NO!!! ahhhhh crash - RC Groups
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Sep 08, 2009, 06:19 PM
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wesley blue's Avatar

NO!!! ahhhhh crash

well,i crashed my bran new ultimate .40 engine kept cuting off in mid air,i dont understand why though my engine was not over heating ,it had plenty of fuel,my glow plug was tight,and it was not flooding.does anyone no what else could make the engine just quit
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Sep 08, 2009, 06:26 PM
Deletedfor proving Nauga wrong
Well.. it happens.

I crashed a .60 cc gasoline power plane Sunday

Not my first crash... not my last. (as much as I wish it would be the last...)


There are MANy causes for an engine to quit...

Idling too low too long.
mixture too rich or lean on the low end and rapidly advancing throttle.
Pinhole in the fuel line inside the fuel tank (that one will drive you insane if you don't know to look for it)

And many more...
Sep 08, 2009, 06:38 PM
Build, crash, repeat...
lee292a's Avatar
I had lots of problems with the engine dying on my Ultimate 40 also. I had a GMS .47 on it with the "tuned" muffler. It turned out that the muffler worked fine as long as the engine was wide open, but it was letting it lean out at midrange. I swapped the "tuned" muffler for one from a Thunder Tiger 46 and that took care of the problem. One thing I noticed about the Ultimate 40 was that the fuel tank was a little lower in relation to the carb than in most of the models I've flown. The low fuel tank could be starving the engine for fuel. Did you bench test the engine, and did it run OK then?
Sep 08, 2009, 06:44 PM
Deletedfor proving Nauga wrong
The tiniest bit of dirt in the needle valve will kill an engine... I highly recommend a fuel filter betweent and and engine.
Sep 08, 2009, 06:58 PM
The reviewer
XJet's Avatar
Originally Posted by lee292a
I had lots of problems with the engine dying on my Ultimate 40 also. I had a GMS .47 on it with the "tuned" muffler. It turned out that the muffler worked fine as long as the engine was wide open, but it was letting it lean out at midrange. I swapped the "tuned" muffler for one from a Thunder Tiger 46 and that took care of the problem.
The symptoms you describe are typical of a GMS47 that has an obstruction in the carby.

It ran fine at full throttle because of the extra muffler pressure and fitting a TT46 muffler helped too because they provide more backpressure which creates more fuel-pressure.

The cure isn't to change mufflers (because those GMS tuned mufflers are *great*), it's to fix your carby.
Sep 08, 2009, 09:36 PM
Sudden Crosswind on Final
skippyspad's Avatar
Just a friendly piece of advice. Once you notice a problem, fix it before you fly again. Once airborne, the problem most likely won't fix itself. Now you have to try to land with the problem. I watched a fairly new guy fire up his trainer and noticed the elevator servo had a small shutter to it with no input to it. It seemed to go away after a few minutes. He was airborne for about 5 min when the plane shot straight up, stalled and gravity took over. We brought the pieces back and found the elevator servo locked full up. The servo had failed. Had he checked it before he took off, he probably would still be flying it.

Deadstick practice is helpful though.

Sep 08, 2009, 10:12 PM
Registered User
wesley blue's Avatar
i dont have a GWS .47 THOUGH i have a thunder tiger .46 on it,it worked fine on my somethin extra. u no,my engine did sound a little to lean yesterday.luckily i can still fix my ultimate .40 so i should have her flying by this weekend,if im still having problems with her i will check in with yal again. see ya thanks 4 the help so far . wes
Sep 10, 2009, 04:21 PM
Build, crash, repeat...
lee292a's Avatar
Originally Posted by skippyspad

Deadstick practice is helpful though.

Been there, done that! Coaxing a draggy bipe back to the runway dead stick is definitely a high pucker factor activity! Had lots of practice on that Ultimate before it went to the Great Hangar in the Sky! Interestingly enough, it didn't die from a dead stick. Lost orientation, got into a death spiral and before I could correct, CRUNCH!
Sep 11, 2009, 12:06 AM
Registered User
you know what.. when your running on the ground or fixed to a "bench" the engine runs a bit different than when its up in the air..

Ive found that on the ground its a bit better to have it running just a TINY bit richer than you think is optimum.. the reason I am presuming this is the case is because when its in the air and has air speed - there is more air running in to the mix than when the engine is being held on the ground..

The way I came up with this was while during straight and level flight the air generated by the prop was similar to while being held on the ground where the mixture was set up of course.. so when flying level everything was ok.. but then when i entered into a dive and airspeed increased the engine started to mutter a bit and die out. or just generally nto sound healthy.. this is how i came up with this theory.. so then i adjusted the mix to being a little bit richer while its on the gruond in my hands and this problem did no occur anymore..

Try this out and let me know what any of you thinks..

Sep 11, 2009, 03:28 AM
Registered User
My initial reaction if an engine keeps cutting after a few, or several, minutes flight is that it's too lean.

As ryank has suggested, I always tune slightly rich on the ground because it always seems to lean out in the air. The recommended test I always do before take off is to open the throttle to full, and then hold the model in a vertical nose-up position for several seconds. If it's too lean (i.e. just right for level flight) it will die after a couple of seconds. If it's slightly rich you might hear it speed up a little when you lift the nose, as it leans out to optimum richness, but it won't die on you.

If it runs okay nose-up, but still dies in the air, you need to look for something else, as has been suggested in other posts.
Sep 11, 2009, 07:11 AM
Closed Account
I don't put a fuel filter in the feed line from the tank to the carb., as I want only clean fuel to get to the airplanes fuel system, so I filter in my filling line from my fuel supply to the tank. This way I'm not putting a possible fuel restriction in the feed line. Yes, having a filter in the feed line will stop garp from getting to the engine! However, everytime you fuel, you are blowing the garp in the filter back into your fuel tank and thereby building up the amount of garp in your tank and sooner or later the filter will certainly plug!

Better to filter before the fuel gets to the fuel system of your airplane.

Checking the high speed needle the way described above is the way I do it. If checking this way doesn't help a thorough check of everything in the fuel system is needed, down to possibly replacing all the fuel lines in the system.
Last edited by Mode One; Sep 11, 2009 at 07:24 AM.
Sep 13, 2009, 08:14 PM
Registered User

engine quiting

make sure your vent line is at top of fuel tank and the bottem line has weight on it and it feeds the carb.i got mine backwards one time and it did this also i had one do this today and it was the weight on the end of the fuel line had came loose
Sep 14, 2009, 07:52 PM
Registered User
wesley blue's Avatar
it turns out that the problem was the o-ring on the needle valve was eaten up and was leaking pressure which made the carb not get any fuel.thanks for the help guys.Wesley
Sep 15, 2009, 08:41 AM
What goes up, will come down
Mulciber126's Avatar
that wouldve drove me insance lol sounds like you started replacing everything and see what you got lol
Sep 15, 2009, 03:15 PM
Closed Account
There you go, a thorough inspection revealed the culpret, don't you feel good about determining your own problem, yourself?

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