A diet for G-THER

Work on the customised fuel system is progressing well — the centre tank is now in place and I’ve now found the FSX C208 gauges to modify in order to add a gauge to display the quantity of fuel in the additional tank.

However, 400 US gallons of additional fuel comes at a price — weight. Jet-A1 weighs 6.8lb per US gallon, so 400 gallons will weigh 2720lbs. The 332 gallons already in the wing tanks would weigh 2257lb on its own, so simple addition tells us that if we top off all the tanks — as well will need to for the longest legs — the total weight of fuel will be 4977lb.

Why is this a problem? Well, the Caravan’s maximum takeoff weight is 8750lb. Its standard empty weight is 4570lb, which tells you that the maximum weight that we can carry is 4180lb. As we need to load a pilot and a small amount of baggage as well — it’s apparent that G-THER is going to have to go on a diet.

The first thing that’s going to have to come out are the seats. The FSX Caravan has 12 passenger seats installed, and research suggests that the average passenger seat weighs around 45lb. Thus, removing all twelve seats saves us 540lb immediately.

This still leaves us with around a further 400lb to lose to enable us to add a pilot and a small quantity of essential baggage when the tanks are full. Time to examine further opportunities!

In to the workshop

First preparations for the trip are under way.

Here’s the aircraft that will be carrying us on our journey:

She might not look much, but the Cessna Caravan has plenty going for her for a flight of this type. The turboprop engine offers jet-like reliability and performance, and there’s plenty of interior space that we can use in order to customise the aircraft for the unique challenges of this journey.

The first thing we’re going to do is rip out the seating and install an additional fuel tank for the long over-water sectors that we’ll face when we cross first the Pacific, then the Atlantic oceans. I’m keen to keep this realistic — I don’t want to just bung in an arbitrarily large fuel tank that wouldn’t fit inside the real aircraft. So I’ve researched the interior dimensions of the Caravan’s cabin. From this, it would appear that if we were to rip all the seats out, we could fit a 400 gallon tank in the cabin.

This has complications which we’ll get in to shortly, but first and foremost it’s very easy to add a new tank in FS. The very first thing I did, by the way, is duplicate the default Simobjects\Airplanes\C208B folder in order to keep our modifications entirely separate from the default aircraft. On my machine, I’ve called in C208B RTW.

Having done that, the first thing to do is open up the aircraft.cfg file. After modifying the title of the aircraft (you can’t have two aircraft with identical “titles” in FS) from “Cessna Grand Caravan” to “Cessna Grand Caravan RTW” and renaming the variation to “FSGlobeFlight” so we can find it easily in the aircraft list — I scrolled down to the [Fuel] section.

[fuel]
LeftMain = -17.0, -1.1, 2.5, 166.0, 3.6 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
RightMain = -17.0, 1.1, 2.5, 166.0, 3.6 //Longitudinal (feet), Lateral (feet), Vertical (feet), Usable(gallons), Unusable (gallons)
Center1 = -20.2, -1.5, 0.0, 400, 2.1 // longitudinal, lateral, vertical positions from datum (feet), Usable(gallons), Unusable (gallons)
fuel_type = 2 //Fuel type: 1 = Avgas, 2 = JetA
number_of_tank_selectors = 1
electric_pump=1

I’ve highlighted in red the text I added. I copied the longitudinal, lateral and vertical positions from the payload stations section of the file.

Now we have a brand new tank, and opening the aircraft in FSX reveals that we can load fuel in to this tank.

The next thing to do is to add a gauge to display the quantity of fuel in the new centre tank, and ideally I’d like to add a three-position fuel selector as well. Gauge editing is something I’ve never done before, and so I’m in the process of researching this now. I had hoped to use the default C208 fuel gauge as a starting point, but it appears Microsoft have packaged it as a DLL rather than an XML gauge that I could read and edit, so it looks as though I’ll be going back to the drawing board.

Lots of other things to do as well — updates to follow!