[kjelle69]

I have a temp sensor in the venturi in the Marvel carb.

The u-Monitor in our 4 is set to sound an alarm as soon as the temp is below the freezing point. (0 degrees celsius) The question is, when should you become worried for real, as the temp is almost always near or below the freezing point if the Carb heater is not activated.

I know it also has to do with the dewpoint and outside temp, (when to be worried about carb ice), but I would like to lower the limit for the alarm as it gets a bit annoying. Still i want to have an alarm, but at a more critical temperature below zero.

 

[David Paule]

Rather than an indirect sensor for carb ice, which is what the temp sensor is, why not get an ARP carb ice detector? I've got one in my Cessna 180 and once adjusted (there's an adjustment knob, operate on run-up) it is a reliable sensor that tells me when I've actually got some ice.

I regard it as a must-have for carbureted engines.

It warns me when there's so little ice that I haven't fetected any loss of performance yet.

Aircraft Spruce sells these.

Dave

 

[YellerDaisy]

The question is, when should you become worried for real, as the temp is almost always near or below the freezing point if the Carb heater is not activated.

Good question - I'd like to know the answer too. Last winter, I just kept decreasing the alarm point so it would quit bugging me for the same reason you cited - it was simply cold outside.

 

[John Clark]

There are two factors at work here, temperature and moisture. The moisture is usually expressed as dewpoint. With a high enough dewpoint you can ice a carb with an OAT of over 100 F. Here is a chart:

http://www.kfackler.com/gtuf/carb_ice.html

Yes, it says "ultralight" but a venturi is a venturi.

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

 

[az_gila]

Interesting question. Even the instrument makers can't get a consistent standard.

They do all agree that it is a Yellow Warning level though, not a Red Alert signal.

UMA 15 F to 50 F

Westach -10 C to +10 C (14 F to 50 F)

EI 10 F to 40 F

Since there is only one probe location possible in our carbs, I guess you take your pick...

 

[RV6_flyer]

Interesting question. Even the instrument makers can't get a consistent standard.

They do all agree that it is a Yellow Warning level though, not a Red Alert signal.

UMA 15 F to 50 F

Westach -10 C to +10 C (14 F to 50 F)

EI 10 F to 40 F

Since there is only one probe location possible in our carbs, I guess you take your pick...

Each manufacturer uses a different probe and each probe and meter has different accuracy.

For the last 15-years, my microMonitor had the alarm for CAT turned off. In 15-years and over 2,600 flying hours, I have never had an indication of carb ice. I was using the recommend Richter (spelling) probe.

Today was the first flight with a Dynon EMS D10. Yes I removed the microMonitor in working condition for the upgrade. I also have the alarm turned off on the EMS D10. The flight today had CAT well above freezing the entire flight. I had to replace the CAT probe with the Dynon CAT probe as they do not have their unit programed to work with the standard AN probe.

 

[az_gila]

Each manufacturer uses a different probe and each probe and meter has different accuracy.

For the last 15-years, my microMonitor had the alarm for CAT turned off. In 15-years and over 2,600 flying hours, I have never had an indication of carb ice. I was using the recommend Richter (spelling) probe.

Today was the first flight with a Dynon EMS D10. Yes I removed the microMonitor in working condition for the upgrade. I also have the alarm turned off on the EMS D10. The flight today had CAT well above freezing the entire flight. I had to replace the CAT probe with the Dynon CAT probe as they do not have their unit programed to work with the standard AN probe.

There is still only one probe location....

What numbers do Dynon recommend for CAT warning?