Originally Posted by IFMU
How do you balance out the torque between the engines? I don't know how they do it, if the pilot has 2 throttles or if they do it in rigging. But either a torque measurement or manifold pressure should be close enough of a measurement to keep everybody happy.
IFMU, diesels are not as bad as avgas because there is no throttle. Like a turbine the power is a direct function of fuel flow (assuming it burns well), so torque is unlikely to go far out of alignment. I could see Shawn's point if there was a differential between the engines, or each was connected by a torque converter (fluid equivalent of free power turbine). Easiest is just to mechanically connect diesels to same transmission input and calibrate the injector pumps. Direct measurement of torque is difficult because you need a strain guage in the system (often on a shaft). With a differential input, rpm control would work well since torques would be balanced.
What i do find amazing is that the TGRHelicorp machines are full fly-by-wire! They may only be CAD renderings, and no mention of price is made, but it does make the dream of FBW in a light heli closer. I wonder what sort of additional safety features they are thinking about putting into cyclic & collective control. The system may be a simple gyro feedback rate control system, or there may actually be control software. One to watch for sure.
Final note on
Deltahawk is that quoted BSFC is 0.38 lb/HP-hour, which to my metric mind is 190 g/kW-hour. Using the figure i ealier worked out of BSFC 83.7 g/kW-hour for 100% efficiency (most aviation fuels), this makes the engine 44% efficient when running at optimum rpm.
Mart