A Change of Direction

It still amazes me how quickly time goes and how much time it takes to maintain a blog. I have not written a lot in the last six months because I’ve been trying to figure out what I am going to do with my blog and how I’m going to make it work. Last March I was promoted to a supervisor position at Acme airlines. This supervisory position came with tons of email that contains a lot of proprietary information. Obviously because it’s proprietary I can’t share it and it has became a very hard to differentiate between proprietary information and common knowledge information.

I still like writing blog posts I still like sharing my knowledge about the aviation industry but I need to take this blog into a different direction. A change of course you might say. I have decided that I am going to start writing blog posts from your questions and emails that I’ve received from you but also I’m going to write about interesting news stories that I come across. I have am going to subscribe to aviation newsletters so I can be on top of the current events in the aviation industry. I promise that I am not going to just regurgitate all the news that is out there. My hope is to give a link to the article that I read or briefly summarize the article and then give my opinion about it based on my experiences.

I hope that you understand the tough situation that I am in and please know that I am open to your questions and your feedback. Please let me know how the change in the blog affects your readership. I am grateful for everyone that reads my blog and I am looking forward and am excited about this new course that I am undertaking.

Diversions, Mechanical Diversions (Part 2 of 3)

This post is the second part in a three part series about some of the major causes of diversions. In part one I talked about weather diversions.  In this part the focus will be mechanical diversions. Just like part one I will start off with a small scenario and then talk about procedures regarding mechanical diversions.

Imagine you are on a flight and everything is cruising normally.  All of a sudden it gets quieter and you feel that the aircraft is slowing down and turning. After a few minutes the captain gets on the intercom and says: “Ladies and Gentlemen, sorry to tell you but we are going to have to stop short of our destination. We lost all oil pressure and quantity in the right engine and we have shut it down to prevent any further damage. As you probably can tell we just descended and we turning away from Chicago towards Cleveland to land there. Airplanes are made to fly on one engine and the copilot and I are trained in handling the situation. We will be on the ground in about 15 minutes. Just to let you know, when we get on the ground there will be emergency equipment out to meet us on the runway. I requested this just as a precaution just in the very unlucky event that anything should happen. Again, I’m very sorry about this but will be on the ground in 15 minutes. Flight attendants please prepare the cabin.”

A Turkish Airlines B777-300 experiences a compressor stall on climb out of Tokyo-Narita airport.

A Turkish Airlines B777-300 experiences a compressor stall on climb out of Tokyo-Narita airport.


The diversion I just described above is very rare. Jet engines are very reliable pieces of equipment and they are well maintained. Engines also get changed after a certain amount of hours so they do not fail enroute like this one, but all mechanical things can fail.

I have had to dispatch a scenario just like the one above. It was an afternoon shift later in the evening and the crew called up on the radio.  They had lost all oil quantity and pressure in the right engine and had shut it down. They were right over the top of Norfolk, Virginia. I told the crew that they needed to divert to Norfolk. I briefly told them the weather was good and I would be contacting the local station to let them know that they were coming. It took the flight about 15 minutes to get on the ground. Once on the ground the captain called me, he said that their engine had blown oil all over the place and it was pooling on the ramp below the engine. Obviously, this was a major mechanical failure of that engine. I found out the next day that the engine blew a seal.

Engine failures are so rare that an airline pilot can go his whole career without actually having an engine failure. This has been my only engine failure in the 8 years I’ve been working as a flight dispatcher.  Other dispatchers in my office have worked over 30 years and never had an engine failure on any of their flights. While an engine failure is the most obvious reason to divert an airplane, there are some other subtle things that could cause an airplane to divert for maintenance as well.  Some of these could be issues with the fuel pump, air-conditioning packs, potable water issues and several others.  These concerns, while not directly impacting passenger safety, may affect the ability of the aircraft to proceed to its next destination.  It is always wise to address the issue before it becomes a matter of safety or canceling flights.

Mechanical problems happen often on an airplane but they are usually very minor and only the pilots and dispatchers know about them. There is a book on every airplane that gives detailed instructions on the procedures the pilots need to follow in case any of the systems has a mechanical failure. My airline calls this book the Quick Reference Handbook or QRH. Some airlines might call it by a different name but the purpose is the same. Most of these mechanical failures just require the crew to fly the aircraft in a different configuration and continue to the destination without any problems. Some of the procedures in the QRH have the words “land at the nearest suitable airport” This means the crew needs to land as soon as possible and the safety of the flight is in jeopardy.

The QRH procedure for the engine failure scenario that I described above has that phrase in it. Some of these other mechanical problems also carry the “land nearest suitable” verbiage:

  • Cracked windscreen
  • A single source of electrical generator power
  • Any sort of fire
  • Pressurization failure
  • Engine fuel leak
  • Crew oxygen system low

The QRH procedure doesn’t always have to say land at the nearest airport to make the plane divert. There are many times where it would be safe and legal to continue to our destination but instead we decide to divert somewhere and have maintenance look at the aircraft before we continue; as in some of the situations I mentioned earlier. This happens a lot on our transoceanic flights. There are many times where there might be a mechanical problem with an airplane and we choose to stop along the coast before heading across the ocean- imagine a potable water issue that is not addressed before heading over the ocean (not good!). We know we can only get the plane fixed or change to a different aircraft before heading over the ocean. Being careful ensures the safety of all involved and also makes sure the return flight does not cancel.

As you can see there are many things that can cause a flight to divert due to mechanical reasons, they all might not be as severe as an engine failure but when we feel that the safety of the flight is in danger it is always better to put the aircraft on the ground somewhere.

Tomorrow in part three I will cover passenger related diversions.

777 photo from Airliners.net photographer somtam

Diversions, Weather Diversions (Part 1 of 3)

This is the first in a three-part post about diversions, while diversions are uncommon, they do happen, in my opinion, on average once out of 3000 flight at my airline.   There are generally three main causes for diversions: weather, which I will be the topic of today’s post, mechanical problems, and passenger issues. Each post will start out with a scenario that describes the type of diversion; these scenarios are from my past experiences. I hope you enjoy.

Imagine this. You’re on an airplane and you are approaching your arrival city of Chicago, it’s nighttime, you see that there are some thunderstorms off in the distance. You see the lightning coming out of the clouds and they are getting closer. Just as you notice this, the captain comes on the intercom and says, “Ladies and gentlemen, from the flight deck. I’m sorry to inform you that we are to be entering into holding do to some whether at the airport. There are thunderstorms at the airport and the no one is able to land at this time. We will try our best to sit and wait out the weather but it looks like it might be a while.  We will keep you updated from the flight deck until then please remain in your seats because it could get turbulent as we approach the weather. I have also asked the flight attendants to be seated for their safety.”

You are glued to your window and you are watching the lighting outside and feeling the jolts of turbulence as you gradually feel the airplane doing circles in the sky. After about 45 minutes of holding the captain once again comes on the intercom and says; “Well ladies and gentlemen the airport is still not opened and unfortunately we have ran out of holding fuel. We still have plenty of fuel on the airplane but we are going to have to divert to another airport. Instead of landing in Chicago will be diverting to Indianapolis. Our hope is to get some more fuel and get on our way back to Chicago once the weather clears. Again thank you for flying at Acme airlines and we will do our best to get you home tonight!”

If you are a leisure traveler the chances are you’ve never had this happen to you before. If you are a business traveler, or someone who flies quite frequently, chances are you have heard of, or have experienced this exact same scenario. If airlines could control the weather we would; and remember no one ever wants to divert including the airline.

Weather diversions:

Weather is the number one cause for diversions. Between thunderstorms, winter storms and fog; they all prevent the pilot’s ability to land the aircraft at an airport. Lets break these weather events down further. We will start with thunderstorms.

If there’s a thunderstorm over the airport you can’t land the airplane-it’s just not safe. There have been many crashes throughout the mid-70s and 80s that were attributed to microbursts, which are byproducts of some thunderstorms. Thunderstorms also reduce the visibility and create strong winds and even wind shear.  If there is wind shear present while an aircraft if trying to land the flight could loose the airspeed that is keeping the airplane landing.  There are instruments on board the aircraft called EGPWS that will give the pilots warning when they might encounter this wind shear.  This video explains the EGPWS system.

Winter storms, like a snow or ice storm, have two things that affect the ability of the pilots to land. The first thing is the visibility, which I will discuses with fog. The second obstacle to landing is the runway conditions. As most of us know, snow and ice create slippery roads, which means it also creates slippery runways. As you can imagine it is very difficult to stop an aircraft on a slippery runway. Quite often during a snowstorm the airport authority needs to close the runways so they can clear them and treat them. If there is more than one runway at the airport they will usually alternate them. This means only one or two runways will be open which reduces the amount of airplanes that can takeoff and land. When the airport authority closes a runway it is usually closed for about 15 to 20 minutes while the machines get on and clear the runway. If you have never been on a runway before think if it is clearing a 4-5-lane highway that is 1-2 miles (1600-3200m) long and you have to clear it from edge to edge. If able airport authorities will plan the runway closures for times where the arrivals and departures are low. The video below shows a runway team in action.

Another weather phenomenon that could cause diversions is fog. During heavy thick fog when the visibility is really low airplanes just can’t land. Every instrument approach has a set of landing limits or landing minimums. The crew cannot attempt an approach if the weather is below the published minimums. Due to today’s modern technology, diverting due to fog is becoming less and less common. Most modern airliners have the ability to land with just 600-foot (75M) visibility. In most cases, these CAT III landings are being flown by three autopilots on the aircraft with the pilots just monitoring to make sure the aircraft is doing what the pilots tell it to do (to my pilot readers, I know it’s a lot more difficult than that, and I admire your skill). Some of the regional jet airplanes do not have the ability to fly these lower landing min approaches. If the visibility is too low then these airplanes will not be able to attempt an approach. In many cases when an airport goes below CAT I landing minimums ATC will issue a ground stop for CAT I only aircraft.

Landing Minimums section of an approach plate

Landing Minimums section of an approach plate

The final weather phenomenon that could cause weather diversions is wind.  Strong winds coming from specific directions could cause strong crosswinds. All aircraft have crosswind limits, but it also depends on how the airline got certified and how they train their pilots. Most crosswind limitations range between 28 and 40 knots.  The rudder effectiveness determines crosswind limitation.  If the wind is too strong the rudder will not be able to straighten the aircraft to land and the airplane could land sideways.  A side loaded landing could cause damage to the landing gear or even cause the aircraft to crash.  In many cases crosswind landings are not a temporary condition. When there’s a strong crosswind the airport could be shut down for hours at a time.  To counteract this weather phenomenon, most airports have runways in multiple directions. However there are many major airports around the world that only have parallel runways.  When these airports get a strong wind perpendicular to their runway complex, there is no other option but to divert to another airport.  I know we have all seen the videos on YouTube of strong crosswind landings but there’s one below in case you have never seen a crosswind landing.  The airport is the old Hong Kong airport Kai Tak.  This airport closed in the late 90s but a large mountain at the end of the runway created a great vantage point for watching aircraft land.

I hope you enjoyed part one of this three part series about diversions. Tomorrow I will be talking about the next largest contributor of aircraft diversions; enroute mechanical failures.

Removing Dispatchers from the Cockpit Would be a Huge Mistake!

I am sure you have read by now that Southwest Airlines flight 4013 from Chicago Midway airport to Branson, MO landed at the wrong airport. As I said in my post Landing at the Wrong Airport is More Common Than You Might Think, this wasn’t the first time and it won’t be the last.  I am relived that the pilots were able to stop the aircraft on the short runway and there were no injures to the passengers or the crew.  I was surprised to hear that a dispatcher was reported to be in the jumpseat of the flight.  There has been some backlash from the media regarding people other than pilots to sit in the jumpseat.

I feel the greatest privilege and benefit that I have as a dispatcher is access to a flight’s jumpseat.  The reason a flight dispatcher is allowed to sit in the cockpit comes straight from the Federal Aviation Regulations.  FAR 121.463 states: “No certificate holder conducting domestic or flag operations may use any person, nor may any person serve, as an aircraft dispatcher for a particular airplane group unless that person has, with respect to an airplane of that group, satisfactorily completed the following: (2) Operating familiarization consisting of at least 5 hours observing operations under this part from the flight deck or, for airplanes without an observer seat on the flight deck, from a forward passenger seat with headset or speaker. This requirement may be reduced to a minimum of 21⁄2 hours by the substitution of one additional takeoff and landing for an hour of flight”  

A picture I took on my last required Jumeseat ride

A picture I took on my last required Jumeseat ride

This requirement for the flight dispatchers to observe the operations on the “routes they would normally dispatch” enhances the dispatcher’s knowledge of pilot procedures and allows dispatchers to see the procedures for flying in different types of airspace.  When I first became a dispatcher I did not know what it was like to fly a jet aircraft, I had only flown small prop aircraft.  Even though I had a commercial pilot certificate I was far from being certified to fly the aircraft that I was now dispatching.  The jumpseat requirement allowed me to understand the performance and complexity of flying a jet.

A few years ago I took my annual jumpseat ride to Mumbai, India.  I had been working the flight to Mumbai for about 6 months before I went on my jumpseat ride.  I really learned and understood the procedures that I needed to follow and provide the pilots for the high terrain over Turkey and the overflight procedures for flying over Iran. The only way for me to fully experience that route was to actually fly it from the jumpseat.  That jumpseat experience changed how I worked that flight.  After I returned from that trip I was able to provide more useful release remarks on my flight plans and I was able to accurately and confidently brief the pilots who had never been to BOM.

Photo from the Jumpseat on a personal trip.

Photo from the Jumpseat on a personal trip.

As you can see these jumpseat rides can be very useful and informative.  Not only can we sit in the jumpseat for our required trip but this requirement opens the jumpseat up to us for personal travel.  This personal travel is what allows me to get where I am going when the flights are full.  Sometimes I will choose to sit in the jumpseat to allow other standby passengers to get on the aircraft.  Every time I ride a jumpseat I see it as an opportunity to learn something new or to help the crew if needed.

While I do not know what happened on the Southwest flight that landed at the wrong airport, I do not think it will be prevented from happening again by banning jumpseat riders from the flight deck.

Related stories:

NTSB Issues Investigative Update on the Southwest Airlines Wrong Airport Landing Incident

Third person in Southwest plane cockpit may have distracted pilots

My experience with Fatigue and Ultra Long-Haul flying

Inside a Operations Control Center: The Brain of an Airline


FAR 117, the new pilot rest rules, started January 4th 2014.  As is predicted in my post FAR 117: The New Pilot Rest Rules Could Lead to Many Cancelations, these new crew duty rules have lead to cancelations.  This past week I have come to realize the true effect of FAR 117 on the airline industry.  Airlines will need to make changes to their operation to conform to these new rules.

These first few days with FAR 117 have been stressful; not only for the people in the operations centers but also to the crews and even the passengers.   As an airline, we are seeing a lot more “crew reroutes”.  This is when a crew gets pulled from the trip they bid and placed on someone else’s trip.  They still work the same amount of days but their hours might be less.  This new arrangement interferes with any personal plans the crew may already have had in place.  The passengers are affected because they’re seeing a lot more delays or cancellations.   The operations center has been a lot busier then normal the last few days.  People have been trying to learn these new rules in the middle to two major IROPS (irregular operations) and it seems like we have been scrambling to keep the operation together. These new problems are not specific to any one airline.  They are affecting the industry as a whole.

In a quick review, FAR 117 breaks the pilots duty into two types:  the pilots block time which is the point from pushback to taxi in and their duty day which is their total hours worked from check in to release.  Depending on the crew’s report time, their block time is limited to either eight or nine hours.  Their total duty day is dependent on their report time and how many legs they fly.

flight xld

This New Year has seen most of the Midwest and Northeast of the United States affected by winter storms.  The first winter storm happened right after the New Years and blanketed the Northeast with up to 20 inches (50.8 cm) of snow.  Today, a second winter storm is moving through the Midwest dumping a foot of snow (30 cm) and caused freezing rain in New York.  New York’s JFK airport was closed today for two hours as freezing rain made the runways and taxiways too slick for airlines to operate safely.

We ended up canceling flights between the Caribbean and the United States today.  The pilots were scheduled to fly from the United States to their destination in the Caribbean, then turn around and fly back to their origin airport.  Seeing as the crews took so long to deice out of the United States they ran out of block time.  This meant that the return flight had to be cancelled because they did not have enough block time left to fly back home.  In some cases the crews were just 10 minutes short on their block time limitation.  All of the canceled flights will operate tomorrow under a different flight number so the passengers will still get to where they want to go.  Domestically, as pilots get deeper into their duty day their block time becomes critical.  This means the afternoon shift faces the FAR 117 restrictions a lot more then the dayshift does.  I have not worked an afternoon shift since the new rest rules went into effect so I really don’t know how bad of a problem it is but I am told it is very busy.

While there’s going to be a learning curve at all of the airlines, I have notice some things that airlines can change to help mitigate the challenges of the new pilot rest rules.  The challenges start with crew scheduling and the people that build the pilots rotations.  At my airline, pilots have been given very little “wiggle room” on their block time and or duty day in their rotations.  In irregular operations like airlines have faced at the start of this year, “wiggle room” is needed.  Today if those flights to the Caribbean were two day trips instead of out and backs the pilots could have deiced, flown to the destination and laid over taking the return flight the next day.  While this looks like a great idea on paper airlines do not have enough pilots to allow this change.  Also, a pilot rotation like this would significantly increase the airlines costs.

The second problem that I noticed was a lack of training.  Many people do not know the difference between block time and duty time.  Most of the knowledge that I have on the new rest rules I have found on my own instead of from my company.   These new rest rules take into account both a crews block time and their duty day.  From what I have experienced it is usually only one of those two that limits that effects a crew.  As operations employees we really need to know how to identify a flight crews limitation and understand impact of those limitations before we make any decisions.  Airlines can not master their operation under these new rules until their decision makers fully grasp and understand the differences between block time and duty time.

One thing I am thankful for is increased visibility to the time that a crew has remaining to their day.  My airline has deployed some great automation to make everyone aware of each crews limits.  While the tools are great the knowledge to use those tools is lacking.  While my airline is only five days into these new rest rules I think that we can overcome the challenges they have brought.  It is going to take a few months before the airline industry fully perfects our operation under FAR 117 but I’m confident that we will get there.

In the meantime, I have a few suggestions for the flying public and airline employees:

For the flying public- Take morning flights, the morning flights will be less likely to have any FAR 117 issues and you will be able to make to your intended destination without any problems.  I also suggest that you have some patience.  Be kind to the airline employees that you encounter,  it is not their fault that your flight is delayed or canceled and if they could they would make sure your flight was on time.

For pilots and airline employees- bid early morning shifts with early report times.  If you can end your shift by 4 PM you should avoid most of the delays and cancelations.  For pilots, getting up very early limits your block time and your duty day because of the early start.  In doing that you are less likely to get rerouted because your scheduled flying gets you to your limitation faster.

This is going to be a chaotic few months but I think we will be able to look back on these few months and realize that these new rules really aren’t that bad and they do make aviation even safer.

It’s never a Good Thing to Have Jim Cantore on Your Flight

Today was my first day back to work since the New Year’s holiday. I was working a domestic desk that was working flights primarily to the Northeast; more specifically to Boston. Today there is a major winter storm that is moving out of the Midwest and across the Northeast. It is impacting Boston the hardest. When it is all said and done Boston is going to get between 15-20 in (38-50 cm) of snow. This was the first major winter storm that I’ve worked so far this season. There are many things that you have to consider when working a winter storm but the thing that worries me the most is the condition of the runway on landing. As you know, unlike rain, snow does not come off the runway on it’s own, it requires heavy equipment to remove the snow and to do so they have to close the runway about every hour depending on the intensity of the snowfall.

In winter events like this fuel is always your friend. On all of my flights to Boston I was carrying a good alternate and at least 45 to 60 minutes of holding fuel. This extra fuel onboard gives both the captain and I options when unexpected delays occur. I was making sure to update my crews on the conditions of the runways and what other aircraft were reporting as far as breaking. Pilots report braking action in terms of “good “, “fair “, “poor ” and “nil “. Today at Boston almost all of the breaking action reports were considered to be in the “fair” category. This means that the braking deceleration is noticeably reduced for the wheel braking, or directional control is noticeably reduced. Overall, I wasn’t too concerned about the conditions of the runways with all of the pilot reports calling it fair. When my flight was getting close to Boston they sent me a ACARS message telling me that they were entering a hold because runway 4R was closing so it could be cleared of snow. They also told me that runway 33L was now going to be used but first they wanted to hear what the braking action was before they attempted to land.

While the flight was holding north of Boston I decided to call up our scanner in the Boston area so I could listen to air-traffic control. Being able to actually listen to the air traffic control frequencies really helps aid and speed up the flow of information. I can hear real time what other aircraft are reporting and relay that information quickly to my flights that are inbound to the airport. I was watching all the Boston arrivals on my flight following monitor and I saw that another airline’s airplane that was the same type as my flight was going to be landing on runway 33L first. As I was listening for them to getting their landing clearance what the tower said triggered something in my memory, the air traffic control tower called the winds 050 16 gusting to 25 knots. When that other airlines aircraft called the braking action fair I knew that we could have a problem. My airline has a restriction that says we cannot land on a runway that has braking action less than good with more than a 20 knot crosswind. With the wind that the tower was reporting that runway had a 25 knot crosswind. I reminded the crew of that restriction because it is not often that we have to follow it and it is a restriction that is easily forgotten. The crew and I decided to try and hold until runway 4R opened.

Finally the crew called me on the radio. The captain I discussed the situation in Boston, the runway, the restrictions that we had and their fuel on board. The captain also mentioned they had encountered some moderate icing and had had to climb to get out of it. Aircraft icing happens when supercooled water droplets from the clouds hit the aircraft and freeze. The word moderate indicated that the ice was building up at a pretty heavy rate. We began to talk about where we should divert. I listed Hartford/Windsor Locks Airport as the flights alternate on the release, but just because that was the alternate that I chose during the planning process it does not mean that we had to actually divert there. After some consideration the crew told me that they thought that Providence would be a better alternate because it was closer and the weather was about the same. I looked at the field conditions in Providence and read the notams; I agreed that Providence could be used as an alternate and considering the icing, the aircraft’s fuel on board, the wind speed and direction, and the runway in use at Boston the captain and I decided to divert the aircraft to Providence to get more fuel.

Whenever your diverting an aircraft there’s a long list of people that you have to tell. First of all I had to call the station to let them know they were getting another flight. Then I needed to call the aircraft router to let them know that the flight was diverting so they could delay the aircraft’s next flights. Sometimes you might need to call maintenance so they can get mechanics to meet the flight. Once all that was finished I now needed to issue a flight release from our diversion alternate of Providence back to Boston. All of this takes place while you are still handling your other flights so your workload is increased. Whenever you divert a flight you always want to make sure you have enough gas on board for the return so you don’t end up diverting again. When he got on the ground the captain called me just let me know that they were on the ground safely and what was going on with the aircraft. That is when the captain told me that the icing on the aircraft was the worst he’s ever seen. He said there had to be over an inch of ice on the airplane. This meant the deicing out of Providence was going to take a while. After the crew told me that I asked them if they had taken any pictures (I have seen some iced up aircraft before and I am amazed how the ice builds up on the airplanes), they told me to watch “The Weather Channel” because, of all people, Jim Cantore had taken pictures!

In case you don’t know who Jim Cantore is, he is a famous meteorologist that works for The Weather Channel. In fact, as I’m writing this post I am watching him on TV hoping to catch a glimpse of some of the pictures that he might have taken of the airplane. Looking at his Twitter feed he did post this picture:

View of ice buildup on the ice detector.  Photo from @jimcantore

View of ice buildup on the ice detector. Photo from @jimcantore

His twitter feed also gave the passengers perspective on the diversion. There is a weather Channel commercial about Jim going on vacation to the beach during hurricane season, and everyone that sees him runs because they think a hurricane is coming. The video can be seen here. I have had him on my flight in the past, and the crew sent me an ACARS that said “Jim Cantore is on our flight, Anything we should know?”

While today was a stressful and busy day, I am glad that all of my flights landed safely and Mr. Cantore got to Boston so he could stand out on a snowy Boston street corner to report on today’s snowstorm.

Dancing the Medicine Bow Shuffle – Turbulence Avoidance was the Top of Yesterday’s Agenda

Dancing the Medicine Bow Shuffle – Turbulence Avoidance was the Top of Yesterday’s Agenda

While the Northeast United States was getting hammered with snow yesterday I, thankfully, was working flights to the Southwest United States. The weather was much better in the southwestern part of the United States with almost all the airports being VFR.  The only thing I needed to do on the flights I planned was avoid the turbulence.  Just because turbulence is common while flying, it does not mean that it is unavoidable. There are many things that dispatchers and pilots can do to avoid turbulence and give the passengers a smooth ride.  Most turbulence avoidance starts with the dispatcher during the flight planning process.  Dispatchers have the ability to plan the flight around the turbulence by either changing the altitude or the route the flight takes.

The turbulence that I was avoiding yesterday was a unique type of turbulence called mountain wave turbulence.  This type of turbulence occurs mostly in the wintertime when winds hit the side of a mountain range and get pushed upward.   The stable air that happens in the wintertime causes all of the air to be pushed up causing a wavelike action.  Below shows an illustration of what the waves look like, as you can see it’s called Mountain wave turbulence because it literally looks like waves on an ocean.  When a flight encounters a mountain wave, the airspeed decreases and increases and the altitude changes by a few hundred feet as the aircraft moves over the waves.  Mountain wave turbulence can be very predictable but also can be very severe.  The meteorology department at my airline has spent decades researching mountain waves in an attempt to better predict their occurrence and severity.  Their research is very specific to wind speed, direction and atmospheric stability of the air over specific mountains throughout the world.

As you can see the air hits the side of the mouton and because of the stability of the air a "wave" occurs

As you can see the air hits the side of the mouton and because of the stability of the air a “wave” occurs

The mountains over Alaska, Western Canada and the Western United States generally produce the most mountain waves.  On my flights yesterday the mountains that spread over Colorado, Wyoming and New Mexico were causing moderate mountain waves.  The meteorology department has broken the mountain wave areas into many different regions.  When they tag an area open, we have two ways to avoid these mountain wave areas: we can either fly completely around the area, or we can fly through the regions while following specific routes and avoiding the altitudes that the meteorologist defines.  Yesterday, I chose the first option; it was more economical to avoid the area completely than it was to descend and fly through the area.

I learned very quickly once I started working here the routes to use to avoid the mountain wave in this area.  The route uses the same two navaids; these VOR‘s are Medicine Bow (MBW) and Myton (MTU).  In our office we call this route the Medicine Bow Shuffle because it seems that we are shuffling all of our airplanes around the active areas. I took a screen shot of my graphical flight flowing display in the middle of my shift yesterday.  The magenta lines are the routes that my flights were taking and the small pink airplanes are my actual flights.  As you can see, most of my flight paths were intersecting at either MTU or MBW and than flying the route between those two VOR’s.  All of the airplanes are avoiding the orange polygons, which are the active mountain wave areas.  The other white dashed lines are other mountain wave areas that are not active.  While some of my flights still reported some mountain wave action there was no turbulence associated with that wave while they were on the shuffle.

Green shot of my flights today avoiding the Mountain wave areas over the fixes Myton and Medicine Bow

Screen shot of my flights yesterday avoiding the Mountain wave areas over the fixes Myton and Medicine Bow

While yesterday’s flight planning and turbulence avoidance was specifically because of mountain wave turbulence, the concept of avoiding turbulence also applies to all the other forms turbulence.  A few times a day our meteorology department produces upper air depictions that show us where light, moderate, or even severe turbulence might be.  It is my job as a dispatcher to analyze the risk of the turbulence and decide if I’m going to fly through it or avoid it.  My personal rule of thumb is I will avoid any turbulence that will last over an hour, or if the turbulence is forecasted to be moderate or greater. My goal is to give passengers the smoothest flight possible while also taking into account the economics of the airline.  When the turbulence is completely unavoidable I always want to make sure the crew is going to know when and where the turbulence will start and how long it will last.  I feel if the crew has that information they can mitigate most of the risks on the airplane by telling the flight attendants to take their seats and make sure the passengers have their seat belts fastened.  While the ride through the turbulence might not be the smoothest at least it will be safe and no one will get injured.

If you want to learn more about mountain waves the YouTube video below is by some meteorologists in Alaska and gives more specific scientific information.