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Carb icing anyone?


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Hi group,

 

still flying around with a carb like I do? :)

 

In my neck of the woods (NW-Europe) carb icing is a real issue, not just during the cold months...

 

I found a little graphic - courtesy of the British CAA - that gives information about which conditions and operational use of the aircraft can induce several types of carb icing... Very educational and entertaining...

 

Grab it from http://ibis.experimentals.de under the downloads/documents section.

 

What really was an eye-opener to me was the realization that with a relative humidity of less than 40%, serious carb icing is still possible when ambient temperature and dewpoint are within certain ranges.

 

Grab it and study it, it may save your day... :D

 

bye

Hans

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Carb Icing? Oh yeah, we've met before. Gail and I were flying in a Cessna 150 from Norfolk to Annapolis to visit friends. We were on an IFR fight plan even though it was gorgeous day, not a cloud in the sky.

 

Level at 5,000 feet just east of Williamsburg, the engine suddenly started dying without warning. During training, you're always told the engine RPMs will decrease slightly as a warning that ice is developing in the venturi.

 

Wrong, there was no warning at all. The Cessna 150 is notorious for carb icing. It has a very small venturi in the carburetor, and the induction air doesn not run through the oil pan like on Lycoming engines. The engine immediately began coughing and sputtering. It couldn't even hold an idle. I instantly applied carb heat, but guess what, the engine stacks don't make alot of heat while spinning lower than idle.

 

I called ATC as I ran through the rest of the emergency checklist. He asked my intentions. I said I just wanted to loiter over this 8,000 foot runway underneath me and see if I could regain the engine. ATC replied, "Sir, you can't do that." "Huh?" I replied. "Sir, that's Camp Peary."

 

Camp Peary is the secretive CIA training camp, known locally as "The Farm". The FAA says you can land there in an emergency, but if you do, the CIA insists that you drive your disassembled plane out on the back of a flat-bed truck!

 

Long story somewhat shorter, the engine started showing some signs of coming back to life 4 minutes later as I passed through 3,000 feet. It would ONLY run with carb heat on. Push it in, the engine would stop. Pull it out, the engine would fire up again. After cycling the carb heat a few times, my wife finally screamed, "Leave it alone!" Good advice considering she was white as a ghost and about to puke.

 

I was confident enough that I flew from there to Williamsburg (KJGG), which was about 20 miles away. There must have been ALOT of ice in there, for the water was still dripping from the cowl after we landed. We had lunch there and then flew the plane back to Norfolk.

 

Sad thing about it is, this plane had a carb ice detector in it (temperature gage), but the FBO had never fixed it. This is the same FBO who swore they had fixed the glideslope indicator. This is the same FBO who never told me about the phantom loose connector on the turn coordinator either. I found that out when I was in solid IMC and realized the turn coordinator had inexplicably stopped working. The FBO got their asses chewed out about that one. Needless to say, I never rented from that FBO again.

 

In fact, I have them to thank. It is because of them that I am building my own plane. It is because of them that when it came time to buy an engine, my wife insisted that we buy one with fuel injection, sans carb.

 

And don't believe that all planes give you warning (RPM decrese) about carb ice. Smaller bore Continentals are more prone to carb icing than their small bore lycoming counterparts. Lycoming runs their intake pipes through the oil pan, which heats the induction air slightly. Continentals don't do that.

Wayne Hicks

Cozy IV Plans #678

http://www.ez.org/pages/waynehicks

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I bet 'The Farm' doesn't have an ICAO location identificator... :D

 

I've had similar - but less extreme - experiences in a C150, which was a good thing since I was cruising at some 2000' AGL south of EDLS. I wouldn't have made it back though...

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After cycling the carb heat a few times, my wife finally screamed, "Leave it alone!" Good advice considering she was white as a ghost and about to puke.

I could just about visualize this.

 

I bet it took some doing over lunch to convince her that the problem had melted away.

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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