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Icing and Storm

Icing and storm information can be displayed on the map and you can view them when building a flight plan. Icing and Storm information is based on your subscription to N-Flight Planning (NFP). If you do not see the function on the map screen, you do not have the module. Icing and storm data are only available from the Telvent weather source. You must set the Default Hazard source to TEL, DTN, EFH, or ERP on FOMS 170 to use turbulence data in flight plan calculations. 

Note: The TEL and DTN options will soon be removed.


The Icing and Storm check boxes display icing and storm information on the map.


View icing and storm data on the map


There are 3 icing options: 

  • light

  • moderate 

  • heavy. 

Icing displays as the light to dark blue color on the Map. Select the Icing checkbox and choose the intensity level to display icing on the map. Icing is only displayed for Flight Level (FL) 280 or below. If a planner chooses a higher flight level, icing will not be displayed. Icing is measured in Percent Power Increase (PPI): 

  • Light (0.0 - 0.1)

  • Medium (0.11 - 0.4)

  • Heavy (0.4 and above). 

Right-click on the icing display to view information on the icing levels.



Select the Storm checkbox to display the storm information on the map measured in vertical velocity. Thunderstorm vertical velocity indicates the intensity of the storm. For example, hail does not appear unless the vertical velocity is above a certain value. It is one value per latitude/longitude and not a millibar based.Thunderstorm Tops indicates the height of the storm. Tops is displayed in the right corner or on-screen if a user right clicks on the area. NFP outputs data in hundred feet. Thunderstorms display in the light to dark green color on the map.  


Icing and storm avoidance

Fields in the FOMS 220 menu and Aircraft Characteristics menu allow you to enter icing and thunderstorm avoidance parameters.

FOMS 220 Menu

Aircraft Characteristics Menu


You can set these parameters (except for Icing Acft Category) in the FOMS 170 (Airline Code Parameters) menu. If the parameters are set in the FOMS 170 menu, they apply to all aircraft, but are overwritten if set in the FOMS 220 menu or Aircraft Characteristics menu for a particular aircraft.

  • Icing PPI - Icing Percent Power Increase (0.0 – 2.0).

  • Acft Ice Cat - Icing PPI aircraft category (L = light / M = medium / H = heavy). If this field is blank, the NFP system looks at the Item 9 setting (wake turbulence category).


  • Vert Velocity - Vertical velocity in meters/second.

  • Fly above by / Fly over Tops - Allow flight above thunderstorms by this value in hundreds of feet.

Apply Ice Penalty (PPI) for ETPs (FOMS 231)

If a PPI (percent power increase) value between 0.0 and 2.0 is entered in FOMS 231 for an ETP scenario, NFP will only apply the icing penalty on the route section with PPI forecast above this value.


This only works when icing penalties for either airframe or engine anti-ice are set to “T” (total). If set to any other option, you will get the message shown below:


The ETP station fields are green when this feature is enabled.


FOMS 170 parameter – Default ETP Ice

Options are A (auto), Y (yes), and N (no). If blank, same behavior as A. If set to A, ETP fields are green. This means that using TEL winds and having Aircraft Characteristics and/or FOMS170 configured properly allows NFP to apply icing penalties for ETPs if the PPI values for the icing area(s) encountered between ETP point and ETP alternates exceed the value entered. If set to Y, ETP fields are blue if icing penalties exist in FOMS 231 for the ETP policy used. When blue, the NFP system calculates icing penalties regardless of whether an icing area is present or not between ETP point and ETP alternates. If set to N, no icing penalties are applied.


ETP Scenarios - Web FOMS 231

Web FOMS 231 is available from the NFP Database screen accessible through the Maintenance screen. You can use this screen instead of the traditional FOMS 231 screen.


MEL Penalty - Ice allows NFP to avoid areas of icing with PPI values greater than the value entered in FOMS 428.


  • Effect - Effect type applied (ICE)

  • Value - Icing PPI (percent power increase) value (0.0 – 2.0)

When applied to an aircraft, users will see MEL in the info screen.


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