Summary, Recommended Reading, and Icing Checklists

Summary

6-1. GENERAL. Ice-contaminated aircraft have been involved in many accidents. Takeoff accidents have usually been due to failure to deice or anti-ice critical surfaces properly on the ground. Proper deicing and anti-icing procedures are addressed in the current editions of two other pilot guides, AC 120-58 and AC 135-17. Any ice encountered in flight, even in trace amounts, can be dangerous. This guidance should help educate pilots about the potential hazards of in-flight icing, ways to avoid such hazards, and how to cope with potential hazards effectively.

6-2. AVOIDANCE. The pilot of an aircraft that is not certificated for flight in icing conditions should avoid all icing conditions. This guide provides guidance on how to do this, and on how to exit icing conditions promptly and safely should they be inadvertently encountered.

6-3. VIGILANCE. The pilot of an aircraft that is certificated for flight in icing conditions can safely operate in the conditions for which the aircraft was evaluated during the certification process, but should never become complacent about icing. Even short encounters with small amounts of rough icing can be very hazardous.

6-4. GUIDANCE. The pilot should be familiar with all information in the AFM or POH concerning flight in icing conditions and follow it carefully. Of particular importance are proper operation of ice protection systems and adherence to minimum airspeeds during or after flight in icing conditions. Monitor airspeed, pitch attitude, and do not rely on the airplane’s autopilot or stall warning system in icing conditions. There are some icing conditions for which no aircraft is evaluated in the certification process, such as SLD conditions within or below clouds, and flight in these conditions can be very hazardous. The pilot should be familiar with any information in the AFM or POH relating to these conditions, including aircraft-specific cues for recognizing these hazardous conditions.

 

Recommended Reading

1. This advisory circular (AC) was developed as an easy-to-read resource on flight in icing conditions. As of the date of publication, this AC contains the most current information available. The suggested reading list that follows may not have been updated recently but may contain other useful and valid information. For more detailed information, pilots are referred to the current editions of the following U.S. Government publications:

a. Aeronautical Information Manual (AIM).
b. AC 00-6, Aviation Weather for Pilots and Flight Operations Personnel.
c. AC 00-45, Aviation Weather Services.
d. AC 20-29, Use of Aircraft Fuel Anti-icing Additives.
e. AC 20-73, Aircraft Ice Protection.
f. AC 20-113, Pilot Precautions and Procedures to be Taken in Preventing Aircraft Reciprocating Engine Induction System and Fuel System Icing Problems.
g. AC 20-117, Hazards Following Ground Deicing and Ground Operations in Conditions Conducive to Aircraft Icing.
h. AC 20-149, Installation Guidance for Domestic Flight Information Service-Broadcast.
i. AC 23.1419-2, Certification of Part 23 Airplanes for Flight in Icing Conditions.
j. AC 91-79, Mitigating the Risks of a Runway Overrun Upon Landing.
k. AC 150/5220-16, Automated Weather Observing Systems (AWOS) for Non-Federal Applications.
l. National Transportation Safety Board (NTSB) Aircraft Accident Database.
m. P-8740-24, Winter Flying Tips — FAA Accident Prevention Program Publication.

 

Icing Checklists

The following checklists contain icing-specific items that should be considered before operating in possible icing conditions. The checklists are intended to supplement pilot information. These checklists should not replace or supersede Airplane Flight Manual (AFM) or pilot’s operating handbook (POH).

1. Piston Aircraft.

a. Preflight.

(1) Always obtain a thorough preflight weather briefing. Evaluate cloud types, bases, and tops; types of precipitation; freezing levels; and pilot reports.

(2) Pack additional items in your flight bag such as a large flashlight, spare fresh batteries, and transceiver.

(3) During preflight planning, identify alternate airports along the route of flight to be used if unscheduled weather is encountered. Choose airports with longer runways.

(4) Always know how to escape icing conditions (either climb or descend to warmer areas, make a 180 degree turn, etc.).

(5) During the preflight inspection, clean all ice, frost, and snow off the aircraft in accordance with the POH or AFM.

(6) Check that pitot heat (and static heat if installed) are operable.

(7) Check pitot/static openings, fuel drains, and stall warning sensors to ensure they are not clogged with ice.

(8) In accordance with the POH or AFM, cycle any deicing and anti-icing systems to check for proper operation.

(9) Clear any accumulated ice or snow from brakes and wheel fairings.

(10) Check controls externally for ice/snow binding.

 

b. Taxi/Takeoff/In-Flight.

(1) Use brakes carefully during taxi to prevent skidding.

(2) Ensure that carburetor heat or alternate air is working.

(3) Check controls for full range of motion.

(4) After takeoff, if recommended by the manufacturer, cycle landing gear to clear snow or slush from wheel wells.

(5) During flight, monitor engine revolutions per minute (rpm). A drop in rpm or manifold pressure may indicate induction ice. Apply carburetor heat or alternate air if required.

(6) If your aircraft is not certified for flight into icing conditions and icing is encountered in flight, you should exit the conditions immediately. Anti-icing systems are to be activated prior to entering icing conditions, while deicing systems are normally activated at the first sign of ice accretion. Refer to the AFM or POH for proper operation of anti-icing and deicing systems.

(7) Use visual cues to identify ice formation and regularly check for ice accumulation behind protected areas on the aircraft. If ice forms on the wing, there is a possibility that the tail may be accumulating ice as well.

(8) Stay alert for any performance or handling degradation that may be an indicator of ice accumulation.

(9) If using an autopilot, if workload permits, periodically disengage and manually fly the aircraft to identify handling changes caused by airframe icing.

c. Approach and Landing.

(1) Be prepared for unexpected attitude changes when changing the airplane’s configuration. If the aircraft begins to roll or pitch unexpectedly, return to the previous configuration.

(2) In accordance with the POH or AFM, use a higher approach speed into the landing when carrying an accumulation of ice. Use a longer runway if available.

(3) After touchdown, use brakes sparingly to prevent skidding or in case of ice buildup in brakes.

 

2. Turbopropeller Aircraft.

a. Preflight.

NOTE: Professional flightcrews flying complex, high-performance aircraft should always refer to the AFM or POH and company guidance materials as the authority for procedures for flight into icing conditions.

(1) For ground deicing operations, refer to company manuals, AC 120-58, and AC 135-17 for guidance.

(2) Always obtain a thorough preflight weather briefing. Look for cloud types, bases, and tops; types of precipitation; freezing levels; and pilot reports.

(3) Preflight icing inspections of the aircraft in ground icing conditions are essential. Tactile inspections are mandatory for some aircraft and are very valuable for detecting clear ice. By physically touching the surface, any fine contaminants not easily visible can be detected. Refer to AFM or POH to determine if a tactile inspection is mandatory for your aircraft.

(4) Clean all ice, frost, and snow off of the aircraft in accordance with the POH or AFM.

(5) Check that pitot heat and static heat are operable.

(6) Check pitot/static openings, fuel drains, and stall warning sensors to ensure they are not clogged with ice.

(7) In accordance with the POH or AFM, cycle anti-icing and deicing systems to check for proper operation.

(8) Clear any accumulated ice or snow from brakes and wheel fairings.

(9) Inspect the engine inlets of turbine engines and remove any accumulated ice from the nacelle inlet as well as around the nacelle drain hole and around the fan blades.

b. Taxi/Takeoff/In-Flight.

(1) Use brakes carefully during taxi to prevent skidding.

(2) Check controls for full range of motion.

(3) Perform regular engine power run-ups to shed accumulated ice while taxiing, per the AFM.

(4) After takeoff, if recommended by the manufacturer, cycle landing gear to clear snow or slush from wheel wells.

(5) Refer to the AFM or POH for proper operation of anti-icing and deicing systems. A rule of thumb is that anti-ice systems should be activated at the first sign of visible moisture with air temperatures some margin above freezing. Deicing systems should be activated at the first sign of ice accretion.

(6) Power settings with bleed air on should be set according to the POH or AFM reference section.

(7) Use visual cues to identify ice formation and regularly check for ice accumulation behind protected areas on the aircraft.

(8) Stay alert for ice formations on wings that may cause control problems.

(9) If there is a need to use wing-deicing systems, there is a possibility that the tail may be accumulating ice as well.

(10) If using an autopilot, if workload permits, periodically disengage and manually fly the aircraft to identify handling changes caused by ice. This is especially important if operated in slow flight or in a holding pattern.

(11) Use airspeed bug to monitor changes to airspeed.

 

c. Approach and Landing.

(1) Be prepared for unexpected attitude changes when changing the airplane’s configuration. If the performance characteristics change suddenly, return to the previous configuration.

(2) Determine if freezing drizzle or freezing rain are being reported and avoid flying into these areas. A ground observation of ice pellets indicates possibly freezing drizzle or rain aloft. A ground observation of any type of precipitation when temperatures are near freezing may indicate freezing precipitation aloft, so be vigilant for severe icing conditions.

(3) In accordance with the POH or AFM, use a higher approach speed into the landing when carrying an accumulation of ice. Use a longer runway if available.

(4) In accordance with the POH or AFM, carry some power on flare and flare slightly faster than normal if carrying ice. Use a longer runway if available.

(5) Cycle boots just before final approach.

(6) After touchdown, use brakes sparingly to prevent skidding or in case of ice buildup in brakes.

3. Turbojet Aircraft.

a. Preflight.

NOTE: Professional flightcrews flying complex, high-performance aircraft should always refer to the AFM or POH and company guidance materials as the authority for procedures for flight into icing conditions.

(1) Because turbojet airplanes have the performance capabilities to fly around or quickly pass through areas where icing conditions are encountered in flight, icing will pose more of a hazard during the takeoff phase. Therefore, particular attention should be paid to ground deicing.

(2) For ground deicing operations, refer to company procedures, AC 120-58, and AC 135-17 for guidance.

(3) Ensure that deicing fluids are not sprayed into engines, auxiliary power units (APU), pitot inlets, probe openings, or static ports.

(4) Do not spray heated fluids onto cold windows.

(5) Deicing fluid fumes are a potential irritant. If the aircraft is being sprayed with passengers on board, close all outside vents.

(6) Always obtain a thorough preflight weather briefing. Look for cloud types, bases, and tops; types of precipitation; freezing levels; and pilot reports.

(7) Preflight icing inspections of the aircraft in ground icing conditions are essential. Tactile inspections are mandatory for some aircraft and are very valuable for detecting clear ice. By physically touching the surface, any fine contaminants not easily visible can be detected. Refer to AFM or POH to determine if a tactile inspection is mandatory for your aircraft.

(8) Ensure that all ice, frost, and snow is removed from the aircraft in accordance with the POH or AFM.

(9) Ensure that heated flight information warning sensors, Angle of Attack (AOA), pitot/static, etc., are operating properly.

(10) Check pitot/static openings, fuel drains, and stall warning sensors to ensure they are not clogged with ice.

(11) In accordance with the POH or AFM, cycle anti-icing and deicing systems to check for proper operation.

(12) Clear any accumulated ice or snow from brakes and wheel fairings.

(13) Inspect the engine inlets of turbine engines and remove any accumulated ice from the nacelle inlet as well as around the nacelle drain hole and fan blades.

 

b.Taxi/Takeoff/In-Flight.

(1) Ensure that controls have full range of motion.

(2) Refer to the AFM or POH for proper operation of anti-icing and deicing systems.A rule of thumb is that anti-ice systems should be activated at the first sign of visible moisture with air temperatures some margin above freezing. Deicing systems should be activated at the first sign of ice accretion.

(3) Power settings with bleed air on should be set according to the POH or AFM reference section.

(4) For turbine engines, perform regular engine power run-ups to shed accumulated ice while taxiing, per the AFM.

(5) Use visual cues to identify ice formation and regularly check for ice accumulation behind protected areas on the aircraft.

(6) Stay alert for ice formations in front of control surfaces that may cause control problems.

(7) If there is a need to use wing-deicing systems, there is a possibility that the empennage may be accumulating ice as well.

(8) If using an autopilot, if workload permits, periodically disengage and manually fly the aircraft to identify handling changes caused by ice. This is especially important if operated in slow flight or in a holding pattern.

 

c. Approach and Landing.

(1) Be prepared for unexpected attitude changes when changing the airplane’s configuration. If the aircraft’s performance characteristics change suddenly, return to the previous configuration.

(2) Determine if freezing drizzle or freezing rain are being reported and avoid flying into these areas. A ground observation of ice pellets indicates possibly freezing drizzle or rain aloft. A ground observation of any type of precipitation when temperatures are near freezing may indicate freezing precipitation aloft, so be vigilant for severe icing conditions.

(3) Cycle boots before final approach, if equipped.

(4) In accordance with the POH or AFM, use a higher approach speed into the landing when carrying an accumulation of ice. Use a longer runway if available.

(5) Carry some power on flare and flare slightly faster than normal if carrying ice. Use a longer runway if available.

(6) After touchdown, use brakes sparingly to prevent skidding or in case of ice buildup in brakes.