Aeronautical Information Manual (AIM), page 541

Index   540 -- Page 541 -- 542

4. Protect your aircraft while on the ground, if
possible, from sleet and freezing rain by taking
advantage of aircraft hangars.
5. Take full advantage of the opportunities
available at airports for deicing. Do not refuse deicing
services simply because of cost.

6. Always consider canceling or delaying a
flight if weather conditions do not support a safe

c. If you haven't already developed a set of
Standard Operating Procedures for cold weather
operations, they should include:
1. Procedures based on information that is
applicable to the aircraft operated, such as AFM
limitations and procedures;

2. Concise and easy to understand guidance that
outlines best operational practices;
3. A systematic procedure for recognizing,
evaluating and addressing the associated icing risk,
and offer clear guidance to mitigate this risk;

4. An aid (such as a checklist or reference cards)
that is readily available during normal day-to-day
aircraft operations.
d. There are several sources for guidance relating
to airframe icing, including:

1. http://aircrafticing.grc.nasa.gov/index.html
2. http://www.ibac.org/is-bao/isbao.htm

3. http://www.natasafety1st.org/bus_deice.htm
4. Advisory Circular (AC) 91-74, Pilot Guide,
Flight in Icing Conditions.

5. AC 135-17, Pilot Guide Small Aircraft

Ground Deicing.

6. AC 135-9, FAR Part 135 Icing Limitations.

7. AC 120-60, Ground Deicing and Anti-icing


8. AC 135-16, Ground Deicing and Anti-icing

Training and Checking.

The FAA Approved Deicing Program Updates is
published annually as a Flight Standards Information
Bulletin for Air Transportation and contains detailed
information on deicing and anti-icing procedures and
holdover times. It may be accessed at the following
web site by selecting the current year's information


7-5-15. Avoid Flight in the Vicinity of
Exhaust Plumes (Smoke Stacks and
Cooling Towers)

a. Flight Hazards Exist Around Exhaust
Plumes. Exhaust plumes are defined as visible or
invisible emissions from power plants, industrial
production facilities, or other industrial systems that
release large amounts of vertically directed unstable
gases (effluent). High temperature exhaust plumes
can cause significant air disturbances such as
turbulence and vertical shear. Other identified
potential hazards include, but are not necessarily
limited to: reduced visibility, oxygen depletion,
engine particulate contamination, exposure to
gaseous oxides, and/or icing. Results of encountering
a plume may include airframe damage, aircraft upset,
and/or engine damage/failure. These hazards are
most critical during low altitude flight in calm and
cold air, especially in and around approach and
departure corridors or airport traffic areas.

Whether plumes are visible or invisible, the total
extent of their turbulent affect is difficult to predict.
Some studies do predict that the significant turbulent
effects of an exhaust plume can extend to heights of
over 1,000 feet above the height of the top of the stack
or cooling tower. Any effects will be more
pronounced in calm stable air where the plume is very
hot and the surrounding area is still and cold.
Fortunately, studies also predict that any amount of
crosswind will help to dissipate the effects. However,
the size of the tower or stack is not a good indicator

of the predicted effect the plume may produce. The

major effects are related to the heat or size of the
plume effluent, the ambient air temperature, and the
wind speed affecting the plume. Smaller aircraft can

expect to feel an effect at a higher altitude than

heavier aircraft.

b. When able, a pilot should steer clear of

exhaust plumes by flying on the upwind side of
smokestacks or cooling towers. When a plume is
visible via smoke or a condensation cloud, remain
clear and realize a plume may have both visible and
invisible characteristics. Exhaust stacks without
visible plumes may still be in full operation, and
airspace in the vicinity should be treated with caution.

Potential Flight Hazards 7-5-13

Page 541 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   540 -- Page 541 -- 542