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What I Learned in Pilot Training: Hypoxia

I realized I have not been holding up my end of the bargain when it comes to all of the things I am learning at pilot training, so I am going to do my best to start to remedy that.

For the first two weeks of training the vast majority of what we talked about was the physiological aspects of flying airplanes.  I talked about some of this in my last post, but there is one area that I feel warrants its own separate discussion, and that is hypoxia.

A quick Google search tells us that hypoxia is a “deficiency in the amount of oxygen reaching the tissues”.  This definition is pretty general, but that is because the effects of hypoxia can vary dramatically.  That is one of the scary things about hypoxia is that it is different for everyone, so there is no way to give anyone a surefire way to know it is happening.

Maybe even scarier is that some of the potential symptoms can be exact opposite.  Some people will feel euphoric, or extra happy.  Other people will feel sick and miserable.  Some of the other symptoms are tingling in the extremities, headache, feeling warm, decreased visual acuity, cyanosis (blueness in the lips), and loss of mental capacity.

The last one may be the biggest threat to pilots, but if you are struggling to think clearly, how likely are you to notice it?  Your brain isn’t working well, but somehow it is supposed to realize that it isn’t working well?

As part of our training, we go into an altitude chamber to experience the effects of hypoxia, and determine what our own individual symptoms are.  It is invaluable training and helps you to recognize how you respond so that should it ever happen in flight, you are more likely to notice it.  To add to the challenges of hypoxia, your symptoms can change over time.

When I did the altitude chamber in navigator school, my only symptom was a very slight headache across my forehead that took forever to appear.  When I did it this time it was tingling in my fingers and feeling warm.  You may notice that most of these symptoms are things that could happen for dozens of different reasons.  Lots of people get headaches when they fly because they are dehydrated or a little sick, or because they had too much fun at the bar the night before.

Which brings me to some of the different reasons that you can experience hypoxia.  There are four general types of hypoxia: histotoxic hypoxia, stagnant hypoxia, hypemic hypoxia, and hypoxic hypoxia

Histotoxic hypoxia is the type that would be created by having too much fun at the bar the night before.  Substances like alcohols, narcotics, and other drugs impact the cell’s ability to accept oxygen and even though there may be enough in the air, it can’t get into the cells to do work.

Stagnant hypoxia happens when the blood is not flowing to the tissues properly.  In the military world this is usually driven by pulling G’s which causes the blood to pool in the lower extremities and thus not flow to your upper body.  It can also happen when you get cold and your circulation decreases.

Hypemic hypoxia is similar to histotoxic, but instead of the cells not accepting oxygen, it relates to the blood’s inability to carry oxygen.  In aviation this is most often caused by the inhalation of carbon monoxide either from a bad heater, or even just the exhaust on the ground before you get in and takeoff.

Hypoxic hypoxia is when the air simply does not have enough oxygen for your to breathe, which happens at higher altitudes.  Clearly an issue for flying an airplane.  It is also the most common type of hypoxia experienced in aviation.

We can all agree that hypoxia is a bad thing as it prevents us from thinking clearly and from using our body to safely operate an airplane.  So what can we do to prevent it, or recognize it when it does happen?

First, prevention because it is ALWAYS better to prevent a bad situation that it is to deal with it after it arises.  Being physically prepared to fly is the simplest way to prevent hypoxia, and a host of other issues.  That means that if you have not gotten enough rest, or you have been feeling sick, or you are hung over, or drunk, then you should not be flying.  We all want to fly as much as possible, but you have to know your limits and never cross them.  Even in the military we regularly talk about how there are almost no flights that cannot wait until another day if the crew is not physically fit to fly.

Another part of prevention is ensuring that you have the proper equipment for the flying you will doing.  If your flight is going to be mostly around sea level hypoxic hypoxia is not very likely, but if you have a broken exhaust system, or a cabin heat system that is not working properly, you put yourself at very real risk of hypemic hopxia, and that is every bit as dangerous.  Hypoxia is not only a matter of flying at high altitude!

Generally speaking we talk about oxygen deficiency starting at around 10,000 feet MSL.  So if you are planning to fly anywhere near that altitude for very long you need to have the right equipment.  That could be a pressurized cockpit, or it could be supplemental oxygen.  If you will be flying at night, some people push that altitude as low as 5,000 feet MSL.  Once again, everyone is different, and has different tolerances.  If in doubt bring along the extra oxygen because it may save your life.

I realize that going to an oxygen chamber is not realistic for most people, nor is it really necessary for someone cruising around in a 172, but if you get the opportunity I would highly recommend it.  That being said, there is still plenty of education and experience you can get to learn more about the effects of hypoxia and how it can affect you.

My only experience with hypoxia, other than in the controlled environment of an altitude chamber, was actually on a hiking trip.

I was climbing Mt. Fuji in Japan, which only goes up to about 12,300 feet, not that much above 10,000.  As we got to the summit it was rainy and cold and I was miserable and I had a headache.  But, I didn’t even realize it until we were on our way back down and I started to feel better.  Sure I recognized that I was tired, but it wasn’t until I headed lower and started to lose my symptoms that I realized I had even had symptoms.

The odds of this happening in aviation are not very high, at least if it has become a critical issue.  If the symptoms are minor then descending may be enough to clear your head and fix your symptoms, but descending may not always be an option, and if it has to do with poor equipment, it is not likely that the equipment will just fix itself.

So how do you recognize that you are having issues?  The key to this is not waiting for extra signs.  At the first indication that you may be hypoxic you need to take action.  Some people can go hours with symptoms before it becomes life threatening, but for others the symptoms may come on and only minutes later the person will be incapacitated.  So if you even think there is a small chance you might be hypoxic, try to fix it immediately.

If you are fortunate enough to be flying with someone else, ask them how they are feeling, or if they see anything different with you. Sometimes just bringing it up will key the whole crew off that something is not right and you may save everyone.  Maybe it is just you having an issue though, and they can help you remedy the situation and get back to normal.  The point is to not keep it a secret if you don’t feel right.

Many people do most of their flying alone so what can they do?  In many cases, you can still tell someone, whether that be ATC or anyone else that may be on frequency with you.  Again, just mentioning that something doesn’t feel right can help key off your mind that something isn’t right and can help you down the path to fixing it.

If there is legitimately no one around then just say it out loud to no one.  The brain is pretty amazing and just vocalizing it may be enough.  Most importantly, if you are by yourself, don’t hesitate to take some action if you feel even the slightest possibility that something isn’t right because you have no idea how far you are from just passing out.

This ended up being way longer than I expected, but I would argue that I didn’t even scratch the surface on the topic, or at least on aerospace physiology.  There are people whose entire career is in that field.

Hopefully what I have done is given you some things to think about when you fly, and encouraged you to spend some extra time thinking about how your body is performing when you fly.  We spend a lot of time checking on the plane, and our equipment but most of us don’t take enough time to check on our physical ability to fly.

It doesn’t have to be a huge drawn out process, but even taking the time to stop before you step to the plane and just ask yourself how you are feeling may be what saves your life.  I would also encourage you to spend some time learning more about aerospace physiology.  That could be through articles, or YouTube, or seminars, or other classes.  No matter where it comes from, understanding how our bodies work when they are in the unnatural state of flying will only make you a better aviator.

October 12, 2019 I Written By

I'm Dave and I am a proud Avgeek. It goes way beyond liking airplanes. It is a passion that cannot be subdued.

Setting Personal Limits for Flying May Save Your Life

It is interesting that I have been thinking about writing this post for almost two weeks now as I have seen numerous people post comments or tweet about this exact subject.  No matter how many times I see this message though, I will always keep repeating it, because the concept may very well save your life.

If you have read the last few posts that I have written (if you haven’t, you should go read them now) then you will know that I had a week chock full of flying about two weeks ago.  When I started the week I was planning to fly six times in three days; three flights each for work and towards my private pilot certificate.  It was a little ambitious, but the weather was good and I wanted to take advantage of it after a bunch of crappy weather.

The first two days went very well and I got a lot of good stuff done, including my very first solo, which I am still pumped thinking about.  When the third day rolled around I was still planning on a third doubleheader in a row, especially with as motivated as I was after my solo.  However, as I went through the next few hours of flying I felt my body starting to wear down.  I was still able to fly at work safely, but as we landed after the sortie, I just knew that it wasn’t a good idea to push for another flight again that night, especially considering we were planning to do a three-hour night flight to knock that out.

I sent a message to my CFI telling him I would need to cancel for the night, which he totally understood and agreed with.  As soon as I sent the message I started to regret it a little because I am so anxious to get this thing done, and like I said, I was still pretty jacked from my solo the night before.  But as I got back to my desk and started to wind down from my flight and take care of some paperwork I knew I had made the right decision.  I could feel the effects of five flights in three days, and my body needed to take a break and recover.

I ended up having to wait a few weeks to get that flight in thanks to a family vacation and a busy schedule, but I am even more convinced now that I made the right decision.  Would I have had any problems getting through that flight, probably not.  Even if I was struggling my CFI would have been there to make sure we got back safely.  But, why would you want to risk it?  The only thing I would have gained is maybe finishing my certificate a little earlier, and the only thing I would have been risking is my life.  Seems like a fair trade-off, right?

The point is that many of us love flying and are anxious to spend as much time as we can in the air.  Whether we have been grounded for a while due to bad weather, work, or even just anxious to finish a rating or upgrade that you have been working on for ten years, none of us would rather be on the ground when we could be in the air.  Which is why it is smart to set personal limits for yourself above and beyond the limits the FAA sets.

In the Air Force we fill out a risk management worksheet before every flight that accounts for things like fatigue and health of the crew as well as the type of mission we are planning to fly and weather.  If the score is too high we have to get approval from leadership who checks to confirm that we have properly mitigated the risk and that we are safe to fly.  Sometimes the number is just too high and the risk isn’t worth it, so we don’t fly.  That may mean missing out on rare training opportunities, or even delaying a mission, but nothing is worth risking your life.

So what kinds of things can you set limits for?

Weather is an obvious one.  Maybe you set a ceiling and visibility limit that you will not fly with less than.  Similar to weather mins for an instrument approach you may set a limit for both VFR and IFR flight that you won’t bust.  As you get more proficient, especially as an IFR pilot you may lower those mins, but understanding your abilities and comfort level will go a long way to keeping you safe.  You may also have wind limits, or certain types of weather you won’t fly with.  One example for us is that if we have severe turbulence forecasted we don’t fly, period.  Maybe for you it is fog, or rain, or some other weather that you just don’t want to mess with.

Rest is another important one to consider that can be very easy to overlook.  The Air Force, as well as airlines, have rules on crew rest that delineate how much time to rest you must have before a flight.  In the Air Force we also limit what types of flying we can do a certain number of hours into the day.  Things that are more challenging are restricted to early in our duty day because we want to make sure we are sharp in those high risk situations.

You may opt to only go to fields with certain runway lengths, crosswind limits stricter than the plane can handle, length of flight, or any other limits that you feel are important.  The point is to keep yourself safe, no matter how experienced you are.

I would never suggest a specific limit for anyone else, because each of us know how proficient we are, and what our limits should be.  If you aren’t sure what your limits should be set something conservative and roll with that for a while.  Then as you feel more comfortable change the limits to match your skill level.  However, don’t change your limits as you are stepping to fly.  Find a time when you have no pressing concerns to sit down and honestly assess how you feel about the limits you have set.  This way you won’t feel inclined to lower your limits just to meet a deadline or take that trip you have been planning for months and get into a risky situation.

While I mentioned lowering your limits, also don’t be afraid to raise your limits if your situation reflects the need.  If you haven’t been flying for a while, or if you are in a new type of aircraft, or if you have gotten into a few situations that were more uncomfortable than you would like, be honest with yourself and raise those limits to keep yourself safe.

Now thinking of every possible variable that could happen during a flight and creating a limit for it would be an incredibly daunting task, so I would say start with the basics.  Set some weather limits for yourself, and some sort of rest limit as I see those as two of the simplest protections that will keep you out of the vast majority of unsafe situations.  Then as you get more experienced and start trying new things spend some time in your mission planning to set limits for yourself as well.

Maybe most importantly, write your limits down so you don’t forget, or try to fudge on them later.  The whole point of this is to keep yourself safe so make sure you are clear about it.

Lastly, don’t ever budge from your limits when it comes time to fly.  I mentioned this briefly before, but it bears repeating.  Limits are there to make the decision for you when you may put yourself in a questionable situation.  They allow for a good level-headed decision when the stress and temptation are not part of the equation, or in other words, way before you are going to go fly.  By all means change those limits when you are not in your flying bubble, but never do it in the heat of the moment because you set those limits for a reason and that is to keep you safe.

One last dynamic of this that I want to point out is that setting limits doesn’t mean you can’t still do something flying related.  In my case I spent my extra time studying for my written test, which I passed with a 100% this past week, so I guess that time was well spent.  You could do some work on your plane, you could better prepare for taking that flight the next day.  Maybe you have a local flight school with a simulator you could use instead.  Or maybe you could even just hang out at the airport for a little while and get to know your hangar neighbors and build some relationships for the future.

As much as it sucks having to miss a day of flying, there is still a lot you can do to not let the day be a waste.  Setting limits for yourself may keep you from flying, but it will also keep you safe so that you can have many more flights for years to come.

April 15, 2018 I Written By

I'm Dave and I am a proud Avgeek. It goes way beyond liking airplanes. It is a passion that cannot be subdued.

There is No Black and White in an Aircraft Emergency

For better or worse, mostly worse, we live in a world today where many people take every snippet of news to extremes.  Much of this is driven by the 24 hour news cycle, and the obsessive need of every media outlet to be the first to break any news that might be even remotely relevant without checking for confirmation, or even the facts.  Sensationalism is the name of the game in the media these days, and it is causing many problems that really should not be issues at all.

There may be no sector of the world where this is more true than aviation.  Some of this comes from the relative ignorance of the public, the potential for major tragedies in flight, and the complex nature of what we do.  Unfortunately, many media outlets don’t even take the time to find real experts to support their stories, because, let’s be honest, the truth wouldn’t sell nearly as well as the sensationalism they opt to offer.  Instead they prefer to scare the public into thinking a situation is worse than it actually is.  That is exactly what happened with two recent emergencies that garnered a fair amount of attention.

The first was the engine fire of British Airways Flight 2276 in Las Vegas.  In short, there was an engine fire on the ground that caused the crew to abort their departure, and evacuate the aircraft.  They did a beautiful job of getting everyone to safety, and the aircraft was taken care of about as well as could be expected.

In this instance much of the extremism came from Twitter and other social media outlets where people completely shredded passengers who had taken their bags with them while evacuating.  While I agree that it was not the smartest move by these passengers, they certainly do not deserve much of the vitriol that has been thrown at them from the masses.  Rather than explaining further I would direct you to a piece written on the Airline Reporter website that does a far better job of conveying my feelings than I probably could.  Again, taking your bag in an evacuation is generally not the best idea, but there are certainly scenarios I could see that taking your bag could be justified, and you never know how you will respond in an emergency.

The second emergency that took place recently was the in-flight death of an American Airlines pilot.  While this is a terribly sad situation, the plane and the rest of the people on board were in no real danger just because one of the pilots was incapacitated.  For some reason the media is making a huge deal about the “co-pilot” having to land the plane by himself.  This is where ignorance and aviation colloquialisms come into play.  Again, I have been beaten to the punch by a much more qualified expert than myself so I would direct you to the writings of Cap’n Eric Auxier who very clearly and simply explains how the media has screwed up the reporting on this story.

Now I didn’t write this post just to direct you to other writers and their opinions, I have a point of my own to make.

As I alluded to in the title, there is no such thing as black and white in an emergency, nor do any of us know how we will respond in an actual emergency.  Because every emergency is incredibly unique there are always variables that will tweak the response of those involved.  The interesting thing about many of the extreme responses to this story is that not a single person I have seen respond has ever been in an actual emergency themselves.  They are surely out there, but I have not come across them.

In the military, as well as with the airlines, there are very clearly delineated emergency procedures and how to respond to them.  We refer to the first few steps of some of these emergency procedures as boldface in the military because they are written in bold and all capitals in our regulations.  All of these steps must be memorized because they are so important that there is no time to go looking through books for the procedure that you are supposed to follow.  Even with that being said, there are still situations where the best decision is to hold off on the boldface steps to return the plane, and its crew, safely home.

During my time in the C-130 I have been on board a handful of times when we had to shut down an engine, or perform some other emergency procedure.  Admittedly, shutting down one engine when you have three other good ones is not nearly as stressful as shutting down one of only two engines, but it is an uncomfortable situation nonetheless.  While each of these emergencies called for the same procedure to shut down an engine, not one of them was carried out in exactly the same way.

There is no black and white in an emergency, there is only an opportunity for a well-trained crew to make educated decisions that will ultimately lead to a safe outcome.  The safety record of the vast majority of aviation is a credit to the crews that have been well-prepared and have prevented many of these potential emergencies, and when they do happen, they have been mostly well handled saving many people a lot of heartache.  It is easy for armchair quarterbacks to question the decisions from the ground in the safety of their homes sitting behind their computer, but until you have been in an emergency you really have little room to talk.

Emergencies exist in every part of life in one way or another.  No matter how hard you try to prevent them they will eventually happen because that is just part of living.  We can mitigate them, and we can prepare like crazy so that we can respond appropriately when they do happen, but no matter how well we prepare we can never know how we will respond until an actual emergency is placed before us.

It is also important to keep faith in the pilots that safely transport us all over the world everyday.  If you don’t understand the terms we use in aviation and you are worried about what you hear on the news, ask someone who actually works in aviation and they can explain it better than the media.

The term co-pilot is merely in reference to the person sitting in the right seat of the flight deck.  It is incredibly common for us to fly with the most experienced pilot in the right seat, so that the less experienced pilot can gain experience in the left seat.  The reality is that no matter who is sitting in which seat, they are both qualified pilots that are perfectly capable of getting the plane safely to its destination.

So the next time the media or social media try to tell you that an emergency situation was handled wrong, or that someone in particular is at fault, take the time to do a little extra research and gather some more information.  The real information is out there if you will only take the time to find it.  No matter what you do find, never forget that no emergency situation is ever totally black and white.

October 13, 2015 I Written By

I'm Dave and I am a proud Avgeek. It goes way beyond liking airplanes. It is a passion that cannot be subdued.