Certification Basis

Pilot should be aware of how icing certification has changed over the years. For example, there was no analysis or testing required to approve normal category airplanes for flight in icing (of which numerous are still flying today) prior to 1973. Advisory Circular 91-74B, Pilot Guide: Flight in Icing Conditions, has a good summary of icing certification history.

Stall warning

For airplanes equipped with pneumatic deicing boots and that do not have a stall warning system that biases stall warning speed higher in icing conditions, aerodynamic buffet, or stall warning, whichever occurs first, should be trained as the first indication of an approach to stall.

Autopilot

For airplanes not equipped with an autothrottle, if not closely monitored, the autopilot may mask dangerous airspeed losses when in a vertical mode.

Susceptibility to Ice Contaminated Tailplane Stall (ICTS)

1. Except for the airplanes addressed in paragraph b., pilot training shall:
   • Include any airplane manufacturer recommendations regarding operations in icing conditions;
   • Include NASA Video GRC-508, "Ice Contaminated Stall," dated October 1, 2016; and
   • not include the 1998 NASA/FAA "Tailplane Icing" video
2. Pilot training of airplanes originally type certificated after 1994, and certain airplane models listed here shall:
   • Emphasize Airplane Flight Manual (AFM) limitations and procedures in icing (particularly maximum allowable flap deflection in icing conditions);
   • not include a tailplane stall recovery procedure; and
   • not include the 1998 NASA/FAA "Tailplane Icing" video.

Note: The year of type certification can be found on the Type Certification Data Sheet (TCDS) which can be found in the Dynamic Regulatory System (DRS).

Flight Test Safety

• FAA Order 4040.26, Aircraft Certification Service Flight Test Risk Management, requires risk assessments for flight testing. Although tests should be evaluated on a case-by-case basis, ice shape flight testing is classified as high risk and natural icing as medium risk in Appendix G. Risk assessments that have been used on Part 23 single engine certification testing are provided as examples below. For more risk assessments and lessons learned, consult the NASA/FAA Flight Test Safety Database.
• Risk Assessment Examples
  • Ice Shape Testing - General
  • Ice Shape Testing - Stalls
  • Ice Shape Testing - ICTS
  • Natural Icing Tests - General Risks
  • Natural Icing Tests - Departure Risks
  • Natural Icing Tests - Engine/Propeller Risks

Resources for Flight Testers to Find Icing Conditions

• National Weather Service (NWS) Aviation Weather Center Icing Page
  • Alaska Aviation Weather Unit
• "An Aircraft Flight Test Program in Natural Icing Conditions: Part 1 – Forecasting for the Desired Meteorological Conditions", presented at the American Meteorological Society (AMS) 9th Conference on Aviation, Range, and Aerospace Meteorology, September 2000, and available from the American Meteorological Society

Icing Research Resources

• NASA Glenn Research Center - Aeronautics Icing Research

• FAA Report DOT/FAA/CT-88/8 - Aircraft Icing Handbook (1993 update to original 1991 handbook)
• FAA Report DOT/FAA/AR-97/66 - Snow and Ice Particle Sizes and Mass Concentrations at Altitudes Up to 9 km (30,000 ft)
• FAA Report DOT/FAA/AR-00/14 - Effect of Large-Droplet Ice Accretion on Airfoil and Wing Aerodynamics and Control
• FAA Report DOT/FAA/AR-00/30 - Icing Design Envelopes (14 CFR 25, 29, Appendix C) Converted to a Distance-Based Format
• FAA Report DOT/FAA/AR-00/37 - Report of the 12A Working Group on Determination of Critical Ice Shapes for the Certification of Aircraft.
• FAA Report DOT/FAA/AR-01/28 - Capabilities and Prospects for Improvement in Aircraft Icing Simulation Methods
• FAA Report DOT/FAA/AR-01/91 - A History and Interpretation of Aircraft Icing Intensity Definitions and FAA Rules for Operating in Icing Conditions, November 2001
• FAA Report/DOT/FAA/AR-02/1 - An Investigation of the Number of Time Steps on Ice Shapes Calculated by an Ice Accretion Code
• FAA Report/DOT/FAA/AR-02/68 - Effect of Residual and Intercycle Ice Accretions on Airfoil Performance
• FAA Report/DOT/FAA/AR-03/48 - Assessment of Effects of Mixed-Phase Icing Conditions on Thermal Ice Protection Systems
• DOT/FAA/CT-TN86/11 - Fluid Ice Protection Systems

These documents are published by aerospace research and standards bodies, who may charge a fee for distribution.

American Institute of Aeronautics and Astronautics (AIAA) Documents

• American Institute of Aeronautics and Astronauts (AIAA) 2007-1090, Residual and Intercycle Ice for Lower-Speed Aircraft with Pneumatic Boots, 45th AIAA Aerospace Sciences Meeting and Exhibit, 8-11 January 2007, Reno, NV

These documents can be ordered from the AIAA Aerospace Research Central library. 

RTCA Documents

• RTCA/DO-160, Environmental Conditions and Test Procedures for Airborne Equipment
• RTCA/DO-178, Software Consideration in Airborne Systems and Equipment Certification

These documents can be ordered from RTCA, Inc.

SAE Documents

• Aerospace Recommended Practice (ARP)
  • 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment
  • 5903, Droplet Impingement and Ice Accretion Computer Codes
  • 5904, Airborne Icing Tankers
  • 5905, Calibration and Acceptance of Icing Wind Tunnels
• Aerospace Information Report (AIR)
  • 1168/4, Ice, Rain, Fog, and Frost Protection
  • 4367, Aircraft Ice Detectors and Icing Rate Measuring Instruments
  • 5504, Aircraft Inflight Icing Terminology
• Aerospace Standard (AS)
  • 5498, Minimum Operational Performance Specification for Inflight Icing Detection System
  • 5116, Minimum Operational Performance Specification for Ground Ice Detection Systems

These documents can be ordered from SAE International