By Doug Morris
At 4:01 pm on Jan. 13, 1982, Air Florida flight 90 crashed into the ice-filled Potomac River just 30 seconds after takeoff from Washington National Airport.
By Doug Morris
At 4:01 pm on Jan. 13, 1982, Air Florida flight 90 crashed into the ice-filled Potomac River just 30 seconds after takeoff from Washington National Airport. The crash killed 78 people, including four who were in cars on the 14th Street Bridge over the river. The story of what happened on that January day is one of tragic human error in the face of extreme weather conditions.
Unfortunately, the history of air travel is filled with similar tragedies as the airline industry in Canada, the US and elsewhere took a decidedly ‘laissez-faire’ approach to the task of deicing. On Dec. 12, 1985, a DC-8 loaded with American soldiers stalled at the end of the runway in Gander, Nfld. in freezing drizzle, killing 248 soldiers and eight crewmembers. For years the telltale scar it gouged in the terrain sent a vivid reminder of what ice on wings can cause. The crash of a commuter jet in Dryden, Ont. in 1989 also exemplified the perils of airframe icing. The Fokker 28 crashed 15 seconds after takeoff, unable to achieve enough altitude to clear the trees beyond the end of the runway because of ice and snow on the wings. The crash resulted in the death of 21 of the 65 passengers and three of the four crew.
A Change in Regulations
In the early years, the decision to deice a plane was made by the captain or the airline. Throughout the industry, there was a tendency to push resistance against deicing to the limits because of time constraints, low operating budgets, and a general lack of knowledge about the perils of ice on an aircraft.
In both Canada and the US it took a horrific crash related to airframe icing to instigate a change in deicing regulations. These days, any second-guessing is removed from the equation, and the old grey area no longer exists. Both Canadian and American regulations now prohibit takeoff when ice, snow and frost is adhering to any critical surface of the aircraft, including lifting and control surfaces, wings and tail, and upper fuselage surfaces on aircraft with rear-mounted engines. The rule is known as the “clean aircraft concept.” The main exception to the new regulations allows a coating of frost up to one-eighth of an inch on wing lower surfaces in areas cold-soaked by fuel, between the forward and aft spars. Deicing also is not mandatory if the captain expects dry snow lying on top of a cold, dry and otherwise clean wing to blow off during the takeoff roll. Although pilots are in charge of deciding whether or not deicing is needed, the lead ramp attendant can overrule a decision not to deice.
Toronto’s Central Deicing Facility
In Canada, icing conditions can lurk nearly nine months of the year, so the deicing checklist is always within reach because it’s part of doing business. As the old aviation adage goes, “If you think safety is expensive, try having an accident.”
The Central Deicing Facility (CDF) at Toronto’s Pearson International Airport is the largest deicing facility in the world. Fully operational since the 1999-2000 cold season, this 65-acre “drive-through airplane wash” consists of six huge bays capable of handling hundreds of aircraft daily. It has an official deicing season of Oct. 1-April 30. Many pilots jokingly refer to the CDF as the “Central Delay Facility,” but the fact that most pilots are paid by the minute takes the sting out of any wait. In addition, the short time it takes to spray a plane with deicing fluid is insignificant compared with the potential for disaster if a pilot did not take the time to deice the aircraft.
Moreover, the CDF actually has reduced time between deicing and takeoff because it was built closer to the runways and has increased overall throughput and improved turnaround times. On the way to the CDF, pilots radio “pad control,” which assigns the aircraft a deicing bay. Because this is a “live” or “engines-running” operation, precise terminology and electronic signboards are used to eliminate any potential for accidents. Pilots then contact the “Iceman” in the deicing control centre, appropriately nicknamed the “Icehouse.”
Once the aircraft is in position to receive the spray, a Danish-made Vestergaard Elephant Beta springs into action. The CDF has 27 Beta machines, each of which costs about $1 million. (Two Beta 15s able to stretch nearly 76 feet into the air have been acquired capable of deicing the mammoth Airbus 380). The Iceman tells the pilot the exact time deicing started, the type of fluid used, and when the vehicles have retreated to their safety zones. A safety zone is an area ensuring a safe distance between the aircraft and deicing vehicle. The deice vehicles must be behind these lines before an aircraft can exit the deicing area.
While many airports still employ the manually operated ‘cherry pickers’ staffed by two (one driver and one in the bucket) ground crew who must brave the bitter winds and backspray, the CDF machine is operated remotely from the heated enclosed cab. It is armed with deicing fluid, nozzles, whisker-like probes to prevent aircraft contact, and a telescopic boom to reach distant spots and critical flight surfaces.
The deicing procedure involves spraying fluids that remove or prevent ice buildup all over the aircraft. Made up of combinations of glycol and water, deicing and anti-icing fluids come in different varieties that serve a specific function. The difference between the types of fluid is the “holdover time,” or the time from when deicing commences to the time the airplane must be airborne based on temperature and precipitation rate and type. For most operations, the deicing Type I fluid (orange) is used to remove the snow and ice and type IV (green) is to prevent further adhering of ice. (Type II, which is longer lasting, more expensive and designed for jet aircraft, is rarely used and type III is not available in the US and Canada but is found in Europe).
Once an airplane has been deiced, all of the extraneous fluid that falls off the aircraft is collected in massive holding tanks to ensure compliance with environmental regulations; deicing fluid can be a hazard to nearby bodies of water. The tanks can hold a whopping 13 million litres of reclaimed fluid while it waits to be treated. Some of the spent fluid is used to make car windshield wash and engine coolant. (You may even see a large vacuum truck called the Glycol Recovery Truck (GRV) a.k.a the “slick licker” sucking up fluid). It cannot be re-used for airplane deicing because possible degradation of the fluid means its effectiveness cannot be guaranteed. Most airlines prohibit the use of recycled fluid.
Joe Forbes, senior manager of deicing operations at the Greater Toronto Airports Authority, says a typical Airbus A320 in light snow conditions requires 303 litres of Type I fluid and 261 litres of Type IV fluid, with actual deicing time taking just over four minutes. The throughput time at CDF for an Airbus 320 is 12 minutes.
At a dollar a litre for Type I and over double that for Type IV, deicing an airplane is an expensive proposition. During one three-day ice storm in April 2003, the CDF used over 1.5 million litres, the highest amount in the facility’s history. “At one point the CDF actually ran out of deicing fluid and scrambled to get more,” Forbes said. One truckload of 17,000 litres from Chicago was dispensed on a single “heavy.” (That day I arrived direct from Tokyo. It made for an even longer day waiting for a gate to open because of the backup).
Taking a back-seat approach to aircraft icing is passé; getting rid of it is today’s only option. The number of aviation accidents related to airframe icing has decreased considerably in recent years, thanks in large part to the stricter regulations and the construction of more effective deicing facilities like Toronto’s CDF. Maybe one day soon you’ll experience a coloured fluid flowing down your airplane’s window knowing full well the deice man has cometh.
Doug Morris flies the Airbus A320, is a certified meteorologist and is author of “From the Flight Deck: Plane Talk and Sky Science.”