Very odd problem w/DA60

[Av8r RC]

Hi all,

I've got an extremely odd problem going on with my plane, hoping maybe someone out there has maybe experienced it or has a possible cause for it.

I flew my plane 10 times this weekend, but this issue only appeared on the last two flights. Every single time I tried it on the last two flights the motor would almost die consistently in the exact same spot in the snake maneuver.

Every time I roll inverted and push down elev to transition to the upright portion of the snake the motor would almost die. The motor has no problem with ANY other aspect of flight. We flew it inverted for 3mins straight, and ragged the crap out of it. Motor never missed a beat. I had one of my flying buddies try it, he even did the snake (not as hard as mine) and couldn't get it to do it. But as soon as I got the tx back and went to the snake it did it instantly.

And it's not like its just "missing" it sounds like you flipped the throttle kill. The clunk is fine and not too long, plus doesn't matter how much gas is in it, full or empty or getting tangled up. So we thought maybe it was something electrical so we wiggled all the wires every which way but nothing, and we were throwing so many more g's at it in other maneuvers without a problem also.

It's just in that one single spot during a snake that it wants to quit.

Any ideas? I'm just going to re-plumb all the fuel lines and try it out again in two weeks. But I'm very open to hear what you all might thing it is.

 

[quadracer]

Do you have plenty of vent space behind the carb?


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[Av8r RC]

Yes, it looks a little different right now (old pic). But the hole is the same size.

 

[Joe's Dad]

Clean the Carb filter

Make sure your electrical connections are good. Visually check them.

 

[Av8r RC]

Thanks for the suggestion. I will do that.

 

[Av8r RC]

I haven't gotten to the plumbing or wires yet. But last night I took the covers off the carb. The screen looked pretty good only two little specs of something in there, nothing that would cause it not to get enough fuel.

 

[BENCHASON]

It sounds like a cowl pressure problem. I had a Yak that would do that in a fast knife edge. You may need to make the air exit bigger.

 

[gyro]

It sounds like a cowl pressure problem. I had a Yak that would do that in a fast knife edge. You may need to make the air exit bigger.

I've heard of this technique as well. Also, I've heard of something like adding a lip at the opening of the air exit to create a vacuum for exiting air?

 

[SnowDog]

Which airframe is this motor in? Is it a round cowl like a Yak or Sukhoi? If so, one option to help with the cowl pressure issue is to baffle or partially block the cowl opening so not as much air can get in. I had to do this on my Su-26.

 

[Av8r RC]

I doubt it is a cowl pressure thing. I have ran about 6 gal thru this 60 with about 20 fights now since trying the snake. And this problem just started on the last three flights, the problem is extremely repeatable.

I have experimented with cowl pressure on this plane. The first DA (crank to rod bearing exploded) I had on here had a real bad gurgle around mid throttle. No matter how much tuning we did to it, we couldn't get rid of it. (I had help tuning it from fellow club members) So the theory was maybe the cowl was getting pressurized. I tried removing the covering on the bottom between the lg and the spar, no difference. Then I tried blocking off the "nostrils" in the cowl with clear lexan, again no difference. I now have the bottom covered with about a 6" long vented section, that I made, and the nostrils blocked, no better or worse than before. We never could get it out of that motor.

Off to check the lines and wires