Many people take air travel for granted. Thousands of flights traverse the United States each day and flying is so common that sometimes we forget that it’s not as easy as driving a car from point A to point B. Sure, arriving to the airport several hours before your flight, waiting in long security lines, and then the wait to get your back at your destination, assuming it arrived with you, all add to the agony and stress of air travel. It’s certainly not as luxurious as it used to be. However, barring all those inconveniences, there is one thing that is out of everyone’s control: the weather.
Airplanes certainly aren’t magical machines of the sky. They can’t fly through everything and come out without any adverse effects. The weather plays a major role in aviation every single day. The busy holiday travel season makes flying more difficult with additional people flying to and from, more airplanes, more people on airplanes and then, yes, the weather. Is there a big snow storm impacting New York? Is Chicago coated in ice? And is San Francisco socked in fog again? An airline and its pilots must know what the weather is going to be like not only at their destination but also where they depart from and everything in between.
Winter air travel can be difficult. From snow storms to ice storms and strong winds, flying can certainly be a challenge. You might wonder what airlines, pilots, and even air traffic controllers do to help minimize the impacts of winter weather. Here’s some food for thought.
Airline dispatchers receive weather forecasts prior to planning a flight and submitting its flight plan into the air traffic system. Many things are taken into account such as winds aloft, weather conditions at both the departure and arrival airport and any adverse weather impacts en route. They must also file an alternate airport in case they are not able to land at their intended arrival airport. Weather can play a role as to which alternate airport the dispatcher will file for the flight.
Sometimes it’s best to delay a flight to allow the weather to pass. Airlines commonly use this feature in the summertime but not as often in the winter. Significant snow storms and ice storms can delay flights for several hours or last for a couple of days, making delays impractical. More recently, if a big storm is forecast to impact a major airport, airlines are now more likely to cancel flights impacted by the storm rather than delay them. In the past 3-5 years, we have seen airlines do this in advance of the storm. One advantage of this is the fact that you’re not stuck on an airplane on the ramp, snowed in. You’re also not sitting at the gate holding onto some hope that the snow magically lets up and you’ll be able to depart shortly afterward. When it doesn’t happen and the airline finally cancels your flight that wouldn’t have departed anyway, you’re stuck at the airport scrambling to decide on what you will do next. Instead you’re at home, or your hotel, or your in-laws house, wondering when you’ll be able to depart. You might be a little irritated by your in-laws but at least you’re not spending a night at O’Hare sleeping on the floor.
Air Traffic Controllers constantly review forecasts to help plan several things. At the airport, controllers often have to deal with snow removal. No they’re not out there shoveling however they still need to figure out how they will get planes to and from the runways. Typically, these plans are made months in advance and agreed upon between the controllers and the authority operating the airport. It’s a detailed plan on how snow will be removed from the runways and taxiways that everyone knows and understands. When the snow falls, these plans begin to go into effect.
Enroute, weather forecasts help controllers determine where the weather will make the most impact and which routes will be affected. They may need to reroute traffic to avoid certain parts of the weather. Wind forecasts are especially critical to both airlines and controllers as it affects how fast planes can move. It also impacts fuel usage, which costs the airlines money and reduces the overall range of the aircraft. Strong winds can also create turbulence, which pilots like to avoid as it can mean a fairly unpleasant ride for passengers.
What To Do About All This Snow?
You’re in Washington, DC and it just got done snowing. Yep, all 18 inches of snow has fallen and covered everything in a fresh coat of powder. It looks pretty but you’re due to catch a flight soon and you’re wondering if you’ll depart on time. Fortunately the roads aren’t all that bad and as you head to the airport you’re hoping the runways are clear.
We discussed how airports and controllers work together to devise a plan on how to clean snow off of runways and taxiways. It takes several hours to clear snow off of all surfaces at a large airport, so many airports have a tiered plan where only certain surfaces are cleared or are cleared first, followed by others at another time. Fortunately, they have been plowing the airport and are doing a pretty good job of getting things clear. But the airplane is buried in snow.
Planes cannot fly with snow on them. The snow won’t magically fly off the wings when it starts moving. Further, ingesting large amounts of snow or ice into the engine has severe impacts on performance and can damage the engine. Planes have tried to do this before. It happened January 13, 1982 when Air Florida Flight 90 tried to depart Washington-National Airport with snow on the wings and in the engine cowls. The aircraft couldn’t produce enough lift due to the contaminated wings and the engines also ingested ice. The plane made it airborne for a short period of time before striking a bridge and crashing into the icy Potomac River. Of the 74 passengers and 5 flight crew members, only four passengers and a flight attendant lived. Four motorists on the bridge were also killed. It was from this crash that the industry began to take deicing seriously.
To get the snow off the wings, you need a very large snow brush. Ok, so they don’t have any of those. However, there are a few things that do get used. De-icing and anti-icing fluids are sprayed on to the aircraft to remove any snow or ice contamination prior to the aircraft taking off. There are two common types of fluid you’ll usually see: Type I or Type IV (Type one or type four). Type I is a de-icing fluid, which is meant to remove any accumulated snow or ice present on the aircraft. It will also counter any light precipitation falling at the time however the “holdover” time is typically short. This means that the airplane needs to be deiced and in the air fairly quickly before additional snow or ice begin to build up again. You’ve probably seen this fluid as it is usually dyed orange. We don’t recommend eating orange snow.
Type IV fluid is an anti-ice fluid. Its job is to prevent accumulation of additional snow or ice for a specified period of time, which is determined by several factors such as temperature and the current conditions at the time. It’s a thicker fluid that won’t run off the airplane quickly. One the airplane reaches a certain speed when taking off, the fluid will run off the airplane. It’s green in color. We also don’t recommend eating green snow, either.
The next time you fly in the winter and have to go through deicing, you’ll know what is being applied to the airplane by just looking at the color of the fluid being sprayed. In snowy conditions, you will see both sprayed on the airplane. Type I to remove any current accumulation and Type IV to prevent accumulation.
Holiday Travel Volume
Airports are busy places during the holiday season. In addition to more people flying, there’s usually more airplanes in the air too. Since we all can’t land at LaGuardia at once, there needs to be some kind of order. We have that in our Air Traffic Control system.
While we can’t flood the controller working arrivals into LaGuardia all at once and expect a miracle to happen, we can certainly give that controller airplanes at a certain interval, in order to make everyone’s lives easier. This is done through several traffic management initiatives. We’ve all heard of a ground stop, where planes are not allowed to depart or arrive from a particular airport for some given reason. There are others too that get used daily.
Ground Delay Program: Airplanes are delayed at their departure airport because of demand or weather at their arrival airport. Aircraft are assigned a certain time in which to depart and have a small window in which to depart, usually 10 minutes. This helps bring demand to a more manageable level and spread out arrivals so as not to exceed the airport’s capacity.
Something (or someone?) known as “Traffic Management Advisor” (TMA)
Effectively known as “time based metering,” this is an air traffic program that uses a specified time interval to have planes depart an airport destined for the airport in which time based metering is in effect. Controllers may use “minutes-in-trail” or more commonly, “miles-in-trail” to space out arrivals to the same airport so that they arrive at pre-determined intervals over specified airspace fixes. This spreads out demand and keeps the airport from exceeding capacity. It is most commonly used for the busier airports such as Chicago, airports in New York and Washington, DC and others. It can also be used to help spread out demand when weather impacts an airport. Sometimes these delays can be a little long, but in the end you’ll arrive where you want to go.
And sometimes, a plane just has to be rerouted because its usual route isn’t usable due to the weather. Strong winds, icing, heavy snow and other factors may make a particular route unavailable. That means more flying time and a longer airplane ride. Sometimes this can be done before the plane departs and at other times, it has to be done in the air.
There are several other programs that controllers use to help with demand both when the weather impacts an airport or just the usual holiday travel demand. Ever go skiing in Aspen, CO? It’s pretty popular this time of year and because of that, the small airports in the area see huge demand and controllers follow pre-determined routes and use pre-determined departure times for flights going to those airports in order to spread out demand.
The next time you are traveling, take a look at the forecast not just at your destination, but also at the airport you’ll be departing from and then take a look at the big picture: is there anything that might impact my flight en route? If so, how might it impact your flight? Could they delay our departure, re-route us, or cancel the flight? These are all things you can consider before you get to the airport and help in making any last second decisions if your flight gets affected by the weather.
Additional Sources of Information:
- Tools Used for Traffic Flow Management: https://www.nbaa.org/ops/airspace/tfm/tools/
- Deicing Fluid: https://en.wikipedia.org/wiki/Deicing_fluid
- Air Florida Flight 90: https://en.wikipedia.org/wiki/Air_Florida_Flight_90
Mark Spencer is a professional air traffic controller and a pilot, with over 10 years’ experience in the aviation field. Mark has worked at both terminal and en route facilities, giving him experience in controlling aircraft to and from an airport and while en route to their destinations.
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