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What does the Helicopter Option Do?

The Helicopter Option changes several things with the IFD.  

#1 - The Aircraft Symbol on the Map page will show as a Helo instead of a fixed wing aircraft.

#2 - The Fuel Range Rings typically assume a 45 minute reserve for fixed wing aircraft, this changes to a 20 minute reserve for Helo's

#3 -  Projected imminent impact with terrain occurs when the aircraft flight path is projected to intersect with terrain up to 3.0nm (1.2nm for helicopters) for a yellow caution or up to 1.5nm (0.6nm for helicopters) for a red warning in front of the aircraft flight path. By way of reference, this means an aircraft traveling at 180 knots of ground speed will have 60 seconds of notice for a caution and 30 seconds for a warning. Reduced terrain or obstacle clearance occurs when the aircraft flight path is not projected to impact the terrain but the projected clearance between the aircraft flight path and nearby terrain or obstacles falls below a designated safe vertical distance.  Red Terrain alert changes from 100' to 50';  Yellow Terrain caution changes from 100'-1000' on fixed wing to 50'-500' on Helos.  And Terrain Alerting is turned off at 1,500' for Helo's, but 3,000' for fixed wing.

#4 - The helicopter option disables Negative Climb Rate Alerts ("Don't Sink" alerts go away).

#5 - The IFD can supply a pseudo weight on wheels output generally used to drive automatic transition on the transponder.  Since this output is driven from a GPS ground speed calculation it is not useful with helicopters.  When the helicopter option is installed, the system will change the function of the Gray Code Altitude Encoder input on the D1 line to be used as a discrete input from the collective switch.  When this input senses a ground, it will output a logic low on the pseudo weight on wheels output.  When the collective is raised (opening the switch), the IFD will then sense the open on this input, and drive the pseudo weight on wheels logic high for "in air".


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  • 21-Aug-2020