The pilot reported that while descending from cruise flight to traffic pattern altitude, the CubCrafters CC11-160’s engine began to run rough. He applied carburetor heat, which made the roughness worse and when he then turned off carburetor heat, the engine lost all power.
He made a forced landing to a farm field near Lancaster, Ohio, where the airplane nosed over in the high vegetation.
According to a carburetor icing probability chart, the temperature and dew point were in the range of susceptibility for serious carburetor icing at descent power settings.
The pilot’s report of the accident listed no mechanical malfunctions or failures of the airplane, and a recommendation to apply carburetor heat earlier at the beginning of the descent.
Based on the information available, the airplane’s engine likely lost power due to accumulation of carburetor ice due to the delayed application of carburetor heat.
Probable cause: The delayed application of carburetor heat by the pilot which led to accumulation of carburetor ice, eventual loss of engine power, and the subsequent forced landing in high vegetation.
NTSB Identification: CEN18LA370
This August 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
The should called a head to get the weather at deference altitude In which he is flying in .then he could be perade for it an he could read the Manual for the airplane in witch he is flying.lack of reading the manual an the training of the pilot.
Here we go again…was it pilot error of pilot training error?
Q&A most aircraft accidents are
1. Pilot error or
2. Pilot training error?
your thoughts ?
You give a class and in conclusion ask if there are questions. Two out of fifty have questions. Does that mean forty eight aren’t very bright, or two are exceptional, or the presentation was generally lacking, or the presentation wasn’t adequately conformed to a lower mentality level of the attendant group majority?
Point being in retrospect you don’t know what level of instruction was given. Nor in the present you don’t know the mental acuity of the pilot.
There is a reason much of academia grades on a curve.
As a low-time pilot, I had a carb icing incident in the early 1970s over SoCal mountains on a high/thin ceiling day in the heart of winter… in a C-150. No Ice accumulation and good visibility… slightly hazy and OAT ~30F and it was a spectacular day in every respect. Then…
My first indication of ‘something’ was a subtle change in RPM… I heard/felt first… and confirmed by RPM gage dropping from 2400 [set] to ~2300. Huhhhh? Then I added power to step back-up to 2400 and adjusted mixture for altitude. The RPM picked-up a bit, but then began dropping in microscopic increments back toward 2300. OK stupid… really-cold-air… and suddenly I heard my instructor [dad] yell… “apply full carb heat and wait”.
There was a momentary RPM drop that gave me a visceral-shock and I instinctively started checking terrain for a forced landing site… crappy options everywhere. BUT about 30-seconds after ‘full carb heat’ [or so it seemed]. there was a positive/smooth surge in RPM as the ice cleared-out… RPM stabilizing at 2550. To say I was relieved is an understatement.
After crossing the mountains and descending toward Hemet-Ryan I started closing-down carb-heat at ~40F OAT and had no ‘further worries’. While taxiing-in I discovered that I’d forgotten to enrich the mixture control. Daaammm… almost got it right.
I have to re-emphasize one point. IF you are developing carb ice, the initial indication will be a little roughness in the engine. That is because the ice is narrowing the venturi in the carb, causing the mixture to go very rich, to the point of making the engine rough. Pulling on carb heat will initially make the engine go very rough, as the hot air added to the already restricted venturi will make the mixture VERY rich. You might even think the engine is going to quit. DO NOT push the carb heat back in. The additional roughness is the engine telling you that you do have ice. And ice does not melt right away. Keep the carb heat applied, FLY THE PLANE, and wait for the carb heat to do its work.
Some aircraft are more susceptible to icing than are others. In my experience, I will have icing issues in a Cessna (carb, not injected) where if I had been flying a Piper, it would not have happened. Don’t get me wrong, I’ve had a Piper get ice.
Also, CS props with carb, you have to recognize that this is happening because the prop will change pitch to maintain the RPM. I’ve not flown one for a long time, I fly injected engines with CS prop and they are a bit different in the way you detect and handle icing.
Carb ice has been a problem since aviation began. if I may, (at age 76 with 10K+ hours of instruction given). Carb ice is most prevalent in outside air temps of 20 degrees F to +70 degrees. High humidity makes it worse. Carb ice forms usually right at the venturi butterfly, because at that point the air pressure is the lowest, therefore the incoming air has the greatest ability to lose temp, and moisture, at exactly that point. As the ice builds up, it makes the air inlet that much smaller, and since the incoming fuel amount doesn’t change, you get a very rich mixture. That is what causes the rough engine which is the primary notice that you are developing carb ice.
Checking for Ice on your runup. You run up just a little, and pull on carb heat, you see a drop, you push back in and the engine goes back to full speed. O-K, right? N-O!! IF YOU HAD CARB ICE, that ice doesn’t melt right away. Pushing the heat knob back in quickly hasn’t told you one single thing that is so important. KEEP THE HEAT ON for at least 20 seconds. Watch your RPM closely. Initially, IF YOU HAVE CARB ICE ESPECIALLY, there will initially be an RPM drop, probably a little more than you might normally expect. The important thing is that there not be an RPM RISE in a short time. If you had ice, that would have been when the ice melted.
Well, you had ice form as you taxied out, you sure don’t want to take off with that ice forming again, what do you do? KEEP THE CARB HEAT ON, all the way through your initial acceleration. Then when you have full power applied, push the carb heat back in. That will insure that you have a clean ice-free carb until you get to full power, where the problem will not normally re-occur.
As you climb out, and for the rest of your flight, monitor your RPM closely. If you see any indication of ice, that is an RPM or power slow drop, yank on that carb heat again.
In the air, if you have carb ice, the normal indication will be a slowly increasing roughness in the engine. Yanking on the carb heat, since that will INCREASE the rich mixture that was the cause of the roughness, will initially make the problem worse. LEAVE THE CARB HEAT ON. The engine has just told you it has icing. It might take 30 seconds to melt the ice, and I can guarantee you, it will be a long 30 seconds. But when the engine roars back to full life and power, you can pat yourself on the back for good knowledge.
War Story. I was taking off from a high mountain valley in my Cessna 140. Nice day, about 60 degrees.
As I climbed out over the surrounding ridge, with a long slope downward afterwards but not high enough to turn back into the valley, the engine went a little rough. Rugged mountain rocks below me. I yanked on carb heat, the engine REALLY went rough! Almost quitting. I set up for a crash into those rocks, and just before touchdown, the engine roared back to full life.
Carb ice had starting forming as I climbed out at full power, and after I had passed the point of no return to the valley, the ice had gotten bad enough to make the engine go rough.
It took quite a while for the carb heat to melt it.
One very cold, soaking-wet pilot finished his trip.