ETLB Squawk Forums — Archive

Late afternoon flight on Christmas Eve day.

Finally got a break in the weather, volunteering schedule, and honey-do's on the afternoon of Christmas Eve. My wife drove with me to the hangar at 4:00 to both deliver a Christmas package to the owner, and "monitor" my anticipated flight.

I hadn't flown since the end of October, but like riding that proverbial bicycle, I hadn't forgotten how. Pulled the engine through three times, switched on the master and that 503 Rotax sprang to life on the first ignition-on pull of the Armstrong Starter.

Temperature was dropping quickly from 50 degrees as the sky clouded-up and things started getting misty with fog. The sun had gone into hiding. My plan of visiting three local airports and flying for about 45 minutes quickly changed once airborne.

At about 200 feet AGL mist accumulated on my windscreen making it appear as though I was looking through IFR foggles.  Realizing that I may have put myself into carburetor icing conditions I decided to terminate my flight plan, stay in the pattern and land.

My anxiety level climbed rapidly as I continued to scan the ground for likely landing sites if the engine quit before making it to the runway. Visibility was a bit over a mile. All went well, after landing I hangared my wet airplane and called it a day.

I have often flown in colder temperatures (as low as 30 degrees) but never with this much humidity. So the thought is, what is the likelyhood of a 2-stroke engine icing up to the point of quitting? Because of the way the 2-stroke engine "breathes" does some heat get back into the carbs to reduce the level at which icing would occur?

Your opinions and experiences would be valuable to me, any comments?

Paul Fiebich

Paul carb icing on a slide carb is rare and I never heard a case...yet. Usually the problem occurs on carbs with a butterfly type throttle since the thin metal cools down enough to form ice. The bing type carb has one area at the needle jet that could ice and disrupt the atomization of the fuel but again I have never heard about it. I generally don't fly in low temp and high humidity mainly because I don't enjoy it. I went out Saturday morning to fly but couldn't see the runway. Oh well better safe than sorry.

Monte

Paul here is a good article on icing.
http://www.cps-parts.com/cps/pdf/Part44.pdf

Monte

Great article......Monte

My engine Rotax CDI 447.

PAUL...

My experience is that Ive had..."ICE" twice.....

I dont know what type it was .....I do know...that both times, the engine ran quite rough with reduced power.....

Both times were after a High power setting ...and then going back to cruise power....in very damp / humid conditions. Cloud base was low....maybe 1000 feet agl.

The fix was.....pump the throttle...clear the ice with more rough running....then change altitude and fly over paddocks capable of landing in...!!!..Both times I was away on a journey...and had to be somewhere, and miles from home base. Weather can be frustrating.

regards Arthur

Thanks Monte, the article was a good read and provided valuable information. In my flight configuration with the Rotax 503 and Bing carburetor, I now realize that I had no reason for concern. However, since visibility was diminishing that day I would have discontinued the flight anyway. I am still happy to error on the side of caution, if I don't fly today because of weather, I will be able to fly another day.  Thanks for the link.

Paul Fiebich

Thank you Paul for the question and thanks Monte for the article. This was one of the many questions that I had swirling around in the ol' melon, I had already forgotten about. That's the great thing about this forum, you always learn something you didn't know you wanted to ask...or something like that.

I had icing once.  I was flying a Quicksilver with a Cuyuna UL II-02 engine with a Mikuni slide valve carb.  It was a cold December day....in the high 30s.  I had been flying for about half and hour when I noticed that the engine was losing power....rpm was dropping even with the throttle wide open.  The problem grew progressively worse over the course of a few minutes  until I was forced to land.  I landed in a friends pasture and he came out to see what I was up to.  I told him what happened and he said "carb ice".  The carb itself was dripping in moisture at this point.  After a few minutes on the ground I restarted the engine and it went to full power with no problem.  I took off and headed home.  By the time I reached the airport the engine had started to lose rpm again.

This was the only time I was sure that icing was happening with a two stroke engine.

Quoted from radfordc I had icing once.  I was flying a Quicksilver with a Cuyuna UL II-02 engine with a Mikuni slide valve carb.  ..........
This was the only time I was sure that icing was happening with a two stroke engine.

I had the same experience with the same engine/carb set up on a Robertson B1RD. It was a warm morning, but very humid - almost raining. I landed beside the highway and removed the foam air filter because I thought that was the problem. I advanced the throttle to full open and I could see water droplets on the inside of the throat of the carb. I figured it must have been carb ice that melted. I restarted the engine, took off in normal fashion and flew the 1/2 mile back to my strip and put her up for that morning.

This was the only time I had a problem like this with my Cuyuna or Rotax 503.

I would personally be more concerned with airframe icing instead of carb ice. You can land with no power, but difficult to land with no lift.

Quoted from flycanadianguy I would personally be more concerned with airframe icing instead of carb ice. You can land with no power, but difficult to land with no lift.

Airframe ice on an Air-Bike? Really?

I have put on my insulated coveralls, snowmobile gloves (gift from a friend), scarf and helmet and flown in temps of about 40 F, but not through visible moisture. Airframe ice is so easy to avoid in this class aircraft or UL that it should not be a real concern. Perhaps flying days are much more rare in Canada.