In-Flight Simulation

In-Flight Icing and its Effects on Aircraft Handling Qualities

This course will consist of a ground school covering all pertinent aspects of aircraft icing, and a ground based simulation and a flight simulation of icing effects on aircraft stability and control characteristics. A combination of guest lecturers, who are experts in various fields of icing technology, flight testing, and flight operations, will provide a comprehensive curriculum covering the following subject matter:

  • Icing Meteorology including Supercooled Large Droplet (SLD) icing
  • Ice shape formations and how they relate to the physical properties of icing clouds
  • Aerodynamic effects of icing on airfoils
  • Practical applications of aircraft stability and control characteristics and performance to selected icing certification testing
  • Flight test results of icing effects on aircraft performance, stability and control, including SLD and Ice Contaminated Tailplane Stall
  • Icing related upsets
  • Methods and facilities for icing simulation: computation fluid dynamics codes (LEWICE), wind tunnels, airborne tankers
  • FAR 23/25 icing certification requirements including discussion of AC 25-25
  • A one hour ground based simulator training session in the NASA Ice Contamination Effects Flight Training Device (ICEFTD)
  • A one hour training flight in a variable stability research aircraft (VSRA) that simulates actual icing related longitudinal handling anomalies as reported in NASA’s inflight icing research program and typical lateral-directional handling anomalies.


  • Test pilots, Flight Test Engineers and engineering personnel who are involved in development and certification flight testing
  • Engineering personnel who are involved in aerodynamic analysis and icing simulations, especially those using computational fluid dynamics (CFD) tools
  • Pilots, flight department managers and flight training personnel
  • Military pilots, especially those operating transport category aircraft


There are no technical prerequisites for students; however, a number of topics both in the ground school and simulation laboratories will be presented in a format where familiarization with basic algebra will facilitate understanding of the material.


By completion of the course, the participant will be able to:

  • Become familiar with and understand how to apply the Airworthiness Standards for FAR Part 23 and FAR Part 25 in an aircraft icing certification program.
  • Understand the meteorological aspects of how, when, and where icing clouds form as they apply to the various types of ice formations. Learn about use and availability of weather forecasting tools for planning aircraft icing flight test operations.
  • Understand the physics of ice formation, and how various ice shapes affect aircraft aerodynamics.
  • Become familiar with the flight test process for conducting an icing certification program, and how manufacturers approach this process.
  • Describe how strategic and tactical planning is used in an icing flight test program and how the safety risk management process is conducted.
  • Gain knowledge of how ice accumulations on aircraft surfaces affect performance, stability and control, and handling qualities. Understand the reasons and characteristics for upset conditions due to aircraft ice formations.
  • Provide a summary of capabilities and availability of icing wind tunnels, inflight icing tankers, and climatic laboratories, which may be used to support an icing certification program.
  • Understand the capabilities and application of computational ice accretion codes in the icing certification process. Participate in a laboratory exercise and practice using the LEWICE ice accretion code.
  • Conduct ground based simulator training in the NASA Icing Effects Flight Training Device, which represents critical flight conditions as discovered in NASA’s Tailplane Icing Program. Demonstrate how icing affects aircraft flying qualities, upsets, and safety of flight.
  • Conduct flight training in the Navion Variable Stability Research Aircraft, that mirrors most of same characteristics as shown the ICEFTD, but in a much higher fidelity training environment.


The ground and flight simulations provide a unique opportunity for course attendees to safely experience and understand important cues related to icing induced handling anomalies. Flight profiles are structured to provide a series of progressively degraded handling characteristics where attendees, under the guidance of experienced instructors, practice flight control techniques to mitigate the loss of stability and control effectiveness. The ground and flight simulations are complementary. The ground based icing simulation represents reduced longitudinal handling characteristics with a reversible control system and associated force and dynamic feedback. The inflight simulation represents those same characteristics with an irreversible control system and artificial feel system. A major aspect of the inflight simulation is that it represents a modern aircraft equipped with a fly-by-wire (FBW) flight control system. Other aspects of the inflight simulation are that it provides important motion feedback cues and the effects of real atmospheric winds and turbulence that impact handling evaluations.

The NASA ICEFTD simulator operates with a full computing aerodynamic database, derived from extensive wind tunnel testing on a subscale model of the NASA Twin Otter icing research aircraft, and verified by full scale flight testing. The simulator provides a high resolution three screen representation of cloud and visibility conditions. It also provides a realistic simulation of anomalous longitudinal control system forces and dynamics associated with tail plane icing conditions. A structured one hour training session is provided to all course attendees.

The VSRA is equipped with an analog FBW flight control system, in addition to standard mechanical controls. The flight demonstration is conducted with the FBW system programmed to represent the stability and control characteristics just discussed, but also includes training profiles from full scale flight tests with the NASA Twin Otter during the Tailplane Icing Program. These profiles represent the most severe tail ice shapes tested by NASA. Additionally, a hybrid configuration is presented to the attendees, which couples typical lateral-directional stability and control effects due to wing icing with the longitudinal effects discussed above. The training focuses on recognizing aspects of stability and control problems, and pilot control strategies that are appropriate for continued safe flight. Flight profiles are structured for both pilots and non-pilots. Pilots are primarily tasked with evaluating handling qualities in various icing configurations while flying simulated instrument approaches in simulated icing configurations, and non-pilots are primarily tasked with performing basic flight maneuvers in these same icing configurations “up and away” as a means to understand the aircraft handling issues caused by aircraft icing. The training flight is approximately 1-1/2 hours in duration.


The course is scheduled from October XX-XX, 2015. The full course fee is $X,X00.00, limited to 12 attendees, which includes a CD containing all lecture materials and a DVD of each attendee’s training session in the ICEFTD. Daily refreshments will be provided. Early registration is encouraged.


Day One – Icing Theory

Icing Meteorology
Case Study: Weather Brief
Inflight Icing Testing
Aerodynamic Effects of Icing and Wind Tunnels
Icing Effects on Stability and Control, Performance, and Aircraft Handling

Day Two – Icing Certification

FAR 25 Icing Certification
FAR 23 Icing Certification
Current Issues in Icing Certification
Engine Icing Research
VSRA Brief
Icing Effects Flight Training Device (ICEFTD) Brief

Days Three to Five (depending on number of attendees) – Simulator Sessions and Variable Stability Flights

ICEFTD Simulator Sessions
VSRA Flights
Discussion and Adjourn