Here's an update on what's been done so far:
> Deleted sections in the airfile that are no longer used in FSX. These sections are now in the aircraft.cfg.
> Tuned flight model to exhibit some basic stall and spin characteristics (WiP).
> Tuned control surface effectiveness to make them feel more smooth and less abrupt.
> Added Section 521 "Failure Level" in the airfile.
> Reduced fuel tank size from 170 gallons to 110 (tanks on real G-21 are 110 gallons), with 108 gallons being usable.
> Changed fuel gauge .xml to properly show fuel quantity.
> Deleted auxiliary fuel tank entries from the airfile.
> Adjusted fuel tank datum to more closely represent location on real aircraft.
> Changed fuel metering from "Fuel Injected" to "Gravity Carburetor".* (see notes)
> Adjusted fuel pressure. Is now at 3-4 psi at idle and ~6 psi at power.
> Added engine driven fuel pump.
> Changed fuel flow rate. In cruise settings, standard conditions, at 5000 ft (27" Hg, 1900 RPM), lean fuel mixture at high EGT, fuel flow is now ~16 GPH.
> Adjusted oil pressure and oil temps/change rate, and cylinder head temps/change rate, to indicate more realistic values.
> Changed G-loads, per FAR part 25-27 for Normal Category aircraft. Specifically, 3.8 positive G limit (2 with flaps), and 1.5 negative G limit.
> Changed max gross weight to 8000 lbs.
> Changed wing area and span to real data (375 ft^2 and 49 ft).
> Adjusted engine datum to more closely represent location on real aircraft.
> With engine damage turned on in FSX, engine can now be damaged if manifold pressure limit is exceeded.
> Cylinder displacement adjusted to more accurate value.
> Turbocharger removed** (see notes).
> Supercharger added** (see notes).
> Changed prop diameter to 95.5 inches, (per Hartzell R10152-5.5S Blades).
> Changed prop blades from 4 to 3.
> Changed prop MoI to 15.
> Changed Beta Max and Min to 38.1 and 15, respectively (per Hartzell HC-B3R30-2 hub).
> Removed propeller sync.
> Changed min RPM for prop feathering to 500 RPM.
> Changed Beta Feather to 85 degrees.
> Adjusted tail-wheel pivot to be less sensitive during taxi.
> Adjusted contact points so that hull floats deeper in the water.
> Adjusted flap extension time, now longer.
> Corrected activation and location of nav, taxi, and landing lights*** (see notes).
> Declared effects for engine smoke, piston failure, oil leak, and engine fire.
* P&W R-985 Wasp Junior engines were equipped with Stromberg NA-R9 carburetors. There is no provision for fuel injection.
** By default in FSX, the two Pratt and Whitney R-985s Wasp Jr. engines on the Goose were configured as turbocharged engines, which is not the case on the real aircraft. The R-985 is built with an integral supercharger, attached to the rear of the crankcase, geared at a 10:1 ratio. The P&W R-985 SB-2 modeled in this package was configured for horizontal mounting on a conventional fixed wing aircraft, and had a critical altitude of 5000 ft (maximum altitude at which maximum MP could be maintained).
There are some differences in how a turbocharger and supercharger operate, and those differences affect how you operate the engine, particularly during takeoff and climb. As a simple example, without going into detail that is beyond the scope of this readme, turbochargers are driven by exhaust gasses. With turbocharging, you can simply advance the throttle to takeoff and climb settings and leave it there until the critical altitude is crossed, at which time you advanced the throttles during the remainder of the climb to maintain MP until they hit the stops or until you reached your desired altitude. The turbo wastegate offered some measure of protection from over-boosting.
Superchargers, on the other hand, are mechanically driven through a physical connection to the crankshaft, and the type of installation in the R-985 means that it is possible to overboost the engine by applying too much throttle, potentially damaging or destroying it (with engine damage turned "on" in FSX), or resulting in unrealistic performance (with engine damage turned "off"). When applying takeoff power, be careful not to use more than 36.5" of manifold pressure, and when transitioning to climb settings (33.5" Hg and 2200 RPM) you will need to continually apply the throttle to maintain climb power as you ascend, until the either the throttles are 100% open or unitl you've reached your desired altitude.
In case you were wondering, the exhaust plumbing on top of the engine nacelle that routes back inside the rear nacelle is used for cabin heating, not to drive a turbo bucket wheel.
*** The red and green nav lights mounted on the wingtip floats, when turned on, will remain in their "retracted" positions when the wingtip floats themselves are deployed. The white nav light mounted on the rudder will only turn on when the landing light is turned on.
I'm still working on the flight and stall dynamics. I was hoping to find propeller efficiency curves for the propeller modeled here, but no luck. In the interim, default propeller curves are used until I get around to doing the math in figuring it out.
Of course, if anyone has any suggestions, I'm open.