Great pics, thanks for posting!
Nick M wrote:Yeah, I don't suppose a turboprop simulation is on A2A's roadmap any time soon. However, I still desperately hope that they'll create an external PT6A Accu-Sim module some time in the forseeable future.
In regards of PT6 simulation, the eternal project by Marcel Felde (Aerosoft PC-6) looks promising.
Nick M wrote:[...] PT6's are definitely the next best thing to speed brakes when it comes to the frequent and fairly abrupt airspeed changes required for the survey work. I was actually pretty surprised at how notable the deceleration g-forces were in level flight.
They can be
better than speed brakes if so adjusted!
How PT6 is controlled makes up a modestly complicated system actually. Unlike some others, the PT6 takes use of something called "flight beta". Effectively, the beta range (where power lever movement directly controls the blade angle) extents well
above the flight idle power setting (in TPE331 for instance, the flight idle is defined to be the exact point where the constant speed governing and the beta range transition to and from). There is an important, installation-specific propeller blade angle, called primary blade angle, that is more or less the maximum directly commanded blade angle available at beta range. Pulling the levers back from there will reduce the fuel flow while eventually catching the blades from the governed position into our direct control. Pushing the power lever further forward instead increases the fuel flow, bringing the prop up to set RPM and into constant speed governing range.
The flight idle can be so adjusted that it allows the blade angles to go pretty "flat" with appropriate fuel scheduling to keep the blades from overspeeding. This makes one fine air brake.
In principle, there is no direct technical limitation on going all the way to ground beta and reverse range in flight - for impressive stunts if nothing else. The problem is, however, that the propeller is on high positive torque, and the engine is scheduled to provide quite a bit of power, while the blade angles are negative. As the propeller would, in case certain things go not in the way one wanted, move naturally towards feather - and therefore right through the flat pitch angles - while under heavy load, such a situation can easily be enough to dramatically overspeed and disintegrate the prop and the engine before one likely even notices an issue.
-Esa