Symptoms of unbalanced CG

[Victory Pete]

Hi
I have a T-34 and when I first flew it with an instructor I noticed the nose would dip down a bit when checking CG. My instructor said it was fine. I have since made some repairs and upgrades to the plane. It is definately dipping nosedown even more. When I fly at medium throttle the plane seems to fly level, I have flaps on and the elevator is trimmed with the flaps for 15 down. But when I bank and turn the nose seems to drop, also my recent landings seem to be nose heavy. I can easily shift the battery back a bit to change it. If I do would I expect drastic changes to the handling and trim settings?
VP

[WJCJR1]

VP before making any changes you must measure and document the current CG point. So;

Grab a notebook, sharpie, pen, tape measure and painter's tape.
Get the plane fully set up to fly with battery mounted, prop on, canopy on etc, just don't plug in the plane.
Put some painter's tape onto the top of your wings directly beside the fuselage.
First mark the tape on the tape on the wings with the Sharpie at the standard E-Flite stock CG mark which is 4.75"-4.875" as described on page 34 of your instruction manual. Go with 4.75" for now, draw a line on the tape to represent E-Flite's CG recommendation.
Flip the airplane over and balance the plane on the lines you made. Use caution with this step the plane could get a bit awkward to balance on two single points especially if CG is off. Fingertips will work fine, having a helper makes this quick and easy. Note how the airplane is balanced whether it is nose up meaning tail heavy or nose down meaning nose heavy, record this in your notebook.
Now move the plane forward or aft on your fingertips or on a commercial or manufactured CG tool until you reach a good balance with the nose pointing slightly down. Mark this dimension on your wing with a dot/mark/line etc from your Sharpie. Put the plane down and measure.
Compare your measurements to E-Flite's recommended CG measurement. If your CG is off I would suggest first getting your CG set to the recommended CG of 4.75" before you begin experimenting much. You can move your CG around by moving the battery as you had suggested or adding some weight to the nose or tail in the form of ready made stick on weights, double-sided tape with a weight on it etc.
Fly at the recommended 4.75" and see how you like it.
If you are at the E-FLite recommended 4.75" and you are feeling nose heavy which sounds like you are with fast landings and nose drops move the CG only an 1/8" at a time. Fly with the new CG setting, critique performance and either make changes permanent or readjust.
VERY VERY VERY dramatic differences in flight character can come about with CG changes, so heed my advice and change CG slowly.
Nose Heavy airplane lands fast, sluggish reaction to elevator input but is usually very stable with good control.
Tail Heavy airplane landings are usually longer as the glide path is lengthened, plane becomes very twitchy and elevator input induces a hazardous snap.
Flying with the flaps deployed all the time can cause some weird stuff to happen too. My Deuces Wild feels like flying in Jello in the air if I fly with the flaps deployed at anything other than a landing approach speed. These airbrakes cause A LOT of resistance. When you are cornering with the flaps deployed this could be a reason for the nose drop, get too steep into a bank and the flaps will help roll the plane horizontally over. Think of your plane banked and now you push it from underside of the plane it will want to push to the top-side into the corner almost like pulling on the elevator.

Have you flown without the flaps deployed before?

What is the size of your airfield?

Wayne

[Victory Pete]

VP before making any changes you must measure and document the current CG point. So;

Grab a notebook, sharpie, pen, tape measure and painter's tape.
Get the plane fully set up to fly with battery mounted, prop on, canopy on etc, just don't plug in the plane.
Put some painter's tape onto the top of your wings directly beside the fuselage.
First mark the tape on the tape on the wings with the Sharpie at the standard E-Flite stock CG mark which is 4.75"-4.875" as described on page 34 of your instruction manual. Go with 4.75" for now, draw a line on the tape to represent E-Flite's CG recommendation.
Flip the airplane over and balance the plane on the lines you made. Use caution with this step the plane could get a bit awkward to balance on two single points especially if CG is off. Fingertips will work fine, having a helper makes this quick and easy. Note how the airplane is balanced whether it is nose up meaning tail heavy or nose down meaning nose heavy, record this in your notebook.
Now move the plane forward or aft on your fingertips or on a commercial or manufactured CG tool until you reach a good balance with the nose pointing slightly down. Mark this dimension on your wing with a dot/mark/line etc from your Sharpie. Put the plane down and measure.
Compare your measurements to E-Flite's recommended CG measurement. If your CG is off I would suggest first getting your CG set to the recommended CG of 4.75" before you begin experimenting much. You can move your CG around by moving the battery as you had suggested or adding some weight to the nose or tail in the form of ready made stick on weights, double-sided tape with a weight on it etc.
Fly at the recommended 4.75" and see how you like it.
If you are at the E-FLite recommended 4.75" and you are feeling nose heavy which sounds like you are with fast landings and nose drops move the CG only an 1/8" at a time. Fly with the new CG setting, critique performance and either make changes permanent or readjust.
VERY VERY VERY dramatic differences in flight character can come about with CG changes, so heed my advice and change CG slowly.
Nose Heavy airplane lands fast, sluggish reaction to elevator input but is usually very stable with good control.
Tail Heavy airplane landings are usually longer as the glide path is lengthened, plane becomes very twitchy and elevator input induces a hazardous snap.
Flying with the flaps deployed all the time can cause some weird stuff to happen too. My Deuces Wild feels like flying in Jello in the air if I fly with the flaps deployed at anything other than a landing approach speed. These airbrakes cause A LOT of resistance. When you are cornering with the flaps deployed this could be a reason for the nose drop, get too steep into a bank and the flaps will help roll the plane horizontally over. Think of your plane banked and now you push it from underside of the plane it will want to push to the top-side into the corner almost like pulling on the elevator.

Have you flown without the flaps deployed before?

What is the size of your airfield?

Wayne

Hi Wayne
My field is 60 acres. I was trained with an instructor who didnt ever want to use the flaps. After I soloed I started to use the flaps for slow flights. I see what you mean about "Jello". I moved the battery back a bit and now it is more level, it still dips down a bit but it is not as drastic as it had become with my repair modification. I always wondered why the instructor said it looked fine dipping down the way it was even before I made repairs. I followed the manual for checking CG, I put my marks between 4 3/4" and 4 7/8", I guess that is 4 13/16". I noticed it was nose heavy. It was also with the battery all the way forward. There is plenty of room for it to sit further back. Well it still dips down so I shouldnt be alarmed by any drastic changes in performance, except hopefully an improvement in ease of flight. I will be very cautious and ready to compensate tomorrrow.
VP

[ATIS]

they almost always dip a little when you turn, you are reducing the wings lift since the wings arent level.

[rcdude07]

Sounds like tip stalls, are you making super tight (almost knife edge like) turns? If so, try a more gentle banking turn and see if it behaves better. I was trained to always use a smidgen of up elevator when making turns. The tighter the turn, the more up elevator you'll need. If it's too tight, you'll also need rudder input.

[Victory Pete]

Hi
I just came back from the field. CG seems better. There wasnt a drastic change. I did have to put in 1 click of down elevator and 1 click of right aileron. I did still have 1 hard landing, my recent reinforcing of the balsa was a success, no splinters this time. I am still amazed at how long this plane takes to come in and down. I do have to apply a little up elevator from moment to moment as I am coming in, is that a symptom of still being a bit nose heavy? I realized why I have hard landings. As I am trying to level the wings I tend to dip down a bit, resulting in a too late flair. I realized I should do my flairs first and then level the wings. I kept repeating to myself "Lift then Level" That is what I have always been doing now for 2 months, these hard landings have only been recent. I wonder how the landings will be when I take the NACA droops off, I am afraid to think of how long those will be.
VP

[ATIS]

The droops change the airfoil to generate more lift at the wing tips to prevent tip stalls so you will actually land faster as your sink rate will be higher. You need to learn to slow her down. Whats the throw on the flaps in the down position (landing position) measured from the normal up/flat position?

[Victory Pete]

the droops change the airfoil to generate more lift at the wing tips to prevent tip stalls so you will actually land faster as your sink rate will be higher. You need to learn to slow her down. Whats the throw on the flaps in the down position (landing position) measured from the normal up/flat position?

1/2 ".

[phantomphan]

Hi
....I do have to apply a little up elevator from moment to moment as I am coming in, is that a symptom of still being a bit nose heavy? ...
VP

Hi VP, Your plane needs to be slightly nose heavy for stability as others have said before. So having to hold a little up elevator or bump it some is pretty normal while on approach.
If the amount of up elevator required is excessive then your too nose heavy. Being extremely nose heavy can do a couple things. A lot of up elevator will act as an air brake (high drag) and you can actually stall the elevator. To keep from stalling the elevator you end up landing faster than youd desire.

In your case thou with your flaps down and elevator trimmed down for normal cruising flight, my guess is thats the majority of your prob. The amount of elevator trim required for approach will be different then the amount needed for cruise. So its likely that your actually fighting the excess elevator down trim while your on appraoch.

From what youve wrote I think your CG is close and not a big issue.
IMO you need to have the flaps turned off during normal flight to really test the CG. Landing mode is just one way to evaluate your CG.

Im curious...
1. do you have your flaps on a switch?
2. do you have a flap-elevator mix setup?
3. can you fly inverted for any length of time
4. can you fly up 45% inverted

Cheers,
James

[Victory Pete]

Hi James

Thanks for your help, I feel comfortable where I am now. I must be close.
To answer your question
1. do you have your flaps on a switch? Yes, no flaps or 1/2" down
2. do you have a flap-elevator mix setup? Yes, 15 down elevator
3. can you fly inverted for any length of time? Gosh no! I havent tried!
4. can you fly up 45% inverted?

VP

[phantomphan]

VP, please note that I edited my previous post slightly.

Ok, so forget the inverted stuff.

Are you willing to turn off the flaps during normal cruising?
If so, you could reduce the 15 down elevator to 13 and see if thats more comfortable for you on approaches. That way the elevator is working for you on approach instead of against you.
If reducing to 13 doesnt do much you could reduce it to 10 and evaluate again. If after trying the different settings you dont like it, its easy to change em back.
Just a thought.
Cheers.

[Victory Pete]

VP, please note that I edited my previous post slightly.

Ok, so forget the inverted stuff.

Are you willing to turn off the flaps during normal cruising?
If so, you could reduce the 15 down elevator to 13 and see if thats more comfortable for you on approaches. That way the elevator is working for you on approach instead of against you.
If reducing to 13 doesnt do much you could reduce it to 10 and evaluate again. If after trying the different settings you dont like it, its easy to change em back.
Just a thought.
Cheers.
Okay, I have flown many times with out flaps, my instructor never used them.
So I see that trims need different settings depending on airspeed, If I have to trim to 15 for normal flight, it could be messing up the mix on landing. Very interesting. I will try that and only use flaps for landing. Well they market the plane as a trainer and tell you to fly with the flaps while learning, but they never mentioned the ballooning affect and the flaps elevator mix setting.
I guess there is some compromising to do here, there are some gray areas?
VP

[phantomphan]

Yep, you got it. There is some gray area. Give you an example; All planes Ive flown require different trim for airspeed when flaps are down. And while some planes will pitch up with flaps down, some will actually pitch down.

Ive seen a couple guys over the years that instead of using a mix just use the elevator trim (beside your right stick) to adjust trims while in flight for different flight modes. Take off w/ flaps, cruise, landing w/flaps. They change the elevator trims at least twice during a flight. Lots of work.

Me on the other hand, Im a bit lazy. I dont like having to change my elevator trims at all. So with flaps up I trim my planes for cruise. Then when the flaps are down I use the mix to handle the elevator trim. One switch, no fuss. Takes a couple landings to get things dialed in to where Im happy but once its done, its done.

So basically youll get the feal for how slow your plane should be going before deploying flaps so it doesnt balloon like crazy. I normally drop flaps on the down wind leg but thats just my pref. If my airspeed is ok I dont get ballooning.

I set up my mix so I dont have to use a lot of elevator on approach. I basically just manage the throttle to keep a good glide slope. Once the plane is in ground effect, half the planes wing span, then the flare begins followed by the landing.

Some others may have different methods and thats cool, but Ive found that I get more repeatable landings when I can just flip one switch for different flight modes.

Cheers.

[ATIS]

I trimmed mine to fly without flaps at a couple of clicks over half stick. I then went up 2 mistakes high, levled the wings, reduce the throttle to 2 clicks below 1/2 stick and deployed full flaps and watched the planes response. From theirI decided if I need to add a mix...if she ballons you can either 1) reduce throttle till she slows down and flys level or 2) reduce the amount of flap your using...remember the flaps should only drop down about 3/4".

[Victory Pete]

Thanks Phantom
I will reduce my flaps elevator mix setting and see what happens. I will not fly around with flaps anymore. I will try tomorrow morning first thing.
VP

[Victory Pete]

I trimmed mine to fly without flaps at a couple of clicks over half stick. I then went up 2 mistakes high, levled the wings, reduce the throttle to 2 clicks below 1/2 stick and deployed full flaps and watched the planes response. From theirI decided if I need to add a mix...if she ballons you can either 1) reduce throttle till she slows down and flys level or 2) reduce the amount of flap your using...remember the flaps should only drop down about 3/4".

Thanks ATIS
I will try that, my flaps only come down 1/2".
VP

[Victory Pete]

Hi
I was thinking about the trim for the Ailerons. I have it set at 3 clicks to the right to compensate for the counter torque of the motor. What about on landings when the motor is off? Is this why I have to correct my wing level on landing? Is there a way to program the DX6i to adjust the trim for Ailerons with the throttle inputs?
VP

[ATIS]

I wouldnt mix it...you need to learn to fly her. Mixes cant tell what the winds doing or see the ground so they can get you in trouble.

[Victory Pete]

I wouldnt mix it...you need to learn to fly her. Mixes cant tell what the winds doing or see the ground so they can get you in trouble.

Should I center the trim for landing and then put it back for takeoff?
VP

[ATIS]

dont mess with it. At some point you will "forget" and then your going to be in for a nasty surprise!

Trim her to fly at 1/2 throttle or a couple of clicks above that and then dont mess with her other then a little elevator mix if needed for the flaps.

[Victory Pete]

dont mess with it. At some point you will "forget" and then your going to be in for a nasty surprise!

Trim her to fly at 1/2 throttle or a couple of clicks above that and then dont mess with her other then a little elevator mix if needed for the flaps.

So split the difference and compromise!
VP

[ATIS]

I still strongly think you should trim her to fly and control her during landing without messing with the trim but if you dont mind constantly correcting for a slight roll during flight you can split the difference.

[Victory Pete]

I still strongly think you should trim her to fly and control her during landing without messing with the trim but if you dont mind constantly correcting for a slight roll during flight you can split the difference.

Okay I understand the options now. For all of my first flights it was always windy, so I couldnt notice trim that well. Now I go first light and fly with no wind, it is a different animal. It seems with this global warming climate change it is windy every day now.
VP

[ATIS]

global warming, we had the coldest winter in years down here this year!! Now we too have the winds but its that time of year with the hurricanes and tropical storms.

[Victory Pete]

global warming, we had the coldest winter in years down here this year!! Now we too have the winds but its that time of year with the hurricanes and tropical storms.

The average global temperature is rising, no debate there, what is causing it is the controversy. We are getting extreme weather in either season. I will get off the soap box now.
VP

[WJCJR1]

So once you get trimming your plane make certain it flies straight, level NO HANDS. Do this as ATIS suggested at or slightly above 1/2 throttle, couple mistakes up in case you have to regain control after letting go of the sticks.

CG set good, trim properly dialed in and you should be good. I will get for you tomorrow Gary's settings for his flaps on his Mentor. We have his set up so that it comes in REAL NCIE with flaps deployed and a bit of down elevator. I believe it is 8% down elevator, will check for sure.

The Mentor is a great plane but a pure trainer it is not IMO, starting with a simpler, easier to fly/repair plane is very advantageous. The flaps add some complexity to the plane and then a 5# model it is. So be not afraid to look at entertaining the idea of flying an Apprentice, that airplane would serve you VERY WELL and teach you a lot of the basics that you still need to learn.

Wayne

[Victory Pete]

So once you get trimming your plane make certain it flies straight, level NO HANDS. Do this as ATIS suggested at or slightly above 1/2 throttle, couple mistakes up in case you have to regain control after letting go of the sticks.

CG set good, trim properly dialed in and you should be good. I will get for you tomorrow Gary's settings for his flaps on his Mentor. We have his set up so that it comes in REAL NCIE with flaps deployed and a bit of down elevator. I believe it is 8% down elevator, will check for sure.

The Mentor is a great plane but a pure trainer it is not IMO, starting with a simpler, easier to fly/repair plane is very advantageous. The flaps add some complexity to the plane and then a 5# model it is. So be not afraid to look at entertaining the idea of flying an Apprentice, that airplane would serve you VERY WELL and teach you a lot of the basics that you still need to learn.

Wayne

Thanks, I agree.
VP

[Victory Pete]

Hi All
I went to the field this morning and had 2 interesting flights with the T-34. I tried to land with the new CG and trim settings with the flaps and it went by me really slow at about 25 feet up. I tried again, same thing so I put up the flaps and had a rather good but long landing. Second flight I didnt use the flaps either, again nice landing. A club member pointed out that I do my downwind and base leg at a too high altitude. I guess he is right, I like to be 4 mistakes high. Tomorrow I am going to try to reduce my altitude by about 25' I guess. I am slowly getting the hang of this.
VP

[phantomphan]

VP, what was the new elevator trim setting you used. Im just curious. Sounds like whatever you dialed in is working ok as you werent fighting the elevator? Thats positive news.
What were the wind conditions like? You may find that above 6 or 7mph the flaps are really needed. And on calm days they are a great option.
Cheers.

[Victory Pete]

VP, what was the new elevator trim setting you used. Im just curious. Sounds like whatever you dialed in is working ok as you werent fighting the elevator? Thats positive news.
What were the wind conditions like? You may find that above 6 or 7mph the flaps are really needed. And on calm days they are a great option.
Cheers.
Hi Phantom
flap elevator trim = down 10, But it was very floaty, I didnt land with the flaps. The normal elevator trim was center. It was light winds. I though that with no wind flaps where needed to help slow down the plane and give lift. With strong winds you have the extra lift and the reduction in airspeed, right? Maybe?
VP

[phantomphan]

Yeah, I made a typo. Should have wrote...
You may find that above 6 or 7mph the flaps are NOT really needed.