chadxp1

My Feedback: (2)

my plane flys better with flaps down. what can I do to transition to flying with flaps up? Should I trim the ailerons down? Should I trim the flaps down. Should I move the CG back?

Charlie P.

Increase the wing incedence.  That can be done by shimming up the leading edge or lowering both ailerons.

jetmech05

Flying better with flaps down maybe hiding a problem. Either you're flying too slow and are on the verge of a stall when flying flaps up. Or there is a problem with the aircraft. Flaps are designed to give additional lift, this allows you to fly slower. It also increases drag.
What kind of airplane are we talking about?

chadxp1

My Feedback: (2)

It is an AK modelsSimple Flier. With flaps up the noze wants to dive, not real drastic but non the less it does. It did snap on me with flaps up. Luckly I was high enough to recover. So what do you think? I was thinking about moving the CG back. Also the Vtail control surfaces looked to be straight with the stabs so I dont think its out of trim real bad or anything. The CG is back a little from manufacture specs but is forward of what the CG calculator spec'ed out. I dont know...

KitBuilder

Flying to slow will lead to a tip stall on some planes, which is what you're probably calling a snap. Snaps require rudder, elevator to occur under normal conditions. View the video at 2 min and 30 secs and you'll see someone tip stall with disastrous results. THe plan is practically wobbling on the approach. You can hear someone say you got to fly it in and he's right... it's not a cub for pete's sake.
http://www.youtube.com/watch?v=nQJ3TzSZkpo

Moving CG back increases instability (aerobatic ability) which i beleive will just compound your problem. This plane has a long nose and short tail moment... (centered wing)... looks like it needs speed throughout the flight envelope to behave... just my opinion. Could be a thrust line issue as well. What happens when you go idle at speed with flaps neutral?

Charlie P.

Like this?



If you are flying better "with flaps" then it seems your ailerons need to me lowered on both sides or you have to up the airspeed.  This looks like it was designed to be flown flat-out.  If you trim it for level flight, pull up into a 45° angle and then roll inverted and let the sticks go neutral it should hold course for at least a three count.  If it noses up you are tail heavy.  If it noses down you are nose heavy.

chadxp1

My Feedback: (2)

Kitbuilder, if I recall i was flying along at a decent speed (flaps up) when it snapped. I was banking and turning when it happened. I cant say for sure but I think when I idle down with flaps up the plane starts decending real quick but level. I have only flown it three times. each time was nerve racking as it does not fly like my U can Do 3D. I got the impression that this plane would fly some-what stable at low speeds. This is all based on my experience with flying it on the simulator. I know.. I know.

Charlie, That is It! I really like the plane. I built it from a kit so I do have a connection to it and want this to be successful. I will give your advice a try.

Thanks.

Chad

chadxp1

My Feedback: (2)

I love reading the comments from that video. LMAO! I'd hate to be that guy, especially after reading all those replies. I felt sorry for him. I know its not funny but you can tell the people that wrote some of those dont own planes.

Chad

jester_s1

So the only issue is that it wants to drop its nose when the flaps are up? Are you able to trim it for straight flight at all? If you will start working through an aerobatics trim guide you should find the problem. You should be able to get straight flight at full throttle and maintain it down to 1/2 or at least 2/3 throttle also if the plane is trimmed right.

chadxp1

My Feedback: (2)

No it does not drop when flaps deployed. In fact it balloons up. I can trim it fly straight with flaps retracted but I have to be flying fast.It is not what I expected. After practicing on Real Flight this thing was suppose to float through the air. I even read about others saying its a gentle airplane. Mine is not. It is a little heavier than manufacture spec'ed but I dont know if the weight they posted included the optional flaps.

Thanks for the tip about the trim guide. I did not know of this. I will try this. Same thing Charlie said.

Chad

opjose

The Real Flight model assumes a VERY light wing loading. I believe the simple Flyer Physics was not updated in 6.x and that the plane model itself is from the older 3.0 version... distributed as part of the free add-ons pack. The add-ons physics were NOT updated to 6.x levels.

That will make it more "floaty" in the later versions, than it should be.

Also on a plane like this with swept wings, once you go beyond a certain wing loading, it WILL snap on you or get "mushy".

It sounds like your plane was set up to go fast... something this model is designed for.

Either lighten it up ( a lot ), or fly it faster.

Increase the wing loading in the sim until the emulated plane reacts like yours.

chadxp1

My Feedback: (2)

So I did a couple of things to the plane tonight and took it for a run. First I added some weight (I think it was around 1.5 ounces) to the very end of the plane at the tail. This moved the CG about 0.5" to 0.75" back. Second I trimmed both ailerons down. I think it flew better. I crused around for about 5 min with no flaps. Seemed better, and no stallls. I did not lay off the throttle to much though.

I tried Charlies inverted flight test (trim guide) but first I trimmed for level upright flight. The nose definetly dropped down while inverted indicating a nose heavy airplane. In fact I could not make the nose go up by giving it down elevator. It just did not have enough ass, if you will, to overcome the weight.

So what do I do now? Add more weight to the back in order to move CG back? Yes I will move the battery back furhter too! Some more info that may help us is: the current CG is 4.5" from leading edge. The CG calculator says I need to be at 6". The manufacture spec says 3.5"

chadxp1

My Feedback: (2)

heres a pic of mine and yes thats a heli engine on it. Redline Pro53H. Really whines up!

Charlie P.

Whatever you can do to eliminate adding dead weight is worth doing.  Move the battery, shorten engine stand-off, move servos,

jester_s1

I'd double check those calculations or either reread the manual. I've heard of CG recommendations being a little off before, but that's really bad. Either way though, you know you are nose heavy so moving the battery back is the first thing to do. It's not hard to make a hatch for it in the bottle of the fuselage and use velcro to secure it in. Moving servos back helps a little also, but the 2-3 inches you'll get inside the fuselage isn't worth the trouble. If you have to add weight you just have to do it, because as you've seen flying nose heavy just doesn't work.

opjose

No NOT necessarily.

The AMOUNT of nose drop is important.

If you can hold the plane level inverted while pushing the nose down, note how far you have to go to do so.

If you only need SOME stick movement you're fine.

If you need to practically move the stick to it's stop, it is definitely nose heavy.

This is NOT a 3D plane where we trim it to fly level upright and inverted... this is a swept wing plane....

If you move the C.G. back to far the plane will drop a wing severely at stall after it gets very mushy.

You WANT the plane to be just a little bit nose heavy... just like you would on a delta or jet.


Note Kitbuilder's comment... he is right on the money...

"Moving CG back increases INSTABILITY (aerobatic ability) which i believe will just compound your problem. This plane has a long nose and short tail moment... (centered wing)... looks like it needs speed throughout the flight envelope to behave... just my opinion."

It is that INSTABILITY you are encountering with the snap.

The fact that your plane wants to nose down when flying flaps up, indicates it is out of trim for level flight, there is an incidence problem, or a thrust line problem.
You need to check that all out first.



Forget about the flaps for the moment and ESPECIALLY dropping the ailerons as you've done as that INCREASES snap tendencies.

Equalize the ailerons then trim the plane for level flight with no flaps at around 70-80% throttle.

Then use a mix with flaps to prevent ballooning, but given the low speed symptoms you already stated you may want to trim the ailerons slightly UP not down to prevent tip stalls then greatly decrease the amount of flap travel.


When trimmed for level flight ( no flaps ), and flying at 50-60% throttle, does the nose pull down or up when you go to 100% throttle?

If so you have a thrust line problem.