The first thing I must get, was make the ‘Percent RPM’ gauge do no fall bellow 70% when engine is idling or when power is reduced (normal in P&W PT-6).
In conclusion I decided to link the Condition Lever (A:general Eng1 propeller lever position, part) to drive the RPM gauge, instead of reading N1 or N2. And here becomes a stream of new challenges:
In this gauge resides the main work load.
The gauge has two needles, the small one for 10th RPM% each turn and the great one which indicates RPM over a normal 270º scale. How to synchronize the two needles and how to synchronize the levers travel in conjunction with the gauges indications? Consider: full forward is 100% RPM and full back lever position is 70% RPM.
What when engines stops? Keep in mind, RPM gauge has not N1 or N2 info.
How synchronize the two needles? (small must be North each time great is in a 10th of scale).
And what about the speed which I move the Condition Levers? What if I forward the levers in a fast push? How to avoid the small needle ‘jump’?
Other chapter is the sounds. Normally when apply full RPM in a P&W-PT-6 engine, torque gauge go to zero and the sound pitch and volume level decreases accordingly. This is just the inverse must happen with Garrett. It is supposed when you apply full RPM the engines becomes more loudly (in pitch and volume).