Scioly.org

We have a plane that starts out ascending and flying forward, but after a couple of second it starts to swoops backwards and flies backwards until it crashes quickly thereafter. What could be causing the plane to go backwards?
Plane Weight- 7.67 grams
Wingspan 44 cm
Wind Cord 10 cm
Plane length- 49 cm
Stabilizer- 22 cm
Stabalizer cord- 7.5 cm

Does "backwards" mean upside down or directly backwards? (i.e. with the prop spinning the wrong way)

It sounds like your airplane is stalling.

Post a video on YouTube and then a link to that video here.

If you built a kit, is the center of gravity (CG) of your model (with the rubber motor mounted on the same) at the location recommended in the instructions? If not, correct this by moving the wing forward or rearward. Moving the wing forward moves the CG rearward. Moving the wing rearward moves the CG forward. From your description, it sounds like the CG may be too far rearward. If that is in fact the case, you need to move the wing rearward so that the CG will move forward.

You can also add ballast, e.g. poster mounting putty, to the forward end of the motor stick, in order to move the CG forward. However, this is not a recommended fix since your airplane is already over the legal minimum weight.

If it the CG is at the correct location, trying decreasing the incidence of the wing by lowering the leading edge (e.g. by sliding the forward wing post down further into its tube).

It also may be a power stall. Alternatively, are you launching by throwing the plane hard and up? These planes don't like that.
Show us a video and we'll be able to interpret better. Also useful would be some details of how you are winding and how you are launching.

Jeff Anderson
Livonia, MI