Carb icing

[bcg]

How susceptible is the M20C O360 to carb icing?  I know all planes are at risk of it but, some seem to be more prone to it than others.  Pipers seem to rarely have carb icing issues vs a lot of Cessnas that will ice much more easily.

Do most of you fly with carb heat on anytime you're in IMC?  Or do you leave it off until there's a reason to turn it on?  I did some instrument training in actual yesterday, temp was about 40 and we were in clouds pretty much the entire time, in fact we didn't have a visual on the runway at the home airport until right at DA on an LPV approach (as an aside, it was pretty cool to pop out of the clouds on speed, glide and center line).  We had the carb and pitot heat on throughout the flights.  I don't mind running pitot heat unnecessarily, it's just using a little electricity that the alternator is going to make regardless.  I would prefer not to run carb heat if it can be avoided though, I see a noticeable performance decrease and fuel burn increase with it on.  Where I'm typically cruising on 8.5 - 9GPH at 21/2400, I get 9 - 10 GPH burn with same MP/RPM and carb heat on.

[Fly Boomer]

My limited experience tells me that many of the Cessna aircraft use Continental engines, and many of the Piper aircraft use Lycoming.  Continental engines seem to be more prone to ice.  It's not the aircraft manufacturer.

[Janat83]

I had my 1968 M20C since 4 years now, flew it almost 400 hrs, no carb ice issues, it's better to have a carb temp gauge, even though I remember only twice I had the carb temperature warning when it was around icing temp, but no carb icing at all, I don't usually use the carb heat on approach unless If I was in imc and temperature around freezing, pitot heat on whenever near freezing and visible moisture. 

[pirate]

I’ve had my Mooney since 1995 and only experienced carb ice once. 1997 on approach during February in light snow, realized I didn’t have it on so I applied heat and suddenly got the back firing and popping associated with the ice melting. Sure was a attention getter. 

It only took me that one time to never forget to put on barb heat in visible moisture. 

With a temp gauge I rarely ever use it on VFR days. 

[David Lloyd]

About 600 hours in C models, the only time I experienced carb ice was in precipitation and cloud. Precipitation and out of cloud, no. In cloud and no precipitation, no.  Carb heat clears it right up. Till next time. This was at full throttle settings.  Partial throttle settings will increase the likelihood of ice. A rainy instrument approach would call proactively for carb heat.

[RLCarter]

Conti’s seem more prone to Carb Ice than Lycomings. Some say you don’t need carb heat on carbureted Mooneys, some say partial carb heat. My take is ANY carbureted aircraft the carb heat comes on (FULL) any time there is visible moisture, if your needing to run carb heat for an extended period adjust your mixture accordingly. I fly a carbureted 172 and use carb heat year round on low power settings (<2000rpm) ie landings. I’ve had carb ice 3 times (with Conti’s) and it will get your attention, especially low and slow

[Hank]

I've been flying my C since 2007, half of the time based in Furthest West-by-Gawd, Virginny, along the Ohio River. I do have a carb temp gage, and did all of my instrument training there.

I've used Carb Heat in.anger twice, both IFR training flights, in IMC in the winter, with my CFII. The Carb Temp needle touched the orange stripe, and I cracked the Heat enough to get it nicely clear. Never noticed a power loss, MP loss or the aggravated melting of ice as described above. 

So no, there is little need for Carb Heat in an M20-C. But it depends on how, where and when you fly.

As always, NEVER USE PARTIAL CARB HEAT UNLESS YOU HAVE A CARB TEMP GAGE!!

Happy flying!

[Utah20Gflyer]

I use carb heat when my carb temp is below freezing and I am at a low power setting.  I generally only use partial carb heat until I get above freezing by a reasonable margin. 

[AIREMATT]

Any time you have humidity and cool enough temps to form ice you have potential for carb ice. I’ve had it in my C a few times in fog, drizzle and clouds and OAT below 50F. First time was an eye opener on the ground prior to run up. It took a while to get enough engine heat to heat the defroster and while resolving that issue, exacerbated by wet clothes and gear due to rainy conditions loading and preflighting, we taxied slowly for a full length of the taxiway.
As I started the run up, I checked carb heat and low and behold rough engine for a couple seconds that went away after the water ran through. In the next hour plus of flight in IMC, I had to use the carb heat 5 times to clear carb ice indicated by 1+” of MP reduction while cruising each time. I don’t have a carb temp yet so full heat, slight rough engine for a second and then smooth, carb heat off.
It’s not a big deal, you just have to monitor the MP if you don’t have carb temp allowing you to run partial carb heat.
PRIOR TO descent and approach power reductions, definitely use full carb heat to be sure everything is melted and leave it on if still in humid cooler conditions or it can reform and you may not have sufficient heat to melt it.

Lycomings like our C can make carb ice no doubt.

[Hank]

6 hours ago, AIREMATT said:

PRIOR TO descent and approach power reductions, definitely use full carb heat to be sure everything is melted and leave it on if still in humid cooler conditions or it can reform and you may not have sufficient heat to melt it.

Lycomings like our C can make carb ice no doubt.

The easy fix for this is to descend power on. The only power reduction I make to descend is in the pattern, must before turning base. The first power reduction is to slow to flap speed (125 mph) by the time I enter downwind.

Carb Temp Gages are great! Gotta get you one!

[AIREMATT]

12 hours ago, Hank said:

The first power reduction is to slow to flap speed (125 mph) by the time I enter downwind.

We have the older 100mph flap limit on our pre-1970 C’s. Plus, it’s hard to get down if it isn’t smooth without reducing power. I don’t mind being in the yellow, but when bumpy, the mid to upper part of the yellow arc is uncomfortable for sure.

Definitely need the carb temp. It will be in the next upgrade cycle for the panel.

[Hank]

2 minutes ago, AIREMATT said:

We have the older 100mph flap limit on our pre-1970 C’s. Plus, it’s hard to get down if it isn’t smooth without reducing power. I don’t mind being in the yellow, but when bumpy, the mid to upper part of the yellow arc is uncomfortable for sure.

My yellow arc is 175-200 mph, and I do.not enjoy bumpy air at that speed. At 500 fpm and cruise power, I usually settle in at 160-165 mph and rarely have to slow down for bumps. Sometimes do, though. 

The differences between years in a model can be quite interesting!

[AIREMATT]

Our yellow arc is 150-189mph. 165 in smooth air is a comfortable descent with about a 3”MP reduction from cruise if below 5,000’.

Wish I had your speed limits, but I have the old spar before they beefed it up in your model.

[bcg]

1 minute ago, AIREMATT said:

Our yellow arc is 150-189mph. 165 in smooth air is a comfortable descent with about a 3”MP reduction from cruise if below 5,000’.

Wish I had your speed limits, but I have the old spar before they beefed it up in your model.

My 63 is the same as yours.

 

[Hank]

2 minutes ago, AIREMATT said:

Our yellow arc is 150-189mph. 165 in smooth air is a comfortable descent with about a 3”MP reduction from cruise if below 5,000’.

Wish I had your speed limits, but I have the old spar before they beefed it up in your model.

I've descended from 3000 msl at 23/2300 and from 10,000 msl at 20/2500, just pushing on the yoke and adjusting trim, both at 160-165 mph. Strange. 

[Jim Peace]

In my 64c the carb temp can be a lot lower than outside air temp. 
Even in the summer I always seem to be cracking the carb heat a bit when IMC at higher altitudes. 
I always look at my carb temp on arrival and it always seems to be 70-80 plus degrees in the pattern. Even in 50 degree OAT. 
 

the picture enclosed is at a higher altitude cruise. You can see OAT and my CRB temp.