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B21

How to (EN): a Discus BM self-launch walkthrough

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One of the immediate fun things to do with the Discus BM is to do a self-launch power takeoff using it's retractable engine. All the information you need is in the manuals but here's a walk-through for the whole routine to get you moving:

* Don't try your first takeoff in a crosswind - even experienced pilots will struggle with that. If you can have a bit of a headwind straight down the runway, so much the better.

* Get settled in the aircraft and have a look around and identify each of the controls and instruments you'll be depending upon - there are quite a few - I bet you didn't realise modern gliders are so sophisticated.

* Power-up the SDI C4 FLIGHT COMPUTER using the small ON/OFF button at 9-o'clock on the instrument. You'll hear a continuous (annoying) beep which you'll learn to love later on when you try ridge and thermal soaring. At the same time you might as well power up the iPaq PocketPC MOVING MAP computer by clicking the power switch at the bottom center of the panel (beneath the label 'D-KOLC') from left to right.

* The instrument to the left of the central SDI C4 is the ENGINE CONTROL MODULE. Click the switch at 3-o'clock (from down to up) and you'll hear the engine being raised from its fuselage bay. If you switch to the external view you will see the engine pylon raising. When ready the green LED above the switch will illuminate and the noise will stop.

* Once the engine is fully up, click the ignition 'ON' switch (at 8-o'clock on the Engine Control module). This will power up the ignition circuits (but not yet start the engine) and a second green LED will illuminate, next to the 'lightning' icon on the Engine Control module.

* Moving your view over to the right-hand (starboard) cockpit wall, the black knob under the iPaq is the FUEL VALVE for the engine, and a click will move it from ZU (off) to AUF (on).

* Adjacent to the fuel valve, also on the starboard cockpit wall, is the aluminum PROP BRAKE lever, which should be moved fully forward (drag mouse upward).

* Moving your view over to the left (port) cockpit wall, the cylindrical buff THROTTLE LEVER should be moved to 50%. Either drag upwards with the mouse, or use your predefined throttle keys or slider.

* You're nearly ready. Get your view ready straight ahead, the remaining area of interest on the panel are the two switches on the far left side of the panel. One last thing before you start the engine is to move the SEGEL/MOTOR switch down to MOTOR. This configures the sensitive variometers to use a pressure nozzle in the nose of the glider rather than the usual tail nozzle, so they are not damaged by the backwash from the engine. You need to remember to move the switch back to SEGEL after the motor is retracted to get the proper function (i.e. compensation) in the varios.

* OK, you're all set. Hold the wheelbrake on, pull the stick back (the engine wants to push the glider onto it's nose), and push the RED STARTER BUTTON (on the far left of the panel) for three seconds. You will hear the starter fire, the engine will catch and rev up to maybe 2-3000 RPM (displayed on the Engine Management module).

* Slide the THROTTLE all the way forward, and the revs will increase to maybe 6000 RPM, release the wheelbrake, and the glider will start dragging itself down the runway.

* Your first priority is to try and keep the nose straight even though one wing is dragging on the ground (gliders balance on a single mainwheel), and when you have a little forward speed, pick up the wing. Be careful not to let the stick move too far forward or the glider will pitch onto its nose, until you have enough speed that the tailplane bites properly into the air.

* Now just try and follow the centerline as the speed builds up, and at about 50knots/100kmh the glider will leave the ground. It gets a lot easier from here.

* The audio variometer will give you an increasing beep-beep as the climb builds up, but the engine is much smaller, lighter, and less powerful than one in a usual light aircraft so keep the climb rate consistent with an airspeed of 55-60 knots (110/120kmh). If you climb too steeply the speed will drop off and you'll stall.

* Raising the mainwheel with the 'G' key will improve the aerodynamics and the climb rate.

When you've reached the height you want to, stop the engine with the IGNITION SWITCH on the Engine Management module (DOWN to OFF), re-apply the PROP BRAKE (aluminum lever fully BACK), and retract the engine via a RIGHT-CLICK on the 3-o'clock switch on the Engine Management module. Don't forget to move the far left SEGEL/MOTOR switch back to SEGEL (up). One more time, just for those of you that aren't reading this carefully.. it's a RIGHT-CLICK on the engine extract switch to retract the engine.

Congratulations.

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LOL, I likened my first attempt at a self-powered takeoff in the BM to giving a Corvette full power on an icy road without the traction control on - it seemed like I was "fishtailing" left then right for half the runway as I was applying self-correcting rudder and trying to level the wings!

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Hmm, what about making a funny video compilation af all first trys :D

Have seen sooo funny things during testing, lol.

Several people who tried it here at home failed in sometimes very funny movements of the plane.

Well quiet expensive, and Only 9 Discus BM were built. Now they are alltogether a hughe bunch of crap, lol.

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TBH my first attempt at a Discus BM self-launch pitched the Discus onto its nose... I think I got it into the air on my second attempt though.

B21

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You guy's should have seen mine, horrendous :lol: Have a video of it some place and will try to locate and post it. Will not tell you what I done but think along the lines of brakes, speed brakes, air brakes, ok you get the point :wub::lol:

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I got the Discus yesterday and also tried the selflaunch, first try first takeoff :D . But it was hard and for shure in real life some markers along the runway would have stoped me (I know the airfield in RL).

regards,

Günther

PS: thanks for the tutorial :groupwave_s:

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One suggestion for the selflaunch: When I choose a winchlauch a virtual starthelper picks up the wing and levels it before launch. Would it be possible to include this starthelper (maybe assigned to a knob in the cockpit) to pick up the wing when selflaunching? Would be really nice and would ease the selflaunch (and would be more realistic).

regards,

Günther

PS: same for towplane start would be perfect

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Maybe Peter can involve it in Cumulus X licence version, there is already an intelligent towplane :blush: .

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Thankyou very clear and heipful, only took second attempt, forgot to release brake ! cheers revboy.

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