoggyFox

so if the helicopter had to pick up the casualty the boat would be leaving the divers who're still in the water decoing, is this the done thing?

yes, as per my answer previously

Originally Posted by SoggyFox

how long would the boat be away from the divers and would there be anyway for the boat to mark the divers etc for other shipping to see or be aware they are there apart from the bouys on the trapeze?

boat has to steer steady course (into wind to help helo control), winchman comes down, lands onto boat, winch hook wound in, winchman assesses casualty, winch hook returns to boat, winchman connects up with casualty (possibly on stretcher), pair winched off boat

good chance the boat will be away from the shot/in water divers for 20mins

[Padowan]

If you're doing this type of dive, and the diver blows ALL his stops with a runaway ascent, then to be honest, he's as good as dead. In water recompression is about the only short term solution that's gonna give him a fighting chance, and there's a whole load of logistics and complications associated with that: Support diver ready to attend, full face mask for gas delivery, diver hydration and a harness system to keep the diver in place in case he passes out or toxes to name a few.

The skipper cannot compromise the safety of the rest of the team in the event of an incident, therefore he can't leave the station (certainly not for long anyway), all he can do is call in for assistance, and do what he can. In water problem are managable with well planned logistics and the skills, ingenuity and equipment of the rest of the team, staged gas, drop tanks etc.

For a lift-off the boat is requested to make headway into the wind, this is so the downdraft from the rotor doesn't blow the hell out of everything on deck. If the boat is unable to move, then I presume they can do a lift-off with the boat stationary, but I'd certainly not want to be on deck! Whether leaving 9 other divers to fend for themselves for a while, is a suitable reason for not being on the move, I don't know, but if I was still on the station, I'd be a bit annoyed if my surface support buggered off - there are 9 other divers that may need the skippers help.

Having a chase boat is a good solution, as one boat can remaing with the station and have the surface support equipment on board, and the main boat can head off with the casualty. Not the easiest or most practical arrangement to plan, but it probably gives the best safety.

[stevechesh]

When i worked on a (military but not coastguard) SAR flight the typical times were:

From the time phone call received by the helicopter crew to getting airborne was between 5 and 10 minutes.

For a 40 mile trip you'd be looking at approx a 20 minute transit time each way.

There would be 2 winching operations. The first would put the aircrewman on the boat and the heli would stand off. Winching on, kitting up and briefing the casualty would take approx 10 minutes.

Aircraft would come back in and winch back up - probably no more than 5 minutes.

Then a 20 minute transit back to a landing site.

Assume the chamber/hospital has a landing pad on the grounds, then you're in the hands of the chamber/hospital staff

Total time so far is: 65 minutes at the very least.

[Padowan]

Originally Posted by SoggyFox

so if the helicopter had to pick up the casualty the boat would be leaving the divers who're still in the water decoing, is this the done thing?

For the lift offs I've been witness to, all divers were on board before the alarm was raised, and we made headway towards the shore, and met the chopper, then headed into the wind for the lift off.

Originally Posted by SoggyFox

how long would the boat be away from the divers and would there be anyway for the boat to mark the divers etc for other shipping to see or be aware they are there apart from the bouys on the trapeze?

Apart from the bouys on the station, there would be no radar marker for the station. This is one of the biggest risks IMO of leaving the station. Getting one diver lifted off to the chamber and returning to find 9 divers mowed down by a freighter is not something I'd want on my concience as a skipper! Last year we had our support boat literally sitting on the station (the station bouys were between the Cat hulls) while a freighter decided that it was too much effort to make a minor course change, I think we were about 100m away from him.

[stevechesh]

Originally Posted by Padowan

If you're doing this type of dive, and the diver blows ALL his stops with a runaway ascent, then to be honest, he's as good as dead. .

Not always true though. There was a recent incident where a diver missed 67 minutes of stops after a 61 metre dive after an uncontrolled ascent and no stops completed. Only symptoms were a tingling arm and messy underpants!

Originally Posted by Padowan

For a lift-off the boat is requested to make headway into the wind, this is so the downdraft from the rotor doesn't blow the hell out of everything on deck. If the boat is unable to move, then I presume they can do a lift-off with the boat stationary, but I'd certainly not want to be on deck! .

Not quite true. Making headway into wind is to increase airflow over the rotors creating lift which means that less power is required when hovering. There is little downdraft once you're under the rotor disc. A stationary lift can be completed, but it depends on the all up weight of the aircraft and whether or not they have to go away a bit and dump fuel to light the aircarft