Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Predator 500 Problems

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Old 07-31-2004, 05:09 PM
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mumblety-peg
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Default Predator 500 Problems

I need help wiht this one. I've had two flights wiht the ARF version of this plane. The last one ended with a fair amount of damage.

On the first flight I had VERY slow aileron response at first. I was flying fairly slow at first. But at slow speed I nearly lost sight of the plane as it circled past the pits. The plane would also ballon up on a dive. So I thougth it may be a bit nose heavy.

Then the throttle servo failed. Man, that was hairy a first. But I seemed to have control of the plane at high speed. As the servo got worse I ended up at full throttle so I had to run the tank out. The landing was OK. I had a fair amount of control with the ailerons even at the lower speed.

OK... flight two. I'd increased the aileron throws and moved the CG back. This flight was nearly a disaster. It just about looped all on it own. And the aileron control was almost non-existent. The elevator response seemed way too much. The plane pretty much circled back to the strip on its own, I cut the throttle and it floated, and I mean floated, down to the runway. It's last act was to hit a fence. The damge is not too bad. But it's enough too make me think that taking another chance wiht this plane is possibly a bad idea.

I'm going to check the throws again. And measure the CG. I don't know how to check incedence with a v-tail.

One thing I did see that may be the cause. The servo tray is not no longer connected to the fuse. I could have happened in the crash. But I'm wondering if the tray was loose all along. I see almost no glue on it. This could have caused some problems. But it would not explain the aileron response. Or would it.

Any ideas guys? If I can't find a reasonable answer, then the plane cheap enough that I may not risk losing it, or worse, hurting someone, with it.

And this was the only flight ready plane... sigh
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Old 07-31-2004, 09:00 PM
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Default RE: Predator 500 Problems

Aileron response on the Predator is minimal. I would almost suggest using everything you can get out of it, until you get it trimmed for flight.

Some of the predators did have an issue with the incidence of the tail. If it took a lot of clicks of elevator to get it to fly level, you either have an inceidence problem or a balance problem.

Take care of the balance first, and then adjust the incidence of the tail to compensate.
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Old 07-31-2004, 10:03 PM
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Default RE: Predator 500 Problems

Thanks Dave-
Knowing that Aileron response is minimal actuall helps me. I'm going to max out the ailerons. I don't have trouble with a twitchy plane so it will be a good starting point.

The CG on the first flight was 2 3/8 from the leading edge. On the second fligt it was moved back to 2 3/4.

I just checked the xmiter trims. About level for the elevator. But I clearly remember adding down trim on the second flight.

I'm thinking that the plaen was nose heavy on the first flight. (it would level out in a dive) So on that first one I added up trim.

Then on the second flight, after moving the CG back I still had the up trim on the xmitter.

I doubt I'll finsih it tonight, but I'm going to take glue to balsa now.
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Old 08-02-2004, 08:58 AM
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Default RE: Predator 500 Problems

The predator is an excellent aircraft........flys well.....very smooth...... rare any issues with it.

The CG should be set about 2.25 to 2.375" .......usually where I balance most of my Q-500s. Start at 2.25 for now. Even if the stab incidence is out a little, you should be able to trim the plane and have it fly in a somewhat behaved manner.

Trim the plane at HALF throttle to start with (apparently you have a working throttle). You will need no more than 1/2 power to take off as well.

You will have outstanding elevator response at the CG range noted above. You will only need about 3/16" up and down travel. Any more than that is ok, just set it up as a high-rate setting.... usually reserved for landing.

Make sure the hinge gaps on the ailerons are sealed. That will ensure the best control authority at all speeds. Remember, this is not a 3D plane. Also make sure the aileron servo and rods are not hanging up on the RX or battery inside of the fuselage.

Keep in mind the control authority when landing..... the ailerons will get a bit 'slow'.... make sure you have decent airspeed when you line up for final approach and level the wings. Once on final, you can slow the plane down as usual.
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Old 08-07-2004, 05:39 PM
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Default RE: Predator 500 Problems

OK... I finally got all the bits and pieces back in place. The damge to the tale was, as useal, more than I thought at first. I left the CG at 2.5 inches from the leading edge. Maxed out the Aileron throws and cut the elevator a bit. I checked for binding of the control throws and then I was off to the cklub.

With the increased throws this time I could at least control it. I had to add a lot of down at half throttle and at full throttle it really wants to climb. But at least I got it down wiht no damage. I wanted to try another flight too get a better idea of what was going wrong. I powered up the xmiter and rx and check the tail. I had over 1/16 of an inche of down dialed in.

When I landed, with the engine at idle, the plane came in fairly flat with the trims as I mentioned . So I'm thinkin' tail incedence. I hate the thought of taking out the tail. Can I shim the wing to verify that the tail is out of whack?
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Old 08-08-2004, 01:10 AM
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Default RE: Predator 500 Problems

OK...

Here some aerodynamics for you:

If your plane tends to pitch up during a high speed dive, this usually means you have too much incidence on the wing (or tail, whatever... but something is off).
Moving the CG backwards will not help thing... it will just make the handling worse!
What you discribed sounds like a too much incidence... it could also be an aft CG... but if it was that twitchy to begin with, and you moved the CG even more back, it would have become hardly (or at all) flyable. So it's probably the incidence.

The roll control has very little to do with the CG ot the incidences... there can be some influence, but not like you stated.

Adjusting the incidence is a piece of cake. Just shim the wing some, and try it out. When you have found the right setting, fill the gap you have between the fuse and the wing with epoxy and micro ballons.

Happy flying...
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Old 08-08-2004, 08:28 AM
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Default RE: Predator 500 Problems

The tail incidence is off if your balance is correct. This was pretty normal on some of the predators out there.

The front of the tail needs to be shimmed up. I know its not an easy fix, but if you want it to fly properly, your going to need to crack the tail loose or cut just below the tail/fuze joint and shim it up.

You can mess with the wing incidence or thrust angle to compensate, but that is not really solving the problem. Then again, if it is just a fast sport plane, I'd just trim it to fly level and leave it alone.
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Old 08-08-2004, 01:37 PM
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Default RE: Predator 500 Problems

Thanks again guys. I spent a bit of time last night looking at the tail trying to see if I could change the incedence. It looks like a lot of work. I'm going to try shiming the wing as a temp fix. It it helps theny I'll look at the tail again. Maybe I'll just live with it. This plane was just something to keep me happy while I build the Patriot.
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Old 08-09-2004, 01:58 AM
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Default RE: Predator 500 Problems

The front of the tail? Maybe I did something wrong when I checked it this evening. I leveled the wings using a meter. Than ran a straight stick along the to of the tail. I then set a meter on top of the tail and shimmed the rear of the tail until it matched the wing.

Faaa.... I'm just about ready to throw in the towel on this one. I useally crash em at least one time before I mount them on the wall of shame.
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Old 08-09-2004, 03:23 AM
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Default RE: Predator 500 Problems

I bought an ARF PREDATOR a couple of years ago to get my feet wet in Q500. What a comedy of errors, I will never buy another LANIER product. The basic design is right there with the minimums allowed by the rule book, and a "blueprinted" PREDATOR flies like a dream, but the ARF version I have was loaded with problems that had to be corrected from front to back. I have since scratch built a clone and it flies respectibly with a TT 40. The errors that they are making in the LANIER SWEAT SHOP aren't due to humidity, they are gross errors that have more to do with a lack of caring and expertise. How many of us would build a plane that had the seams in the covering facing INTO the wind, and a firewall that comes unglued the 3rd time the plane is run? Knifing into the plane and correcting the incidence problems isn't a big deal, but how hard IS IT to manufacture a straight airplane?
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Old 08-09-2004, 11:18 AM
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Default RE: Predator 500 Problems

You mentioned you had a problem with the plane climbing and that you need to add down trim.

Think about what raising the rear of the tail will do? This will give you MORE elevator and cause a bigger problem than what you already have. The front of the tail is what needs to come up to fly level.

If you are basing your incidence off of the flat portion in the center of the V-tail, that is the problem. It is not level with the incidence of the tail.
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Old 08-09-2004, 03:09 PM
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Default RE: Predator 500 Problems

Dave-
Yeah, I'm thingking my measurement was off. That's why I posted. I'm going to try and cut away the fairing on the tail so that I can get a better measurement.

Could a mis-alignment between the wing and the tail of one or two degrees cause a pronounced climb. The plane will actually loop at full power with no trim.
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Old 08-09-2004, 03:15 PM
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Default RE: Predator 500 Problems

1 degree off should be able to be trimmed. 2 degrees off could definately cause the problem you are talking about, but I'm guessing yours is off more than that.

V-tails can be a bear to get right. My suggestion is to take that fairing cover off, and crack the tail loose. If you used Epoxy, heat it with a heat gun until it softens the epoxy and comes loose (be carefull not to melt the covering however).

Once its loose. Put an incidence meter on the wing (bolted to the fuze) and shim the fuze with whatever you have handy until the wing is exactly at zero degrees (or level to the ground). Once your there, put sand bags or something on the plane to hold it steady. Now take a small bubble level and place it directly in the center of the V-tail. Shim the tail up in the front until the bubble is centered in the level. You may also want to check the firewall at this time, to make sure that is perpendicular to the wing.
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Old 08-13-2004, 07:33 PM
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Default RE: Predator 500 Problems

And it flies... I gave up on measuring the incidence. Every way I tried it came out even. So I made a SWAG about how much to shim and I was almost right. I still need a bit of down trim. But just a bit.

Now that I'm able to fly it a bit I realized that I need either dual rates or expo on the elevator. I'd been flying a DD and realize that I've been in the habit of adding up elevator on the turns. At full throttle just a touch of up really causes the plane to climb.

Not I just need to learn to land an airplane shaped airplane. I'm not used to landing anything with wheels. I could put the DD down right at my feet. I'm lucky to get this plane on the runway. I think I'll put some soft wheels on it for now.

My thanks to everyone for the help.
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Old 08-14-2004, 06:46 AM
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Default RE: Predator 500 Problems

For landing, your best off getting the approach set up, and then killing the engine and landing dead stick.

I use dual rates on my quickees, low rate for taking off and flying, and only high rates to land.

High rates are approximately 20% higher than the low rates. Some people like expo also on these, in the 15-25% range for elevator and aileron.
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Old 08-20-2004, 08:43 PM
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Default RE: Predator 500 Problems

Predator 500 RIP. Some things are just not meant to be. After sawing off the tail and gluing it back on it was finally flying right. Ant then some kind of a control failure. I'll never know for sure becuase all that was left was littly bitty pieces. One brand new RX... gone. One 1600mah battery... mia. But almost everything else survived. The engine needs a throttle arm. But it seems OK. This part is, of course, back ordered.

The good news I bought a Sonic 500 last weekend. Had it's first second third and fourth flight today. I like it a lot. It may not be as fast as the Predator 500. Or so I've read. But I think it makes a terrific sports plane. And it's not a V-tail

Thanks again for the help.
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Old 08-21-2004, 12:21 PM
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Default RE: Predator 500 Problems

With that engine, speeds of the sonic should be very close to what you had with the predator.
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