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cooperplace

Aircraft in forced landing, Moorabbin

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Some thread drift here. We don't know why the Jab crashed.

Agree, unfortunately we probably never will.

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“That would still leave you in almost prime carb ice territory. As facthunter said there are requirements for certification. The chart says serious icing ANY power for the dark blue, lycoming say somthing different.”

 

My point was in reference to post #39, indicating that in some instances it is possible that the application of carby heat may not degrade engine performance ...... Bob

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They arent certified and the basis that hot air degrades performance would depend on mixture wouldnt it?

Generally they run rich

6 cyl has almost nil rpm drop at idle, maybe 100 rpm on cruise and the system melts ice very well, 5 sec or less

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Hot air is simply a mass airflow consideration. Power is proportional to it. Sometimes the mixture is affected too. Over rich mixtures CAN help power output due the cooling effect of the fuel evaporating and making the gas more dense as well as the extra molecules from the extra fuel. Nev

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Id be surprised if Rod ever thought about it that hard

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If major LSA manufacturers can build aircraft (Rotax 912) without carb heat it must not be a problem?

Generally these systems are taking "in cowl" air which is already hot. Effectively having permanent carb heat ON.

When you have a sealed airbox taking outside "cool" air it's more important to have a carb heat option.

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IF your source of intake air is hot enough to prevent icing at all times you are sacrificing power.. There's no way around that. Nev

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IF your source of intake air is hot enough to prevent icing at all times you are sacrificing power.. There's no way around that. Nev

Quite possibly, but I am still turning 3000rpm and getting off the ground with a three second run so I am happy with that for my purposes.

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Posted (edited)

I have seen it said by CASA that carbie ice is most common on take off. I have had it once on a Continental engine in very cold a foggy conditions. Normally I would expect it at reduced throttle on a humid day.

 

Back in the 50s & 60s, when the early ag aircraft, (non WW2 era), such as the C180 with an Continental 0-470, and the PA-25 Piper Pawnee with a Lycoming 0-540, entered service in the industry, there were many accidents due ice. Superphosphate 'spreading' was the main game in those times, and aggies began their working day by doing their DI in the dark, and becoming airborne as soon as one could see enough. Conditions were cool to cold, humid or nearly foggy, engines were coldsoaked, and sometimes wings were lightly ice contaminated. Fuel injection of the Continentals, eg, the IO-470, the IO-520, and the Lycoming IO-540, reduced the carby ice problem - not the airframe accumulation which remains a real winter hazard for us all.

 

I was a proud owner of both a C180 and a C182 with Continental 0-470 engines, over a 20 year period, followed by a C170 with an Continental 0-300 engine for 13 years. Over this time, we flew approx. 250-300 hrs pa, most of which began with a 1st light take-off, and lots of flight in showery wx. Carb icing was always a threat, and never more so than when we began to use 'Mogas' - in the last century it was as 'Super'. It definitely created more carby ice. I'm unsure whether we could assume the same for 95/98 PULP.

 

My Jabiru experience of 700 odd hrs was also one of really being alert to carby ice. We are in a cool, humid location. With my J160, it proved necessary to rewrite my pre-takeoff checklist to place the engine run-up last thing to do, with a minimum 20 secs of carb heat application, (and looking for signs of 'melting' ice). After essentially clearing out any ice, the requirement was to takeoff asap. That certainly reduced the threat for us. Wherever there is a long taxy required, beware of ice buildup, and re-run the engine checks before takeoff using a long carby heat time. I have noticed a lack of appreciation of carby ice accumulation during taxy, and an unwillingness to place the runup immediately pre-takeoff: a lot of inflexibility in our GA & RAAus instructor ranks?

 

Just a few thoughts.... happy days,

Edited by Guest
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At this time of the year in cool humid conditions I often experience carb ice with my Jabiru. It doesn't behave the same as my (ex) C-150 which had a Continental 0-200. Clearing ice with the 0-200 resulted in very rough running followed by an rpm increase. The Jabiru just gently increases rpm by 100 to 200 but remains running smooth.

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Facthunter. I was aware of the story that premix prevents carbie ice, but I don't believe it. I had rough running just as I was approaching tiger country, so put down in the paddock next to my home. I had been told by the self proclaimed expert on Thrusters that my engine had scored bores. I took the plane home and had a good look in the ports and could see scoring. Obviously I had a problem so I pulled it down and the bores were perfect, it was just an optical illusion and there was no sign of any problems. I put the roughness down to carbie ice.

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We have little idea about this EFATO, that's the point

Re ice, Yep, POH written in Bundaberg Is guess and if youre not expecting it would take quick thinking to clear and keep going.

I regularly clear carb ice before take off in cold weather and its hardly noticable when idling. The carb heat check on run ups (if youre not to fast) will let you know if its there with a rpm RISE.

Jabiru carb heat setup has very little effect on power, esp 3300, and can handle normal operation left on all the time, all the air is filtered on nearly all Jabiru aircraft hot or cold.

Carb Ice is more likely in less than “cold weather” conditions.

Have a look at the carb ice likelihood chart produced by BoM / CASA. Carb ice is one of those things you may never have experienced in your flying career, but could catch you out one day. Using carb heat to prevent icing is much smarter than being reactive, because when you’re likely to need it, it may not be effective.

My experience with Carb Ice on takeoff has been a momentary rough running as accumulated ice is ingested. The prolonged rough running / power loss is unlikely to occur at high power settings.

Follow the manufacturers recommendations is your safest bet.

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