Jetdesign

My Feedback: (8)

As many of you know, I just started soloing with my Nexstar. It has 3 days of flying on it. I had a really tough time taking off yesterday, and was wondering if you might have a suggestion. Here's what's been happening:

The first day out I had the speed flaps and the wing droops installed. The plane wanted to take off with just about half throttle; piece of cake. Plane was easy to fly but very slow to respond, and felt very 'floaty'. I removed the training accessories for the second day, in which we were flying into 8mph winds/12mph gusts. My trainer took up the plane and couldn't get it trimmed - couldn't get enough elevator. he had me remove the elevator servo horn and turn it back one click to get some more lift from the elevator I just looked at my plane and realized the elevator push rod is in the farthest hole from the elevator (as well as the farthest hole from the servo which was needed for a 90 degree link). Now it seemed to take off pretty well; obviously it needed more ground speed than with the training gear on, but still take-offs were pretty easy, though the plane had a tendency to make a 10-15 degree right turn (yaw) when it left the ground. It seemed to fly very well. Yesterday, there was little wind. I needed a ton of throttle to get the plane up in the air, as well as 3/4 or more of runway, and the plane was all over the place leaving the ground, most notably a sharp right hand turn (45+ degrees) as it left the ground (engine torque?) The plane flew very well in the sky.
My inexperienced thoughts are to adjust the elevator push rod for more throw and recenter the servo horn, and try to re-trim the elevator. Maybe I just need more up elevator to take off? My instructor the other day was saying that 3/4 throttle should be fine, and I know I haven't seen anyone need nearly as much runway as I've been needing, and I fly a Nexstar!

Thanks for your thoughts.

r2champion

This sounds like it could be a combination of several things. After removing all of the training aids, did you recheck your C.G.? If not, maybe this could explain the change in your elevator sensitivity. It also sounds like one day you had a nice headwind to takeoff into, causing little yaw after liftoff, and more of a crosswind the next day causing more yaw after liftoff, but more importantly resulting in the need for more "groundspeed" to obtain the same "airspeed" as the day before to take off.

wings

Hey FatKat,

The training gear causes the plane have more lift so it can stay in the air at slower speeds, to give a beginner more time to react.

It is normal that you will need to be going faster to get the same amount of lift when you remove the trainer gear.

I think you are on the right track by adjusting to give you more elevator throw. I would adjust it one notch at a time though. As you probably know, each time you move to a farther hole on the horn(on servo, opposite effect on control surface horn) , the more sensitive it becomes. So the elevator will be more "touchy". If you are not careful you may tend to over control the airplane if you move it too much at once. The great thing about computer radios is that you can adjust the end points without adjusting the sensativity. But If you don't have end point adjustments then your only option is to adjust the control horn.

But adjust it slowly, or maybe adjust it all the way, but do it with your instruct and the buddy box in case it is too sensitive for you.

Good luck!

Wings

beau0090_99

One thing I was thinking and it relates to another thread in this forum, is whether or not your ailerons are level with your wing center. With the training accessories installed, maybe they were compensating for ailerons that were position a bit upward, which would decrease wing lift. As for the Yaw effects, I am not sure what might have happened.
Good luck with the search, I guess this is half of the fun of the hobby.
Curtis

ChuckW

Removing the add-ons created a trim change, I've heard of others having the same issue. No big deal. Another factor could be your runway surface. Grass creates more drag, requiring more throttle to get up to speed. As long as the elevator throws match what is listed in the manual and your CG is right, you'll be fine.

MinnFlyer

My Feedback: (4)

Ok, we've got lots of things going on here.

First, the Yaw thing is not unusual at all. Here's what usually happens:

You're traveling down the runway adding right rudder to counteract the torque and steer it straight. As you lift off, most people instantly release the right rudder input - not good. Maintain that rudder input and slowly release it as you climb out.

Next, Are you flying from grass? If so, the grass may be impeding your takeoff speed which will keep a less-than-ideally powered plane from reaching it's takeoff speed very quickly. Note that this will also lead to taking off with a little less speed than what would be ideal, which will also add to the yaw problem.

Finally, if you want more elevator control, you can indeed move the clevis closer to the elevator, but do not move it closer to the servo - that will defeat the purpose. The pushrod does NOT need to be at 90 degrees as you stated.

The further OUT you go on the Control Horn, the LESS control you get.

But the servo end is just the opposite

The further OUT you go on the Servo Arm, the MORE control you get.

Jetdesign

My Feedback: (8)

This is true; whatever wind there was yesterday was across the landing strip. I imagine a cross wind would be one reason my plane had a tendency to roll off the runway?

The bottom of the aileron is perfectly aligned with the bottom of the wing, to within 1/32 of an inch (below wing surface).

The elevator is the only control where I use the full range of control; it is much less 'touchy' than all the other controls, so more throw might be just right.

I understand this, but my concern is really between day 2 and day 3, both without the training aids, and no physical adjustments between them, but again, could be the cross wind?

Definitely will not change anything unless I know my instructor will be checking it out for me.

Thanks guys.

Missileman

I am not sure you really need more elevator throw. Get up high and do a loop, that will tell you if you need more elevator.
If you have enough elevator to fly the airplane you have more than enough to take off.
Grass field? Need cutting?
How well do your wheels roll? (they need to move freely)
From your description it almost sounds like you didn't get enough speed before trying to lift off.
I use full throttle on takeoff on most of my planes and reduce after I get in the air.

Jetdesign

My Feedback: (8)

Interesting. I was able to do a loop, and yes, it did fly just fine off the ground (again, I did use full elevator in tight turns).

Will have to wait for an instructor I guess. All I can think about is when I flew with him on day 2, he said look at the plane during taxi and see what it wants to do. It wanted to leave the ground! Yesterday, it did not WANT to leave the ground, rather it took everything I had to get it in the air! Before you could see it almost skimming the grass, and if it hit a bump it would want to get airborne, now it seems like it wants to dig.

MinnFlyer

My Feedback: (4)

Just a thought...

You may have had a hard landing an pushed the nosewheel in a little.

make sure that the plane sits level, or slightly nose-up when it's sitting on the ground

Jetdesign

My Feedback: (8)

I DID! My nose gear is bent a little. I straightened it as much as I could, but it's definitely not straight! Maybe 5 degrees bent back? I didn't think it would make that much of a difference, but maybe that's it? Maybe that would explain why I can't get the plane on the ground without a prop strike too

MinnFlyer

My Feedback: (4)

You can do one of two things. Either loosen the collar that holds the nose wheel and make it longer, or bend the mains out a little to lower the rear

bkdavy

My Feedback: (1)

When taking off from grass with a slightly underpowered plane, try this method.

When you get the plane moving, give it just enough elevator to start getting the wheels off the grass. This will reduce the drag created by the grass. Keep the plane level just off the grass for a little while and let it build up more air speed. Then pull up into you're normal climbout. This will also help reduce the tendency of the plane to turn suddenly after takeoff. It possible that you're trying to take off too quickly and stalling one wing-tip.

Brad

Jetdesign

My Feedback: (8)

I just called my LHS; he's gonna help me straighten it out. I I tried pulling it down a little but then the spring hit the fuse when I tried to turn. I'll use bending the mains as a last resort. It makes sense that this would cause a problem, but I can't believe it could have made THAT much of a difference...

MinnFlyer

My Feedback: (4)

The thing is: If the plane (or more accurately, the wing) is sitting at a negative angle of attack, the oncoming air is actually holding the plane down on the ground.

Think of putting your hand out of a car window - when you point your hand down, the air pushes it down - the same thing will happen to your plane.

You then need a lot of speed so the elevator can overcome that downward force enough to rotate to a positive angel.

But when you're sitting at a positive angle to begin with you don't need that extra speed.

Now, of course there's such thing as "Too much of a good thing", so you don't want a LOT of positive angle or the plane could lift off before it has sufficient flying speed- the plane should sit level, or SLIGHTLY positive

Jetdesign

My Feedback: (8)

I don't know if it's an illusion or not but it looks like the wing has a negative AOA right now, and straightening the nose gear would probably bring it right about to neutral.

Jburry

Put a yardstick under the wing. Gives a good idea of incidence on flat bottom wings like this...

J

traski

My Feedback: (1)

I have a superstar 40 which is a flat bottom wing trainer and I have bent my front landing gear more than once I am afraid to say.

It should be easy to remove and straighten (well working it over with pliers and channel locks untill it looks straight) and when you reinstall it...make sure the nose of your plane points up when its sitting on the ground. My plane takes off just fine with the old LA .40. I do have to use about 25' of runway on a clam day. Take off is always full throttle for me. Thats how I was told to do it.

With the plane pitched nose up it skims along the grass after the first 10'-15' with a neutral elevator. I just lightly grab some up elevator and its off the ground.

Jetdesign

My Feedback: (8)

The LHS helped me bend my gear back with a vise and a torch. I can't believe the difference! It didn't seem to be bent that far back, but now the front of the plane is sitting up so much higher!. The front wheel hit so hard the screw that locks the landing gear in place was destroyed, and the gear was really bent, even though it didn't look like that much. I think this should do the trick. Thanks Minn!

MinnFlyer

My Feedback: (4)

Yea, I get lucky once in a while