The thing that many American Airlines customers like best about February is its brevity, because the shortest month of the year inevitably brings nasty weather to many of the places we fly to. Cold weather also creates operational challenges for our airline. Safe flight depends on an aircraft having its wings, engines, and control surfaces free of freezing rain, ice, and snow. We spend a lot of money, time, and effort to keep these surfaces of our aircraft clean. Most of the time, we are able to accomplish this and still depart on time. However, because safety is always our top priority, some delays are unavoidable.
Ice and snow have the potential to distort the curvature of a wings upper surface and to disturb the normal airflow, thus interfering with an airplanes control mechanisms. To prevent this from happening, we deice to remove ice and we anti-ice to keep ice from returning. These two processes involve spraying various fluids on the control surfaces of the planes wings and tail, on the wings themselves, and, in some circumstances, on the engine inlets and the fuselage. A single application usually gets the job done, but in heavy weather or when we expect a longer-than-normal wait between deicing and takeoff it can be necessary to apply a second, thicker compound to prevent new accumulation.
The fluids we use are a combination of ethylene or propylene glycol, hot water, and several additives. Referred to as Type I, Type II, and Type IV, these fluids keep ice and snow from building up on the airplanes critical surfaces for a holdover period, which varies according to the weather conditions and the aircraft type. Because these substances, in sufficient quantities, are potentially hazardous to the environment, they are handled according to strict guidelines. In fact, where an aircraft can be deiced depends on each airports collection capabilities. Deicing can take place at a designated area near the end of the runway, at the gate, or at another specified location.
Depending on the weather and on the amount of time between treatment and takeoff, an aircraft may need to be checked one last time before departure. For a given aircraft and wing configuration, the Federal Aviation Administration mandates that the check be done either visually (by the pilots from inside the airplane) or physically (by specially trained ground personnel outside).
Once the airplane has taken off, it keeps its critical surfaces clear of contamination by means of special heaters in strategic locations. Whats more, the temperature, airflow, and humidity experienced at the higher cruise altitudes often cause moisture to pass directly from a solid to a vapor state, thus cleaning the surfaces naturally.
The deicing process, while conceptually simple, is complex in practice. We give our people extensive training in the details of our procedures, the aerodynamic effects of snow and ice, and the chemical properties of the fluids used. Everyone involved gets both initial and recurrent training. Inevitably, some flight delays will occur, but we will never compromise when it comes to safety, and increased knowledge, better compounds, and carefully followed procedures have made winter flying safer than ever.
My hope, of course, is that you will never get caught in a weather delay. But if you do, Im sure you will appreciate the many people working hard to make sure your aircraft is ready to fly safely. On their behalf, and on behalf of everyone at American Airlines, thank you for flying with us today. Stay warm!
Gerard J. Arpey