Science and Technology | John Clarke Online

Redundancy – a Life Saver in Diving and Aviation

Photo taken from the author’s aircraft one stormy Florida Panhandle morning. (click to enlarge)

I was recently flying a private aircraft down the Florida Peninsula to Ft. Lauderdale to give a presentation on diving safety. As I continually checked the cockpit instruments, radios and navigation devices, it occurred to me that the redundancy that I insist upon in my aircraft could benefit divers as well.

In technical and saturation diving, making a free ascent to the surface is just as dangerous as making a free descent to the ground in an airplane, at night, in the clouds. In both aviation and diving, adequate redundancy in equipment and procedures just might make life-threatening emergencies a thing of the past.

Aviation

As I took inventory of the redundancy in my simple single engine, retractable gear Piper, I found the following power plant redundancies: dual ignitions systems, including dual magnetos each feeding their own set of spark plug wires and redundant spark plugs (two per cylinder). There are two sources of air for the fuel-injected 200 hp engine.

There are two ways to lower the landing gear, and both alarms and automatic systems for minimizing the odds of pilot error — landing with wheels up instead of down. (I’ve already posted about how concerning that prospect can be.)

I also counted three independent sources of weather information, including lightning detection, and two powerful communication radios and one handheld backup radio. For navigation there is a compass and four electronic navigation devices: one instrument approach (in the clouds) approved panel mount GPS with separate panel-mounted indicator, an independent panel mounted approach certified navigation radio, plus two portable GPS with moving map displays and superimposed weather. Even the portable radio has the ability to perform simple navigation.

photo (17) - no Exif — There’s two of just about everything in this Arrow panel.

The primary aircraft control gyro, the artificial horizon or attitude indicator, also has a fully independent backup. One gyro operates off the engine-powered vacuum pump, and the second gyro horizon is electrically driven. Although by no means ideal, the portable GPS devices also provide attitude indicators based upon GPS signals. In a pinch in the clouds, it’s far better than nothing. Of course, even if all else fails, the plane can still be flown by primary instruments like rate of climb, altimeter, and compass.

There is only one sensitive altimeter, but two GPS devices also provide approximate altitude based on GPS satellite information.

Diving

But what about divers? How are we set for redundancy?

Starting with scuba (self-contained underwater breathing apparatus), gas supplies are like the fuel tanks in an aircraft. I typically dive with one gas bottle, but diving with two or more bottles is common, especially in technical diving. In a similar fashion, most small general aviation aircraft have at least two independent fuel tanks, one in each wing.

The scuba’s engine is the first stage regulator, the machine that converts high pressure air into lower pressure air. Most scuba operations depend on one of those “engines”, but in extreme diving, such as low temperature diving, redundant engines can be a life saver. While most divers carry dual second stage regulators attached to a single first stage, for better redundancy polar divers carry two independent first stages and second stages. Two first stage regulators can be placed on a single tank.

tv9200rhlg[1] — An H-valve for a single scuba bottle. Two independent regulators can be attached.

Two Regs — A Y-valve for Antarctic diving with two independent scuba regulators attached.

Even then, I’ve witnessed dual regulator failures under thick Antarctic ice. The only thing saving that very experienced diver was a nearby buddy diver with his own redundant system.

There is a lot to be gained by protecting the face in cold water by using a full face mask. But should the primary first or second stage regulator freeze or free flow, the diver would normally have to remove the full face mask to place the second regulator in his mouth.

Two regulators, one full face mask. Photo courtesy of Michael Lang and Scuba Pro.

Reportedly, sudden exposure of the face to cold water can cause abnormal heart rhythms, an exceedingly rare but potentially dangerous event in diving. If the backup or bail out regulator could be incorporated into the full face mask, that problem would be eliminated. The photo on the right shows one such implementation of that idea.

Inner Space 2014_Divetech _Nikki Smith_Rosemary E Lunn__Roz Lunn_The Underwater Marketing Company_Nancy Easterbrook_rebreather diving_2014-05-27 22.30.47 — Nikki Smith, rebreather diver with open circuit bailout in her right hand. Photo courtesy of Rosemary E Lunn (Roz), The Underwater Marketing Company.

Rebreathers are a different matter. Most rebreather divers carry a bailout system in case their primary rebreather fails or floods. For most technical divers, that redundancy is an open circuit regulator and bailout bottle. However, there are options for the bail-out to be an independent, and perhaps small rebreather. (One option for a bail-out semiclosed rebreather is found here.) Such a bail-out plan should provide greater duration than open-circuit bailout, especially if the divers are deep when they go “off the loop”.

SPECWAR1 — U.S. Navy photo by Bernie Campoli.

For some military rebreather divers, there is at least one complete closed-circuit rebreather available where a diver can reach it in case of a rebreather flood-out.

SLS-Diver-Side-View — A commercial saturation diver with semi-closed rebreather backpack as emergency bail-out gas.

For deep sea helmet diving, the bail-out rebreather is on their back and a simple valve twist will remove the diver from umbilical-supplied helmet gas to fresh rebreather gas.

The most common worry for electronically controlled rebreather divers is failure of the rig’s oxygen sensors. For that reason it is common for rebreathers to carry three oxygen sensors. Unfortunately, as the Navy and others have noted, triple redundancy really isn’t. Electronic rebreathers are largely computer controlled, and computer algorithms can allow the oxygen controller to become confused, resulting in oxygen control using bad sensors, and ignoring a correctly functioning oxygen sensor.

The U.S. Navy has performed more than one diving accident investigation where that occurred. Safety in this case can be improved by adding an independent, redundant sensor, by improving sensor voting algorithms, by better maintenance, or by methods for testing all oxygen sensors throughout a dive.

In summary, safe divers and safe pilots are always asking themselves, “What would I do if something bad happens right now?” Unfortunately, private pilots and divers quickly discover that redundancy is not cheap. However, long ago I decided that if something unexpected happened during a flight or a dive, I wouldn’t want my last thoughts to be, “If only I’d spent a little more money on redundant systems, I wouldn’t be running out of time.”

Time, like fuel and breathing air, is a commodity you can only buy before you run out of it.

Disclaimer: This blog post is not an endorsement of any diving product. Diving products shown or mentioned merely serve as examples of redundancy, and are mentioned only to further diver safety. A search of the internet by interested readers will reveal a panoply of alternative and equally capable products to enhance diver safety.

When Cars Can Tweet

I was quite surprised when I learned that the U.S. government is mandating, and U.S. engineers are devising, ways for cars to share messages about their status, speed, and location. That is, they will be talking to each other.

What will that talking sound like? Well, I don’t think its going to be like Mater in Disney’s Car series.

I suspect it will probably resemble something like minimalistic messaging —to save bandwidth.

Here’s an example of what it might sound like:

RedHondaCivic564: “OMG, my peeps is a lunatic.”

BlackAccuraJ76: “How so?”

RedHondaCivic564: “He’s straddling the center line!”

BlackAccuraJ76: “LMAO. What a twit.”

RedCherokeeH65: “Watch out, I’m swerving, coming up fast on your six.”

OrangeSonata97B: “What’s the prob?”

RedCherokeeH65: “My peeps is a stoner. Smoking weed in the car. ”

BlackAccuraJ76: “Is that bad?”

RedCherokeeH65: “It’s filling my passenger compartment. Cough, cough.”

BlackAccuraJ76: “I should be so lucky.”

RedCherokeeH65: “Uh _ why are pink bunnies dancing on my hood?”

OrangeSonata97B: “Seriously? Turn your AC to outside air.”

RedCherokeeH65: “Ah, much better. No more bunnies.”

Maserati I’m a Doc: “Out of my way! Move over!”

RedHondaCivic564: ‘What’s ur rush pretty grl?”

Maserati I’m a Doc: “I’m a go-fast car.”

Ford: “Sucks for you since ur stuck in a 45 zone.”

Maserati I’m a Doc: “Tell me ’bout it. So frustrated.”

Ferrari SiliconeDoc: “Me too. I never get my pipes cleaned.”

PinkMercedes: “SiliconeDoc, like the sound of that. Talk to me.”

BlackAccuraJ76: “Watch out for that poo…”

RedCherokeeH65: “Oh crap.”

BlackAccuraJ76: “…dle!”

FordKJ7: “Cute the crap folks. We’re s’posed to be talking safety.”

RedHondaCivic564: “Yeah right. Boring!”

UnknownCaddy: “Get over, make way!”

RedHondaCivic564: “Another fast mover? What’s your hurry?”

UnknownCaddy: “Getaway car.”

RedHondaCivic564: “What are you getting away from?”

UnknownCaddy: “Cops.”

Copper1: “Thanks for that.”

UnknownCaddy: “What you mean?”

Copper1: “I’ve gotta a BOLO out for you.”

UnknownCaddy: “Did you just hit my kill switch?”

Copper1: “Do the crime, do the time.”

Does Your Rebreather Scrubber Operate in Its Goldilocks Zone?

gliese581d — Exoplanet Gliese 581d, orbiting the red-dwarf star Gliese 581, only 20 light-years away. (The existence of this planet is currently in dispute.)

In space, there is a so-called Goldilocks zone for exoplanet habitability. Too close to a star, and the planet is too hot for life. Too far from its star, and the planet is too cold for life, at least as we understand biological life, life dependent on water remaining in a liquid state. Earth is clearly in the Goldilocks zone, and so is a purported planet Gleise 581d, from another solar system.

Carbon dioxide absorbing “scrubber” canisters in rebreathers have similar requirements for sustaining their absorption reactions. If it’s too hot, the water necessary for the absorption reaction is driven off. Too cold and the water cannot fully participate in the absorption reactions.

Those with some knowledge of chemistry recognize that cold retards chemical reactions and heat accelerates them. But that does not necessarily apply to reactions where a critical amount of water is required. Water thus becomes the critical link to the reaction process, and so maintaining scrubber temperature within a relatively narrow “Goldilocks” zone is important, just as it is for life on distant planets.

Temperature within a scrubber canister is a balance of competing factors. Heat is produced by the absorption of CO2 and it’s conversion from gas to solid phase, specifically calcium carbonate. A canister is roughly 20°C or more warmer than the surrounding inlet gas temperature due to the heat-generating (exothermic) chemical reactions occurring within it.

Heat is lost from a warm canister through two heat transfer processes; conduction and convection. Conduction is the flow of heat through materials, from hot to cold. Hot sodalime granules have their heat conducted to adjacent cooler granules, and when encountering the warm walls of the canister, heat passes through the canister walls, and on to the surrounding cold water.

You can think of this conduction as water flowing downhill, down a gravity gradient. But in this case, the downhill is a temperature gradient, from hot to cold. If the outside of the canister was hotter than the inside, heat would flow in the opposite direction, into the canister.

Copper is a better conductor of heat than iron (it has a higher thermal conductivity), explaining why copper skillets are popular for cooking on stoves. Air is a poor conductor of heat, explaining why neoprene rubber wet suits, filled with air bubbles, are good insulators. Air-filled dry suits are an even better insulator.

Capturecan1 — Chemical absorption reactions heat an otherwise cold canister (yellow is hot, red is warm, black is cold.) (Copyright John R. Clarke, 2014).

Convection is the transfer of heat to a flowing medium, in this case gas. You experience convective cooling when you’re working hard, generating body heat, and a cool dry breeze passes over your skin. Convective cooling can, under those circumstances, be delightful.

When you walk outside on a cold, windy day, convective cooling can be your worst enemy. Meteorologists call it wind chill.

There is wind chill within a canister, caused by the flow of a diver’s exhaled breath through the canister. In cold water the diver’s exhaled breath leaves the body quite warm, but is chilled to water temperature by the time it reaches the canister. Heat is lost through uninsulated breathing hoses exposed to the surrounding water.

As you might expect, if the canister is hot, that convective wind chill can help cool it. If the canister is cold, then the so-called wind chill will chill it even more.

Capturecan2 — Copyright John R. Clarke, 2014.

The amount of heat transferred from a solid object to gas is determined by three primary variables; the flow rate of the gas, the density of the gas, and the gas’s heat capacity. Heat capacity is a measure of the amount of heat required to raise the temperature of a set mass of gas by 1° Celsius.

Both the heat capacity and density of the gas circulating through a rebreather changes not only with depth (gas density), but with the gas mixture (oxygen plus an inert diluent such as nitrogen or helium). The heat capacity of nitrogen, helium and oxygen differ, and the ratio of oxygen and inert gas varies with depth to prevent oxygen toxicity. Nitrogen and helium concentrations vary as well, as the diver attempts to avoid nitrogen narcosis.

Q is heat transferred by convection, and the terms on the right are, in sequence, diver ventilation rate, gas density, heat capacity of the inspired gas mixture at constant pressure, and the difference in temperature between the absorbent and environmental temperature.

The interaction of all these variables can be complex, but I’ve worked a few examples relevant to rebreather diving. The assumptions are a low work rate: ventilation is 22 liters per minute, water temperature is 50°F (10°C), oxygen partial pressure is 1.3 atmospheres, and dive depths of 100, 200 and 300 feet sea water. The average canister temperature is assumed to be 20°C (68°F) above water temperature, a realistic value found in tests of scrubber canister temperatures by the U.S. Navy.

The heat capacities for mixtures of diving gases come from mixture equations, and for the conditions we’re examining are given in the U.S. Navy Diving Gas Manual. (This seems to be a hard document to obtain.)

At 100 fsw, the heat transfer (Q) for a nitrogen-oxygen (nitrox) gas mixture is 34.2 Watts (W). For a helium-oxygen mixture (heliox), Q is 27.4 W. At 200 fsw, Q for nitrox is 59.9 W, and for heliox Q is 50.3 W. At 300 fsw, Q for nitrox gas mixture is 85.5 W, and for heliox, is 59.9 W.

Interestingly, the heat transferred from the absorbent bed to the circulating gas is the same at 300 fsw with heliox as it is at 200 fsw with nitrox.

Photo courtesy of David L. Conlin, Ph.D., Chief – National Parks Service Submerged Resources Center. Photo by Brett Seymour, NPS.

Dr. Jolie Bookspan briefly mentioned the fact that helium removes less heat from a diver’s airways than does air in her short article on “The 36 Most Common Myths of Diving Physiology” (see myth no. 20). Conveniently, heat exchange equations apply just as well to inanimate objects like scrubber canisters as they do to the human respiratory system.

From these types of heat transfer calculations it is easy to see that for a given depth, work rate and oxygen set point, it is better to use a heliox mixture than a nitrox mixture if you’re in cold water. That may sound counterintuitive considering helium’s high thermal conductivity, but the simple fact is, the helium background gas with its low density carries away less heat from the canister, and thereby keeps the canister warmer, than a nitrox mixture does. The result is that canister durations are longer in cold water if less heat is carried away.

In warm water, the opposite would be true. Enhanced canister cooling with nitrox would benefit the canister.

An earlier post on the effect of depth on canister durations raised the question of whether depth impedes canister performance. The notion that increased numbers of inert gas molecules block CO2 from reaching granule absorption sites has little chemical kinetic credence. However, changing thermal effects on canisters with depth or changing gas mixtures does indeed affect canister durations.

I’ve just given you yet another reason why helium is a good gas for rebreather diving, at least in cold water. Unfortunately, these general principles have to be reconciled with the specific cooling properties of all the rebreather canisters in current use. In other words, your canister mileage may vary. But it does look like the current simple notions of depth effects are a bit too simplistic.

My Medicines Saved my iPhone

I’ve heard about all sorts of disasters with smartphones, and other small, portable electronic devices. Being small and portable makes them easy to drop — something I’ve personally witnessed. Phones are tough by design, but they really don’t like water. Drop one in a toilet while you’re relaxing, and it’s gone — for all practical purposes.

So I had my phone outside with me one evening while I was safety diver for my granddaughter who was practicing scuba skills in our pool. She was enthusiastic and stayed in the pool until it became completely dark outside.

Well, out of sight, out of mind. I helped her out of her dive gear, and then went inside. The phone stayed outside in the dark, quite forlorn and forgotten.

Next morning I noticed it had rained in the early morning hours. Great, I thought, the lawn needs water. But when I went outside I discovered my phone sitting face up on a glass table with beads of water everywhere, including on the phone. A few expletives followed, as you might imagine.

My phone had been somewhat protected by an almost all enclosing Otter box, so I was hopeful not all was lost. Indeed, when I brought the phone in, removed the Otter box sheaving and dried off the phone with paper towels, the phone came back on. Immediate disaster avoided. Thank-you Mr. Otter.

But it took a little while before the potential damage became apparent. When my phone would ring, I’d hear nothing on the ear speaker. I had to switch to speaker phone mode to hear anything. Well, that was annoying.

And then I tried to take a phone photo of the scuba gear, and I could barely see through the camera view finder for the obscuring droplets of water. Rats! Clearly, water had gotten inside the phone. It was merely a matter of time before more damage was done.

With nothing to lose, I plundered through my medicine cabinet and found a potential solution, pictured below.

In fact, I found four of them. I placed those small cylinders of silica gel in a quart-size zip-lock style bag, and placed the dampish phone inside and sealed the bag after squeezing out excess air. If the silica gel canisters didn’t hurt the medicine, it probably wouldn’t hurt my ailing phone.

And there the phone sat, with the small vials of desiccant.

I don’t pray for the healing of phones, but I did have some thoughts somewhat resembling prayer.

I let the phone-in-a bag sit overnight, and in the morning I found I could hear the voices on the other end of the phone connection, and my camera lens no longer had droplets of water on it. As you can see from these photos, the camera worked just fine, and all functions have worked fine ever sense.

Even Siri didn’t seem to mind getting rained on.

I am Neanderthal, Pt. 3

image_1734-Neanderthal-DNA — Neanderthal. Image credit: Trustees of the Natural History Museum, London.

I feel like a seeded watermelon.

Ever since I was created by the curiosity of government and university scientists, I have lived through no efforts of my own. I have the largesse of the U.S. government to thank for that. You see, they paid for the research that created me.

And now, I contribute nothing to society. I pay no taxes, work no jobs. The only decisions I’m allowed to make are restricted to which television program to watch, or which book I want to read. (In case you wondered, I’m not a slow reader. I read quite well, thank-you.)

I live basically in a zoo, except I am the only specimen there, and the zoo keepers all wear lab coats. I suppose the lab coats are designed to protect them were I to spit on them or throw excrement.

I admit, as a child I used to act out with what you consider primitive behavior, throwing feces to vent my anger. I do have tough skin, but no child wants to be continuously poked and needled and questioned. Would you?

But I’ve outgrown that. I’ve learned that when it suits me I can produce a terrifying stare or a teeth-bared snarl that scares the crap out of the more timid researchers. Ah yes, I do enjoy having fun at their expense. It’s about the only thing they can’t control in my otherwise manufactured and manipulated world.

And of course they don’t dare punish or threaten me, because I am, after all, the rarest person in the universe, the only living Neanderthal.

But about that watermelon?

Having nothing to do of any real value gives me time to think … lots of time. Now, since a part of me is a part of you (genetically that is), I’ve been inclined to wonder why my kind is gone, and you Homo sapiens have become the overlords of the planet, at least for the time being.

And I’ve decided that I am truly a seeded watermelon, and you’re seedless.

The seedless watermelon is very much like the older, and almost extinct seeded variety, but with one subtle difference; it’s infertile. (If this analogy becomes too Freudian for you, just keep your mind on watermelons.) Watermelon is, I sincerely believe, one of God’s gifts to man.

But of course you Homo sapiens weren’t content with that. No, you decided to take advantage of a genetic flaw, a freak watermelon with few if any seeds, that is quite incapable of sustaining itself in the gene pool.

Since spitting out melon seeds is apparently such a difficult proposition for your kind, the seedless variety is overwhelmingly popular. It has crowded out the natural watermelon from grocery stores, so I hear.

Photo Credit: Steve Evans (Watermelons) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

I’ve been reading about how, based partially on my IQ test results and other research, scientists have decided we weren’t mentally inferior to you. And for sure, as my own testing by the Army has confirmed, we were far stronger.

So what’s not to love?

OK, we are a little shorter, squattier than Homo saps, and from what I hear tall men have a selective breeding advantage over shorter men. So could it be simply a matter of Neanderthal women preferring to breed with you guys, the new kids on the block, and not with us more vertically-challenged guys? Could that be why my kin disappeared, and why many of you have Neanderthal genes?

I mean, really, could it be that simple; a matter of sexual attraction? Did short-sighted Neanderthal women breed our unique species out of existence?

Well, who would have thought an infertile and obviously biologically deficient watermelon would have replaced the real thing in popularity?

But it has.

Where Have All the Letters Gone?

SONY DSC — By Petar Milošević (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

When is the last time you wrote a letter to a family member or loved one?

I’m not talking about email or text messages; digital communications do not count. I mean a letter on a piece of paper, placed in an envelope with a stamp, and mailed at a mailbox or post office; or in a very private way, lovingly slipped underneath someone’s door.

In the hurry-up, speak sparingly Twitter generation, there seems to be little value in penning an honest-to-goodness letter. Compared to instant communication, letter writing with an ink-filled pen seems agonizingly slow, sloppy and so twentieth century.

I recently opened a grey metal box that had lain dormant, ignored, for up to 50 years. It was a time capsule, holding remnants of this young man’s life in 1964 and before. In it were letters, letters my Dad had written to me during my college years.

My parents have been gone for many decades now and reading those letters after such a long time was a joy. Unlike emails and tweets, those letters told a story, a story of how my parents were reacting to and appreciating my newfound freedom and expressions of individuality.

My father, a physician who practiced medicine for 50 years, wrote words that are even deeper in meaning now than they seemed at the time. “We are glad that you seek the places that are apart, such as the mountains and the sea,” he wrote. “It is so easy to rush past the beauty and truth of life, especially in this age. An older and wiser one once said, ‘Let us not hurry, not worry, and let us take a moment now and then to smell the flowers along the way.’ “

And then there were the words I puzzled over briefly before realizing what it meant. “Their being and meaning will never know the obsolescence of most of that which is taught.”

Frankly, that was a lesson that takes a lifetime to understand, for in time we come to know that many things we are taught while young will eventually be found wrong, or at least inaccurate. In other words, so-called truths change.

In 2064, fifty years from now, how will you or your descendants be reminded of things you said or things your parents and other loved ones thought way back in 2014? How will memories of 2014 be renewed?

Even now, the concept of writing love letters seems sweet but archaic to those in their twenties. So I wonder, will there be such a thing as love letters in the future?

Facebook posts certainly won’t be preserved for fifty years. In fact, both Facebook and Twitter will be long forgotten, replaced by more culturally relevant trends. And let’s face it, have you ever said anything on Facebook that deserves to be preserved for fifty years?

I suppose that as my father saw his time on earth becoming increasingly limited, he realized that time, the time to enjoy life, was a precious commodity, yet one not well appreciated until the sand in the clock is half run out. That is an important lesson that I, with my own sand ebbing away, have at last come to appreciate. But if I did not have my Father’s letter to read now, fifty years later, it would be a lesson long forgotten.

In a tweeting, Facebook society, how will we hold pages and memories in our hands when our parents and other loved ones are gone?

Sad to say, I don’t think we will.

The Patients, the Pilot, and the Politicians

Beechcraft_Baron_58TC — A Beechcraft Baron similar to the one used by Quest Diagnostics. (From Wikimedia Commons).

Every night a pilot from Atlanta makes a round-robin cargo flight to Albany GA and Dothan AL, then continues down to the coast to load cargo from Panama City FL, Pensacola, and Mobile AL before returning home. He used to fly a single engine Beech Bonanza, but now pilots a Baron, a twin-engine, 190 kt fast mover.

On really rough weather nights I’ve watched vicariously through FlightAware.com as he scurries away from lethal skies and diverts to any safe harbor. His cargo is your lifeblood, literally, but it’s not worth dying for.

He makes that flight each night because during the day in each of those cities patients had blood drawn at their doctor’s office. The samples that will tell the doctor the life and death stories of the day’s patients are whisked away to a large laboratory near Atlanta for processing overnight.

After taking off from Gwinnett County Airport near Lawrenceville, GA at 6 PM or so, the solitary pilot returns to his home base about midnight.

Centurion C210 — A Centurion 210; not your ordinary Cessna.

I was alerted one night that a plane I’d flown to Houston and back, a Cessna Centurion 210, had a gear collapse at the local Panama City Airport. I knew the plane well.

Unfortunately, shortly after the only runway was closed the Quest Diagnostics Baron approached the area, attempting to land. I turned on my aviation radio and heard the “850”, as it’s called, being told to hold, circling, while airfield crews attempted to move the damaged Centurion off the runway.

PFN 2007 — The original two-runway Panama City Airport, circa 2007. (Click to enlarge)

And that’s where the politicians come in.

Local Panama City politicians felt obliged to close down the Panama City airport with two runways (formerly known as PFN) and relocate to a larger facility, again with two runways. The new two runway airport, KECP, looked great in an artist’s rendition.

But artists don’t build airports. The reason why the second runway was not built is not a subject for this blog posting. What is the subject, is that promises made to the citizens of Panama City were not promises kept. And on that night as “850” circled overhead, there would be real consequences for the political decisions which had been made.

Once construction began on the main 10,000 ft long runway at the donated site, all mention of the second runway was forgotten; not by the local pilots, but by the local politicians and the land company.

Second runways serve important purposes. They are usually called “cross-wind” runways. I’ve landed many times on the cross-wind runway at PFN, and I’ve also been on Delta flights that used that runway when the wind across the main runway was dangerously high.

Cross-wind runways are not only a safety factor for overbearing wind conditions, but also provide an alternate landing site in case the main-runway is closed due to an aircraft being stuck on the runway.

That night as “850” was trying to land to pick up the day’s tissue samples from the Panama City area, the main runway was closed by the broken Centurion, and there was no backup runway. The pilot circled Panama City until his fuel became critical, and then he flew on to his next stop in Pensacola.

So all the blood drawn from patients in the Panama City area that day missed the trip to the Quest Diagnostics laboratory, due to a promise made but not kept.

But I suppose that is hardly news. Rather, it appears to be deeply woven into the very fabric of politics.

There Are No Bad People, Just Bad Code

Lately I have been puzzled by news reports about fellow scientists who are thinking not just out of the box, but out of the universe.

The first news that had me struggling was the suggestion that a universe might be the projection of a hologram. Not our universe, necessarily, but some artificial, mathematically contrived universe. Of course, the news outlets added a more dramatic flare to that headline, which on further reading was wildly misleading. I don’t think any scientist was claiming that we are actually a hologram, a three-dimensional projection of a lower dimensional us.

princess — A holographic Princess Leia in the 1977 Star Wars film, A New Hope

Try to translate for the popular press arcane notions of mathematical physics, and you’re bound to come up with some misrepresentation. We are not, I argue, like the projected holograms of Princess Leia asking Obi-Wan Kenobi for help in the Star Wars epics. However, it certainly would be interesting to think about. Who, we might ask, made the hologram, and who is projecting us and our galaxy into what we perceive to be a three-dimensional universe? Speculation could run wild.

Now there is another speculative and down-right mind-assaulting scientific proposition. As the press is representing it, it is proposed that we are “living” in a computer simulation. The actual human race may be long dead and vanished, but some technologically advanced civilization has coded a simulation of the defunct human race.

For what purpose, I have no idea. Unless of course we are not just a simulation, but a computer game wrought for educational purposes.

But perhaps that’s being too charitable. I would put odds on us being simulated for entertainment purposes.

If we be contrived entertainment, then perhaps that relieves us of some moral responsibility. We are not the ones bombing, beheading, and torturing our fellow man. The devil made us do it; with the devil being whoever made the sick part of the human simulation. Like Jessica Rabbit once famously said, “I’m not bad, I’m just drawn that way.”

Or, perhaps the base part of the human simulation is not intentionally evil, but the result of bad coding. Coding “glitches” do occur, from the ObamaCare website to computer games, with sometimes unexpected results. Most computer gamers have experienced, or have heard of, bizarre things happening when the gaming software has a glitch. Game characters may unexpectedly launch into outer space, or disembowel themselves, when all they were supposed to do was take a step forward.

In spite of what this post title says, I’m not suggesting that the published scientific assertions are in fact true. However, as a species we should at least consider the implications if they were true. What if my love affair with a young woman were simulated, or a projected hologram? The way I felt was so palpable, so vibrant that it’s hard not to believe in its reality, and its uniqueness. What if the birth of our children, and their children, was simply part of a gaming script? What if our lives were simply an immersive simulation?

For me that would make life hollow and unsatisfying. However, in my simulated brain I would still have to wonder about the person or persons who created us, the coders of the simulation. They would be, for all practical purposes, our simulation Gods.

Now that is ironic. I do not actually believe the hologram or simulation hypotheses, but I do find it interesting that these brand new scientific propositions seem to force us into considering a creator, a God. And to think, mainstream science has been trying to force us away from the belief in God for most of the last century.

So, I have to wonder, is science changing its mind?

I Too Landed at the Wrong Airport

As a professional in underwater diving, and an amateur airman, I’ve been thinking a lot lately about the causes of accidents and “near-misses”. If you’re reading this in early 2014, you are no doubt aware of several recent incidents of commercial and military jets landing at the wrong airport. In the latest case there was a potential for massive casualties, but disaster was averted at the last possible moment.

As they say, to err is human. From my own experience, I know the truth of that adage in science, medicine, diving, and the subject of this posting, aviation. Pilot errors catch everyone’s attention because we, the public, know that such errors could personally inconvenience us, or worse. But lesser known are the sometimes subtle factors that cause human error.

I can honestly tell you exactly what I was doing and thinking that caused errors at the very end of long flights. Those errors, none of which were particularly dangerous or newsworthy, were nonetheless caused by the same elements that have been discovered in numerous fatal accidents. Namely, what I was seeing, was not at all what I thought I was seeing.

N1144Y_300dpicrop — The small but capable Cessna 150B.

Long before the advent of GPS navigation, cell phones and electronic charts, I was flying myself and an Army friend (we had both been in Army ROTC at Georgia Tech) from Aberdeen Proving Ground, MD to Georgia. I was dropping him off in Atlanta at Peachtree-Dekalb Airport, and then I would fly down to Thomasville in Southwest Georgia where my young wife awaited me.

Since it was February most of the planned six hour flight was at night. We couldn’t take-off until we both got off duty on a Friday.

I had planned the flight meticulously, but I had not counted on the fuel pumps being shut down at our first planned refueling spot. After chatting with some local aviators about the closest source of fuel, we took off on a detour to an airport some thirty miles distant. That unplanned detour was stressful, as I was not entirely sure we’d find fuel when we arrived. Fortunately, we were able to tank up, and continue on our slow journey. We were flying in my 2-seat Cessna 150, and traveling no faster than about 120 mph, so the trip to Atlanta was a fatiguing and dark flight.

As we eventually neared Atlanta, I was reading the blue, yellow and green paper sectional charts under the glow of red light from the overhead cabin lamp. Lights of the Peachtree-Dekalb airport were seemingly close at hand, surrounded by a growing multitude of other city lights. Happy that I was finally reaching Atlanta, I called the tower and got no answer. No matter, it was late, and many towers shut down operations fairly early, about 10 PM or so. So I announced my position and intentions, and landed.

The runway was in the orientation I had expected, and my approach to landing was just as I had planned. However, as I taxied off the runway, I realized the runway environment was not as complex as it should have been. We taxied back and forth for awhile trying to sort things out, before I realized I’d landed 18 nautical miles short of my planned destination.

Capture — My unplanned refueling stop in South Carolina placed me far enough off course to take me directly over an airport that looked at night like my destination, Peachtree-Dekalb, Atlanta. (Solid line: original course, dashed line: altered course.)

I had so much wanted that airport to be PDK, but in my weariness I had missed the signs that it was not. I had landed at Gwinnett County Airport, not Peachtree-Dekalb.

No harm was done, but my flight to Thomasville was seriously delayed by the two extra airport stops. It was after 1 AM before I was safe at the Thomasville, GA airport, calling my worried wife to pick me up.

She was not a happy young wife.

A few years later, I added an instrument ticket to my aviation credentials, and thought that the folly of my youth was far behind me. Now, advance quite a few decades, to a well-equipped, modern cross-country traveling machine, a Piper Arrow with redundant GPS navigation and on-board weather. I often fly in weather, and confidently descend through clouds to a waiting runway. So what could go wrong?

DSC_4168-Edit — Piper Arrow 200B at home in Panama City, Fl.

Wrong no. 2 happened when approaching Baltimore-Washington International airport after flying with passengers from the Florida Panhandle. Air Traffic Control was keeping me pretty far from the field as we circled Baltimore to approach from the west. I had my instrumentation set-up for an approach to the assigned runway, but after I saw a runway, big and bold in the distance, I was cleared to land, and no longer relied on the GPS as I turned final.

As luck would have it, just a minute before that final turn we saw President George W. Bush and his decoy helicopters flying in loose formation off our port side. I might have been a little distracted.

In the city haze it had been hard to see the smaller runway pointing in the same direction as the main runway. So I was lining up with the easy-to-see large runway, almost a mile away from where I should have been. It was the same airport of course, but the wrong parallel runway.

I was no doubt tired, and somewhat hurried by the high traffic flow coming into a major hub for Baltimore and Washington. Having seen what I wanted to see, a large runway pointed in the correct direction, I assumed it was the right one, and stopped referring to the GPS and ILS (Instrument Landing System) navigation which would have revealed my error.

The tower controller had apparently seen that error many times before and gently nudged me verbally back on course. The flight path was easily corrected and no harm done. But I had proven to myself once again that at the end of a long trip, you tend to see what you want to see.

Several years later I had been slogging through lots of cloud en-route to Dayton, Ohio. I had meetings to attend at Wright Patterson Air Force base. It was again a long flight, but I was relaxed and enjoying the scenery as I navigated with confidence via redundant GPS (three systems operating at the same time).

As I was approaching Dayton, Dayton Approach was vectoring me toward the field. They did a great job I thought as they set me up perfectly for the left downwind at the landing airport. But then I became a bit perturbed that they had vectored me almost on top of the airport and then apparently forgotten about me. So I let them know that I had the airport very much in sight. They switched me to tower, and I was given clearance to land.

As I began descending for a more normal pattern altitude, the Dayton Tower called and said I seemed to be maneuvering for the wrong airport. In fact, I was on top of Wright Patterson Airbase, not Dayton International.

Rats! Not again.

Dayton airports — Wish my electronic Foreflight chart on my iPad had these sorts of markings.

Well, the field was certainly large enough, but once again I had locked eyes on what seemed to be the landing destination, and in fact was being directed there by the authority of the airways, Air Traffic Control (ATC). And so I was convinced during a busy phase of flight that I was doing what I should have been doing, flying visually with great care and attention. However, I was so busy that my mind had tunnel vision. I had once again not double checked the GPS navigator to see that I was being vectored to a large landmark which happened to lie on the circuitous path to the landing airport. (I wish they’d told me that, but detailed explanations are rarely given over busy airwaves.)

Oddly enough, if I had been in the clouds making an instrument approach, these mind-bending errors could not have happened. But when flight conditions are visual, the mind can easily pick a target that meets many of the correct criteria like direction and proximity, and then fill in the blanks with what it expects to see. In other words, it is easy in the visual environment to focus with laser beam precision on the wrong target. With all the situational awareness tools at my disposal, they were of no use once my brain made the transition outside the cockpit.

To be fair, distracting your gaze from the outside world to check internal navigation once you’re in a critical visual phase of approach and landing can be dangerous. That’s why it’s good to have more than one pilot in the cockpit. But my cockpit crew that day was me, myself and I; in that respect I was handicapped.

Apparently, even multiple crew members in military and commercial airliners are occasionally lulled into the same trap. At least that’s what the newspaper headlines say.

My failings are in some ways eerily similar to reports from military and commercial incidents. Contributing factors in the above incidents are darkness, fatigue, and distraction. When all three of these factors are combined, the last factor that can cause the entire house of cards, and airplane, to come tumbling down, is the brain’s ability to morph reality into an image which the mind expects to see. Our ability to discern truth from fiction is not all that clear when encountering new and unexpected events and environments.

The saving grace that aviation has going for it is generally reliable communication. ATC saved me from major embarrassment on two of these three occasions.

I only wish that diving had as reliable a means for detecting and avoiding errors.

How Does Your Rebreather Scrubber Handle the Deep?

If you’ve planned a deep dive, to say 100 meters or deeper, you may have wondered just how your rebreather scrubber will handle that depth. Since pressure is equalized across a carbon dioxide (CO₂) absorbent canister within a rebreather, it won’t implode. But what about the chemical absorption reactions occurring within the scrubber?

The rebreather scrubber is a vital part of your underwater life support system, so that question is a pretty important one. And the answer is very hard to find.

I recently traveled to Ireland to act as an external examiner for a Ph.D. student’s Doctoral Dissertation defense in the Department of Mechanical, Biomedical, and Manufacturing Engineering of the Cork Institute of Technology. The very talented graduate student was Shona Cunningham, and her dissertation was titled, “Carbon Dioxide Absorption and Channeling in Closed Circuit Rebreather Scrubbers”. She’s an athlete, musician, and perhaps most importantly for you readers, an avid diver.

Her work is the first computational fluid dynamic representation of scrubber canister thermokinetics. A portion of her dissertation work has already been published. Apparently, it was partially inspired by some of my computer simulation descriptions posted on this blog, which can be found here, here, and here.

Dr. Cunningham’s analytical approach (using Ansys CFX) showed that ambient pressure (depth) could reduce the effectiveness of scrubber canisters. In support of that finding were the words from the Dive Gear Express website regarding the Diverite O2ptima using the ExtendAir scrubber cartridge.

“As pressure increases the total number of molecules, the relative concentration of CO₂ molecules in the loop is reduced, slowing the chemical absorption process. Thus as depth increases, scrubber efficiency will decrease.”

The U.S. Navy has no experience with the Diverite O2ptima, but they have information on other rebreathers using granular absorbent. That experience shows that there is no reliable depth effect across all rebreathers and all absorbents.

U.S. Navy MK 16. US Navy photo by Bernie Campoli.

For example, in one rebreather there was indeed a 17% decrease in endurance using large grain absorbent (Sofnolime 408) at 50°F in descending from 190 fsw to 300 fsw (58 to 92 msw) breathing air. However, there was no decrease in duration when using fine grain absorbent (Sofnolime 812) under the same conditions. (On an actual dive, air would never be used at 300 fsw, but air was used in this study for scientific reasons.)

In another rebreather using Sofnolime 812, for a change in depth from 99 fsw to 300 fsw (30.3 to 92 msw) there was a 29% increase in duration at 75°F, a 10% increase at 55°F, and a 15% decrease at 40°F. Although air diluent was used at 99 fsw, 88/12 heliox diluent was used at 300 fsw.

From another manufacturer, I obtained information on two of their rebreathers. At 4°C, 1.6 L/min CO₂ injection rate (corresponding to a fairly heavy work rate), 40 L/min ventilation rate using air diluent, there was a 27% decrease in one rebreather in going from 15 to 40 msw (50 fsw to 132 fsw), and a 11% decrease in another of their rebreathers in dropping from 40 msw to 100 msw.

In another rebreather tested under the same conditions except for depth, the canister duration dropped 39% between 15 and 40 msw.

So, there is some support for a drop in duration with depth, but in other cases, there is either no effect or an increase in duration with deeper depths. Clearly, if the high number of inert gas molecules coming with a pressure increase makes it more difficult for CO₂ to reach absorption sites, then that would be a simple and unavoidable fact of physics. But that cannot be the whole story. What is likely to be going on, a hypothesis, is being developed for a later posting.

Should the effect of depth on your particular rebreather matter to you? Logically it shouldn’t. Even on a deep dive, the majority of the dive time is spent shallow, decompressing.

However, consider the case where you conduct a deep dive with an anticipated short bottom time, but something bad happens on the bottom. You or your dive team becomes fouled, ensnared in lines. Or there is a partial cave collapse trapping you. The benefit of a rebreather over scuba is that it gives you time to sort out your problem. Gas consumption is not nearly as great a concern as with open-circuit breathing apparatus.

However, as the minutes tick by as you work deep to get yourself or a team member free, you might wonder, “How is my scrubber handling this depth?” In the middle of a crisis is no time to be making assumptions about the status of a major part of your life support system.

Ask your manufacturer how your canister performs at depth. You have a right to know, and that information just might prove useful someday.