Sunrise

Is the Air on My Plane Safe?

Like all technical questions involving complex interactions between humans, other humans, and complicated mechanical systems, the answer is solidly "it depends".

For starters, it depends on the definition of the word "safe". Humans are famously bad judges of risk as I observe on a nearly daily basis. Statistically, perhaps only elevators are a less risky form of transportation than commercial aviation. And yet watching ostensibly normally functioning people come close to losing their minds as they board an airplane gives one pause when giving odds on the likelihood of the continued existence of the species. But never mind.

Let's start with the basics of how airplane pressurization and air conditioning work. Then we'll talk about the resulting air quality in the cabin and the risk of disease transmission which has been on everyone's mind.

It's Just Like a Balloon

Think of the aircraft as a balloon with two holes in it. Air is being blown into one hole to try to inflate the balloon but simultaneously leaking out of the other. If the amount of air entering equals the amount leaving, the balloon grows neither larger nor smaller. In a nutshell, that is how aircraft pressurization works.

The air we breathe on this planet is made up of many gases with the primary ones being nitrogen (78%), oxygen (21%) and argon (1%) along with many other gases making up the remaining bits. It is the partial pressure of oxygen which keeps you alive. As you climb higher into the atmosphere, that pressure drops. Most healthy humans can function normally up to an altitude of about 10,000 feet and above 14,000 feet cognitive function is impaired in most people.

Of course conditioned and trained people can go much higher with climbs up Everest at 35,000 feet being accomplished without oxygen. But for most people, going above 10,000 feet results in discomfort and light hypoxia. For this reason, aircraft cabins are always pressurized to an altitude below 10,000 feet.

Why not keep airplanes pressurized to sea level pressure? It's an engineering tradeoff. Most commercial aircraft are built to withstand a pressure differential of about 8 psi meaning the maximum difference between the air inside the plane and that outside is about 8 psi. This translates to a cabin altitude of about 8500 feet when the airplane is at it's maximum altitude of 40,000 feet. It could be built to withstand higher pressure (and some business jets are) but the cost and weight goes up greatly with thicker skin.

Now back to our balloon analogy. The air coming into the cabin is bled from the engines. Air enters the engine and travels through a series of compressor stages where most of it is used in combustion with the fuel. However some high pressure and temperature air is bled off and fed to a unit known as the air cycle machine. Using a linear flow model as opposed to a Carnot cycle used in your car's air conditioner, the air is then cooled and expanded before being fed into the cabin. Hot air from earlier stages in the process is mixed with cold air from the air cycle machine to attain a desired temperature.

On the back side of the plane is the second hole known as the outflow valve. This is where the pressure in the plane is controlled as there is a door which modulates open and closed to let air out at a rate to control the pressure inside the plane. For a given inflow rate, when the outflow valve closes, the pressure in the plane goes higher. A pressure relief valve keeps the "balloon" from bursting from over pressure in the case of a malfunction.

The inflow rate is modulated by automatic valves and is kept mostly constant while the outflow valve is controlled by a digital pressure controller. This provides for a gradual pressure climb and descent to match the pressure altitude of the landing airport which is set by the pilot. Were this not the case, the doors, which are essentially plugs, could not be opened at the destination if the aircraft was still pressurized. It's also why these doors can't be opened in flight. The air pressure keeps them closed with many hundreds of pounds of force.

Why Do My Sinuses Bother Me on an Airplane?

Well for one thing, the air in the stratosphere has almost zero moisture contained within it and as a result, the air coming into the cabin at altitude is also nearly zero percent humidity. This is why you will become quickly dehydrated on a long flight. Some business aircraft actually have humidifiers installed for comfort but these are not installed on commercial aircraft to my knowledge due to weight, cost, and corrosion considerations. Dry mucous membranes can also cause discomfort over long periods.

Pressure changes experienced on an aircraft are well known to cause discomfort. The reason for this is the construction of the human head. Aerospace travel was apparently not considered in its design. Put simply, air does not always flow freely into and out of the sinus cavities and ears of the mark-one mod-zero human. When the air pressure is changing outside of said human and congestion or some other problem prevents the air pressure from equalizing, pain often results.

This pain and discomfort most often manifests itself during descent as the pressure is increasing. During climb, air escapes more easily from sinuses but a "flapper" like effect makes increasing pressure more difficult to equalize resulting in sinus and ear blocks. They can be excruciatingly painful. Not flying with a cold is always a good idea but using a nasal inhalant such as Afrin can help greatly in the event of discomfort. It should not be used prophylactically though as there is a "bounce-back" effect and it can become habit-forming if used continuously.

Are the Pilots Turning Down the Oxygen?

Why yes. Yes they are up there wearing oxygen masks while turning the oxygen valve  to make passengers fall asleep and to also save money on oxygen tanks. And cackling wildly as they watch you turn slowly blue. Sometimes, though they need to take a break from that duty to monitor the chem-trail dispersal systems.

Seriously, though, per the laws of physics, the oxygen content of cabin air will decrease with cabin altitude. For customers who have hit it especially hard the night before or have health considerations, the resulting lack of oxygen may result in an extended nap or shortness of breath. My airline does not allow bottled oxygen to be brought on board by customers, but does allow battery powered oxygen concentrators. Checking ahead of time what the policies are is always helpful.

And no, there are no oxygen tanks in use during a normal flight. Your ability to remain conscious at altitude is a function of the cabin pressure. As long as it remains below about 10,000 feet, you'll stay awake and alive. There are oxygen tanks aboard but they are for crew use during emergencies. 

There aren't even any oxygen tanks hooked to the emergency oxygen masks that will drop if the cabin pressure rises above 14,000 feet. Those are actually connected to "oxygen generators" which is a fancy way of saying a chemical stew that "burns" when activated but gives off oxygen as a byproduct. A number of these oxygen generators which were improperly packed caught fire in the cargo hold and brought down a Valuejet MD-80 about 15 years ago. As installed in the aircraft overhead passenger service unit, the heat generated during use is harmless.

Should the "rubber jungle" ever fall down in your face, you will have about 12 minutes of oxygen mixed with ambient air to keep you awake while hopefully your pilot gets the airplane pressurization under control or gets below 10,000 feet. But remember that since the mask mixes oxygen with ambient air, it won't keep you from breathing smoke should a fire ever break out. 

Another favorite conspiracy theory is that pilots recirculate used air to be breathed again and again...to save money. Well, this one is true. A certain amount of the air on most commercial aircraft is in fact recycled. A "recirc" fan recirculates a certain amount of air through a filter like the HVAC system in your house, car, and office. This results in higher humidity and less fuel consumption. And while 100% of the air from your home air conditioning system is recycled, the number is closer to 50% on an aircraft depending on the model.

But How Safe is it Really?

Again, it depends, but air quality on a modern commercial aircraft is probably about as safe as it can reasonably be. According to Boeing, passengers receive between 14 and 20 cubic feet of air per person per minute and this air is essentially particle free. Boeing claims that the HEPA filters used can remove particles as small as .3 microns which includes most microorganisms.

So while the air coming from the airplane is probably safe, it's that guy sitting next to you hacking up a lung you're probably worried about. And probably with good cause. It's not the airplane itself that is the problem, it's the proximity to sick people in the cabin with you.

Put several hundred people in any enclosed space be it airplane, elevator, or subway, and someone with an infectious airborne disease will probably transmit something to someone. But of all those transportation methods, the airplane probably has the freshest air source. Directing one of the overhead gasper air vents towards your face may have some effect in keeping ambient air particles out of your lungs but how much is unknown. And as I mentioned earlier, the air is probably fresher than your home or office. 

While the practice is more often seen in Asian countries than the US, wearing a mask can certainly cut down the risk of acquiring an airborne infection. But other than wearing a mask, there's probably little that you can do to reduce your risk of airborne infection other than staying off the plane altogether.

Is There Anything Else I Should Worry About?

The other and probably equally dangerous threat on an aircraft is the tray table. And also the armrest, and the lavatory. And probably your seat too.

All these things are public spaces and most likely contaminated with germs, fecal matter, and other gross stuff. Just consider the interior of the airplane as one giant Petri dish. It probably isn't a bad idea to carry a supply of anti-bacterial wipes and to wipe down your immediate area when you sit down. Use the anti-bacterial soap in the washroom and learn to unlock and open the door with your elbows.

I personally don't eat or drink on an aircraft either. The flight attendants are handling cash, credit cards, trash and empty cups all day from hundreds of people. Sure they wash their hands and wear gloves at times but is that diet Coke worth a few weeks of flu, or worse? And keep your hands away from your face.

Yes, but aren't the airplanes cleaned every night? Sure they are. We park and a crack crew of uniformed professionals are waiting to scrub down every bit of the aircraft to CDC approved standards using industry standard anti-microbial cleaning agents. Not.

No, the "cleaning crew" consists of minimum wage immigrant labor armed with a vacuum cleaner and a few rags. The plane is also tidied up between flights but not "cleaned".

So What Now?

Well I guess in the words of Dirty Harry, "Do ya feel lucky?" If you've got to go fly, then go fly. I'll be there because I have to be. 

Your odds of catching Ebola or Enterovirus are probably infinitesimal but increasing, due to the madness of our open borders policies inviting the third world and their diseases to our shores.

You are probably more likely to get something more common like the flu on an airplane but a few common sense steps as mentioned above should help. And voting. That will help as well.

Celestial Sightings (from 38,000 feet)

This Wednesday past there was a total lunar eclipse which was visible over most of the United States. This particular event started at about 0420 eastern time. As chance would have it, I was on an overnight in Tampa, with my first leg being to Houston over the Gulf of Mexico.

Having heard of it somewhere on the news the day prior, I was aware that it might be visible the next morning as we were scheduled to leave Tampa at 0650 to head west. The moon wasn't visible from my hotel room but was visible as I walked outside of the hotel to get on the van at 0550.

By the time we got to the airplane, about 0620, the moon was nearly fully occluded. It was being called the "blood moon" by some in the media though it didn't appear especially red to me. My guess is that for those watching it as the moon sets, it appears red for the same reason sunsets appear red. The light is refracted through the atmosphere and dust particles in a process called Rayleigh scattering.

Standing out on the provisioning truck, I attempted to get a photo of it but cell phone cameras are just not up to the task of capturing night sky objects. After dealing with a minor maintenance item of a balky cockpit display, we were on our way. As our customers were being entertained by a live satellite internet feed of the Cooking Channel, we had a somewhat more interesting show up front.

The timing and our course really couldn't have been more perfect. The sun was rising up behind us but we were travelling at a groundspeed of nearly 500 miles an hour away from it, so the shadow of the earth up into the atmosphere created a light and dark area ahead of us. We were also at 38,000 ft so the view was unimpeded by clouds.

The View From the Corner Office

While flying around in a jet all day affords a great view of the earth below, equally inspiring can be the view of celestial happenings. Over the years, I have had the pleasure of having a front row seat to all manner of astral events from comets to meteor showers to eclipses. 

Being above most of the atmosphere does afford the casual observer of the heavens a great view, but one must know what to look for...and where.

Some events are once in a lifetime occurrences such as the appearance of the Hale-Bopp comet in the winter and spring of 1997. Becoming the second brightest object in the sky and being visible to the naked eye for nearly a year and a half, Hale-Bopp was spectacular from the airplane at night and nearly impossible to miss. And it won't be back for another couple of thousand years. 

I was flying up and down the California corridor quite a bit back then and depending on the direction we were flying, the comet was not always visible. The 737, as with most airliners, while having good forward visibility does not afford the best viewing for objects above or behind the aircraft. And in recent years, the small windows above the main wind screen, or the "eyebrow" windows, have been permanently removed and sealed with opaque panels as a cost savings measure.

Meteor showers can be quite striking from altitude and they are recurring events. The Leonids get their name from the constellation Leo, from which the meteors appear to originate. They are visible annually in November and are the remnants of a comet through which the Earth passes. The Perseids occur in August and appear to emanate from the constellation Perseus. While at their peak, a meteor shower appears as many bright streaks across the sky per minute.

The trick to seeing these cosmic light shows is of course to be flying on the night that the phenomena is visible, and then to be flying in the correct direction. The Perseids are visible in the northeast sector of the sky, so if you happen to be flying from say St. Louis to Phoenix that night, you won't see them. Most times this is just pure luck unless you are very careful when bidding your trips.

Chasing the Sun

The most prominent object in the sky, and often the bane of pilots is the sun. Dating back to WWII and before, the sun has been used by attacking fighter pilots to conceal their whereabouts from targeted aircraft and ground emplacements. Coming from the direction of the sun effectively blinded defenders until the attack was upon them.

And the sun is still up to its old tricks blinding pilots. Having an early morning go on an easterly course means that shortly after takeoff, the laminated cards with checklists and other reference data are securely in place nestled between the glare shield and the top of the windscreen. Maps are also handy for this function except that with the introduction of electronic flight bags, paper maps are going away and an iPad makes a lousy shade.

One might complain that blocking the forward view is hazardous due to not being able to see potential collision conflicts. This is true, but intruders are not visible anyway with the sun directly in your eyes and using the maps preserves your retinas for future use.

Takeoffs and landings into the sun can be a challenge as well. Landing on runway 25 in Las Vegas at sunset often finds that golden orb perched just above the runway of intended landing. One hand on the yoke and one held out in front to shield your eyes leaves you one hand short to control the throttles. Sometimes setting your seat higher or lower may work to shield your eyes but at other times you just suck it up and hope you're mostly on centerline for touchdown.

Once I had the opportunity to visit the Phoenix Sky Harbor Tower and asked the controllers why Phoenix always took off to the east in the morning and landed to the west in the afternoon. The winds in Phoenix are almost never a factor in determining the active runway so the decision was up to the tower controller. He told me with a straight face that it was to keep the sun out of the controllers' eyes. 

Great. Wouldn't want the guys sitting on terra firma to be blinded as opposed to the guys actually flying the plane.

While it's well known that most aircraft can't keep up with the sun as the earth spins, this isn't true in all cases. One of those times would be if you were in say an SR-71 supersonic aircraft travelling over about 1000 mph ground speed at the equator. Another is if you move further north to attempt this same feat in a slower aircraft.

Though the math is more complicated due to the rotational axis of the earth being 23 degrees off the vertical of the solar plane, the speed the surface of the earth rotates decreases as a function of the cosine of the angle of latitude. (This is also the genesis of the Coriolis effect which causes most of our weather and bathtub drain water to swirl)  Go far north enough, and your airplane can keep up with the sun, or at least give it a good run.

That means you might have the sun hanging in the middle of your wind screen for hours on end. Which once long ago we did. Leaving Anchorage for Yokota Air Base, Japan one afternoon in a C-5 had us taking off just as the sun was camped directly in our face. The C-5 is a large aircraft, with a very large windscreen. It probably took most of the maps in our worldwide kit to paper over the cockpit to keep the sun out. 

And there it hung in the windscreen for nearly eight hours until we started our descent into Japan. 

Stars, Planets, and Northern Lights

On moonless nights at altitude, the sky is an amazing tapestry of things most earthbound observers never see. The Milky Way is easily visible snaking across the sky with the dark areas such as the Great Rift also visible. Though modern aircraft navigate with GPS and inertial systems, the stars that ancient mariners used to navigate the seas are familiar friends for those who care to look. Orion, Cassiopeia, the Big and Little Dippers, the Pleiades, and many more are always there waiting for your next journey above the clouds.

When I started in this business several decades ago, some pilots were never without their handy printed night sky guide replete with glow in the dark print. Those have now been replaced by mobile phone apps which automatically orient themselves to your current location and time for an accurate sky depiction.

The planets can play tricks on unwary pilots around dawn or dusk. More than a few times I've overheard irate pilots insisting to air traffic control that they have converging traffic which the controller had failed to point out. This always gets the Venusians to laughing wildly. 

Occasionally we might see a single re-entry of a meteor or perhaps some space junk. It can look like a roman candle with many pieces flying off a main part. Once in broad daylight over New Mexico, we saw one of these and I almost caught myself ducking because it seemed as it was just over our position. Then the frequency lit up far and wide with pilots asking "Did you see that?" It apparently looked closer than it was.

My essay wouldn't be complete without a comment about man-made celestial objects. Though I never saw a shuttle launch, I've been told that they were visible for hundreds of miles in the air. Of the launches I have seen, they were both from California's Vandenberg AFB. One of them I saw while flying over Nevada several hundred miles away was very impressive. The other was from over Texas.

We were flying from San Antonio to El Paso and in the distant haze saw a light move from the horizon up into the sky above us. As usual, the frequency lit up with questions about what it was and where it was from. Most of us thought it must've been a launch from the White Sands Army Missile Range north of El Paso. The controller said "hold on, let me check." Then he came back, "not White Sands, Vandenberg." Nearly a thousand miles away.

We'll end our sky tour with the Northern Lights. Though my routes rarely go far north enough to be able to regularly see them, there have been a few occasions when I've seen their eerie green glow pulsating from the north. I once even saw them while on arrival into Chicago, much further south than is normal.

And though I've never seen a UFO, that certainly doesn't mean they're not out there. They have cloaking devices, you know.

The Pilot Shortage Meets Econ 101

As the current pilot shortage worsens, two of the players, commuter airline managements and labor unions are turning up the rhetoric on what is actually happening and who is to blame. A recent article in Business Journals placed the blame squarely on "miserly airlines":

The nation's big airlines want you to know that there's a dreadful pilot shortage and they apologize profusely if their commuter-carrier partners cancel flights to your hometown airport due to the debilitating shortfall. 

The nation's big airlines don't want you to know that their commuter carriers, which operate half of all the nation's commercial flights, often pay pilots so little that it's often financially wiser to drive a truck or flip fast-food burgers than fly a plane.

And in addition, what the author of the article also doesn't want you to know it that he doesn't understand basic precepts of economics (which is kind of embarrassing being a financial reporter).

As we've explained previously, a not insignificant part of the commuter airline pilot's compensation is the flight hours he receives in the course of doing his job. Those highly coveted hours, like passes caught or RBIs for ball players, are the stock and trade of aspiring airline pilots. Without the minimum number of hours required, they cannot even apply to a major airline for a pilot job where the real money is.

In fact, were it not for the quest for flight hours, pilots would never even consider working for the admittedly low wages offered by the smaller cargo and commuter airlines. It is an unstated deal that young pilots stay with commuter airlines only until such time as the pilot gains enough hours to move up to a major airline.

The other half of the equation is that since commuter airline managements know their valued pilot employees have no intentions of making a career at their podunk airline, but are there only to gain hours, there is simply no point in paying any more than is necessary. A basic economic tenet of staying in business is to pay your employees only what it will take to retain them and no more. Not miserly, just common sense. It's not a charity.

Doing that is apparently also some sort of crime according to social justice warriors masquerading as online business 'zine reporters who conflate a profit making enterprise with a social cause.

Normally taking between six and ten years to gain the required hours to join a major airline, commuter airlines might be thought of as a minor league for the major airlines. You may have noticed that minor league baseball doesn't pay much either.

Commuter Airline Managements Have a Problem 

This gentleman's agreement of low wages in exchange for flight hours has now been put in jeopardy by several new government regulations mandating hugely higher hours requirements to even get a commuter pilot job. These flight hours must now be purchased and this raises the entry bar to many tens of thousands of dollars to get that still very low paying job. This effectively destroys the calculus young pilots count on to start their careers.

It also throws a wrench into the business plans of commuter airlines who now complain that they don't have enough pilots to fill their cockpits. Their sweet deal of paying pilots food-stamp qualifying wages is also coming to an end. Pilots will now be required by government regulations to purchase their own hours to qualify for any flying job, and will need to service their flight school loans with higher wages.

This whole process begs the question of why huge numbers of hours are needed to qualify for a major airline job anyway. Around the world there are countries without large commuter airline establishments from which to draw pilots, such as Japan. These countries have what are called ab-initio aviation programs which take a pilot from novice to the right seat of a major airline in about a year with only several hundred hours of intensive instruction.

The US military effectively operates such a program with it's undergraduate pilot training, placing pilots in their 20s with only several hundred hours experience into the cockpits of widebody airliners. If this is the future of US aviation, the commuter airline managements may well have a real problem on their hands. The future may be pilots taking out huge loans for ab-initio programs and leapfrogging commuter airlines straight to a major airline job.

So why don't the 'miserly' commuter airlines simply up the pay of their pilots to attract and retain them in sufficient numbers? It's simple: they can't (and expect to stay in business). Their economic models are built on the assumption of cheap pilot labor and their margins are so thin that increased pilot salaries make them into money losing operations at current fare levels.

So why don't they just raise prices to cover the higher salary costs? A trip back into the Econ 101 textbook reveals that for a demand elasticity curve which is not vertical, a higher price will result in less demand for a given product. In English this means that if the already high price of a commuter flight goes even higher, maybe it'd be easier to just watch the game on TV rather than fly to see it. Or perhaps the businessman doesn't have to attend the meeting in person but rather by Skype. (These are called substitute goods). People will fly less and the business will shrink or cease to exist.

And as airlines must sell their product in prepackaged amounts, (the number of seats on their aircraft), below a certain level of demand, service to a particular city becomes a money loser at any reasonable price. It is well known that smaller aircraft have higher per seat costs to operate, which only makes the problem tougher. Time to sell.

Labor Wakes up on Third Base (And Thinks They Hit a Triple)

Right on cue, labor groups have been crowing that the lack of pilots to staff commuter airlines is just desserts for stingy airlines due not to increased government regulation (which labor itself championed), but rather that managements have paid sub-par wages for too long and pilots just woke up one morning deciding not to take it anymore.

Alpa, the largest airline union, calls the shortage imaginary, instead choosing to call this a pay shortage. Well, semantics aside, if you one day go to the grocery and find that your customarily priced $3 bottle of orange juice suddenly jumped to $12, it is doubtful that your first impulse would be to think that gee, I've been paying too little all these years! No, you'd probably think that an early freeze caused a shortage which caused the price to jump.  

Labor is realizing that a shortage labor-supply mismatch may in fact work out in their favor. That is, in favor of pilots who already have an airline job. The new federal regulations, which quintupled the flight hours needed to get an entry level commercial pilot job, are what's known in economic terms as a barrier to entry. 

Barriers to entry are popular with already established members of a particular profession or business as they serve to limit competition and thereby drive up wages or profits. It's been said that the toughest part of becoming a doctor is getting into medical school and that the difficulty serves only to enhance doctor wages. In fact most professional credentialing has some element of this going on.

The taxi and car-for-hire business is being disrupted to great consternation by mobile-paged car services such as Uber and Lyft. They are being ferociously fought by taxi companies and the urban regulatory bodies which profit through control of outrageously priced medallions or licensing requirements.

So this is all well and good if you already have your airline job and are far enough up the list to avoid a furlough should your airline need to shrink to profitability. No where in any economic text book does it state that any particular service should exist and be generally available to the public at a reasonable price. The commuter airline business model may just find that given current fuel and increased labor costs, the service simply can't be provided as a mass commodity.

One need only think of the fledgling space taxi business. We have the technology to routinely fly passengers into space, but with only the occasional billionaire dilettante as a willing passenger, the demand for space plane pilots is small.

Commuter airlines may shrink into a boutique or air taxi operation for very wealth clients in the model of the current fractional ownership of private aircraft, at least for many smaller cities. That would mean the pilot shortage solves itself on the demand side with commuter pilots being furloughed or shrinkage of the industry through attrition.

The winner in all of this? Well, not the small city customer who, when he can even find a commuter flight, will pay through the nose. And certainly not aspiring pilots who will now need to borrow tens of thousands of dollars just to get their first job. And perhaps not even existing commuter pilots who find their companies shrinking due to decreased demand.

Who wins? Flight schools may see an uptick in students who now have to purchase (at about $120/hr) their experience. Probably lending institutions making loans to these aspiring pilots. And most certainly the politicians who get to claim that they "did something" for the aviation industry.