Crashed my predator

[Andy4124]

Not a happy bunny today :( :( :( :(
Crashed my wren predator.

Worst of it is im not totally sure why :shock: :shock:

Just got it perfect last week( Before the rainy season) When on last flight of day it shuddered very briefly while climbing out ( it locked out and went into failsafe) so i landed and had a play. range check etc, could not get it to fault. Came home took it apart tried to find loose metal bits but nothing. So flew it again a couple of days ago and it did same thing. took it home and replaced receiver.
Went flying today did range check whole works and it seemed ok. Then on first flight while climbing out and turning left, in came the failsafe, engine ran down heli hit ground big bang :( :( :( :(

Now have a broken heli which can be fixed but have not got a clue why it did it. Radio all working fine now apart from one servo with broken gears.

Help please!!!!!!!!!!!!!!!!!!!!!!!!!

[Heli_jack]

No help here, just sympathy. Bummer. Maybe check ground wire at servos. Crap that hurts.

[Coolice]

Hey Andy,

I'm so sorry to hear of your crash mate and just after you got the model going well, we all feel for you :hug:

To me this kind of crash is always the worst as you don't know what actually caused the problem and inturn is the most annoying!

You mentioned that you changed the Rx. but did you by any chance change the crystal at the same time? If not I'd be inclined to say this is the culprit, working one minute and then not the next.

A few years ago I creamed one of my 90's when the crystal failed & I think I had one going down recently again in my PMAX. I lifted into the hover and the whole model felt very twitchy like control was coming & going. I think it also did failsafe just as I was going to touch down, as it hit the floor then bounced back up under power as I was still decending.

At the same time I also changed the switch harness as these can be a source of failure. Probably not so much on the turbines as there is less oily residue to penetrate the switch and also less vibration, but for £10 still worth changing every year.

I have brought myself recently a JR9XII for my flight school and flying my planks etc. it came fitted with the new Synthesiser module that does away with crystals.
I like this idea as it removes the very fragile crystal material from the harsh environment of a model heli, but am yet to risk it on a Predator or Turbine. So far it runs well and will not suffer from frequency drift like crystals will over time.

Interesting read : http://davesrcflight.mysite.wanadoo-members.co.uk/frame_pages/radio_control_topics_frame1.htm

Inside a crystal : http://davesrcflight.mysite.wanadoo-members.co.uk/images/crystal.jpg
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[chopper jockey]

Andy,
I agree 100% with Ian. If your heli went into failsafe, then it`s usually only one of three causes, 1)interference. 2)rx crystal. and 3) the rx itself. If it was low battery then you would have recovered control by lowering the lever. (a bit of a clue there, you said you landed, I wounder if in doing so the battery failsafe was re-set???) I use the synthesised rx for this reason. Bad luck eh? all part of the game though :(

[Andy4124]

Thanks Ian

Just got a 10X with synthesised module. They first receiver had a crystal but second receiver was a new seven channel synth by JR. When it first locked out i thought the same as you( Must be the crystal) but now by using new receiver without crystal that kind of rules that out.

I use two receiver nimih packs witha vario ultra switch which is relitivly new so i dont think that caused it.

It only seemed to go into failsafe when climbing out and turning left. But i could throw it around in the hover and it was fine.

I know it is not transmitter as my other turb doent do it and even after the crash i got massive range with aerial down.

So something must change when its running.

Really puzzling me. I have flown helis for five years with PCM and never had a lock out. I even thought it was a myth.

Now im not so sure :? :? :?

[Laurens]

A PCM RX will go into failsave with LONG interferences. I guess if you flew a PPM Rx you would already have crashed.

[wolfdad]

Andy,
I think Ian was on to something. Never experienced a cracked crystal, however, from what I have read, the symtoms fit.

And, sorry to hear about the crash and hope you are back in the air soon.
Doc

[Coolice]

Hey Andy,

Ah, if the second incident happened with a Synth. Rx then as you say the crystal theory is out the window.
Another option is was anyone else with you at the time, flying or in the pits with a channel number not far from your own or adjacent but adrift of the channel it should be? Unlikely I am sure but has been heard about.

The other thing to look at is perhaps a duff eCCPM servo that is perhaps spiking the Rx. and sending it to failsafe. If a motor is breaking down in the servo this could create interference which either gets fed back to the Rx. or picked up by it even in flight.
Again if a servo is going down and drawing more amps than is needed, then the voltage drop could also trip the Rx. into failsafe I think. I've never experienced this but I think it can happen.

You mention NiMh packs, these are something I am not keen on using as Rx. packs due to their inability to hold a charge and also they are not as good at maintaining constant power under load from what I am lead to believe.

Last year I had a nightmare tracing a lockout problem on my Century Falcon, basically to end the flight I would go up very high and auto down. During the ascent the model would drop a few feet as the failsafe tripped in, but then carried on ok.
I started changing the flight gear piece by piece, servo's, NiCad, Switch, Crystals etc. All to no avail and when it started fail safeing in front of me I had to get rid of it quick.
So I I fitted an older but still good 10X Dual Conversion Rx. (I was using the slimmer R1000DS originally), the next flight the lockout didn't recover. Down comes the model. On stripping the model for repair the reason became very apparent. Basically the main shaft lower bearing, burried out of view in the plastic frame was seized or seizing in flight. The various colours caused by heat and the main shaft backed up this find. Through the flight the bearing was getting hotter & hotter, towards the end I am sure it has seized and the main shaft was rotating inside the internal diameter. Hence in my case it was metal to metal and cured after the rebuild.

The other thing, which is common with electrics is battery wire and motor placement. Have you moved any fuel pump wires about the model and or power supply wires to the ECU?
I'm sure it's not as there isn't a lot of power in the start system, but EMF can be a problem sometimes.

As Laurens said, if the interference is short you will regain control back pretty quickly and in an IC machine as soon as the motor RPM drops under the failsafe condition the interference stops and the pilot can land.
In your case the lockout stayed in meaning it is a constant problem and not sparadic (? :shock: ).

Your not using a base loaded antenna perhaps? Also the aerial lead isn't rubbing on anything or running by metal or power wires?
.

[Andy4124]

Thanks for the help guys.
I will strip it down this week and try and find the cause. :arggg: :arggg:

[wolfdad]

Ian,
You beat me to the bunch on that one. Just walked back in the house and, as usual, was thinking about what had happened with Andy's Predator and the only other thing I could think of, was the possibility of a base-load antenna with a loose or intermitten connection.

Andy, if you are using a base-loaded antenna, either Revolution, Dean's or whatever, check your antenna to rx connection and if it is of the push fit kind, I would recommend soldering.
Doc

[Coolice]

Ian,
You beat me to the bunch on that one. Just walked back in the house and, as usual, was thinking about what had happened with Andy's Predator and the only other thing I could think of, was the possibility of a base-load antenna with a loose or intermitten connection.

Andy, if you are using a base-loaded antenna, either Revolution, Dean's or whatever, check your antenna to rx connection and if it is of the push fit kind, I would recommend soldering.
Doc

Hehehe :wink:

Next logical reason isn't it. This will be a good one to know about once we have the full diagnosis.
.

[wolfdad]

Ian,
I know for the most part, like a lot of us, you guys are using base-loaded antennas. I found out the hard way a couple of years ago when one of the friction-fit connectors came loose on my at the top of a loop. Now, they all go on soldered.
Doc

[LVeillon]

Andy4124...I'm just curious what radio and receiver you were using?

[Coolice]

Hey wolfdad,

Yeah, I must admit I dont use base loaded antenna's, I've never really had faith in them and so never fitted one to my machines.
A few fellow fliers have and are using them without incident, but I'm old fashioned and like to stick to what I know works.
I recently helped a friend fit one to his machine and soldered the connector on for him. The only worry I then have is that the soldered joint becomes an area which can break, the solder mixed with the wire becomes very stiff and can break off with a small bend.

It's the same with these Synthesised Tx. modules & receivers, great idea and possibly more accurate & reliable than the old crystal way. But it is a new technology that I at present dont fancy risking on a £1500+ F3C machine.

LVeillon, I think he's using JR 10X Tx. and JR receivers.
.

[Andy4124]

Yeh, i dont use base loaded antennas

It was new synth 7 channel from jr

[richie1967_uk]

Hi Andy

I had a similar problem with my wren/predator. After building the heli and instaling the turbine i ran it with headloaders for the first few runs, i had not set up the failsafe (my error) and had was running the turbine at about 80k rpms when i lost control. The heli just sat there with the turbine running and the headloaders screaming and no way of shutting it down, there was no way i could get anywhere near it. after about 2 mins and just when i thought the head was going to let go i got control back and shut the turbine down. I checked everything and couldnt find a problem, ran it a few more times and could not repeat the problem.....so i bolted on some blades and test hovered for the first time, (after setting up the failsafe) Everything seemed fine and my confidence grew and the headloader incidence was forgotten. Anyway on my 3rd test hover i was about 5 feet from the ground and the heli just banked hard right, i managed to correct it and got her level and down near the ground and about a foot from terra firmer it banked hard right again and the BANG!! Blades hit the ground, then the boom and that was that. I fixed her up and could not find the problem, i did swap the receiver (I fly futaba) for a new one. It never happened again but i was never fully relaxed flying it as i hadnt tracked down the problem. The receiver that i was using is now in my raptor and i have never had a problem with it so i am at a loss to why it happened...hope you find the problem...keep me informed.

[Andy4124]

Any one want to buy a damaged repairable predator???

[Coolice]

Oooh, what ya doing mister? Switching models? :wink:

Any luck tracing the problem?
.

[Andy4124]

no, I havent had a chance to strip it down. luckuly i have another pred so the flying continues. Just will have to save up for rebuild, these turbines are expensive!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !! :( :( :(

[Andy4124]

A question???

Anyone know if the failsafe will cut in if flight pack falls below a certain voltage.

I flew me other predator today and after one flight with fully charged flight pack i noticed that my volt spy was going into red when i moved my controls a lot.

I use two nimih batterys with vario ultra switch. The idea being that if one battery fails the other takes over. This i use on both models!!!!

So i came home and discharged both batteries at 1.6 amps. I got about 50mamphours out of each battery. ( hmm lucky i did not fly again)
This got me thinking i wonder!!!!!

So ihave discharged both batteries from crashed model. I only got 40mampshours out of one and 50 out of other.

I now wonder if the voltage in flight falls when say the servos are under load then will the failsafe cut in before the battery goes totally flat.

Oh and i delta peak all batteries before each flying session.

:? :? Maybe this is the answer???????????????????????????????? :roll:

[Laurens]

I think so. I had my battery drained with the Caliber once, and failsave kicked in. how much mah are the batteries you use?

[Andy4124]

Actually i got it wrong. I set discharger to cut out at 4.8V when it should be 4 so am trying again, will see what i get out of them.

[Coolice]

Hey Andy,

Yes it can do I think, I've never actually tried it :? or seen it close up, but from what I have heard I think you are correct to assume this.

Another thing is that it could actually just be your NiMh's batterys not capable of delivering the amps when all the servo's are moving. I have heard this to, NiMh's are ok untill you start to put a high load on them and then they cannot cope as well as a NiCad.
Perhaps now's the time to invest in a LiPo Rx. pack & regulator to supply a constant power voltage to the Rx. no matter what way you fly.

no, I havent had a chance to strip it down. luckuly i have another pred so the flying continues. Just will have to save up for rebuild, these turbines are expensive!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!

Yes indeed they are, this where I have been very fortunate as I get to play with a turbine that isn't mine. But alas if anything should happen it will still break my heart as it's a truly amazing machine.
.

[Andy4124]

Hey,

I think I found the problem. :mrgreen:

On the top of the green FOD guard is a screw that was rubbing on the radio tray.
It looks like it was just rubbing. Metal on metal!!!!

Could this have caused it????????

Any ideas. :)

[Coolice]

Hey Andy,

Could be mate, any metal to metal would cause a problem and on a PCM setup you'll see it when the system locks out :?

This is one of the problems with heli's, finding a fault then having the balls to try the model again once rebuilt!
.