In this manoeuvre, the wings provide no anti-gravity support! The only thing keeping the model in the air is the lift provided by making the aircraft's fuselage generate lift, firstly by rolling the aircraft onto it's side then using the rudder as an elevator. Normally, the teardrop-shaped fuselage generates a balanced side force (well, it does if it's straight) but using the rudder forces the fuselage into having a positive angle of attack to the airflow.

This is also a manoeuvre in which things can go wrong very, very quickly! If there is only one thing you remember, make sure it's that the rudder goes in the opposite direction to aileron ie. Roll Left, Right Rudder and Roll Right, Left Rudder - repeat after me - Roll Left, Right Rudder and Roll Right, Left Rudder! Since this is a high drag manoeuvre, you'll need plenty of power.

To start, use full throttle, quarter roll using ailerons and quickly apply opposite rudder. Hold the model in knife edge for as long as you want (or can!) then release rudder and quarter roll back to level.

Aresti Diagram

It's about now that you find out how unstable your model aircraft really is! A number of things are likely to happen and only one of them is a good Knife Edge!

1. The model will want to continue to roll, either with the initial roll direction or against it. This is because there is cross coupling between the ailerons and rudder - "techie term" - yaw induced roll. This can be cured by using the ailerons to control the roll, mechanically ie. you do it -electronically mixing appropriate aileron trim with rudder ie. your transmitter does it or you take a hacksaw to the wings and adjust the dihedral angle - ie. the model does it! This is the most common problem in knife edge. A good aerobatic aircraft will have very little coupling while a trainer (Why are you trying to Knife Edge a trainer?) is not so good.

2. The model will want to pitch nose up or nose down. Again a function of the design, the best bet is to use function mixing if you're lucky enough to own a computerised transmitter. Otherwise, you'll just have to apply the required amount of elevator.

3. The model will not maintain height. This next major problem's solution is real vague! Either too much rudder has been applied and the drag is too great to maintain speed, insufficient rudder has been applied to get the angle of attack high enough or the model doesn't have enough power - take your pick! Try experimenting with the amount of rudder applied first then more 'grunt up front'.

4. All of the above - Stop Knife Edging your old trainer!

5. The model will quickly gain height in Knife Edge and threaten to loop. You lucky, lucky git! I've wanted a model like that for years! You have excess power, excess rudder control - it's perfect! To Knife edge, back off power and rudder on your next attempt.

If you are getting into difficulties, release the rudder, chop the throttle, roll the wings level and use elevator to pull out of the dive which you will inevitably be in. I speak from experience. Do not try using the elevator and aileron with rudder on otherwise you'll be practicing the equally spectacular Flick Roll!

Practice Knife Edge passes rolling both to the left and to the right. You will probably find that the controls you have to input vary slightly depending on the roll direction.