I had the same problem in the beginning.
But in my opinion, the motor works perfectly. I can fly with it until the fuel runs out.
The engine in the Stemme should be regarded as an auxiliary engine. Therefore, even in the G version, you cannot expect the performance and maneuverability of a sports plane.
Cooling is the main vulnerability of the machine.
Therefore, warm it up properly according to the checklist.
Attention:
the engine can also return to a lower temperature when idling with the cooling flaps open.
After a cold start, the mixture can be regulated down again. You can hear that the engine speed increases slightly and then decreases again. The choke should then be increased again slightly until the engine speed increases again slightly.
Always readjust the engine temperature with the cooling flaps and throttle power.
Temperature:
The yellow range is OK, but not permanently. The red range should not be exceeded if possible, both in the lower and upper limits. The upper limit can of course be exceeded briefly in emergency situations, but this will perhaps result in overheating damage.
After taking off and reaching a safe altitude, the landing gear should be retracted to reduce wind resistance.
The RPM should be in the 2/3 range. So do not reach the upper yellow range or red.
Once a low altitude is reached, the flaps are set to -10 and the switch located at the end to the right of the throttle lever is set to “Crusie”. The mixture lever can now be fully retracted.
The throttle can then be increased slightly so that the RPM indicator points approximately vertically upwards.
Now accelerate to approx. 80Kn in horizontal flight.
This is a good cruising speed and will give much air for cooling the motor.
At 80 knots you can achieve a slight climb and remain in this setting until you reach the desired target altitude, which can take some time (no sport or STOL power).
If you want to increase the climb rate, the speed will be reduced when pulling up and you can apply a little more throttle. However, it is essential to keep an eye on the temperature and keep it in the optimum range by changing the cooling flap setting or reducing the throttle.
Important to understand:
Why does the Stemme or other gliders have a minus flap position?
We basically differentiate between spoilers that move vertically upwards out of the wing. These reduce the lift capacity of the wings and at the same time brake by increasing the air resistance.
In addition, some gliders have a second mechanical system, the flaps. In German they are called Wölbklappen. The word is made up of curvature (?) flaps.
Each wing must provide the correct lift at a certain speed. Normaly since the airplane usually flies slower when landing, more lift is generated by increasing the curvature. The wind resistance of the wing increases.
Even with a glider, the wind resistance would be too high if the speed were increased. The lift becomes too strong and the nose has to be trimmed down. For this reason, the flaps can be raised to reduce the curvature to -5 or -10. This slightly increases the surface area of the wing in the direction of flight.
At higher speeds, however, the wing now generates the same lift as at lower speeds with the flaps set to 0. Therefore, we need less power for the increased speed in horizontal flight. The trim can then be set slightly upwards again.
Back to the Stemme:
So don’t try to climb at 60 knots and flap 0 at full throttle. This will ruin the engine. Stay between 70-80 knots at flap position -10 and keep the engine RPM in the middle of the range. Possibly slightly increased RPM. The switch on the center console must be set to Cruise and the light to the left of the landing gear display labeled Prop.Pitch goes out.
As said, you cannot achieve the same climbs as with a sports aircraft, unless you use thermals or updraft support.
Please forgive me if my English is not quite accurate in some of the expressions. I hope I was able to help.
Good luck
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