Anyway that must be the difference in realism settings (all sliders right). The J3 Cub and the Helio Courier both can not generate enough speed at 3300' to get off the ground. The Helio Courier starts to climb but it is not fast enough nor does it have enough room to turn for the circular climb.
Most of the time, I have my sim set to medium realism....I like to fly my planes as much as possible...and I like to do STOOPID things while flying my planes...and on 100% realism, doing STOOPID things results in my planes turning into potato plows too quickly.
OBIO