Hi all,

Promised to keep you informed (see [link=http://www.rcuniverse.com/forum/m_3843931/tm.htm]previous thread[/link])...

Saturday was my third weekend flying with the newly built Kadet MkII. Sofar have appr. 15 flights under my belt, starting to get more comfortable with starts and landings as well.

Anyway, 5th flight on Saturday 'it' happened. Took off nicely, but plane went out of control immediately after takeoff. Veered to the right uncontrollably and made a spectacular dive (full throttle) into the ground. Creating a 10 cm deep hole and a not too pleasant sound.
On inspection I think one of the ailerons came loose, I used the SIG easy-hinges and after the crash of one aileron the hinges were out completely as well as the hinges came loose on the elevator.

The elevator was explainable as the serves were pulled loose and ended up in the nose, this created a strong pull on the elevator that tore those hinges loose. The aileron was strange though as the crash was nose down and I strongly suspect it came loose before the crash, hence the uncontrollability of the plane (and the crash).

The damage:
- Engine looked like a large lump of mud and the engine mounts broke off
- One aileron came loose as well as the elevator
- Servos relocated themselves to the front of the plane
- Tear in the right of the fuselage because the rear wing-dowel pulled out there
- Oh and a broken prop of course

Although it looked pretty bad at first (to me at least) it is actually not so bad at all. Thanks to great help of the guys on the field we cleaned up the engine on the spot, taking great care not to get any mud inside. Using fuel, soaked the whole think of, removed the carb and cleaned that up as well.

Then went home and cleaned up the engine carefully completely, it looks better then new now and on the outset I think is ready to run another day (OS .40 LA btw). I repaired the fuselage, glued everything back together end put reinforcements on the inside where the crack was.
Also put the servos back where they belong, cut a nice new frame for them out of plywood, looks better then before.

Since it looks like I did not put the hinges in correctly I took all of them out (also the surviving aileron) and am now putting new ones, making sure I 'safe' them with pins through the wings. This will not happen a second time!!!

Other then that need to get a set of new engine mounts and put the engine back on and all should be ready to fly another day!!! All in all a good days work.

Lessons learned:
- The SIG Kadet MkII is an incredibly strong plane. Nose-first dive in the the ground at full throttle and actually the damage is not so bad. Especially the nose is incredible, no damage at all (except the cowl came off). The firewall doesn't show anything, which is excellent as I can just put in some new engine mounts....Kudos to SIG (OK. and a bit to the building quality of myself on that part)!!!!
- Hinges are very important!!!! This was my first built and I thought they were put in correctly but boy was I wrong. Once I took them out I could see that the glue did not cover the whole hinge but only a bit on the center where I put the glue...Wonder they didn't come out sooner. Learned my lesson here, will not happen another time...

OK. That's my story, I'll let you know when it flies again (which will be weekend after next only due to other commitments :-( ).

Johan

I believe MinnFlyer has a good how to post for CA hinges, very easy to use & works very well! You may want to contact him for the link to get ya there. Good luck.

Glad the damage was minor -- just a flesh-wound. [&:]

As for the cause, I'm suspicious about a broken aileron hinge -- that is not usually a disaster, unless the aileron actually tears loose in flight & drags in the slipstream -- even then it is very often controllable.

I'm not trying to insult you, but is it possible that you took off with the antenna down?

Another possibility is that you had the aileron servo reversed at the Tx. I don't know which radio you have, but if it is an analog unit, you may have inadvertently bumped the aileron servo reversing switch.

Was your Rx battery too low?

It is also possible that you had a Rx battery failure, or a battery connection failure (either a connector, or the switch).

Was your Tx battery fully charged, or had you been flying for several sessions before recharging?

It is well worth fully exploring all possibilities, so that it can be absolutely determined what went wrong.

I'm kinda suspicious of how little cussin' you're doing about removing the old hinges. They should be hard to "remove" if glued in properly. In fact, next to impossible without a lot of cussin'. How much effort did it take to get them out?

I'm also suspicious of one broken aileron hinge causing a devastating crash like this one. I've flown a pylon racer with one broken aileron and landed sucessfully. Is it possible you took off too soon and stalled it? Since you're suspicious of your CA installing technique, here's a tried and proven method I use:

CA Hinge Installation

There are several rules to follow for an easy, correct CA hinge installation. These rules are good for hinges from different manufacturers, including Great Planes and Radio South. I’ve used them on many planes from pylon racers to Unlimited class Fun Fly planes to even a giant scale Stinger (the 1/4 scale size hinges). I have never seen an in-flight failure using this procedure.

I have seen only two in-flight hinge failures. One failure was from catastrophic flutter, which also destroyed the wing panel. The other was due to doubled hinges and the use of thick CA.

Here we go:

Use a #11 blade to cut the slots.
Cut only once per side/per hinge.
Use only thin CA.
Do not double the hinges.
Do not use “kicker�.
Install after covering.

1. Slot the wood pieces, install the hinges, and mount the control surface. Gently push the pieces together.
2. Flex the control surface both ways for the maximum amount of travel you expect to use. This will automatically create the proper hinge line gap.
3. Slowly drop 2-3 drops of CA on each hinge at the hinge line on one side only. If any CA puddles in the hinge line, blot it with a paper towel.
4. When that is dry, apply 2-3 drops of CA to the other side of each hinge.
5. When both sides are dry, flex the control surface both ways.

That’s it! The wood will pull out before the hinge will let go. The surface will tend to stay centered and will not flop around. Both will help prevent flutter.


Dr.1

Hi all,

No offense taken

The antenna was out and it was the 5th flight of the day so the ailerons were connected properly....

(But I will doublecheck the receiver and connections, batteries were fully charged b4 going to the field and it is computer TX, so no 'reverse' buttons to bump.... Thanks for the suggestions!)

Someone said that the hinges should be really difficult to remove, that's what I thought as well, but it turned out I could get them out fairly easily (no damage to the wing taking them out and I could see that the CA was certainly not covering the entire hinge, far from it). This made me veeery suspicious.

I'm not rulling out a complete hand/eye coordination blackout on my part, and as I am a beginner mistakes are made. I'd be the very first to admit if I screwed up. There was virtually no wind this day, 5th takeoff that day whereby the previous ones went flawlessly...

What I'm thinking is that one aileron came loose and caused an unexpected turn to which my reactions were probably not what they should have been due to sheer surprise (and did I mention inexperience?).

Anyway, we will never know the full truth I suppose but I for one am not taking risks with the hinges anymore....

Also I've read the hinge-how-to on RCU but only after I built my plane, at which point I didn't want to mess with them anymore.

Oh well.....

Johan

Ailerons are not an important surface on trainers. The rudder can be just as effective. When this happens, you should have used the rudder to try and correct. I know things go fast, and it's not your fault. You will live and learn. I've done the same thing before. Turned out the aileron servo was reversed, and I didn't think fast enough to use the rudder.

Pull on your controll surfaces before you fly it..

that bird would never have gotten in the air at my feild...the guys there really inspect every plane the first time it rolls in...pulling on EVERYTHING, pretty hard too...wiggle everything to make sure there is no play, try to move the controll surfaces and look at the controll horns and make sure they have no movement in them...

A good preflight would have prevented that...not saying you need to do that before every flight, but once a week (2 minutes of looking things over vs 2 weeks of rebuilding or a paycheck for a new plane...not too bad of a deal) isnt really too bad.

after 5 flights I think there is a very good chance your rx battery was dead. I noticed you said it was charged when yo went to the field but didn't say anything about checking them after 2 flights. I check mine EVERY flight but most check after 2 or 3. Most of mine last 2 flights but I don't have any that last 5 flights. I'm not saying the hinging is suspect but the battery seems much more suspect to me. Glad you are able to repair. Kadet MK II's are VERY tough. In fact the Kadet Jr's are very tough also. Very impressive line of planes

Your batteries are too small or possibly defective, you've got serious binding in your pushrods, or you're getting in two REALLY LONG FLIGHTS. Most setups should be able to get 4 flights comfortably. However, I'm not disputing your suggestion that a dead rx battery could have been the cause of the crash.

I'm with Chuck. The 5th flight may have been stretching the rx battery some. Do you have a loaded voltmeter? What's the mah rating on the rx pack? If you're using a 4.8v 600mah, you might be cutting it close on the 5th flight?

get 'er back in the air,,

Chuck I have a field charger and use it a lot. No binding, no problem with the setups. BTW I have 11 planes and fly em all, so therefore I know how to notice problems with setup, just don't think getting any where near the lower end of green on my ESV is acceptable. Better safe than sorry.

Oh, so you're not really using up the capacity of the battery, you're just keeping it near full.

I tend to leave my charger at home and just retire the plane for the day when the battery starts getting low. However, this isn't the end of flying, it just means I move to the next plane I brought with me. Since I usually bring at least 2 planes and most have 1200 or 1600 mah packs, I can get in lots of flights in a day.

Hi all, goodmorning.

Thanks for all the suggestions, I have a 4.8v 2100mah battery pack and they were fully charged b4 the first flight. I think it should be ok, but as with all things I will make sure we double-check that as well.

Thanks again and I'll let you know when she gets back in the air...

Johan