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How to (EN): Basics of the SDI C4 flight computer

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This is just a basic guide to getting started with the SDI C4 flight computer - for the real info you have to wade through every page of the owners manual...

* The SDI C4 COMPETITION is a flight computer - the main functions are to drive the variometer displays to show you your rate-of-climb and to compute your likely arrival height at the planned destination. The SDI C4 in the Aerosoft Discus picks up your defined destination from the current flight plan or mission. So to really use the C4 to its full capability, MAKE SURE YOU HAVE A FLIGHT PLAN DEFINED. Otherwise the distance-to-go and arrival height calculations have no meaning (and the C4 defaults to being an expensive altimeter showing your current height....). It is worth repeating, and so easy to do, so when you create your flight, DEFINE A FLIGHT PLAN, even if it is just a straight flight to a destination. The C4 will then continuously display your expected arrival height at this destination taking into account the wind, glider performance, expected thermalling climb rate, water ballast carried, dollar-euro exchange rate etc etc. The iPaq PocketPC will display your route on a moving map and be great for navigation.

* To turn the SDI C4 on, click the SMALL WHITE BUTTON on the instrument at 9-o'clock. This button can also be used to turn the instrument off.

* Control of the C4 is *easy*. It only has two knobs, at 7-o'clock and 5-o'clock. The LEFT KNOB rotates to change the CURSOR POSITION, and the RIGHT KNOB adjusts the value at the current cursor position. There are no other controls to worry about. SDI are the Apple of glider instrument manufacturers...

* When you power up the C4, it will default to the NAV cursor position in the top-left corner of the display. A black rectangle (the cursor) will be drawn next to the current cursor position. (In the image above, the cursor is at "L/D", where the C4 displays your glide ratio, 28 in the image).

* When you use the left-knob to change the cursor position, it is only the two rows of digits in the lower third of the display that change their function. The 'lcd petal' display continues to show the variometer (climb) reading with the two-digit climb average (1.2 meters per second) next to it.

* You can happily fly the entire flight leaving the cursor on the 'NAV' position. The lower 5-digit display (at the bottom of the C4) will display directional information to the destination relative to your current track (e.g. 9 degrees left) and the mid 4-digit display will display the altitude above ground the computer is calculating you will arrive - when computers arrived that could do this calculation the effect was something close to miraculous - the pilot can fly a final glide to a destination watching this value intently as the computer tells you you're gonna make it, now you're not, now you are etc. The trick is to build in a safety margin (e.g. aim for an arrival height of 500 feet / 150 meters).

* If you're watching the route on the iPaq PocketPC device, you can conveniently move the C4 cursor a couple of steps to the 'DISTANCE' position. The lower 5-digit display will now show distance-to-go, and you can see the direction to fly from the red line marking the route on the moving map on the iPaq - if it's straight ahead the line will be vertical on the iPaq...

* Meanwhile the C4 will be controlling the movement of the needles in the 'LCD petal' display and the slave 'vario SC' analogue dial. The 'LCD petal' will be displaying Total Energy compensated climb rate (the same as the Winter vario on the panel but with different movement dynamics) and the 'vario SC' dial will be showing the 'Netto' climb rate which is easiest to think of as the climb rate of the air outside the glider.

* The C4 is also controlling the beep-beep of the audio indication, in line with the movement of the 'LCD petal' display. A broken beep-beep indicates a positive climb rate, while a continuous beeeeeeeep tells you you're sinking. The frequency goes up with a rising climb rate, and falls with increasing sink. In real gliding, particularly competitions, the glider pilot hangs on every nuance of the variable sound.

Good luck,


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Thanks for the tutorial...but I have an embarassing question: How do you turn this on? I've tried pressing the white button (at 9 o'clock position on the face of the instrument) with right and left mouse clicks as well as the mouse wheel...tried one click only and also tried holding the button down for several seconds...no LCD at all. I've read the manuals but am unable to turn the darn thing on.

What am I missing?? Thanks for your help on this. unsure.gif

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LOL Merlinman... are you talking about the same button? It's 4cm or so vertically above the left-knob of the SDI C4 and when the mouse is over it the mouse cursor should change to a 'hand-with-a-pointy-finger' icon. A single left-click will immediately power up the instrument, unless you've turned off the main power with the BATT switch on the very bottom of the panel...

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  • 1 year later...

What I can't find is a knop or something else where I can change the waypoint. I managed to build a task from the last autrian soaring championship in LOGO but after aproaching the first point the C4 doesn't change to the next one :huh:.

Thanks for your help,


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