Gotta_Fly

My Feedback: (2)

Hey Guys

I had a bad day today, I had a H9 Sukhoi 33% with a DA up front, and its been a great flying plane, But I have been wanting to install a Fiber-optic kill switch on it for sometime now, just so I could kill the engine faster incase something went wrong,, Well after I installed it I took the plane to the field, and it started great 2 flips, and my run up was perfect, I then checked all my controls, and then I took off, and it went stright down the run way a slow climb to the left and keep turning to the left until it was inverted and stright into the ground , at first I thought it may have been a problem with ailerons but when it was inverted I gave it all the way up elevator and nothing would work, I tried everything I could possible do, I have no idea what could have happy,I just charged my batteries,and a full tank of gas, so the only thing that I did different was install that Cutt-off switch, which the motor wouldnt even start if I had that on,, But what makes this more strange is, when I brought the plane back to look at it, I flipped the switches on, and all the control services worked, So could a cutt-off switch somehow do this? This happened today at 4:00 and I'm clueless and sick to my stomach. Any ideas guys??
Thanks

Randy

p.s Do you guys think I need to send the motor back into DA, the crash broke off have the prop, but it turned fine and it didnt have any dirt all in it??

bhanley

You don't mentions a range check before the flight. Did you
do one?? Doesn't sound like the fiber optic switch would be
a cause. Don't know which one you have but the failure
mode for such switches tends to be binary, ie, it works
or it doesn't.
Hope you find the cause.

John Murdoch

My Feedback: (11)

I do know that on the Smart-Fly Optical Cuttoff, if the transmitter portion (light blue), translucent portion of the transmitter is in direct sunlight, the unit performs as if it were on, even though it's not. Sunlight (ultraviolet light) can and does make it into fiber cable. It reacts as if you have your receiver on. I contacted Robert Ritchy with Smart-Fly and he told me to make sure it's covered with electrical tape etc. or it's mounted where the sunlight can't get to it. That took care of my problem when it was on where it shouldn't have been. But I don't know how in the world it would have an affect on the entire system.

JohnVH

My Feedback: (38)

Sorry to hear Randy! I too am curious, did you do a range check after installing the new stuff?

And yes, Id send DA the engine to have a look at.

famousdave

My Feedback: (61)

Sounds like the RX went into fail safe. As mentioned, any time you change anything you need to do a radio check engine on and engine off. My guess is you disturbed some wiring or a connector when you moved stuff around to install the kill switch. Maybe it was an intermittent connection and it opened in flight... then the impact re-seated it. When you lost control did you notice a fail safe ? I always program the throttle fail safe to a high idle so that if the plane ever goes into fail safe I know what happened. If you just set servo hold (i.e. all servos hold on fail safe) the plane just appears to not respond and you have no clue if the RX just died or you are in lockout.

Also - I never use the fiber optic cutoffs, they are a hassle and just another thing (or two) to die on you + they consume current when idle, which means you need a mechanical on/off switch as well and they cost 2X more than a cut-off relay. I have been using a $25 RCATS RC-100 relay switch for years on every airplane I build, never once a problem with RFI and it is bullet proof / simple. It also allows me to completely eliminate switches in the ignition circuit (one of the biggest sources of RFI). RCATS installs these on $500K military drones so if they are good enough for that they are fine for my plane. The only thing I will do is install a torroid choke on the lead if it is more 20" long.


About the engine - even it it looks fine - at a bare minimum chuck it up in a vice and put a dial gauge on the prop flange and retainer bolt.. if it was running when the prop contacted the ground, there is a good change you bent the crank enough to run it out.. but not enough to actually see it with the naked eye. Even a little amount of run out will cause severe vibration and crank failure. If you cannot do this, send it back to DA and let them do it. The potential for losing another plane over a bent crank or a deadstick from something you cannot see is not a risk you want to take...

Sorry about the loss.. hopefully you will be up in the air again soon...

DP

torqmeister

DP- Would you please explain " torroid choke"? Thank you.

bhanley

DP - would you please post a link to RCATS.
Thanks

Silent-AV8R

http://rcatsystems.com/rc/electronics.php

famousdave

My Feedback: (61)

torqmeister - A toroid choke is a plastic coated sintered (powdered) metal core shaped like a doughnut, the servo wire is wrapped around it a few times. What it does is shunt RFI emissions that travel the length of the wire to ground. In essence, it shorts the RFI to ground before it has a chance to reach the receiver (hence the name choke).

Attached is a rudimentary picture, but you get the basic idea. Instead of the green wire pictured, imagine servo wire. The best method to choke RFI is by using this toroid core. There are "snap on" RFI chokes, but IMO they are worthless for the RFI we are most likely to encounter (high energy ignition noise).

DP

as722

My Feedback: (1)

Is this the dual receiver cut off unit from smart fly? I had a problem with the same unit. When ever I plugged the unit in to the second receiver the radio would lock up or act up but not all the time. I called them up and got a second unit which did the same thing, so I unppluged the second receiver and only have it plugged in to the receiver that doesn'y have the throttle servo.

Albert Santiago

DENNIS C

My Feedback: (99)

Randy sorry for your loss. but we were just trying to figure out a range check problem on another site. the guy had everything in plance and tied up and out of the way of everything possible. and come to find out he had installed a cut off switch to kill the motor and that was the problem. as soon as he disconnected it all the problems went away. Im not saying this was your problem but anytime i move or add something to the plane i range check it with the motor off and running.

I have my gassers set up with a choke servo to cut the engine or i can kill the motor by using the trim. just like everyone else say's easier the better. just a simple set up is all i do.