I have been thinking about this and wanted to ask and see if anyone else may know an answer. I have had all kinds of planes, jets, warbirds, civilian etc. and pretty much any plane that had flaps I used them, with two settings, Take off, and landing, landing being considerably more to slow down the plane. However on my newest jet, the Carf classic lightning the flaps are different, its a traditional flap on the bottom with what I would call an airbrake/spoiler on top of the wing. I have no problems with the plane it takes off flies and lands like a dream. My question is in regards to take off flaps, aerodynamically would the airbrake on top of the wing counter the lift the lower flap is generating. I have taken off with and without flaps didnt really notice a difference, but it got me thinking, is it beneficial to use this style of flap on a take off, do they actually help with a shorter rollout and get the plane flying quicker?

Its a close run thing, lift versus drag, but I always took off with 15mm flap on the Lightning and 10-12mm on the Flash. Once it starts to rotate the clean lower surface is seeing most of the air.

IMHO...using flaps on the Flash or Lightening is a wash, due to the extra drag created by the spoiler part of this type of flap. Lift is created by the faster airflow over the top of the wing more than the relative wind across the bottom of the wing. Using the flaps on take off for a Flash/Lightening, the spoiler is reducing your lift for take off.. Full scale planes/jets never take off with any system or flight control that deters lift. The Flash/Lightening is using a spoiler when flaps are extended. This would be like a full scale jet taking off with spoilers extended. Flaps purpose is to: reduce take off roll, increase weight off of a given runway distance, and when critical, flaps may not be used on take off due to second stage climb of a jet with engine loss. Due to our jets being over powered, you won't notice the benefits or disadvantages of flaps for take off. Our power on r/c jets is mostly 1:1, while a full scale jet thrust to weight is 1:3. This means the power is about a third of the max take off weight. Flaps then become a necessary flight control to provide more lift to carry more weight off of a shorter runway at a slower indicated air speed and reduced tire speeds.

Yes, but this is not a full scale aeroplane. I did real world testing back in 2005/2006 and it does reduce the takeoff roll.

Same rules and laws of aeronautics apply, or these wouldn't fly. And, we are talking about a spoiler/flap. There is a small help, but hard to notice.

I believe that the spoiler effect at shallow half flaps deployed is at somewhat an opposing exponential curve than that of the lifting effect from the flaps, so it does work, use them Ronnie!

Cheers,
Barry