...I have question about pusher airplanes for indoor or slow flight. Seem to me that as a pusher, I can't get it to a High angle of attack flight.

The prop is "sucking" air pass the wing, so no massive air flow over the wing as the plane slows down. In the tractor plane(normal prop in front), the prop "blows" massive air over the wing to help generate lift even at zero ground speed. Pusher plane is like ducted fan or jet, you need to maintain proper speed to have the wing generate enough lift to stay airborne.

Am I wrong?

From : Don Stackhouse

Well, half wrong.

A prop makes thrust by grabbing chunks of air and accelerating them out behind. Half of that acceleration occurs in front of the prop and the other half behind, so even a pusher prop does see some accelerated flow over the wing in front of the prop. However, this is less than the slipstream effects behind the prop, so you do get less of this "powered lift" effect.

Of course there remains the question of whether it's wise to try to use this deliberately in order to allow a lower minimum flying speed. Consider what would happen if you were at minimum speed and at low altitude or near an obstruction, just at the moment of a sudden power loss. This doesn't necessarily have to be an outright engine failure (although such things can and do happen with electrics, not just with piston engines). Simply reaching the low voltage cutoff setting in your BEC as a result of opening the throttle to arrest a too-steep rate of descent could be disastrous.

Powered lift concepts have been proposed for full scale aircraft, but generally this issue among other things has killed the projects before they could be certified. The ones that did make it tended to have some rather elaborate back-up systems to deal with an engine failure, or were planes that had zero-zero ejection seats and that could not be landed safely for other reasons after an engine failure, such as the case of the engine bleed air driven boundary layer system in the F-104 Starfighter's wing flaps.

OTOH, I don't think powered lift effects are the root cause of what you observed. If you can't get to "high angle of attack" flight, then you probably have a problem with elevator authority, not with wing lift. Any pitch control system with adequate authority should be able to make the wing get to a high angle of attack. Whether or not it has a low enough wing loading and high enough max lift coefficient when at that angle to fly at some desired minimum airspeed is another matter altogether. However, an inability to pull the nose up high enough is an elevator problem, not a wing problem.

Don Stackhouse
DJ Aerotech