M20G Lycoming O-360 Carb Heat on Landing Checklist

[Cruiser73]

Hi All,

I just acquired an M20G  and on the landing checklist carb heat is listed.  My instructor has a M20C with basically the same Lycoming O-360.  We started having a discussion about the carb heat on landing because my POH checklist has it and his doesn't.  He also mentioned discussing it would other guys around the hangars and the consensus was that Continentals need the carb heat on and Lycomings usually don't.   I even found a Lycoming Service instruction from Oct 2007 that stated --

"Landing Approach – In making a landing approach, the carburetor heat is generally in the “Full Cold”
position. However, if icing conditions are suspected, apply “Full Heat”. In the case that full power needs to
be applied under these conditions, as for an aborted landing, return the carburetor heat to “Full Cold” after
full power application."  

I guess I am curious what most guys are doing? Carb heat on or off for landing? Thoughts?

[Utah20Gflyer]

I also have a G model Mooney.  I only use carb heat when my JPI engine monitor indicates carb temperature is close to freezing.  If you don't have Carb temp available I am not sure what the correct answer would be.   

[JWJR]

75C. I follow the pre landing checklist- I pull the carb heat right after putting on the electric FP. Once the field is made (glide) I push it ( carb heat) back in and ensure prop and mixture are set for a potential go-around.


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[JWJR]

Oh yeah one more thing- After purchase in 2013 I researched the FAA documents/history of my plane. I wanted to see where it was based since initial delivery. I found an off airport landing with no damage in the early 80’s
Anyway … that incident was contributed to carb ice.


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[PT20J]

There are two schools of thought about carb heat. 1) Apply it before landing to preclude carb ice during low power operation. 2) Leave it off so that full power is available during a go around. 

Some engine installations are more prone to carb ice than others.

I just follow the manufacturer's recommendations since I don't have any better data.

Skip

[Rjfanjet]

When I instructed in an airplane with a Lycoming I hardly ever used carb heat. Continental was another story.

[RLCarter]

I’ve had carb ice several times in Conti’s…. Your safest bet is to follow the manufacturers recommended procedure…. On the Cessna I pull the carb heat way before reducing power, some on here use partial heat but I’ve never seen any official publication that says partial carb heat, it’s either On or Off for me. The O-300 in the Cessna makes 145hp on its best day, and will take off on a hot Texas day at gross with the carb heat ON. 

[JWJR]

https://www.lycoming.com/sites/default/files/Use%20of%20Carburetor%20Heat%20Control.pdf


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[Hank]

I use carb heat in my C only when the carb temp needle is in the orange stripe ( < 5°C). Check it after start, sure; use it on landing, no. I also descend power on, every couple thousand feet I will nudge the throttle back and the mixture forward to maintain cruise MP & EGT values, so there really isn't prolonged low power operation.

[jamesm]

The times that I tried carb heat being  ON my '67C during landing phase of flight, the engine started to stumble. I wasn't going  wait and see if it was me over reacting or just anomaly too close to the ground. not too mention it is no time to troubleshoot nor is good time to troubleshoot. A lot things are happening and  quickly  that close to the ground, so that is the reason I don't use it. I am unwilling to take that risk. I have flown it for last 27 years without incident.

My Father in his previous 62' B  model (many years ago)  had it where the  carb heat valve butterfly  flapper  when over center on take-off on short runway. causing  carb heat  to be ON during take-off unbeknownst to him. Later to discover it was a design/rigging flaw.

just my opinion

James '67C

Edited November 28, 2021 by jamesm

[carusoam]

Summary…

1) POH ops can often get stale…

2) Data is good to have…

3) Data developed in your own plane is extra useful…

4) Many O360s in Mooneys have gotten their own carb temp gauge…

5) Icing in Mooney carbs is about as common as Mooney pilots scud running… not very often.

6) flying just beneath clouds is ripe for conditions leading to wanting carb heat…

7) without a carb temp gauge… carb heat is digital… only on or off… no modulating the carb temp without a gauge…

8) Nothing sucks more than…. wanting full power, and not being able to get it, because the carb heat is fully applied….

9) Carb heat, uses a smaller intake diameter… it’s not just the warmer air reducing the mass-flow….

10) Solution, get a carb temp sensor… to know how much carb heat is needed to stay out of the red zone….

11) If the carb temp isn’t in the red zone… no carb heat is needed…

 

See Hank’s pic of his carb temp gauge… our carbs are ready to mount this device… just very few got one.

PP thoughts only, not a mechanic…

Best regards,

-a-

 

[FlyboyKC]

The manual caution's using Carb heat too much on the ground.

[Jcmtl]

I have a C with the same o-360 and i don’t use carb heat during landing.  Carb heat + power to idle makes the engine want to quit.

[DXB]

Get a carb temp gauge and use it to keep at about 40F or above when in visible moisture or other high risk conditions.  Otherwise you have to put up with the significant power loss from using full carb heat in IMC or rain.  

Pull full carb heat on when reducing power for descent - the power loss is no issue then, and you don't want the distraction of fine tuning your carb heat during approach to landing. 

On short-ish final, add "carb heat off" as part of your final GUMPS check. Three advantages to doing so: (1) you won't have to remember that step during a stressful event leading to a go around (2) it won't run as rough as you reduce power to idle for landing (3) you won't suck in dirt on the ground

Also make sure your idle speed and mixture are set up correctly on the carb.  That will prevent it from quitting if you do close the throttle with full carb heat on.  

[DXB]

9 minutes ago, Jcmtl said:

I have a C with the same o-360 and i don’t use carb heat during landing.  Carb heat + power to idle makes the engine want to quit.

Your idle speed and mixture need adjustment on the carb most likely.

[JWJR]

I push it back in on short final. A carb temp gauge is great to have otherwise when conditions are ripe for carb ice ( humid- haze- mist- fog…. Visible moisture) one day you may be in for a unforeseen loss of power- The lever/control is there for a reason! I’ve never lost my mechanical fuel pump in the almost 30 years of flying I’ve done,however I still flip the electric one on as per the Poh. The O360-A1D will make ice!


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[Jcmtl]

23 minutes ago, DXB said:

Your idle speed and mixture need adjustment on the carb most likely.

Slightly rich doesn’t bother me, i have the option of leaning it.  And besides idle running maybe a little rich, the engine seems to run great otherwise so i don’t want to mess with it. 

[DXB]

3 hours ago, Jcmtl said:

Slightly rich doesn’t bother me, i have the option of leaning it.  And besides idle running maybe a little rich, the engine seems to run great otherwise so i don’t want to mess with it. 

It's a pretty easy adjustment of two screws on the carburetor, albeit with some trial and error involved. If it really quits with throttle at idle and carb heat full on, I'd say that's a safety issue.  If you go to idle on short final with carb heat on and it quits, that could be more than a little startling.  On the ground it's merely inconvenient.  

[Pete M]

Rule of thumb...use carb heat any time you're operating at reduced power. Carb ice starts to form in the descent. It was very humid here with temps near freezing, i actually picked up some airframe ice outside of visible moisture. I kept the heat on most of the flight including climb. If carb heat makes the engine stumble, get it fixed. Sometimes carb heat makes the engine stumble because there's ice in the carb throat, it melts and, well, the engine doesnt like water:)

Pete

[steingar]

My POH says to use carb heat on landing and I've not done it.  Where I am you don't get much carb ice outside a cloud, and I still can't go in those.  I imagine in more humid places you'd want it when it's cold.

[Jim Peace]

I will enclose two random flights on my C with a JPI and carb temp gauge.  As I descend the carb temp usually goes up.  I keep a good eye on it.  If it is in the amber range I put carb heat on if it is humid or visible moisture, just as I do when at cruise if in clouds or rain etc.   When I put it on it is usually partially to get the temp out of the caution range, about 45 degrees or so.  But almost always it is never needed.  I cant imagine not having one in a carbureted engine.  

These are low altitude flights 2500 and 3500 foot respectively.  

 

[David Lloyd]

The only time I ever had carb ice in a Mooney was in rain or in cloud and rain.  Nowhere else and not every time.  I do know, absolutely the C and G Mooneys will get carb ice and treat the possibility with respect. Use carb heat as directed.  If carb ice is suspected, act quickly and decisively.

[Cruiser73]

I just wanted to say thank you to everyone who added to this topic.  It is awesome to have such a good group of active contributors.

[M20F]

Temperature is only one part of the equation the other is dew point.  You can get carb ice on a 100F day.  The reduction in power is very minimal, really no reason to not use it.  Sometimes pilots have a tendency to over engineer common sense. 
 

https://www.boldmethod.com/learn-to-fly/systems/carb-ice/

[David Lloyd]

Just three weeks ago I posted about carb ice, today for the first time in 35+ years I got carb ice today.  Keep in mind for that 35 year period, I was flying injected airplanes.  Climbed away from Owensboro, KY in rain and low clouds, headed southeast for home.  Going thru 8 for 9, the climb rate diminished somewhat more than expected.  Leveled off between layers but still in rain at 9, the airspeed seemed about 10 knots slow, but we were heavy with fuel, two dogs and a bunch of Christmas stuff.  MP also seemed low at 20", but I really wasn't sure.  Temp was 3 C.  Near Taylor County entered cloud again and some moderate rain and made a turn to the east to skirt the heaviest.  Fuel flow had been about 9GPH and noticed it decreasing to 8.6, then 8.4 and looked at the dropping EGTs.  About that time the engine coughed.  The MP was now at 17".  I had forgotten my own advice!  Pulled the carb heat and in just a few seconds the MP rose to 21".  TAS rose to a more expected 143-144 knots.

I suspect on the climb around 8k a little carb ice formed while still in cloud and rain.  Once a 9, between layers it did not build nor went away, accounting for the slow airspeed.  When re-entering clouds and rain, the ice began building again.  Next time, I will remember to pay attention to what my instruments should be reading and realize these old airplanes will make carb ice.