The flap servo holds the flaps up just fine when turned on, but they fall a little when turned off. Will this cause the battery to drain quickly since it will be holding them during flight? Its a standard futaba s3004 on my Kyosho Focke Wulf. Thanks.

Wow!
Heavy Flaps!
Does the servo buzz when you select "UP" ?
I wouldn't have thought that the servo will be holding them up in flight because the airflow will do that quite nicely, providing you've got the end-point set correctly.
I'd recommend keeping the first flights short and using a battery voltage monitor. If you suspect that the batteries are discharging quicker than on a normal flight, then I'd suggest you use a separate battery for the flaps. But I don't think you'll actually have a problem.

Can you increase the mechanical advantage seen by the servo?

This will give the servo more holding power and not use up a lot of current while the plane is in flight.

Flaps do not need a lot of throw under normal cicumstances anyway.

Not unusual.

When you're flying, the airflow will help hold them up.

As for power drain, it's no worse than if you had a plane that needed a little elevator or aileron trim.

Watch a giant scale with 3 servos on each aileron, as soon as they turn the power off they still droop down.

Don't worry about it.

how old is the servo?
the split flaps on the FW190 aren't that big, the 3004 is a pretty stout servo and should hold the flaps up fine, I use them on all my 60 size warbirds and there isn't any sag at all when the reciever is turned off on any of the control surfaces, I wouldn't worry about the size of the servo, but the particular servo might be a little loose in the gears if its allowing the flaps to droop.

I'll recheck the linkage to make sure I'm not binding anything causing it to pull back once its turned off. The flaps do pull down a little due to the way you have to install the CA hinges on them.

depending what type of servo that you are using. i use jr servo's 8411 digitals on my jets and on my imac model and they droop when switched off