I am wondering since it is a turboprop plane from Bonaire to Curacao and then on to Aruba on DAE - would this mean lower flight levels and shorter no-fly window from my last dive?

Thanks in advance.

Marc

(Message edited by land_locked on June 23, 2006)

Here's a link to one of the many times this has been discussed here on BT: http://www.oldbonairetalk.com/newsgroup/messages/30/264282.html?1145053177

There are MANY opinions on this subject, which I think can be summed up something like this: there is no exact science for what it takes to get bent, only guidelines, and those that want to be conservative will wait longer before flying and those who want to push it will wait less. You can read the thread above or quite a few others on BT and elsewhere to get more detailed thoughts from lots of people.

Here's another BT thread on the topic: http://www.oldbonairetalk.com/newsgroup/messages/30/261550.html?1142777390

Marc, play it safe so you get to return to Bonaire again and again.

24hrs dude!

Marc
I agree that you should play it safe BUT if you absolutely have your mind set on this I would dive nitrox,with a regular dive computer to give you some extra added insurance--also check with the DAN site as they have set some different rules other than 24 hours

Instead of just parroting the 24 hour rule of thumb, what we really need is factual information on how high the DAE planes fly and also what their pressurizing (if any) does.

Remember, long-haul jets fly at 35,000 feet and are pressurized to about 8,000 feet equivalent.

I'm usually happy getting a full day (3 or 4 dives) in and then flying a puddle-hopper the next morning early...

I'll stay out of this issue, but I can tell you about the DAE flights. The flight from Bonaire to Curacao is 15 minutes and they fly at maybe 5,000 in a pressurized plane. Curacao to Aruba is a 45 minute flight about the same altitude.

By the way DAN has changed their diving after flying guide lines to 18 hours for doing no decompression diving. See information from them below. Obviously the longer you wait the safer it is and every persons pysiology is different.

On May 2, 2002, DAN hosted a one-day workshop to review the state of the knowledge of flying after diving and to discuss the need for new flying after diving (FAD) guidelines for recreational diving.

The last FAD guidelines dated from an Undersea and Hyperbaric Medical Society (UHMS) meeting in 1991. Attended by 40 people representing the recreational diving industry, government agencies and Divers Alert Network, the May workshop was chaired by Dr. Paul Sheffield, organizer and leader of the 1991 UHMS meeting.

Discussions during the morning session reviewed the history of FAD, the development of FAD guidelines and the results of recent studies concerning the risk of decompression sickness in FAD. The afternoon session debated whether changes to the FAD guidelines were warranted by data presented in the morning and, if so, what should those changes be. The workshop concluded that changes were justified. The new guidelines are outlined below and will be formally published this spring in the workshop proceedings.


Provisional Flying After Diving Guidelines

The following recommendations, which apply to recreational divers, represent the consensus reached by attendees at the 2002 Flying After Diving Workshop. The recommendations are based on earlier published work and recent experimental trials as described in the Workshop Proceedings. They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The consensus recommendations should reduce DCS risk during flying after diving but do not guarantee avoidance of DCS. Preflight surface intervals longer than the recommendations will reduce DCS risk further.


Dives within the No-Decompression Limits



A Single No-Decompression Dive: A minimum preflight surface interval of 12 hours is suggested.
Multiple Dives per Day or Multiple Days of Diving: A minimum preflight surface interval of 18 hours is suggested.



Dives Requiring Decompression Stops



There is little experimental or published evidence on which to base a recommendation for decompression dives. A preflight surface interval substantially longer than 18 hours appears prudent.

"I'm usually happy getting a full day (3 or 4 dives) in and then flying a puddle-hopper the next morning early..."

Tom, I think you are risking it, unless your "puddle-hopper" stays below 2000 feet or so. The DAE planes are not puddle-jumpers.

The actual DAN study was to look at flying-aftr-diving DCS incidence epidemiologically. At 17h after multiple dives in a day, the odds were very good. Shorter than that, they rose significantly. The guideline was set at 18h for convenience and a small safety padding. The oft-quoted 24h adds in more safety factor, and is better matched to the off-gassing time from some of the decompression models. What is not published (because the data are so sparse) is for folks who are flying to places like Denver...which is itself at high altitude.
for this case DAN (phone call) suggests 48h, not 24h, before flying.

At the very least, on the day before flying, especially if cutting the 18 or 24h a bit short, one should stay shallow, use 36%, and keep the dives short.

I'm probably older than you, so I'm sensitive to the ability of my body to off-gas. I'd rather miss that final 30-min dive than risk the consequences. Of course, there are no guarantees; all you can do is improve your odds.

- Mel

I'm not trying to push people to do something diving-related they are uncomfortable with. What I'm interested in is factual information that we can use for informed decisions.

I suspect the DAE planes are pressurized, so the bottom line is the "effective altitude" of the passenger cabin. We need someone from here to fly DAE with a personal alitimeter (http://www.thealtimeterstore.com/digital.html) to find the answer for us.

A while back, I got an email from Turks & Caicos Director of Flight Operations saying that their small aircraft are pressurized to sea-level, and that they have (wealthy) divers flying from Provo to Grand Turk and back for a days diving with no ill effects...

Just to add to the controversy, even tho aircraft are pressurized, there is always the small chance that there can be a loss of cabin pressure, or just a decrease, due to malfunction which is not catastrophic... unless you are pushing the no-fly time...IMO better to be safe than bent.

I highly doubt that the DAE planes are pressurized during their flights to Curacao & Aruba. I believe the planes are JetStream 31's, so they are capable of pressurization, but for a 15-20 minute flight, I doubt they do it. A flight at/below 5000 feet mean sea level is already below the pressurization level.

And remember, part of pressurizing means pumping oxygen into the cabin. That means extra weight allowances for the equipment and systems. Extra weight means carrying fewer people, luggage, and fuel. I doubt the tradeoffs are economical for a 15 minute flight below 5000 feet.

As a sidenote, the FAA doesn't even mandate oxygen be supplied to the pilots of an aircraft until the plane is above 12,500 feet, and thats only after being at that altitude for longer than 30 minutes. I believe the mandate for passengers is 14,000 feet. (I'm a little rusty on my FARs, but I think I'm close.....).

So why would DAE pressurize at 5000 feet for a 15 minute flight??

Pressurization and oxygen are two separate things, similar as in scuba diving.

The percentage of O2 in air, even at 40,000 feet, is about the same 21% as at sea level, only the PRESSURE is different. Also, they don't use oxygen in the pressurization process, just a pump to squeeze more thin air into an enclosed space (the aircraft cabin) to get the air pressure back closer to sealevel.

Oxygen is on-board for emergency use only, when those cute little masks drop down due to a pressurization system failure at altitude.

And to answer your question on why DAE would pressurize, it's for passenger comfort, to reduce the equalization/ear-popping sensation below what it would be otherwise.

Still, we need to get someone with a hand-held altimeter on a DAE flight to find out what the situation really is. I'll be doing this myself on a dive trip next May on a short hop between Grand Turk and Provo.

I emailed DAE and asked about flight altitude (between Aruba, Curacao and Bonaire) and pressurization. I got a reply from their Estelle Buchmuller:

"Between the ABC islands we are flying at 5,000 feet with immediate pressurized cabin, to SXM St Maarten 17,000 feet.
For divers the rule is to allow 24 hours between your last dive and your flight. It is your responsibility to follow this rule for maximum security. However if some divers do not want to follow this rule no airline can be held responsible."

She then clarified about the immediate pressurized cabin item:

"As soon as the aircraft is in the air the cabin is pressurized this happens automatically"

That's interesting because here is the response I received from DAE:

Dear Mr. X,

We fly on an altitude of 10.000 feet between Bonaire - Curacao - Aruba.

Kind regards,

Alexandra
Reservations
Dutch Antilles Express

If anyone has a hand-held altimeter they want to lend to me I will be happy to take it on my flights in August. :-)

Marc

A few corrections/comments to the above:

(1) DAE presently uses ATR-42 aircraft on it BON-CUR-AUA flights, not Jetstream 31's. ATR's website says these can be configured with 46 - 50 seats, and I believe DAE now uses the 46 seat configuration. The Jetsream 31 seats 19.

(2) My recollection of the flight announcements is they fly at about 5,000 feet on the above routes.

(3) I can not say for certain whether DAE pressurizes, but based on the 100,000 miles I fly each year on United, most of the big aircraft slowly pressurize (versus the outside ambient conditions) as they gain altitude, eventually stabilizing at an internal pressure equivalent to an altitude of about 7,000 ft. My recollection of the changes I felt in my ears leads me to believe DAE does NOT pressurize its aircraft. Perhaps Marc will get the hand-held altimeter he requested and gives us a definitive answer.

Well, if they fly at 5000 ft, in order to "pressurize" they'd have to suck air *out* of the plane...to get the internal pressure up to 7 or 8000 feet. I doubt it!

- Mel

Last time I was on Bonaire I flew in on Divi Divi. The 10 seat "Islander" plane certainly flew plenty high (I seem to recall 6,000 to 10,000 feet), and this is not a pressurized aircraft. I am quite sensitive to pressure changes and could definitely tell I was at a lower pressure on the Divi Divi flight from CUR to BON than the pressurization level on the AA flight from MIA to CUR.

Now it's certainly possible to transport divers by airplane. This is done by at least one dive operator in Australia... they use a flying boat to ferry divers to/from live aboards, but they fly skimming the wavetops. Must burn a lot of fuel to do that, but doing it avoids risk to the divers.

As an engineer and pilot may I add a few comments:

As stated it would be usual to pressurise even if it is planned to fly at 5,000ft.

Pressurisation is applied differentially, so at 5,000ft it will not be sea level.

Even though an operator may normally fly a route at X ft there are factors that could require them to fly higher, i.e. clearing weather or temporary restricted areas/zones.

From thousands of flights I could not count on my ears to determine if an a/c was pressuring.

DCS does not just depend on SI, it also depends on age, fitness, weight, life style etc.

There is an old Chinese proverb; "You are never as important as you think you are". Perhaps this could be changed to; "You are never as young/fit/slim as you feel".

At the end of the day its your choice, but what would your dependants want?

Have a safe flight.
Dave