Trainer Knife Edge
 

I have a Alpha 60 (RTF version, so it has the evo .61) I want to be able to do a knife edge. I've practiced on my simulator, and today I went out to try it. I would roll it over, then hit opposite rudder, and the rudder would only lift it up a bit, but the plane was still angled down and losing altitude. Is there a way to help my knife edge by like changing the CG or anything (im on the lowest throw for rudder, so obviously next time ill go up one hole). But other than rudder throw, is there anything i can do. Or of course. you can just tell me a knife edge isnt really a trainer type maneuver, but i love how they look, and i really want to be able to do one.

RE: Trainer Knife Edge
 

You need more power.

KE is basically flying on the side of the fuse. There is no lift from the wings, so in order to maintain altitude, you need enough power to pull the plane up by it's fuse.....with brute force.

KE's with a trainer re-define the word 'coupling'.....have fun!

RE: Trainer Knife Edge
 

There are airplanes that just can't do a knife edge.
My RV-4, a more aerobatic plane than a trainer, can't hold one for very long before the nose drops, maybe 50 feet.
Center of gravity is important. Move it back some for a knife edge but be careful, a tail heavy airplane is difficult, if not impossible, to handle.

RE: Trainer Knife Edge
 

I guess, ill put my rudder at full throw and see what happens. If it doesn't work, I guess ill have to wait till my second plane.

RE: Trainer Knife Edge
 

It takes more than rudder, the plane and set up has a lot to do with it. Trainers don`t K.E well. But will teach you the skills to move forward. Don`t get discourage, trainers are made to fly with their bottoms down.

RE: Trainer Knife Edge
 

with a little creative ballancing and adjustment of control throws, my alpha 40 will do it (takes quite a bit of attention to what the plane is doing to keep it there though). it does lose some altitude, but it sustainable for a full pass more or less. you really have to stay in control of the roll axis to keep it there and quite a bit of elevator work is required to keep it straight as well. but i assure you it can be done. now on the other hand, my profile will do it till i can't see it anymore quite easily.

RE: Trainer Knife Edge
 

The dihedral wing on most trainers and the small rudder throw make KE a nearly impossible maneuver on trainers. Yes there are those that can do it.

You can try pulling the nose up before you enter the maneuver. That will at least get you started at the right attitude. Unfortunately, the combined effects of small rudder authority, rudder induced roll on dihedral wings, and the inherent desire of the plane to roll back to a belly down condition are all working against you.

If you're to the point where you're trying to learn knife edge flight, its time for a second plane.

Brad

RE: Trainer Knife Edge
 

as missile man said Knife edge flight is flying on the fuse. most planes that can do long flat
KE flight have a massive amount of fuse side area. When the pane rolls into KE the fuse acts as
a wing. It doesn't matter how much rudder you have, adding more throw or enlarging the rudder
will slow thw plane down.

RE: Trainer Knife Edge
 

I can do successful KE with my arrow trainer. I just increased the rudder throw to the maximum amount and it will KE fine. It does try to roll back but I can keep it straight without major problems. It also maintains altitude fairly well. I'm sure it is much easier with planes that have more power, more rudder, and less dihedral but still possible none the less. Have fun.

RE: Trainer Knife Edge
 

You can always practice semi-knife edge flying which is also called side slipping. Hold the plane in a 45 degree bank while flying in a straight line. This will require the rudder and ailerons to be cross-controlled which results in a lot of drag, a great way to shave off excess speed and altitude while making a short approach for landing. Good for crosswind landings also. It's a skill that everyone should learn and most trainers can do it.

RE: Trainer Knife Edge
 

trainers are trainers they try and right themselves, thats what you want a trainer to do.

RE: Trainer Knife Edge
 

Even low wing aerobatic planes have a considerable amount of control cross coupling. Rudder doesn't just yaw the plane, it also makes it roll and pitch. If you carefully refine a plane's design to get rid of all control cross coupling, you end up with a modern pattern plane. Even those sometimes resort to computer mixing to remove the last traces of cross coupling. Sometimes you have a plane that is neutral at one throttle setting but isn't at another throttle setting etc. There's no substitute for being able to watch the plane and applying whatever control is needed to make the plane do what you want it to do.

There is no substitute for practice. A million dollar violin won't make you Joshua Bell and the world's most expensive pattern plane won't make you Chip Hyde.

RE: Trainer Knife Edge
 

Exactly!

The high wing dihedral causes the plane to roll while at the same time it pulls opposite the belly. Right thrust also tends to make the plane behave differently depending upon which direction you are attempting to knife edge.

Couple this with trying to fly the plane in a knife edge and you have a disaster waiting to happen.

It CAN be done with enough power, but it is certainly much harder than on most aerobatic planes.

As he said, it's time to move up!

RE: Trainer Knife Edge
 

Hi Shortymet55
As a trainer your plane is probably a bit nose heavy. If it is less nose heavy it will not go nose down in knife edge. If you feel experienced enough, add a little tail weight. Go very slow. Best to use an instructor. You will have to input and hold some aileron, rudder and elevator to knife edge a trainer. Learning to knife edge a trainer is a very good excersise to improve your flying skills.

RE: Trainer Knife Edge
 

after seeing a plane with sfg's (side force generaters)in the crash and rebuild forum, these would add to the lateral area of the fuselage around the wing mounting area and would help with knife edge but you would have to remove the dihedral from the wing.and since this is a high wing plane there probably should be more sfg area below the wing than above it.

RE: Trainer Knife Edge
 

Don't get discouraged. You can do it. True, some trainers knife edge easier than others, but stick with it, and find what it takes for your particular plane to KE. I have a WM Sky Raider Mach I trainer with an OS 40 LA on the nose. It will knife edge. I can't think of a less powerful 40 engine than the 40 LA, so raw power is not the answer.

When you enter the knife edge, make sure the plane is inclined upward slightly to help hold the KE. Good luck! ;)

RE: Trainer Knife Edge
 

I've been trying to do the KE on the sim with no luck. I had tried alot of different models including the trainer. I can't keep the plane going straight. It keeps turning. What is the correct procedure? I'm using opposite controls on the rudder and ailerions.
Thanks
chopper man

RE: Trainer Knife Edge
 

Use elevator to correct for direction.

RE: Trainer Knife Edge
 

Makes sense. It still amazes me how something can be right in your face but still to blind to see:D:D
Thanks
chopper man

RE: Trainer Knife Edge
 

Coming from a beginner that flies a Eagle 63 trainer w/ .40 2stroke:

For what it's worth, I just performed my first knife edge last Sunday. It takes a lot of Aileron/Elev to move the plane in position, all the rudder you can muster by moving the pushrod to it appropriate holes, about 50% aileron to counteract the dihedral wing trying to right itself and a fair amount of elevator to keep it from sliding in circles. Oh, did I mention WOT?

But that's on mine. Start with a lot of altitude cause she comes out of the sky pretty quick. As mentioned by someone else, the fuse doesn't provide much lift so your engine needs to be big to hold altitude. Mine was about 15seconds and I lost about 100ft altitude in the manuever.

It's takes a lot of intense concentration on my trainer. Good luck!