Yet another question about carb ice!

[Paul-WI]

Hi everyone. Hope you all had a great holiday!

I hate to ask this question, but here it goes. Yesterday I went up with my CFI working on my taildragger endorsement with my 55 170B. Run up and everything went well. We where going to fly up to the Rainbow Flowage and look for mt brother's Ice Shack and decided to "follow the river. Anyway. I descended to about 100' AGL and had the carb heat on and RPM's around 2200. My CFI did not think we needed carb heat so I pushed it in. After a couple of minutes with out any noticeable warning we lost a lot of engine power. This did not come on gradual like I thought Carb Ice would but more like someone flipped a switch and we where running poorly. I began to climb and pulled the carb heat on, got the noticeable drop in RPM and ran that way for a few seconds (15?). When I pushed it back in, we still had low power output. The Carb Temp was in the green for what that is worth. After climbing to about 1300" AGL, the engine ran better and we followed the river back to the airport where we landed without any further problems. (other than my heart trying to jump out of my chest ). I did some reading and searching on this site and read a lot of info on this. As I looked at the Icing Chart, we where prime for Carb Ice (30F amb. 25F Dewpoint). My CFI does not think that this was carb ice though because of the suddenness of the power loss. I never experienced carb ice before and though I am not trying to second guess my CFI, I am looking for some other thoughts on this. Can Carb Ice give you a sudden loss of power like I experienced?

As a side note, I had a rough mag corrected a couple of weeks ago (plugs where gapped wrong from the previous annual) and he checked the exhaust. I do need to replace the mufflers as they are starting to deteriorate internally and we are thinking that a piece may have broke loose and caused this.

Sorry for the long post. I am still trying to learn the characteristics of this plane. So far it has been a BLAST flying it!

Paul

[Bruce Fenstermacher]

Paul

The question I have is does your engine produce full power now?

I've had a total mag failure which while I was in the air I thought was carb ice. I had had a few instances of carb ice prior to this so it was on my mind. I didn't discover the mag problem till the next day when I did the run up.

As it turns out we think that I'd been having an intermittent mag problems for a few flights prior to that I had miss diagnosed as carb ice.

Carb ice could seem to come on fast if you don't notice the early stages as it builds.

When I've had carb ice after applying carb heat and after a few seconds of stumbling and perhaps a slight lose of RPM the engine will gain RPM as the ice is gone.

If you think your mufflers might be coming apart you need to at the very least inspect them.

[Paul-WI]

Hi Bruce;

Thanks for the response. As we flew back to the airport, the engine did seem produce full power. I unfortunately did not do a run up once I was back on the ground like I wanted to.

As far as the mufflers go, I did have them inspected and the A&P told me they are bad - if he had done the annual, he would not have passed them. I am getting a price quote from him now and am going to have them replaced asap.

As a side note, I was very disappointed with the previous owner's mechanic? as there where a number of items missed that should have been caught on the annual.

A. ELT batteries 8 years old and a screw preventing the ELT from going off
B. Plugs gapped wrong
C. No right brake (air in the lines)
D. Starter not working (just needed an adjustment on the arm)
E. Mufflers Bad
F. Who knows what else will crop up?

I will NOT be letting this particular guy perform my annuals in the future!

Thanks again for your input

Paul

[AR Dave]

The first time I really had Carb Icing scare me, was exactly like you've described. My wife and I immediately turned for a small airstrip we just happened to be passing in the Yukon Territory. The engine sounded horrible when I pulled carb heat, but it shortly melted the ice and smoothed out. Congratulations on the best of the best 170's.

[futr_alaskaflyer]

Remember when you suspect carb ice you are never supposed to push the carb heat back in...leave the knob out until problem is resolved! Then leave it out after that! Ride it into the ground with carb heat out! Too many accidents in the database where the pilots stated "pulled carb heat, got no response, so pushed it back in" and then the NTSB refers to the prob charts and turns out the icing risk was high (and make conclusion that loss of power was likely due to...you guessed it.)

Reduced power due to carb heat should be the least of your concern in that situation...and much of that can be eliminated by readjusting the mixture. Serious icing can take much longer to melt than you might think. Use the carb heat. Anyway, this isn't the AOPA forum so 'nuff said.

[Paul-WI]

Thanks for all the input! After this problem occurred I had the mufflers rebuilt ($) thinking a piece may have come off. The mechanic (Russ) said that had he done the annual, they would not pass. Anyway, the day after they where installed we went flying. On the take off roll, I commented to my buddy Ron that the engine "didn't feel right". We circled the airport and landed and did another run up - this time with full power. We noticed that we could barely turn 2000 RPM's with carb heat off so back to the shop it went. Russ took the carb off and sent it out to have checked. They found crud inside the carb and dried out gaskets. I am thinking that some dirt was floating around and plugging off a metering port inside the carb. I guess that sitting around for 10 years and flying only 9 hours plays a role in that . This weekend I hope to have the carb back on and fly the heck out of it. I'll post again and let everyone know how that pans out. Once I get more confident in myself and the dependability of the plane, I hope to expand my flying circle and hit some fly-ins and maybe meet some of you. Not quite ready to head to Alaska yet but some day.......



Paul