Dynon HSI Display


  • HSI can be displayed on any Dynon EFIS or EMS (when linked to an EFIS).
  • Enabled by a single serial connection to the EFIS or EMS instrument or via an optional expansion module supporting multiple interfaces.
  • Cost-effective replacement for mechanical HSI or CDI instruments.
  • Includes CDI, glide slope (when connected to a Garmin SL30 or other radios via the HS34 HSI Expansion Module), and graphical bearing pointers.
  • Displays calculated winds aloft, crosswind and true airspeed.
D100-Series HSI Split Screen Displays D10-Series HSI Full Page Displays


Dynon’s EFIS-based instruments now include an HSI page whenever connected to a supported external navigation source. The HSI page offers a precise navigation tool to guide pilots throughout the enroute, terminal and approach phases of flight. It also reduces pilot workload and offers a cost-effective and space-saving alternative to traditional mechanical HSI or CDI instruments.

The HSI data comes from external panel mounted or portable navigation devices. These devices can either be interfaced to Dynon’s EFIS or EMS systems via their single wire serial connection or through Dynon’s optional HS34 HSI Expansion Module. When utilizing the instrument’s single serial port, the system currently supported devices includes the Garmin SL30 NAV/COM and many GPS units that use the NMEA-0183 or aviation data formats. The HS34 module expands the interface to include multiple connections to analog, ARINC-429 and serial signals to facilitate a larger variety of NAV radios and devices.

The HSI always displays the current operating mode to inform the pilot which external navigation source is presently in use. The different modes include: GPS, VOR, LOC (Localizer) or BC (Back Course).

When slaved to a GPS source, the HSI displays a CDI indicating the course to the next waypoint.  When slaved to a NAV radio, the HSI can display a CDI from a VOR or localizer, as well as a  GS (glide slope) when tuned to an ILS. NAV and GS warning flags sent out by the SL30 are displayed on the HSI as well.

Dynon’s HSI additionally provides the following functions not typically found on mechanical HSIs. They are:

  • Textual information supplied by the navigation source like the waypoint identifier, radio frequency, distances, etc.
  • Graphical bearing pointers which always point directly at the selected navigation target
  • True airspeed when equipped with an OAT
  • Current wind direction, velocity and crosswind component when connected to GPS and OAT
  • Synchronized Zulu clock time across all interconnected Dynon instruments whenever slaved to a NMEA format GPS signal

Pilot control over the primary navigation settings like waypoint or OBS selection are directly set on the external navigation device(s) connected to the Dynon HSI. Dynon’s HSI page additionally supports selecting the desired navigation source (GPS or NAV), setting the magnetic heading bug and GPS CDI scale. These controls are accessed by the instrument’s keypad via a softkey menu system.

In total, the Dynon HSI display offers a powerful navigation tool that augments a moving map system, is easily installed and easy to use. Independent of whether you intend to fly VFR or IFR, the Dynon HSI display offers an affordable approach that is hard to pass by.

Instruments equipped with HSI Capability

The following instruments come equipped with the HSI page:

Primary instruments equipped with magnetic heading:

  • EFIS-D10A
  • EFIS-D100
  • FlightDEK-D180

When networked to a primary instrument above via the Dynon Smart Avionics Bus (DSAB) the HSI page can also be displayed on the following instruments:

  • EMS-D10
  • EMS-D120

Navigation Input Configurations

When connecting an external navigation source to the EFIS’s serial input, only one device can be connected at any given time. If more than one navigation device is installed, an external switch can be used to select between them. The HSI will automatically detect anytime a different navigation signal is present and switch the HSI page to reflect the different mode.

Panels equipped with either Dynon’s FlightDEK-D180 (combo EFIS/EMS product) or a pair of EFIS and EMS instruments have two serial inputs available to connect the GPS and SL30 simultaneously. Pilots can switch between the navigation sources via the onboard menu system, so no external switch is required.

Optional HS34 HSI Expansion Module

Dynon offers its optional HS34 module to support those seeking to interface to NAV radios other than the SL30 or who wish to connect to multiple devices simultaneously. The HS34 also offers dedicated knobs and controls, synthetic voice annunciation and more.

What is an HSI?

The horizontal situation indicator (commonly called the HSI) is an aircraft instrument normally mounted below the artificial horizon in place of a conventional directional gyro (DG). It provides an easily understood pictorial display and is one of the most popular navigation instruments ever devised.

An HSI combines a heading indicator with a CDI display, reducing pilot workload by lessening the number of elements in the pilot’s scan. The HSI instrument may also include a glideslope needle so that an ILS instrument approach can be flown with reference only to the six basic flight instruments. Among other advantages, the HSI offers freedom from the confusion of reverse CDI needle sensing.

The HSI has several components that help you navigate. The whole instrument turns, much like a directional gyro or magnetic compass card. Heading is indicated at the twelve o’clock position on the instrument. One of the key benefits of this behavior is that the compass card carries the CDI display with it so that the HSI always shows the pilot a CDI deflection toward the selected course. This provides the pilot with a “track up” birds eye view of the aircraft relative to the selected course. Overlaid on the heading ring is a bug which is manually set by the pilot to the desired heading.

The lateral deviation needle performs the same function as the CDI in a basic CDI indicator, depicting how far you are off course. Each dot on the course deviation scale represents 2 degrees for VOR navigation. When you are on course, the lateral deviation needle is aligned with the course arrow. Since the TO/FROM indication rotates with the CDI needle as well, it becomes much easier to interpret. When the arrowhead is pointed to the head of the course arrow, the selected course is inbound. When pointed away from the course arrow, it is indicating an outbound course from the station.

Some HSIs additionally present a glide slope indicator to provide vertical navigation when shooting an ILS approach. The glide slope pointer indicates aircraft position in relation to the ILS glide slope. If the pointer is above the center position, the aircraft is below the glide slope, and vice versa.

The accompanying picture below presents Dynon’s HSI page with each of the elements just described plus many others. Dynon’s HSI page presentation will vary depending upon which instrument it is displayed on and which navigation source it is slaved to. On the larger 7” size LCD instruments, the HSI page is viewed as a 1/3 screen size split screen with the remainder devoted to another instrument page. On any of the smaller 3.8” LCD instruments, the HSI page encompasses the entire screen. The example below presents a 1/3 page split screen slaved from a Garmin SL30 NAV/COM radio.

Note: This simulated illustration depicts numerous HSI elements to describe their position and purpose and does not reflect an actual or possible navigation scenario.