SkyDemon Mobile Documentation: Using the Instruments
Instruments are displayed around the edges of the main map and also in their own dedicated view on the Mobile MD. To adjust settings for the instruments, choose Instruments from the Settings menu.
Instrument View
There is a dedicated instruments view on your SkyDemon device that replaces the moving map. To access it, select Instrument View from the main menu. To get back to the chart, select Chart View, again from the main menu. You can also swipe your finger upwards from the virtual radar instrument to access the instruments view or downwards from the HSI instrument to get back to chart view.
There is no separate Instrument View menu on the iPad version of the software as the screen is large enough to accomodate all of the important features on the main map. To find out how to access the HSI instrument and more on the iPad read on.
Direction Indicator / Course Correction Indicator
The direction indicator is a compass rose displayed at the bottom of the main map, which rotates such that your current track over the ground is displayed at the top as an orange arrow. When flying a course, a bug appears on the outside of the dial representing the track you should be flying to get to your next waypoint. Aligning the bug with the orange marker at the top of the dial will ensure that you reach your next waypoint.
The values shown on the direction indicator are in degrees true by default but can be switched to degrees magnetic from the instrument settings. You can also choose to hide the direction indicator, if you find that you would rather see more of the map. To hide it, click Settings, then Instruments and highlight the option to show course correction indicator.
When hidden, the direction indicator is replaced by a small instrument called the course correction indicator. When you are navigating towards a waypoint, this simply appears when you need to make a course adjustment such as to turn left by 10 degrees. You can see both instruments in the figure on the right. Both are showing the same status (you need to turn left by 10 degrees) but the DI shows more information and therefore occupies a lot more screen space.
By touching the direction indicator, iPad users can toggle between that instrument and a the smaller course correction indicator as described above. Furthermore, it is possible to pull out the direction indicator revealing the full Horizontal Situation Indicator, allowing for a better understanding of your position. This instrument is overlaid on the map and can be moved around or enlarged as desired, as well as being see-through so as not to obscure any important points underneath.
Groundspeed
Groundspeed is shown in a simple square instrument (with the GS heading) in the chart view or in a dynamic tickertape-style instrument in the instruments view on the Mobile MD unit. The exact speed of the aircraft over the ground is displayed, with knots being the default unit.
TIP: To change the units used throughout your device for distances, speeds and more, open the Settings menu and select Change Units.
Altimeter
Altitude above local mean sea level is shown in a simple square instrument (with the ALT heading) in the chart view or in a dynamic tickertape-style instrument in the instruments view. The altitude is derived from GPS, which means it will not normally be as accurate as a properly-set pressure altimeter. Units are always feet. A small coloured flag in the top left corner of the simple instrument, or a coloured band on the tickertape instrument, indicates the accuracy of the altitude readout with a 95% certainty:
 | Blue Accuracy within 50 feet |
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 | Green Accuracy within 100 feet |
 | Orange Accuracy within 250 feet |
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 | Yellow Accuracy within 150 feet |
 | Red More than 250 feet of inaccuracy |
The simple square altitude reading can additionally be switched to display height rather than altitude. When in height mode it shows your height above the highest terrain within half a nautical mile. This means that if you switch to height mode while standing on the ground you will normally see a negative reading. The height mode is designed to facilitate navigation underneath airspace whose lower boundary is defined by a height above ground level.
Horizontal Situation Indicator / Pseudo ILS
The HSI is shown in the instruments view on your Mobile MD, or as mentioned previously, can be viewed by dragging the DI out onto the main map on your iPad. It combines a direction indicator (with bug) on the outside of the dial with a display of the aircraft's position relative to the leg you are currently navigating in the interior. A dotted scale (each dot represents 1 mile) makes it easy to determine at a glance how far away from your planned course you are.
When you are on final approach to a runway and the SkyDemon charts contain sufficient data, the HSI will switch into ILS mode. A corresponding change will be observed in other instruments: the distance instrument will read the distance to the threshold, the time instrument will read the time to the threshold, and the position instrument will read something like "Apch: EGDY R27". When in ILS mode the HSI functions in a similar way to an ILS, although all information is based solely on GPS readings as opposed to any ground-based instrument. This brings benefits such as being able to practice instrument approaches to strips that do not actually have a localiser or glideslope but you should always bear in mind that being based on GPS, the data cannot be relied upon as your sole means of guidance.
The ILS can also provide vertical guidance along a user-defined glideslope. This facility is disabled by default and needs to be manually switched on from the instrument settings window (tap Settings then Instruments in the main menu on the Mobile MD, or Navigation Options on the iPad), and an additional disclaimer agreed to. Any vertical guidance offered by the SkyDemon ILS should always be compared to your cockpit instruments. Regardless, the vertical guidance will cancel when you descend through 500ft above aerodrome level.
When in ILS mode, each lateral dot is half a degree, so the entire visible scale spans about six degrees. On the vertical scale each dot is 0.1 degrees, with the field of view approximately 1.4 degrees in total.
Virtual Radar
This powerful instrument placed underneath the chart shows a projection of your current course and all the objects of relevance in your path. This data is a snapshot taken every five to ten seconds, laid out with your current position on the left and the extremity of your path ahead on the right.
The aircraft symbol represents your current position. A line denoting vertical trajectory projects from the aircraft, with the same dots representing 2, 5 and 10 minutes ahead (or miles, if you have specified this in Preferences, or the Navigation Options menu in Setup on the iPad). This gives an idea of current vertical speed and where your ascent or descent will leave you after a period of time.
Terrain is laid out in front of you, making it very easy to detect any unintended proximity to it. Airfields, towns, reporting points and obstructions that you will pass close to are displayed as well.
This instrument has a context menu that can be used to inspect certain features on it, just like the main map. Hold your finger on any part of it to see the list of objects that you can inspect. Another feature of the context menu is that it will tell you the distance and time to reach the point at your fingertip. So, if ATC ask you for your estimated time to a reporting point, you have only to hold your finger down on the reporting point and you'll be able to give an exact answer.
The Virtual Radar also acts as a shortcut to other useful features. If you're a SkyDemon Mobile MD user you can swipe your finger from left to right across the Virtual Radar window to quickly access the Direct To list, or swipe from the bottom of the Virtual Radar upwards to flick to Instrument View (and swipe down again to return to the map).
On the iPad the Virtual Radar gives quick access to the scratchpad with a simple swipe of the finger from right to left.
