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 and any contamination 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.
The use of deicing boots may enable some aircraft to be certified for flight into known icing conditions.
Several disadvantages are associated with the use of deicing boots. Boots need to be replaced frequently (on the order of 2–3 years), and 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.
The use of boots may not be sufficient to handle extremely severe icing. In these cases, ice can accumulate faster than the boots can shed it, or ice can accumulate on non-booted surfaces to the point where it disrupts airflow enough to cause a dangerous loss of lift or control.
Invention and use
Deicing boots were invented by the B.F. Goodrich Corporation in 1923 in Akron, Ohio. 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. 
Deicing boots are most commonly seen on medium-sized airliners and utility aircraft. Larger airliners and military jets tend to use heating systems that are installed underneath the wing's leading edge, keeping it constantly warm and preventing ice from forming.
Other deicing techniques for larger commercial aircraft include electrothermal systems and bleed air systems. Electrothermal systems draw electrical current in resistive parts, usually the leading edges themselves. These systems require substantial electrical power and are generally used on large aircraft. Bleed air systems use high-temperature, compressed air from the engine compressor sections, and duct it towards the deiced sections where it absorbs heat before being released into the airflow.
Boeing uses electrothermal ice protection on the wings of the 787. Electrothermal ice protection systems are being considered more often than boots and bleed air systems on commercial aircraft. General aviation jet manufacturers also are studying the effect on thrust and fuel consumption of bleed air and additional benefits of its removal.
- "Artificial Blizzards Help To Protect Planes", February 1931, Popular Mechanics illustration of blizzard machine and how de-icing boots work
- "Overshoes For Planes End Ice Danger", November 1931, Popular Science bottom of page 28
- paper AIAA 2006-228 by John Ensign and Dr. John Gallman from the Cessna Aircraft Company
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- Investigations of Performance of Pneumatic Deicing Boots, Surface Ice Detectors, and Scaling of Intercycle Ice, FAA report, November 2006
- Aircraft Deicing and Anti-icing Equipment, AOPA Air Safety Foundation, Oct 2004
- NTSB Warns Pilots To Use De-Icing Boots Early, AVWeb, Dec 2008