690B CG

[KenFlo]

As I am new to the Twin Commander, could someone explain to me why the CG moves forward as you add fuel.  Its all in the wing leading one to believe that the station essentially remains the same.  I noticed as I add fuel with the higher gross weights it creates a forward CG issue before I exceed gross weight.  Thanks, Ken

[JimC]

The station does, in fact, change as you add fuel. The first 10 gallons are at station 253, the last 10 are at station 229. It's not just one big tank in the wing.

And it's not the fuel throwing you out of cg range forward, it's the payload you already have. Try this thought experiment: remove one of your 200 lb pax from any seat and replace that person with 200lbs of fuel. Notice how the cg is farther aft?

Throw some more stuff in the baggage compartment and you'll find a solution that works. Make it useful ballast - tools, oil, spares, etc....

[donv]

I believe it's because the fuel is not all in the wing-- some of it is in bladder tanks in the fuselage, just forward and above the baggage-- in the wing root.  So the first fuel goes there, and then as you fill up, it goes into the bladders in the wings.

Also, look at the plan view of the wings, and you'll notice that there is a little bit of a reverse sweep, so as you get to the last bit of fuel, it's even more forward.

[KenFlo]

OK, makes sense.  Thanks for the info......