Weather Hazards In Aviation: Icing
"Weather is an important factor that influences aircraft performance and flying safety" (PHAK, 2016).
For this week's blog I chose to talk about icing and how it is one of the greatest weather hazards. According to the journal of Aerospace Science and Technology, aircraft icing can cause severe aerodynamic and flight mechanical effects (Cao, Tan, & Wu, 2018). We cannot control the weather or temperatures when flying, so it is important to understand the hazard. I did not know a ton about icing, so I thought this would be interesting to talk about and research, and it did also make me realize how important de-icing fluids and ground deicing is. The FAA requires a "clean aircraft" at takeoff under FAR Parts 121 and 135 (FAA, n.d.)
The different types of icing include induction icing, carburetor icing, structural icing, and ground icing.
Induction icing is when ice forms on the aircraft's air induction ports and filters, which can lead to loss of power of the engine from ice blocking the air before it enters (AOS, n.d.). Carburetor icing is when ice forms in the throat of a carburetor when moist air drawn into it is cooled to the frost point, and this can lead to adverse effects on engine operation which leads to loss of power (AOS, n.d.). We all know what structural icing is, which is ice forms on the airframe/structural part of the aircraft during flight through clouds or liquid precipitation (less than 32 degrees F). Anything less than this temperature and cloud formations/precipitation present makes icing possible and a threat to operations. When ice accumulates on an aircraft's airframe from freezing temperatures, the weight increase which can lead to adverse effects such as reduced performance, blockage of pitot tubes/static vents, loss of lift, and loss of control which can lead to a stall. An early symptom of airframe icing is decreased airspeed. Lastly, ground icing occurs on the ground at the airports from freezing rain/drizzle, wet snow, and frost, which negatively effects takeoffs and landings. (Information retrieved from the University of Wisconsin-Madison Atosphere & Oceanic Science)
There are also different icing types and intensity. I am going to paste something in I found from the same source on weather for pilots so the information is straightforward:
- Icing types
- Clear ice - The formation of a layer of hard, smooth, glossy ice on an aircraft. It is relatively transparent or translucent. Clear ice is heavy and difficult to remove.
- Rime ice - The formation of a white or milky and opaque granular deposit of ice on an aircraft. Rime ice is the most common type of icing.
- Mixed ice - A combination of clear ice and rime ice.
- Icing Intensity is related to the rate of accumulation of ice on the aircraft. The different intensities are listed below:
- Trace - Ice becomes perceptible. Rate of accumulation of ice is slightly greater than the rate of loss due to sublimation.
- Light - The rate of accumulation may create a problem for flight in this environment for one hour.
- Moderate - The rate of accumulation is such that even short encounters become potentially hazardous.
- Severe - The rate of accumulation is such that de-icing/anti-icing equipment fails to reduce or control the hazard.
Cao, Y., Tan, W., & Wu, Z. (2018). Aircraft Icing: An Ongoing Threat to Aviation Safety. Aerospace Science and Technology, 75, 353-385. DOI: 10.1016j.ast.2017.12.028. Retrieved from https://www-sciencedirect-com.ezproxy.libproxy.db.erau.edu/science/article/pii/S1270963817317601?via%3Dihub
Federal Aviation Administration. (2016). Pilots Handbook of Aeronautical Knowledge (PHAK). Retrieved from https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak
Federal Aviation Administration. (n.d.). Ground DEICING and Anti-Icing. Retrieved from https://www.faa.gov/documentLibrary/media/Advisory_Circular/ac135-16.pdf#:~:text=The%20current%20regulations%20in%20FAR%20Parts%20121%20and,of%20the%20airplane%20%28FAR%20Sections%20121.629%20and%20135.227%29.
University of Wisconsin-Madison Atosphere & Oceanic Science. (n.d.). Weather for Pilots: Lesson 12. Retrieved from http://www.aos.wisc.edu/~aos152/lesson12/content.html
Arbogast, S. (2013). Aircraft Icing and How it Affects Your Flight. Universal Weather & Aviation, Inc. Retrieved from https://www.universalweather.com/blog/aircraft-icing-and-how-it-affects-your-flight/
ReplyDeleteThis is an interesting topic, icing in general is considered one of the most adverse conditions that can be encounter by an airplane in flight that can adversely affect the maneuverability that could possibly lead to loss of control. On the ground all forms of icing can affect the airplane will behave if takeoff is attempted without any precautions such as: airframe deicing and anti-icing fluids to prevent airfoils contaminants during the take-off roll and initial climb.
While this chemicals are available on the ground to assure a safe takeoff under the right conditions and application process it may not prevent further structural icing while in flight. For that reason, the use of anti ice equipment is necessary to maintain the smooth flow of air over the wing to continue to generate constant lift. Weather experts recommend to avoid icing conditions, and if encounter in flight the best decision is to find your way out, even with anti-ice equipment structural icing could easily overcome the system. Severe rime icing conditions will stick to the entire aircraft (while in flight), this will cause an increase in drag, the unprotected flying areas of the airplane (wing/tail camber and bottom, fin...) will rapidly get ice formation and, while icing may not add a lot of weight in the aircraft the most significant effect is the disruption of airflow.
Here is the problem, I mentioned that icing adds drag thus, in flight power is added to compensate for the added drag lifting the nose up to maintain altitude, as the nose lifts the angle of attack increases, this operation exposes the unprotected areas of the airplane producing more formation, ice is now form on every surface of the airplane. In big airplanes it can cause severe aerodynamic changes causing a tail stall one of the most unfavorable types of stall in large transport aircraft, mostly unrecoverable.
In small General Aviation aircraft, some may be equip with deice systems, most of them made to fly thru light icing conditions at low flight levels, but not to fly in icing conditions (if it make sense). Other piston power airplanes lack of deicing equipment and they’re are prohibited to fly in icing conditions, the effects of airframe icing will cause a much higher stall speed, engine stoppage, carburetor ice, among others...all this conditions added may cause the airplane to roll and pitch uncontrollably, also the recovery may be imposible.
Finally, the best practice is to study the enroute weather carefully, understand all the types of icing, the limitations and capabilities of your aircraft and mostly be prepared to have an escape plan if icing is encounter during flight. Understanding weather will allow you to chose the best route to avoid all weather hazards.
Aerial- thanks for sharing all those types of icing, I glad you research an explored this weather phenomenon that pilots encounter during the entire year. Great job!!
MANUEL