Weird Flight Characteristics....

[scaleguy]

Well after the big storm last night I went out to the field and is was a beautiful evening, no wind and the sky was clearing.

I took the opportunity to try and get a few practice rounds in with the Yak. While doing so I cam across a problem that has me baffled. While trying to do andy vertical maneuvers the aircraft yaws to the left or really more of a turn to the left and once you establish the upline and neutralize the stick the a/c will pitch the nose down and level off all by itself. :shock: :shock: :? :?

OK lets separate the two things.
1) Again if I try to establish an upline the aircraft yaws or turns to the left and will continue to do so till it falls out of the manoeuver.

2) Once I correct the yaw if I neutralize the elevator while the a/c is climbing vertically it will fly out of the manoeuver by arching over the top to upright level flight.

What the heck is going on? Now that I finally have the engine sorted out... something else goes wrong. :( :(

The NATS are this weekend and I have to try and figure this out before then. Thanx in advance for any help

[samsrc]

It sounds like you need more right thrust, and more up thrust.

Just a thought :)

Sam

[can773]

Well after the big storm last night I went out to the field and is was a beautiful evening, no wind and the sky was clearing.

I took the opportunity to try and get a few practice rounds in with the Yak. While doing so I cam across a problem that has me baffled. While trying to do andy vertical maneuvers the aircraft yaws to the left or really more of a turn to the left and once you establish the upline and neutralize the stick the a/c will pitch the nose down and level off all by itself. :shock: :shock: :? :?

OK lets separate the two things.
1) Again if I try to establish an upline the aircraft yaws or turns to the left and will continue to do so till it falls out of the manoeuver.

2) Once I correct the yaw if I neutralize the elevator while the a/c is climbing vertically it will fly out of the manoeuver by arching over the top to upright level flight.

What the heck is going on? Now that I finally have the engine sorted out... something else goes wrong. :( :(

The NATS are this weekend and I have to try and figure this out before then. Thanx in advance for any help

Definately more up thrust/less downthrust....

The other problem needs to be established more clearly, is the the model rolling or yawing on the upline (forget the push for a moment). I doubt its rolling (if it is you have a real bad something?!)...if its yawing you can add more right thrust which is fine but you will need left rudder for just about anything you do at reduced power settings, and you will double the amount of work you need to do.

Trim the upline with right rudder trim so its straight, then mix a throttle to rudder mix (throttle being the master), start at half throttle and mix out the trim at idle. Basically what you want to be able to do is fly the plane away from you at ANY throttle setting without any yaw, typically with only right thrust the model will yaw right with power removal on a straight line.

Get the idea? It will take some fiddling, probably not the best time to be doing it right before a contest though LOL.

The bigger the prop the less useful right thrust is as it causes other problems. With the electric pattern stuff we are spinning huge props (22" on a small plane) and right thrust is just completely useless, the only way to get the model to fly right is a throttle to rudder mix.

[samsrc]

Jim,

Another test you may want to try, is to fly the model straight and level across the field at about 3/4 throttle. Once the model passes in front of you, chop the throttle. I'm betting your plane will go up/or climb. A definant indicator that you have too much down thrust or not enough up thrust.

If it's the case, put a few washers in your motor mount to move the thrust angle, then try it again. I'm sure with a little fiddling you will get it.

Regarding the right thrust, you may want to experiment as Chad suggested, using your throttle/rudder mix, and see how that pans out for you. Regardless, It definately will take a little fooling around.

Sam

[jamesbissonjr]

Hey Jim, not sure if you noticed or not but that Wild Hare Edge we flew on the weekend has the same problem with regard to flying left on the uplines. It doesn't 'flatten out' like you said yours does but we think it also needs a little more right thrust. The rudder trim was already over a couple clicks to the right and every vertical I had to input more! Not sure if I'll be bringing that plane to the Nats or whether I'll have to fly the little .46 sukhoi. We'll see.......

[Randy Brown]

torque

[scaleguy]

OK I guess I should have mentioned that she flys pretty good in straight and level. If I look at the engine setup I think that the thrust line may be off a little to the left. I don;t know why as the top of the beam of the engine mount is in line with the thrustline but when the cowl is on the engine looks offset to the left.

I guess with the 1.20 the power wasn't there and didn't really come into play. Hmm Guess I'll have to try and feed in appropriate rudder till I figure it out.

I don't think she needs upthrust as she climbs under power as it is now. If anything shee needs downthrustr to counteract the uptrim I need to fly straight and level.

Bummer since i got all the vertical I want now.

In the imortal words of Kevin Reinhardt..... Giddyyy Up! :D :D

[scaleguy]

torque

So whats the soloution>,... throttle back? defeeets the power needed for uplines. Or should i have more right thrust? :? :?

[can773]

OK I guess I should have mentioned that she flys pretty good in straight and level. If I look at the engine setup I think that the thrust line may be off a little to the left. I don;t know why as the top of the beam of the engine mount is in line with the thrustline but when the cowl is on the engine looks offset to the left.

I guess with the 1.20 the power wasn't there and didn't really come into play. Hmm Guess I'll have to try and feed in appropriate rudder till I figure it out.

I don't think she needs upthrust as she climbs under power as it is now. If anything shee needs downthrustr to counteract the uptrim I need to fly straight and level.

Bummer since i got all the vertical I want now.

In the imortal words of Kevin Reinhardt..... Giddyyy Up! :D :D

Verticals is the only way to determine up/down thrust, there is no other good cure for it. The chop the throttle test IMO is completely useless as you are dealing with gravity....uplines dont care much about gravity and are determined soley by the force balance setup of the motor/wing/stab.

If you are carrying uptrim there are a couple of things, first.....you are too nose heavy....what does the plane do on a downline ? I bet $5 it pulls to the canopy...how about knife edge? A CG adjustment can also affect the uplines (again because of the trim) so that may be what is causing the pitch on the upline as well. Possibly move the CG back for a quick test before doing anything else.

Second, you dont have enough positive incidence in the wing....

Third too much positive incidence in the stab......

You should always endevour to have aendeavoretup such that there is no trim being carried on the elevator.

Depending on how much adjustment is built into the plane will dictate how flexible you can be with the last two items.

To have a good flying plane it cannot pitch on an upline or you will never earn high scores without a crapload of work. My Enigma was doing this when I switched over to electric and had to reduce the downthrust compared to the glow setup from last year.

Right thrust, you have a couple of options here.....fly it the way it is and live with it (hardest), add more right thrust and deal with the fact that you are likely going to need some left rudder at pulling and pushing when at idle, do a throttle to rudder mix and spend a bunch of time making sure its correct, but offers the least amount of correction effort while flying.

PS: All planes fly good straight and level (even trainers) that doesnt mean they are setup/trimmed properly :D

[50%300SFlyer]

Jim,

The amount of right thrust and/ or throttle to rudder mixing required, is a function of engine / propeller torque, and airspeed. The faster the plane travels in the upline, [airspeed] the less will be required. Different props can require different amounts too.

I would suggest you start off with about 2 degrees of right thrust ,and see what that does for you. You may end up needing 3 or even 3.5. Go out and fly it and go from there. Eventually, you should be able to pull an upline at full throttle, and have it continue straight up without touching the sticks. [assuming wind is not a factor]

If your plane tends to slow up on the uplines, [not unlimited vertical] you will eventually have to add some rudder input as it begins to slow down. This is where more than enough power is better. :wink: Anyways, add some right thrust and give it a try.

Hope that helps! :)

[scaleguy]

Thanx for the suggestions guys... I'll try them and let you know what happens :D :D

[can773]

Thanx for the suggestions guys... I'll try them and let you know what happens :D :D

????

Doesnt the Nats start tomorrow....surely you got the plane all trimmed up prior right? :shock:

[scaleguy]

Thanx for the suggestions guys... I'll try them and let you know what happens :D :D

????

Doesnt the Nats start tomorrow....surely you got the plane all trimmed up prior right? :shock:You would think so but.... gona test fly later this afternoon in Chatham. May just have to suffer through it though.

[can773]

You would think so but.... gona test fly later this afternoon in Chatham. May just have to suffer through it though.

tsk tsk tsk :D

[scaleguy]

You would think so but.... gona test fly later this afternoon in Chatham. May just have to suffer through it though.

tsk tsk tsk :D
Well some of us do have to work you know! :wink: :wink: :wink: :lol:

[can773]

Well some of us do have to work you know! :wink: :wink: :wink: :lol:


Well, there's your problem!!!

<Chad soon to leave work to go flying at lunch!>

[juice90]

just a thought, after reading everything, how big of a prop r u useing. I am in the stages of flight testing a stuadacher s300. Useing a webra 61 for power. My first test flights were done with a 3 blade 12-6 i think it was, and had similar problems, includeing the plane wanting to turn left. Changed to a 11-7 2 blde and the problem went away. ( includeing the insane vertical pull. )
just a thought.

[scaleguy]

Juice,

I am currently using a 16 x 6 on the Enya 155R.

Is there really such a thing as "insane Vertical"?..... I think not! :wink: :lol: