I have a 4*60 ARF that I crashed yesterday and demolished the front end of the fuselage. I'm repairing the plane and would like to know if there is any up/down or side thrust built into the firewall. The engine is a Hobby Towers 75.

Great site with lots of help! I've been reading posts for about 6 mos.

Thanks
Cecil

I just checked the plans I have for my 4*60 kit. They show 0 deg side thrust and the thrust line was 2 5/8" from the bottom of the firewall. I have had mine for 2 1/2 yrs she has 150 some flights on her. still enjoy flying her put on dual rates and she rolls pretty well.
so what happened.....how did you find that tera was firmer?

Hi jetmech

Thanks for the info.

This is my second plane and I had flown it about 10 times, mostly in windy conditions. It was flying pretty good but I was having a hard time trimming it due to the wind. Finally, the other day the wind was pretty calm and I was able to trim it out and it flew very well.

On the second flight I was doing loops, rolls and flying inverted. I was having a great time (this thing really scoots with that .75). I began my landing routine and on the downwind leg the plane was flying away from me. I gave it right aileron to bring it back parallel with the runway. It rolled right and began diving. I gave it left aileron and up elevator. The plane started responding then began a downward spiral to the right that I couldn't correct with left aileron and up elevator.

It went into the ground nearly vertical and the spinner was completely shattered. The engine cylinder was buried. 8 inches of the fuselage was destroyed totally and both wing tips have severe damage as well as the center section of the leading edge where the pegs fit into the fuselage. Both plastic srcews on the back of the wing were broken. The radio does not work. When I turn the receiver on the servos do not move. There is no responce when I move the sticks. The radio is in a box to be sent to Futaba to check out. The plane was a Christmas present so the radio is not that old. The carburetor was full of mud. I removed it and thoroughly cleaned it. I'll take the back plate off today and check the inside for dirt.

I went to the LHS and got the wood to repair it. I'm going to try to make the fuselage a little longer since I had to put 6 oz lead in the nose section to balance it.

I've rebuilt the front end of my SuperStar 2 times so I think the 4* will be flying again fairly soon.

Cecil

If it's not too late, be sure to send batteries and switch harness too. Send EVERYTHING that might have been the problem or damaged in the crash. Are the servos OK? Not sure? Send them in.

Bruce

Thanks for the tip. I checked the servos with my other radio and they seemed to work normally. The switch was demolished and some of the wiring was ripped from the circiut board on the switch but I'll open the box and send everything that came with it when it was new. They may find something that I couldn't check and take care of it. It sure would be bad if I got the radio equipment back and reinstalled it, then found out while the airplane was in mid flight that I had a bad servo and have to go through this again.

Cecil

Time to make lemmonade. I would really think about adding a cowl and turning the engine on it's side while you are at it. I just finished my 4*60 and flew it for the first time Friday. I was thinking I should have bashed the kit and done the two changes. I did use tapered aileron stock and replaced the stock ailerons. I also deep sixed the CA hinges for Dubro pinned nylon hinges set with epoxy.

Were you able to determine if a hinge let loose, or a control rod popped off a horn or servo arm?

Don

Don

The right aileron was completely pulled off the wing. Three of the CA hinges were still in the aileron and 2 were still in the wing. All the hinges had wood stuck to them on both sides where they pulled out.
When I installed the ailerons I pulled the aileron at each hinge to test for secure attachment. I thought this happened at impact because the plane was flying so good and the spiral began at a fairly slow speed but I guess it's possible that it just let go at that time. I just assumed that the radio failed. There were no other loose or broken mechanical connections.

I like the idea of putting a cowl on the plane and mounting the engine sideways. I was unable to view your attachment (page not found).

Thanks
Cecil

I had an incident with mine a few months ago. Came out of a roll and the plane kept rolling, needed full left aileron to correct it. Managed to bring it in safely but dropped a wing tip at the last minute and broke two of the CA hinges near the tip. Easy to fix, just cut the aileron off and used Dubro pinned hinges to reattach it. Found that problem was that I had not soldered the clevis (the one supplied with the kit) on properly, it eventually failed and slid down the push rod a bit giving a lot of aileron. Made sure to re-do the solder joint on the other side at the same time.

Hey guys I've had a 4* 60 for about 4 years and just loved it. I did not bash it much and still used the CA hinges on her. This winter I wanted to build a bigger one so I did. Here are pics of both my 4* the larger one has a gas engine mod and I put Robart hinge points on her enjoy. I live here in Iowa not far from the town where the kits are made I fly and build Sig kits almost exclusively.

Cecil, I'm not sure where that attachment came from. I posted the message eariler today from my Daughters Mac. So, you didn't miss anything.

One of the young guys at the field pulled the rudder off his 3D plane getting ready to launch it. This is an ARF, kind of hard to guess what it started life as since it is covered with duct tape, with an OS 91 four stroke. The hinges pulled wood, but only for the first 2mm or so. I think he may have glued them with med or thick CA as there was zero penetration. If you had wood and stiff hinges full length, it is more likely you tore them out in the crash. Still, they should have held.

Also, along those lines, if you had lost the hinges in flight, I would think you would have seen the aileron flaying around on the servo linkage, or fluttering to the ground a long ways from the plane. They may have loosened up enough that the hinge line was way open and that would have put a lot of down aileron on that wing. It could have then just finished comming off in the crash. Just a guess, but it is one possible reason.

Take a hard look at the hinges again. Is the hinge material really stiff from a good soaking with CA, or is there some flexability other than at the hinge line? Also, is there hunks of wood, or just some fine fibers along the hinge. The CA should have soaked into the wood quite a ways and as such, it should have pulled all that soaked wood out when the hinge pulled out.

At least you got enough back to allow a little detective work. I lost a plane about two months back that I never found. No way to even guess what went wrong. My instructor at the time said it was dumb thumbs, but his wern't any smarter, because when he took control, nothing happend from what I was trying. It went in like a lawn dart from about 700 ft and landed in the creek bed that is full of bramble so thick you can't see more than a couple feet into it. I really liked that plane, so I built an exact clone of it and am now flying it.


Don

If you're wondering at the cause of the crash, it sounds like a classic stall-spin situation. Holding the up elevator all the way to the ground was making things worse, not better.

Basically, you over banked the turn, then stalled the wing with a combination of elevator and aileron imput. I doubt there was anything wrong with the plane prior to impact.

Vogan

You did a good job getting that plane on the ground with minimum damage-good job!

Solder is kind of funny sometimes. It'll look pretty good even if the joint is cold soldered. The solder should be pretty shiny if the joint is good. If it looks a little dull you need to maybe redo it. The parts should be clean and you should use flux. Don't put the flame on the solder-heat the metal then apply the solder. I used acid core solder on mine and they seem to be holding up so far, even if the rest of the plane isn't.

Cecil

Don

I rechecked the hinges and found that the 2 hinges that pulled out of the wing had big chunks of wood on them. the 3 that pulled out of the aileron had smaller chunks. All of the hinges were stiff and covered with CA (I used thin). Maybe I didn't use enough glue. When I repair the aileron I think I'll use toothpicks to pin the hinges to both wings and ailerons. Then go to the tail and do the same with the rudder and elevator.

Thanks
Cecil

There is no doubt that crashes in this hobby will always be a fact of life. We can learn to fly and build better planes and even buy the best equipment for it. However we still can crash it and sadly we may never know the reason why. Nothing can be built crash proof and due to the fragility of these structures often little remains as to real cause of the failure. This makes it very difficult to determine the cause of a crash with so much destruction after impact. More often than not it’s simply pilot error and even the old school guys do that too. We like to find fault in other things if we can, for who likes to admit they did something dumb. Sometimes if we think about the possible root cause of the crash we can learn from that. I don’t like to speculate to a cause when it’s not real obvious what went wrong. I like to take a more investigative approach and ask questions that may give some insight as to a root cause. Like did you charge those batteries last night? Then you hear some silence and an ooops I forgot. Anyways my point here is to learn what you can from the crash and put it behind you and get back on that horse as soon as possible. Remember when learning to fly RC airplanes you start with a full bag of luck and an empty bag of experience. Your goal is to fill the experience bag up before your luck runs out.

Cecil, good plan. If you bash the front with a cowl, send us some photos.


Don

Montague

Thanks for your input. What should I do the next time this happens?

Thanks
Cecil

Montague, only one thing wrong, it wasn't spinning. It did exactly 1/2 turn and went straight down from there. I may have gotten a clue today though. My transmitter synthesizer module gave up the ghost. Same on I was flying with then. There have been a couple of "what the hell was that" times over the last month or so and it could have well been the Tx. There have been not of the wthwt with my other module, a fixed chan 50 one. At least it failed before I got the engine running today. I'm sure I'm one plane ahead of the game right now. I left the house with only one plane today, because the wind was blowing so hard that I was sure there would be no flying. When I got to the field, it was as good as you could ask for. The wind never topped about 2mph and clear blue skys. And me with no plane to fly. Disapointing, but no where near like comming home with a couple inches of mud on your shoes from waiding the farm fields looking for the lost plane.

Don

sticktickler

I understand what you are saying and agree. I'd like to know what caused the crash but there are several good possibilities. As you say, after the crash, it's sometimes very hard to pinpoint the problem.

1)After the crash I checked the radio system and the reciever had no response to the transimitter but the battery operated the servos in my other plane when I checked it after I got home. The transmitter battery indicator showed 100%.

2)The right aileron could have come loose before the crash-it was most certainly loose afterwards. The aileron, linkage and servo were all hanging by the wire that goes to the receiver which was pulled loose from the "Y" harness.

3)I could have dumb thumbed it.

At any rate it's water under the bridge and I am in the rebuilding process. Hopefully I'll have it done by the time the radio gets back from Futaba.

Thanks
Cecil

ps Nice plane! Is that your copilot showing it off?

My loving daughter when the camera comes out she aint far away a bit of a cam ham I guess oh well she makes the plane look even better.

When a plane drops nose-down out of a turn, then you've probably stalled the wing by getting the AOA too high. The way out is center the controls, let the plane build up a little airspeed, then pull out gently. The problem here, obviously, is that this kind of crash happens most often when turning to final, low and slow, and there isn't always enough altitude to make the save. Sometimes, once the plane gets too slow, you've crashed and just don't know it yet.

The good news is that for most models, you actually don't have to build that much airspeed back up, most sport planes will get enough airspeed almost instantly, and you can just release the controls, then almost immediatly start pulling out.

The key is the pull as gently as you can, since if you pull too hard here you'll just stall again and be back where you started, just lower.

Obviously, higher wingloadings and rearwards CGs make this kind of thing worse. I see that the plane is question is a .40-size plane with a .75 in it. How's the all up weight compare to the kit recommended rage? half a pound on the heavy side, but still flys great? Wouldn't surprise me. I have a .40 size Sukhoi with a S.T. .75 in it that's a alot of fun, but is really nasty if it gets slow.

Btw, while you might not think the plane was in a "spin", and it probably wasn't in a fully developed spin like you get when you do one as an acrobatic maneuver, the effect is the same, you stalled the wing. In a "spin looking spin", you stall one wing much more than the other, and get that fast rotation, while the less stalled wing still produces some lift to hold the nose up. When falling out of a turn, you usually end up with both wings stalled almost the same, just a little differnece to get some rotation going, but not enough to pop the nose up. The result looks like a diving spiral, but you're still stalled. In these cases, the ailerons sometimes work backwards, since when you try to roll left, you increase the AOA on the right wing, and decrese the AOA on the left. But if the right wing is stalled, increasing the AOA over there just makes the stall worse, and instead of increasing lift over there, lift decreases. In this way, holding left aileron to get out a sping going to the right can actually make the situation worse. It does depend on the plane though.

Bruce

I put the entire radio system plus the extra servo back in the original Futaba box and shipped it off yesterday. Hopefully I'll have the plane repaired by the time it returns.

Cecil

Montague

Thanks for the explanation. That last paragraph is a little scary, though. If I'm in a spin to the right and I give right aileron the spin will worsen. You say that sometimes in a spin to the right and give left aileron the spin will worsen. That doesn't give me anymore options with ailerons.
I guess the best thing is to avoid spins unless I have plenty of altitude and a good, clear view of the plane.

Thanks
Cecil

It does depend a lot on the spin and the airplane. But yes, opposite aileron can sometimes turn a spin in to a flat spin, or make recovery worse. So, when exiting a spin, center the ailerons.

Cecil, we talked a little about gluing hinges, so I tested mine today. The photo on the left is how a hing pulled from the aileron look when there is a good epoxy joint. Notice the very long slot for the orginal CA hinge, the slot is over3" long. The photo on the right shows how a hinge should break, the whole tang is still in the aileron but the hinge lugs are broken off. This is why I like the nylon hinges vs the CA hinges. They just plane hold.

Don

I forgot to show the test bed I used to test these hinges. The fence wins again.

Don