Hello,

 

I've been working on the airfile and aircraft configuration file for the FSX G-21 Goose for a while now and the work is nearly complete.  However, I was wondering if it were possible that someone with actual experience with the real aircraft could chime in on what the plane actually does and says during different phases of flight, and what it's stall characteristics are, to help confirm the results of the work done so far.

 

The reason I took on this project is because the G-21 is one of my all time favorite aircraft, and the 985 is one of my all time favorite engines, and though the visual and aural quality of the FSX Goose (especially the work done by OZx on the textures) is very good, the flight model still needed a lot of work.  The engine and prop configuration in particular were rebuilt virtually from scratch because there were multiple errors in their default form.  Just a couple of the more glaring examples: by default the R-985s were configured as turbo engines instead of the supercharged engines that they actually are, and a four-bladed propeller model was originally used (visually, three blades are modeled, but four blades were doing the work in the config and air file).

 

Much of the work is based on info from type certificate data sheets and maintenance manuals.

 

Thanks!

Treetop

Can't help ya other than give a shout of encouragement as I am sure there are a lot of Goose fans out there like me.  I even have an overhead throttle quad setup just for my beloved goose.  Looking forward to your addition.

 

Clutch

I appreciate that.  Thanks!

I'm interested as well. Please keep us up to date on what's going on.

 

Hook

Sounds like a great idea, I'd certainly be interested in this. I currently use the HD upgrade for the Goose (can't remember who's it was, but thank you!) and it really gives it a 'payware' quality. 

 

Keep us informed!! B)

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.

This sounds great.  It looks like you're very familiar w/ round engines and the Goose.  Can't wait to fly the update!

 

Slim

Yes, that does sound great and I'll try it for sure!

 

CK

Astonishing that so many basic errors were made on what has long been considered the best-modeled default airplane in FSX!

 

Makes you wonder how much worse the others are.....

 

I stopped by Shimofusa airport (default FSX scenery) today. Runways are there, but no airport?!

 

Certainly will be a good job.
Goose had interest in, even not knowing the real airplane, I realized that there are things wrong with the aircraft provided in FSX.
I will follow this topic.

João Alfredo

That sounds great already! Thank you very much for the effort you put into this plane, I am excited already about flying teh updated Goose.

The work is complete and the file has been uploaded to the library, called "goose_dynamics.zip".  I only just uploaded the file, so it may take some time for the file to show in the library.  If it's not there, then check later.

 

Enjoy!

Will definitely be checking this out. Only started regular flying the Goose recently. It does have a few handling/balance quirks, so a fdx upgrade from someone who knows what they're doing will be most welcome.

Great work, Treetop.

Thank you very much. Downloaded it right now, hopefully I can test it next week.

Hi guys,

So I followed the instructions in the readme, and since I have the OZx Goose Redux, followed those instructions as well. However, it seems now that the only Gooses (Geese?) that are showing in the "select aircraft" menu are the HP versions that aren't modified. What do you think caused this?