A deicing boot is a type of ice protection system installed on aircraft surfaces to permit a mechanical deicing in flight. Such boots are generally installed on the leading edges of wings and control surfaces (e.g. horizontal and vertical stabilizer) as these areas are most likely to accumulate ice which could severely affect the aircraft's performance.
A deicing boot consists of a thick rubber membrane that is installed over the surface to be deiced. As atmospheric icing occurs and ice builds up, a pneumatic system inflates the boot with compressed air. This expansion in size cracks any ice that has accumulated, and this ice is blown away into the airflow. The boots are then deflated to return the wing or surface to its optimal shape.
Boots require proper care. Holes in the boot may create air leaks that will decrease the effectiveness of the boots. As such, boots must be carefully inspected before each flight and any holes or cuts must be patched.
Deicing boots were invented by the B.F. Goodrich Corporation in about 1929–1930 in Akron, Ohio. The work was begun by retired Ph.D chemist, William C. Geer. In its quest to develop deicing boots, the company built a large indoor facility in Akron to replicate bad weather and icing on aircraft wings. [1] [2] [3]
The use of deicing boots may enable an aircraft to be certified for flight into known icing conditions. However, they may not be sufficient to handle extremely severe icing, where ice can accumulate faster than the boots can shed it, or it accumulates on non-booted surfaces to the point where there is a dangerous loss of lift or control, or increase in weight.
Deicing boots are most commonly seen on medium-sized airliners and utility aircraft. Larger airliners and military jets tend to use heating systems within the wing, keeping it constantly warm and preventing ice from forming. Sources of heat include:
'Ice bridging' is the theory that activating deicing boots early may lead to a condition where slushy ice is pushed into a hollow shell around the inflated boot, then freezes in place. This shell can then no longer be dislodged by any further operation of the boot. Bridging was described by the aviation writer Ernest Gann in his memoir Fate Is the Hunter .
The bridging theory is now disputed. In 2008 the NTSB issued an alert [4] that pilots should, "activate boots as soon as the airplane enters icing conditions". [5] Their claim was that bridging was "extremely rare, if it exists at all" and that there were no instances where it had led to an accident. Unwarranted fear of ice bridging contributed to the fatal crash of Comair Flight 3272.
Freezing rain is rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow or ice pellets, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter, including the ground, trees, electrical wires, aircraft, and automobiles. The resulting ice, called glaze ice, can accumulate to a thickness of several centimeters and cover all exposed surfaces. The METAR code for freezing rain is FZRA.
Air Florida Flight 90 was a scheduled U.S. domestic passenger flight operated by Air Florida from Washington National Airport to Fort Lauderdale–Hollywood International Airport, with an intermediate stopover at Tampa International Airport. On January 13, 1982, the Boeing 737-222 registered as N62AF crashed into the 14th Street Bridge over the Potomac River just after take off from Washington National Airport.
The General Electric GEnx is an advanced dual rotor, axial flow, high-bypass turbofan jet engine in production by GE Aerospace for the Boeing 747-8 and 787. The GEnx succeeded the CF6 in GE's product line.
Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine compressor sections; low stage air is used during high power setting operation, and high stage air is used during descent and other low power setting operations. Bleed air from that system can be utilized for internal cooling of the engine, cross-starting another engine, engine and airframe anti-icing, cabin pressurization, pneumatic actuators, air-driven motors, pressurizing the hydraulic reservoir, and waste and water storage tanks. Some engine maintenance manuals refer to such systems as "customer bleed air".
Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prevent adhesion of ice to make mechanical removal easier.
USAir Flight 405 was a regularly scheduled domestic passenger flight between LaGuardia Airport in Queens, New York City, New York, and Cleveland, Ohio. On March 22, 1992, a USAir Fokker F28, registration N485US, flying the route, crashed in poor weather in a partially inverted position in Flushing Bay, shortly after liftoff from LaGuardia. The undercarriage lifted off from the runway, but the airplane failed to gain lift, flying only several meters above the ground. The aircraft then veered off the runway and hit several obstructions before coming to rest in Flushing Bay, just beyond the end of the runway. Of the 51 people on board, 27 were killed, including the captain and a member of the cabin crew.
Continental Airlines Flight 1713 was a commercial airline flight that crashed while taking off in a snowstorm from Stapleton International Airport in Denver, Colorado, on November 15, 1987. The Douglas DC-9 airliner, operated by Continental Airlines, was making a scheduled flight to Boise, Idaho. Twenty-five passengers and three crew members died in the crash.
In aviation, icing conditions are atmospheric conditions that can lead to the formation of water ice on an aircraft. Ice accretion and accumulation can affect the external surfaces of an aircraft – in which case it is referred to as airframe icing – or the engine, resulting in carburetor icing, air inlet icing or more generically engine icing. These phenomena may possibly but do not necessarily occur together. Both airframe and engine icing have resulted in numerous fatal accidents in aviation history.
Atmospheric icing occurs in the atmosphere when water droplets suspended in air freeze on objects they come in contact with. It is not the same as freezing rain, which is caused directly by precipitation. Icing conditions can be particularly dangerous to aircraft, as the built-up ice changes the aerodynamics of the flight surfaces and airframe, which can increase the risk of a stall and potentially accidents. For this reason, on-board ice protection systems have been developed on aircraft intended to fly through these conditions.
American Eagle Flight 4184, officially operating as Simmons Airlines Flight 4184, was a scheduled domestic passenger flight from Indianapolis, Indiana to Chicago, Illinois, United States. On October 31, 1994, the ATR 72 performing this route flew into severe icing conditions, lost control and crashed into a field. All 68 people aboard were killed in the high-speed impact.
In aeronautics, ice protection systems keep atmospheric moisture from accumulating on aircraft surfaces, such as wings, propellers, rotor blades, engine intakes, and environmental control intakes. Ice buildup can change the shape of airfoils and flight control surfaces, degrading control and handling characteristics as well as performance. An anti-icing, de-icing, or ice protection system either prevents formation of ice, or enables the aircraft to shed the ice before it becomes dangerous.
Comair Flight 3272 was a Comair flight from Cincinnati to Detroit on Thursday, January 9, 1997. While on approach for landing, the Embraer EMB 120 Brasilia aircraft crashed nose-down 18 miles (29 km) southwest of Detroit Metropolitan Wayne County Airport at 15:54 EST. All 29 aboard, 26 passengers and three crew members, were killed.
In ground deicing of aircraft, aircraft deicing fluid (ADF), aircraft deicer and anti-icer fluid (ADAF) or aircraft anti-icing fluid (AAF) are commonly used for both commercial and general aviation. Environmental concerns include increased salinity of groundwater where de-icing fluids are discharged into soil, and toxicity to humans and other mammals.
Belavia Flight 1834 was a scheduled international passenger flight from Yerevan, Armenia, to Minsk, Belarus, operated by Belavia. On the morning of February 14, 2008, the Bombardier Canadair Regional Jet carrying 18 passengers and three crew crashed and burst into flames shortly after take off from Zvartnots International Airport near Yerevan, the capital of Armenia.
Aircraft systems are those required to operate an aircraft efficiently and safely. Their complexity varies with the type of aircraft.
Colgan Air Flight 3407 was a scheduled passenger flight from Newark, New Jersey, USA to Buffalo, New York, USA on February 12, 2009. Colgan Air staffed and maintained the aircraft used on the flight that was scheduled, marketed and sold by Continental Airlines under its Continental Connection brand. The aircraft, a Bombardier Q400, entered an aerodynamic stall from which it did not recover and crashed into a house at 6038 Long Street in Clarence Center, New York at 10:17 pm EST, killing all 49 passengers and crew on board, as well as one person inside the house.
United Express Flight 2415 was a regularly scheduled flight in the northwest United States from Seattle to Pasco, Washington, operated using a BAe Jetstream 31. Late on Tuesday, December 26, 1989, Flight 2415 crashed while attempting to land at Pasco's Tri-Cities Airport, killing both pilots and all four passengers aboard.
Ryan International Airlines Flight 590 was a cargo flight carrying mail for the United States Postal Service from Greater Buffalo International Airport (BUF) in Buffalo, New York, to Indianapolis International Airport (IND) in Indiana, with a stopover at Cleveland Hopkins International Airport (CLE) in Cleveland, Ohio. On February 17, 1991, the McDonnell Douglas DC-9-15RC operating the flight crashed on takeoff from Cleveland during icing conditions. Both pilots, the aircraft's only occupants, were killed. The National Transportation Safety Board (NTSB) determined that the causes of the crash were the flight crew failing to deice their aircraft, and the inexperience of the Federal Aviation Administration (FAA), McDonnell Douglas, and Ryan International Airlines with icing condition on DC-9-10 aircraft.
Pilgrim Airlines Flight 458 was a scheduled United States passenger air commuter flight from LaGuardia Airport in New York City to Logan Airport in Boston, Massachusetts, with stopovers in Bridgeport, New Haven, and Groton, Connecticut. On February 21, 1982, the de Havilland Canada DHC-6-100 operating the flight made a forced landing on the frozen Scituate Reservoir near Providence, Rhode Island after a fire erupted in the cockpit and cabin due to leakage of flammable windshield washer/deicer fluid. One passenger was unable to escape the aircraft and died of smoke inhalation, and eight of the remaining nine passengers, as well as both crew members, received serious injuries from the fire and crash-landing.
In aviation, ground deicing of aircraft is the process of removing surface frost, ice or frozen contaminants on aircraft surfaces before an aircraft takes off. This prevents even a small amount of surface frost or ice on aircraft surfaces from severely impacting flight performance. Frozen contaminants on surfaces can also break off in flight, damaging engines or control surfaces.