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Trim Problem


daveb

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I can not trim my aircraft. Full forward is insufficient at any more than economy cruise one up. I have to hold the stick forward in fast cruise. At full forward stick I get buffetting on the canard which is a concern. Backing off slightly prevents this.

 

With a big GIB at around 1580lbs AUW it trims nicely.

 

1989 LE, Roncz canard, P51, 0-235, 932lbs BEW, battery in the front, old IFR steam gauges, PIC is 165lbs

 

1. Am I nose heavy?

2. Do I just need stronger/shorter trim springs?

3. What’s with the canard buffeting?

4. If I need so much trim am I producing excess drag?

 

Any help always appreciated.

Dave

VH-JZE

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Your "problem" is indicative of the pitch trim system not being adequate (strong enough) for the task. You need more trim authority. If you are using the plans trim system, try changing out the springs to stiffer ones. It's a common trait for Long-EZs that are using the plans-built trim system. The canard develops more and more lift the faster it flies. You don't have a lot of weight forward of the CG to counter the increasing lift.

 

Also, check the canard's incidence. You'll need a template to do that. If the Long is like the Cozy, the incidence angle should be at 0 degrees or slightly positive above 0.

 

If you still have problems, try checking the plane's weight and balance. You just might be flying at too far an aft CG?

Wayne Hicks

Cozy IV Plans #678

http://www.ez.org/pages/waynehicks

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"Full forward" [stick] is not enough"? That right? I thinks it's more a problem of canard incidence, or CG, than trim, Wayne. He cannot get enough UP elevator at high speed.

 

How does it stall, Dave? If the canard incidence is too nose high, it would require a lot of forward-stick at high speeds and the canard stall would occur at a higher speed than designed due to higher AOA of the canard.

 

OTOH, if the CG is way aft, it would also require more up elevator at high speed but the stall could be dangerous in that you might encounter wing-stall. I would guess that the canard buffet you see is from excessive up-elevator required to hold the canard down

 

I would recheck the canard and wing incidences relative to the waterline (upper longerons). Just make sure all the flight surfaces are set right. And get some to eyeball your CG calculation.

 

It might be that your elevator has insufficient up movement, too, or a combination of things. Let us know how it goes.

-Kent
Cozy IV N13AM-750 hrs, Long-EZ-85 hrs and sold

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He cannot get enough UP elevator at high speed.

 

Negats! He said he cannot get enough forward stick .... i.e. Down elevator.

 

In either case, I'm guessing (emphasis is on guessing) that the place to start is at the incedence.

 

What is your airspeed when this starts to be a problem?

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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Ya to all of the below.

 

Did you do a proper W&B?? where was the CG with respect to what is considered "normal?" This is the absolute first thing, and easiest thing that must be checked, not the last!!

 

All planes are precariously balanced between CG and CL. There is some wiggle room (CG range) but you must know where yours is.

 

The fact that your problem increases with airspeed indicates that as your airspeed increases the lift of the canard increases much faster than that of the wing and thus gives you an upward rotation which you then counteract with down (up) elevator.

 

I agree that it is probably canard incidence, however the shape of the canard may also be at fault (way down on the diagnostic list). When you are at high cruise, what is the position that the elevators must be at to get you to go straight and level?? (I am assuming that you are not just complaining about how much strength you need to keep S&L but are referring to actual elevator position.

 

The buffeting may be blobs of air skipping off of elevators which are greatly deflected hitting the wing. (much like the buffeting one gets in a conventional aircraft just before the stall)--- or not.

 

First correct the need for elevator and then see if the buffeting stops.

 

Did you say that with GIB the problem stops???

I Canardly contain myself!

Rich :D

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1) What is the status of the Weight and Balance???

 

2) Is this a new problem that started suddenly, OR, is this an existing problem??

 

(If this is a new problem that started suddenly, GROUND THE PLANE until you figure out whats going on)

 

Waiter

F16 performance on a Piper Cub budget

LongEZ, 160hp, MT CS Prop, Downdraft cooling, Full retract

visit: www.iflyez.com

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Jeez, guys.

 

1. He said he runs out of full forward, pitch down trim. He does not run out of forward, pitch down stick.

 

2. On my plane and the ones I've flown, trim forward and stick forward move the elevator trailing edges up, not down.

 

3. I personally know of at least 3 Long-EZ drivers who had to change to stronger, stiffer trim springs because they also ran out of forward trim. (And they, too, had to hold forward stick to augment the trim until they got off their butts and changed to stiffer springs.) They are many other cases reported in Cozy archives, CPs, and Central States.

 

4. Yes, I do copy what he said about buffeting at full forward stick. I don't quite know what to say about that because with full forward stick at any speed he should be heading down to Mother Earth at break neck speed. So yeah, check the incidence and yes, check the weight and balance. But I bet the trim authority will be better once he changes to stiffer springs.

Wayne Hicks

Cozy IV Plans #678

http://www.ez.org/pages/waynehicks

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Jeez, guys.

 

1. He said he runs out of full forward, pitch down trim. He does not run out of forward, pitch down stick.

 

2. On my plane and the ones I've flown, trim forward and stick forward move the elevator trailing edges up, not down.

 

3. I personally know of at least 3 Long-EZ drivers who had to change to stronger, stiffer trim springs because they also ran out of forward trim. They are many other cases reported in Cozy archives, CPs, and Central States.

 

4. Yes, I do copy what he said about buffeting at full forward stick. I don't quite know what to say about that because with full forward stick at any speed he should be heading down to Mother Earth at break neck speed. So yeah, check the incidence and yes, check the weight and balance. But I bet the trim authority will be better once he changes to stiffer springs.

 

Wayne,

 

1) perhaps I am misreading his post, however the statement that buffeting occurs at full forward stick gives me the impression that it is the forward stick position, not the trim that he needs to do to keep straight and level. If this were not so, why in the case of some imbalance is he trying flight with the full forward stick???

 

2) I agree with you in terms of what happens to the elevators in a canard, that,s why the (up) was in parentheses. Canards, as you know are different than conventional aircraft, however in both cases when you push the stick the aircraft goes down, even though the elevator goes (up) in canards.

 

 

3) If it is simply a matter of the trim not holding then I agree with you completely, if not----NO

 

 

4) See rebuttal # 1 Yes. However if you change to a stiffer spring, which if as per #2 it is the correct solution to a weak spring, this will do it. If however changing to a stiffer spring, and he is compensating for a different error, the plane may fly OK, however the original problem still exists and may or may not be important. That would be called a band-aid:mad:

I Canardly contain myself!

Rich :D

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DaveB,

 

how does this differ from the feeling when you are 2 up in the plane ... is it still the same on the trim?

 

What is your calculated CofG position when you are experiencing this required forward stick force?

 

How does it feel when you come in to land, do you have sufficient up trim?

Solo and dual?

 

cvh

 

PS, I have experienced same and got a massive speed increase by forcing the stick forward (stick forces = quite tiring).... after altering the battery position in my Cozy I have not been able to replicate the speed! 200,454 Kt to 179 Kt ...

I live in my own little world! but its OK, they know me here!

Chris Van Hoof, Johannesburg, South Africa operate from FASY (Baragwanath)

Cozy Mk IV, ZU-CZZ, IO-360 (200hp) 70x80 prop

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DaveB,

 

how does this differ from the feeling when you are 2 up in the plane ... is it still the same on the trim?

 

What is your calculated CofG position when you are experiencing this required forward stick force?

 

How does it feel when you come in to land, do you have sufficient up trim?

Solo and dual?

 

cvh

 

PS, I have experienced same and got a massive speed increase by forcing the stick forward (stick forces = quite tiring).... after altering the battery position in my Cozy I have not been able to replicate the speed! 200,454 Kt to 179 Kt ...

This is true when you fly with the CG at the rear end of the envelope the top speed is higher. its do to the less lift needed from the canard. when I have raced it that way it was faster but very tiring as the plane is very twitchy in pitch.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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It worries me that the poster does not apparently know his CG. If he does...then it worries me that he did not feel it important to post.

 

Going from a 0235 to a O320 required stiffer springs for me at the same CG---got lots more speed that the "old" trim system could not over come.

 

If he really has to hold full forward stick as opposed to full forward trim----with O235 engine----either the CG is too far aft or the incidence is too high. However, having flown at (or beyond---I will never admit) the aft CG limit, it is readily apparent that you are there----you are now actively controlling the airplane. Any up elevator has to be countered with down elevator----no natural returning forces-----no one can fly aft of CG and not know it---won't even trim.

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I've flown with Dave several times in this LEZ. I'm occasionally that GIB. Seeing that Dave hasn't bother to wake up this morning :), here's want I know of the issues.

 

- It is definitely full forward trim. He can trim all the way forward and it's just not enough. His inquiries to the previous owners revealed that it has always been that way. We have discussed shortening the existing springs to add more tension. Before doing this Dave ordered in a spare set of springs. That way if the original 20 year old springs break, then the new ones can go on without waiting for them to be ordered.

 

-W&B. I know DaveB & his lame (A&P) maintain the plane to a very high level. Anytime something needs done, Dave has no problem spending the time & money to do it right. So Dave will have a current W&B and he does do the pre-flight calcs regularly.

 

-Buffeting. Hmm. Dave, is that new? I don't recall that from our conversations.

 

sorry for stepping on you Dave, but thought I would help stop some of the speculations.

Drew Chaplin (aka the Foam Whisperer)

---

www.Cozy1200.com - I'm a builder now! :cool:

---

Brace for impact...

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I've flown with Dave several times in this LEZ. I'm occasionally that GIB. Seeing that Dave hasn't bother to wake up this morning :), here's want I know of the issues.

 

- It is definitely full forward trim. He can trim all the way forward and it's just not enough. His inquiries to the previous owners revealed that it has always been that way. We have discussed shortening the existing springs to add more tension. Before doing this Dave ordered in a spare set of springs. That way if the original 20 year old springs break, then the new ones can go on without waiting for them to be ordered.

 

-W&B. I know DaveB & his lame (A&P) maintain the plane to a very high level. Anytime something needs done, Dave has no problem spending the time & money to do it right. So Dave will have a current W&B and he does do the pre-flight calcs regularly.

 

-Buffeting. Hmm. Dave, is that new? I don't recall that from our conversations.

 

sorry for stepping on you Dave, but thought I would help stop some of the speculations.

He should just install the Alex Strong electric pitch trim system and get rid of the stock springs. its a very good system simple and easy to install

http://www.strongpitchtrim.com/

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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He should just install the Alex Strong electric pitch trim system and get rid of the stock springs. its a very good system simple and easy to install

http://www.strongpitchtrim.com/

So the Strong completely replaces the spring system. Hmm. That sounds like reasonable solution.

Drew Chaplin (aka the Foam Whisperer)

---

www.Cozy1200.com - I'm a builder now! :cool:

---

Brace for impact...

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PROVIDED:

-the W&B is correct

-the incidence of the canard is correct

-the incidence of the main wing is correct

-the elevators are in trail at cruise in S&L flight

 

I would strongly suggest you take a close look at the setting of the ailerons, are they both in trail at neutral or in your case are they both slightly up? And by slightly up I do mean you will need to have someone lifting the other one while you lift one of them (to take out any slop). If they both are above trail this may have an influence on your stick forces and you can begin to add a 1/2 turn each side until they are both in trail.

Some believe having them reflexed up slightly may improve their top speed but it can cost you in terms of trim and personal fatigue, not to mention reserve down elevator and safety.

Given everything else is rigged right you can sometimes neutralize some of your stick force with careful trim of your ailerons, both up or down WITHIN REASON.

...Chrissi

CG Products

www.CozyGirrrl.com

Cozy Mk-IV RG 13B Turbo

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He should just install the Alex Strong electric pitch trim system and get rid of the stock springs. its a very good system simple and easy to install

http://www.strongpitchtrim.com/

Is it not a little premature to suggest that this is a trim problem? Should not the more critical things be checked out first, for example:weight and ballance, canard incidence, elevator shape/gap/wieght etc?

 

(OK, now I just see that Chrissi has covered all that and more....)

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I've flown with Dave several times in this LEZ. I'm occasionally that GIB. Seeing that Dave hasn't bother to wake up this morning :), here's want I know of the issues.

 

- It is definitely full forward trim. He can trim all the way forward and it's just not enough. His inquiries to the previous owners revealed that it has always been that way. We have discussed shortening the existing springs to add more tension. Before doing this Dave ordered in a spare set of springs. That way if the original 20 year old springs break, then the new ones can go on without waiting for them to be ordered.

 

-W&B. I know DaveB & his lame (A&P) maintain the plane to a very high level. Anytime something needs done, Dave has no problem spending the time & money to do it right. So Dave will have a current W&B and he does do the pre-flight calcs regularly.

 

Awake now. Wow thanks everyone for the input. I'll try and address some of the missing info. Drew has filled a few gaps.

 

All I've built is a Rutan bookend so far and that was a challenge. Technical is not my happy place. I do have about 1800 hours in things that fly. This plane was built by a LAME and the second owner flew an F/18 Hornet for a day job. So it can’t be too bad even if she is a bit heavy, she has about 900 hours flying.

 

W&B are within limits although I haven’t done measurements myself (or quite understand how from the owners manual). Stall is about 55 knots and one up. I go for just under 60 knots touch down with a 70 knot approach. She lands no problems with or without the landing brake. I just put the trim all the way back on downwind and fly the plane.

 

Trim fully forward, the canard looks to be UP with the stick forward. At 2500 rpm I have enough trim, just. At 2600+ rpm I have to hold the stick with forward pressure to maintain S&L. At 2700 I get 150kts at 7000’DA.

 

The vibration in the canard (I can see it) is when I push all the way forwards and just relaxing a tad stops it. It’s quite subtle but shouldn’t be there. The elevator has natural returning forces as Drew S. refers to. It flys OK, light or heavy.

 

At MAUW I can get enough trim to fly hands off at 2650rpm with a bit more forward trim available. I guess this is a clue? The exact weight numbers are in the handbook in the plane which I’ll grab next trip.

Dave

VH-JZE

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Hi, Dave/Group.

 

 

As a relative rookie to all things EZ, I really shouldn't be offering any advice regarding your problem, however, coincidentally, I was reading the Canard Pushers tonight and came across just this topic. Have a look at Canard Pusher #47, page 8. Half-way down the right column, is a discussion of elevator shape which seems to match the problem you are having.

 

This may or may not be your particular problem, just thought it might help. Good luck.

 

Tom.

(Got Plans!)

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Dave;

 

If the original owner didn't have these types of problems, then I would guess that the original owner was a heavy pilot (compared to you). i.e. You weigh less, so there is less weight on the canard, and it doesn't need to lift as much weight, AND, the farther aft the CG is.

 

You really need to do a W&B.

 

A couple of reasons!

 

1) The most important component in the aircrafts ability to maintain controlled flight throughout its design range is an accurate W & B. (Note, you said you were having control issues)

 

2) Trust everyone, but cut the cards. I'm sure the original builder did a good W & B. HOWEVER, Are you willing to stake your life on it. I'm a high time Canard pilot and have performed many first flights in EZs. To Date, I have never performed a first flight unless I personally have supervised the W & B.

 

Yes, I want to see the plane on the scales, and I want to see the measurements made.

 

 

3) I notice in your original post that you weigh 165 lbs. If the original pilot who did the weigh and balance weighed more than this and use his weight, then your CG has moved aft, the more the original pilot weighed, the farther aft your CG is. (i.e. If the original Pilots weighed 210 lbs, using your weight of 165, the CG has moved aft by 2 inches.)

 

 

If you look on my web site;

 

www.iflyez.com

 

You'll find a good article on performing a W & B and also a sample spread sheeet that you can use.

 

Keep us posted on your findings.

 

Waiter

F16 performance on a Piper Cub budget

LongEZ, 160hp, MT CS Prop, Downdraft cooling, Full retract

visit: www.iflyez.com

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She lands no problems with or without the landing brake. I just put the trim all the way back on downwind and fly the plane.

I think you gave us a clue there. I have a Long similar to yours (O-235, Roncz canard) and have never gone full aft on the pitch trim. I do run out of forward pitch trim when racing and have to keep just a little forward pressure on the stick, but never get close to running out of trim at slow speed. I too believe your pitch trim springs are too weak.

 

I agree with several items mentioned before:

 

  • Do your own W & B.
  • Check the trailing edge position of the elevators ( I can see mine in flight).
  • Check your elevator contour (should be concave on upper surface).
  • Check incidences.

I don't understand your vibration on the canard. It doesn't sound like flutter, because you would be more excited when talking about flutter experience. I don't understand why the GIB makes that much of a change for you. The GIB is very near the C of G.

 

Good luck with it,

 

Dave

Dave Adams

Long EZ N83DT

Race 83

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