Engine Kill...By choke servo or by ignition kill
 

I was planning on using a smart-fly ignition kill for my next giant scale gasser using a DA-85

I have been thinking that I may not have to use the ignition cut-off if I use a servo for choke.

I could just choke it to death instead. Or I could set up a manual choke and save the servo weight.
But then I would need to use the ignition cut-off.

What do you guys think?? I don't have very much experience with gassers so you replies are
very important to me.

Thanks in advance

MR G

RE: Engine Kill...By choke servo or by ignition kill
 

Either method works. If the carb linkage is properly adjusted the engine can be killed with the throttle trim on the transmitter, just like a glow engine. Then you simply turn off the ignition switch by hand.

Why is it when people fly glow engines of any size there is no choke servo, optical cut offs, or other extra kill switches but the moment they go to gas there has to be upteen different methods of stopping the engine? Does adjusting the throttle linkage to shut off fuel to the carb limited to glow engines????

RE: Engine Kill...By choke servo or by ignition kill
 

I was in the same quandry when setting up my gasser. I decided to go with a simple solid state switch from rcatsystems ( http://www.rcatsystems.com/electronics/rc100.php ). The main problem I have with killing with the choke is the ignition system is still hot, so theoritically the engine could fire if the prop is turned. With the ignition kill switch the chance of this is reduced. Also if the reciever loses power the switch is normally open so the engine will die. So at least the engine won't be running when it hits the ground.

RE: Engine Kill...By choke servo or by ignition kill
 

I'd suggest that a second method of shutting the engine down is desireable. Certainly, the throttle should be set up correctly first, allowing low throttle trim shut down.

What happens, tho, when the throttle linkage binds or comes loose? We've all seen it happen in a glow plane, and the pilot roared around at full throttle (or whereever it left off) until the fuel ran out.... Well, a gasser's fuel usually is enough to last alot longer than glow, and how long do you wanna roar around before she quits?

So, a second kill is a good thing, and new to the newbies, thus the questions!

J

RE: Engine Kill...By choke servo or by ignition kill
 

If you lose the throttle servo you can't control engine rpm, correct? Just where does one cut the engine and at what speed will that happen when the decision to land the plane takes place? Personally I have not been able to find a benefit to additional kill methods beyond idle cut off and the external ignition switch. Unless one is using a tank much too large for the application or engine flight times would not generally exceed 30 minutes at full throttle. At reduced rpm levels it's possible to put the mains on the ground and hit the prop with a dash of down elevator. Odds are high that should an engine have the engine cut in flight from a choke or optical switch the prop would get broken in the ensuing rush to get the plane on the ground, along with some bent landing gear.

RE: Engine Kill...By choke servo or by ignition kill
 

Pat,

The only reason I see fit to have a redundant throttle cut-off system is for personal safety concerns. I could not find neither IMAC or AMA regulations that requires a redundant engine kill system (AMA only requires it for Experimental over 55lb. aircrafts).

Some folks don't remove the throttle return spring so if the servo linkage breaks the throttle returns to idle, and if you have removed the idle adjustment screw the engine shuts off. That should be sufficient to satisfy any safety concern. Choke servo actuations is primarily a convenience choice.

Now, this doesn't solve the problem if the servo gets stuck in full throttle. Myself I like to remove the throttle return spring to unload the servo working against the spring pressure, and install a choke servo just for convenience (easy on/off from transmitter) and remove the idle screw so I can shut down the engine with the throttle trim (or transmitter kill switch ) if I need to. That gives me a redundant system, but as you say that's not required or necessary.

RE: Engine Kill...By choke servo or by ignition kill
 

The problem comes with the higher power to weight ratios of the 3D planes (I assume your flying 3D since you are talking about a DA85). There is no way I could land my yak at anything above 1/4 throttle, without doing damage to the airfame. And no, my yak is not overpowered for a 3D plane, it will hover at about 2/3 throttle.

If I were to have the throttle servo/linkage fail, I have the choice where/when to kill the engine so a controlled landing can be made with no damage to the airframe or the prop for that matter.

And you really don't have a choice it the matter, the plane will come down sometime. I just like to be able to choose when/how that happens.

RE: Engine Kill...By choke servo or by ignition kill
 

This is a discussion I always find to be fun. Keep the responses comin':D

RE: Engine Kill...By choke servo or by ignition kill
 

I've seen this can of worms opened several times here on RCU. It's a never ending opinionfest. LOL

RE: Engine Kill...By choke servo or by ignition kill
 

This is another good argument for having a redundant system.

RE: Engine Kill...By choke servo or by ignition kill
 

Maybe it's just me but in over 25 yrs of flying I've never had a throttle linkage fail. I fail to see how this redundant kill switch question became such an issue. Do we all need a redundant right aileron in case that particular one fails or is it best to build and install every control properly so there is no reasonable chance of it failing. No national RC organization has seen fit to make this kill switch mandatory so what's all the fuss about. Each person decide for themselves and that's the end of it.

RE: Engine Kill...By choke servo or by ignition kill
 

Haha never thought of that although you wont see me trying that with $70+ props :D

Personally I like the Smart-Fly system and use it on all my big planes. I have had a muffler come loose or fall off a couple of times, lost throttle servos and been stuck where I was too fast to land and couldnt get the idle down.

The 2 times I lost throttle servos were at very low settings during 3D. I was once left with a plane that barely had enough to fly yet was still too fast to land.

The first time I didnt have a kill so I had to fly it out.. at a low setting that takes a long time considering I like to have a big enough tank so I can fly 20 mins any style I like. I prefer to be able to fly 20-25 mins at any giving time. At 10 or 12 mins I am just starting to have fun! :D

I prefer an optical kill over a choke servo.. I replace the switch with it and save the weight of the servo setup.

RE: Engine Kill...By choke servo or by ignition kill
 

Consider yourself lucky then. It has happed twice to a guy at our club.
I like the optical killswitches for that reason as well as minimizing the RFI risk.

RE: Engine Kill...By choke servo or by ignition kill
 

I don't consider myself lucky when my elevator linkage doesn't come loose or the rudder or ailerons. See what I mean? :D Luck doesn't usually play a part when you install everything correctly. I do however use a choke servo on my big gas engines. It's there mostly to make it easy to choke the engine for starting but it can be used to stop the engine in an emergency. I routinely stop my engines by using the trottle kill function on my radio. Been doing it that way for years and it hasn't failed yet.

RE: Engine Kill...By choke servo or by ignition kill
 

Please explain how an optical kill switch minimizes rfi. You still have an ignition switch and battery so at best the throttle servo was removed (isolated) from the equation. All the associated engine and ignition components are still in the airframe, so the rfi risk never left.

BTW, I'm another that has never had a throttle servo fail. I've had linkage come off of a carb in flight but that just let it fall back to idle. More than 35 years of flying r/c.

RE: Engine Kill...By choke servo or by ignition kill
 

Well as they say in golf, "is better to be lucky than good". Since I happen to run low on luck I rather bulletproof my planes as much as I can afford.

Full size airplanes are required to have redundancy in most of their critical systems, but then you are sitting on the plane that is going to take you to the scene of the accident.

So why not buy a little peace of mind when we are spending lots of money on this hobby. When one invest $2500 plus dollars on a plane is foolish to loose it because you saved $15 bucks on a battery switch. A penny wise a dollar foolish is not my idea of sound decision making. I witnessed during the scale aerobatics AMA Nats some years back a 40% plane loosing an elevator half because the servo case broke off around the output shaft. On that occasion the (very skilled) pilot was able to land with the remaining elevator. A lot of skill, a redundant system and a little luck can work together to help you save a lot of cash$$$$$.

I agree whit you that everyone decides by himself. And since my luck is kind of low and my skills mediocre at best I can use all the help I can afford.

RE: Engine Kill...By choke servo or by ignition kill
 

It seems all the gas pilots at my field have a servo actuated choke for convenience's sake if their engine is cowled (i.e. not a stick). I'm just getting into gassers so this is a good thread.

RE: Engine Kill...By choke servo or by ignition kill
 

I've seen it happen.......and while the guy was flying around waiting for the tank to run dry his rx battery beat it to it...........[;)

RE: Engine Kill...By choke servo or by ignition kill
 

Gas engine-powered airplanes tend to be heavier and costlier than glow-powered aircraft, so it makes sense to build some reliability and redundancy into flight-critical (and also safety- ) systems. And opto-isolated kill switches make good sense, too: it is good practice to put the RFI-producing ignition components up front and the RFI-sensitive radio components to the rear, distance is the key here.

My 2c...

--Bill

RE: Engine Kill...By choke servo or by ignition kill
 

[/quote]
I don't consider myself lucky when my elevator linkage doesn't come loose or the rudder or ailerons. See what I mean? :D Luck doesn't usually play a part when you install everything correctly.
[/quote]

Sometimes luck does play a part. Obviously, it helps to set the plane up "right" but I had a throttle servo die and had to fly around WOT for 20 minutes. There is no way I could have predicted that. I have never used a kill switch but lately I have been considering it.

RE: Engine Kill...By choke servo or by ignition kill
 

I am just building a new 50cc gasser and its going to have two Rx's which of course need two battery systems each, which means four power boxes as well, so thats four switches which could fail so I will double those as well, opti kill switch for the ignition of course two of them double aileron servo's just in case and I better put two rudder servo's on and do I need four elevator servo's in case the servo on one side goes west, I think I will be able to keep the weitght down to around 25Lb's for the 85" span, does this sound OK. ;)

Mike

RE: Engine Kill...By choke servo or by ignition kill
 

LOL Exactly my point. Looks like you're on the right track Mike. I'm getting ready to put together a 35% Yak so with all the redundant stuff I apparently need I should be able to bring her in just under 100 lbs. :D:D:D

RE: Engine Kill...By choke servo or by ignition kill
 

Reasons for a fiber optic kill switch

1 My most important reason if I loose power to my plane at full throttle I don't want to watch my plane fly into a crowd and hurt or even kill someone. Some would say leave the spring in place would solve the problem but the spring wouldn't return in the event of a jammed servo.

2 Last flight of the day servo fails at 1/4 throttle battery runs out before fuel. Sorry but a fast landing nose in to hit the prop is way to risky for the average flyer. Potential for plane damage high.

3 Firewall comes loose changing linkage length throttle stuck. I don't want to fly around with loose engine till engine dies or risk plane on high speed landing

4 In case off throttle failure with kill switch I decide when to kill the motor leaving me in a good position for dead stick landing. This allows a good potential for your average flyer to bring his plane in safely

I have seen all and or read about all of the above scenarios. I have never had to use my fiber optic kill switch but for 60 bucks I think its cheap insurance. You may build the best plane , linkage, firewall whatever but you don't have any control over a receiver, battery, switch, servo failure. Pat no offense I have read many of your posts and regard you as a professional builder flyer and generally appreciate and agree with your posts but must disagree with your stand on this topic

RE: Engine Kill...By choke servo or by ignition kill
 

Like I said in the beginning. This topic always ends up being a matter of personal choice. You can come up with all the scary stories anyone can imagine but in the end we all do what we think is best and necessary. If the AMA, IMAA, IMAC aren't concerned enough about it to make it mandatory then just maybe It really isn't necessary to spend that $60.00.

By the way. Has everyone seen the combination smoke pump/optical kill switch offered by RC showcase. Pretty sweet gaget and the price isn't all that bad considering you get a complete smoke pump system with your kill switch. You can get the smoke pump alone or for just 20 buck more you get the kill switch along with the smoke pump. For 20 bucks I might consider using one but that's the only way. Check it out.

http://rcshowcase.com/html/accessories/smokepumps.html

RE: Engine Kill...By choke servo or by ignition kill
 

If we go back to the original question, think about what is happening in your engine if at runaway revs you put on the choke to kill the engine, you flood the engine with fuel at best you have taken a few thou off the cylinder bore, at worst you have hydolocked the engine and bent the con rod, not saying that it always happen but it can, if you must have a Tx operated kill system doing it on the throttle trim is the first option, if you want more than that its up too you, fill your plane with as many redundent systems as you like it does not make any difference if you have confidence in what you are doing and you are conforming to the local by-laws and any air traffic navigation order in your area, just enjoy yourself and let others do the same.

Mike

RE: Engine Kill...By choke servo or by ignition kill
 

There is a saying in general aviation regarding twin engine aircrafts: "The second engine will make sure you arrive at the scene of the accident" and that's truth of any redundant system.

Ask the designers of the shuttle Columbia if their quadruple redundant computer systems could have prevented their disaster. My point is that it doesn't matter what we do to prevent a catastrophic failure fate has its way in the end, but that doesn't prevent engineers from trying to increase the odds in our favor. Of course you must exercise an analytical decision making process when designing your system. That means evaluating every component and then deciding which options satisfy your mission requirements. In my opinion in the case of a 3D machine, which options will be the lightest, most reliable, easier to install, and least expensive.

In any case I don’t see how a 0.3 oz. optical kill switch is going to ruin your 30 lb. plus 110” wingspan, overpowered 2.5:1 3D machine wing loading. Or for that matter the cost of such unit is not going to drive you directly to bankruptcy court because you are going over budget on your $3,000 dollars project.

RE: Engine Kill...By choke servo or by ignition kill
 

I personally use optical kill switches on all my big planes? Why? Because I like having the ability to immediately cut my engine at any time from my transmitter. I use the spring loaded trainer switch on my 9C--it's a big switch so I can hit it fast and yet it's spring loaded so it doesn't get hit accidentally.

I still have a 4*60 that I fly occasionally and for fun flys. Years ago my throttle linkage came off the carb arm. The plane flew around at 3/4 throttle until it ran out of fuel and then I deadsticked it--it's a 4*60 so there's no problem there. I don't use an optical cutoff on this plane.

One of my warbirds is a 1/4 scale ME109G (34lbs; 102" wingspan; 75cc engine). One time several years ago the fuel line slid forward through the firewall into the cowl because of engine vibration. I had some excess fuel line behind the firewall so that I could pull the tank back for inspection without removing the fuel lines from either the tank or the carb. I had full throttle down to about 3500rpm--it wouldn't go any lower because the fuel line was interfering with the movement of the throttle arm. I flew it around a while trying different throttle settings but couldn't fix the problem. I ended up bringing it in for a landing and once over the end of the runway cut the engine using the optical ignition cutoff. I was able to cut the engine at the exact point that I wanted and deadsticked the plane perfectly. If I did not have the optical kill switch I would have had to fly around up high until the plane ran out of fuel. I use a tank sized to give me a reasonable amount of flying time--say 15-20 minutes, so I was not in danger of my batteries getting too low. But, I would have had to do a deadstick from high altitude not knowing when the engine was going to stop. I don't think this necessarily would have been a problem, but this particular plane is difficult to deadstick. It is highly preferable to land under power! I was glad that I was able to kill the engine from the transmitter right when I wanted to. Throttle trim would not have worked in this situation, although a choke servo would have.

I have not had any other situations like this, but once was enough for me to keep using optical kill switches. I can still use the throttle trim, and on occasion do, but I like being able to cut the ignition from my transmitter.

-Ed B.

RE: Engine Kill...By choke servo or by ignition kill
 

All the Gloom and Doom testimonials are fine. I use the throttle kill function in my radio to stop my engine whenever I need to. Again, maybe it's just me but I've never had a run away engine, had a linkage fall off an engine of any size, or used an optical kill switch. Sure I can afford one but why.........because of what could happen. Live life like that and you'll soon be living in a bubble. I think my money is better spent avoiding what is probable rather than what is possible. One in thousands of RC flights may end up with a throttle linkage coming off for the simple want of a pre flight check or routine maintenance on these MEGA BUCK aircraft. Lack of kill switches I can almost assure you is not the problem.

RE: Engine Kill...By choke servo or by ignition kill
 

Mr G.

As you can see there are many opinions about what to use as a secondary method to shut down the engine (and whether even necessary). You can use either a choke servo or an electronic switch of some sort. I personally think an optical switch is not necessary and therefore use a solid state switch. The choke servo has the added advantage of not having to rig up a manual method, especially on the rear carbed DA.

To each his own.

I hope you got the answer you were looking for.

RE: Engine Kill...By choke servo or by ignition kill
 

N7160F,

I have been monitoring this thread for all of the replys.

I would first like to thank everyone for their input, it has been a great help.

There were a few post brining up issues I had not thought of. For example: Choking to death could result in
excess fuel in the engine with a LIVE ignition!! Their are a few others also.


I have not yet made up my mind on what I will do, but the posts in this thread have really got me thinking. Thankyou

After I have reached a decision I will post my decision as well as the reasons for it.

Thanks again to the guys at RCU!!

MR G

RE: Engine Kill...By choke servo or by ignition kill
 

Having almost lost a scale warbird when the cutoff switch failed off, I do not put a kill switch on my planes anymore. I set the throttle to kill the engine with low trim.


Larry

RE: Engine Kill...By choke servo or by ignition kill
 

Another vote for the optical kill---Whats another 60$ when Im spending $2500.00 or more in a plane...Worth the peace of mind for me.

RE: Engine Kill...By choke servo or by ignition kill
 

I put a optical kill on my ignition because I get a single spark when I turn my ignition switch on. It gives me a extra measure of safety in case I forget. Bob

RE: Engine Kill...By choke servo or by ignition kill
 

Sent post twice OOps.

RE: Engine Kill...By choke servo or by ignition kill
 

I put my first optic kill switch in when I was invited to fly a demo at a local air show. I felt it added a extra measure of safety. I know after a good inspection of my plane the chance of a problem are remote. If there was a problem and the plane hurt someone I want to know I did every thing I could to be safe and yes it is a personnel choice. To say you do a good preflight inspection so I'm not likely to have a problem doesn't cut it for me. I didn't build the batteries, receivers, switches, transmitter, or servos. When guys in our club ask me if they should put one in there plane I tell them its not necessary but I feel more comfortable with one.

RE: Engine Kill...By choke servo or by ignition kill
 

Not gloom and doom, but practical common sense.... if anyone has ever had bolts loosen, thus preventing throttle servo closure, or throtlle pushrod / link failure, or (and this happens more frequently than many probably admit) throttle servo failure..... I want to be SURE I can kill that sucker. As others have said, "to each their own", but I find a lot of PRACTICAL reasons to have a secondary kill that doesn't depend on mechanical integrity of the firewall, mounts, throttle servo, or linkage.

Worth thinking about.

RE: Engine Kill...By choke servo or by ignition kill
 

Like I said in the beginning. This topic always ends up being a matter of personal choice. You can come up with all the scary stories anyone can imagine but in the end we all do what we think is best and necessary. If the AMA, IMAA, IMAC aren't concerned enough about it to make it mandatory then just maybe It really isn't necessary to spend that $60.00.

I agree with Surfer! I set up with throttle spring and Hi-torqe servo. I only have 15 years of exp and only 2 years of gas and I have never had a problem with linkage coming off or throttle servo problems (KNOCK, KNOCK). But I do check batteries before every flight to ensure I have safe flying voltage. Planes that go out of control from no rx voltage are much more dangerous than no ign cut off! I see countless people bring their planes out and say I charged it last night! And they fly 5-6 flights, after the 6th flight they are walking out to pick up the pieces. Then its bad rx, radio hit, someone shot me down. Its never OH my batteries were dead I f$#@@d up. I should have used an ESV before every flight. Any how, I heard another say do it right the first time and preventative maintenance is everything. Just my Nickle

3DAP

RE: Engine Kill...By choke servo or by ignition kill
 

For those of you that believe an optical kill switch is a practical small device that will enhance the safety of your gas powered birds; 42 Percent Products is offering a very inexpensive [link=http://www.42-percent-products.com/gas-accessories.htm]OPTO Coupled Kill Switch [/link] designed for igniton fired engines.

They also manufacture a Kill Switch for magneto fired engines and other nifty devices like high voltage digital switches, servo testers and a very inexpensive voltage regulator.

I tried to check on the I4C Product line since I think they carry similar products but their web link is dead (400 Error). Does anyone knows if thery are still in bussisnes?

RE: Engine Kill...By choke servo or by ignition kill
 

A few months back the I4C web site had a notice posted informing everyone they were getting out of the RC market.

RE: Engine Kill...By choke servo or by ignition kill
 

Sure there will be some who think different on this... but I have heard atleast 5 times where that switch hasn't worked properly... in fact I know someone who had 3 of them shipped to them just to get one that worked properly.

The best option is the Smart-Fly Product... sure its a bit more money but it works.