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Old 01-27-2022, 01:50 PM
Koelemon68 Koelemon68 is offline
Join Date: Jun 2021
Location: Haslet, TX
Posts: 9
Default O-320-D2J

I have a O-320-D2J on my 7. I am looking for information on when to use the carburator heat. The Lycoming operating manuelsays:

(5) Landing Approach In making a landing approach, the carburetor heat should usually be in the Full Cold position. However, if icing conditions are known or suspected, the Full Heat should be applied. In the case that full power need be applied under these conditions, as for an aborted landing, the carburetor heat should be returned to Full Cold prior to full power application. See the aircraft flight manual for specific instructions. As a safety measure, there is no objection to the use of carburetor heat during landing approach provided that on a go-around, or touch-and-go landing, the carburetor heat is returned promptly to the cold position.

I know we are not flying a Cherokee or a Cessna but the Piper says not to use carb heat for landing, where Cessna (Lycoming) says to use carb heat at lower power settings.
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Old 01-27-2022, 02:18 PM
jrs14855 jrs14855 is offline
Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,768
Default Carb Heat

With the standard carburated Lycomig the carb is mounted to the bottom of the oil sump. The sump transfers at least some heat into the carb. The second factor is that the tighter cowls on RV's keep the carb warmer. The so called carb heat on many homebuilts is more of a alternate air in many cases. It all depends on the design of the hot air intake and whether there is a proper heat rise with carb heat on.
Also consider the power setting when you apply carb heat. If you apply carb heat on downwind abeam the numbers and almost immediately reduce the power to near idle you will not get much heat.
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Old 01-27-2022, 04:22 PM
PilotjohnS PilotjohnS is offline
Join Date: Jan 2016
Location: Southwest
Posts: 2,164
Default Just Me

I would think that if the go around is initiated at an airport that doesn't require full power to clear an obstacle, and the air temp is in the danger zone (OAT at 65F) then I think one has to be careful of icing during go around. I think following the manual is prudent, just be aware that icing can occur on go around on a 65F day.
John S

WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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Old 01-28-2022, 06:59 AM
fixnflyguy fixnflyguy is offline
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,533
Default My experience (RV-4)

I have an O320H2AD 160hp that was liberated from a Cessna 172, with a MA4SPA carburetor..pretty straightforward set-up, with per plans Vans FAB. During run-up and standard carb heat check, I can barely see a drop in RPM, and most others will probably agree similar results. I use it during landing decent most of the time when temps are below 60 or so, mostly because I'm conditioned to my old T-Craft (always us CH). I have purposely used it on cold and hot days, and initiated go-around just to see the effect. My CH knob is located on my panel forward of the throttle quadrant lever, and if I point my fore finger out advancing throttle closes CH simultaneously. The RV's have such good performance, leaving it on isn't going to kill your climb dramatically like some spam cans may experience. As others have said, the tight cowl and warm oil sump arrangement on Lycos are keeping things warm anyway.
Bill E.
8A7 / Advance NC
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Old 01-28-2022, 07:09 AM
Kyle Boatright Kyle Boatright is online now
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,856

Originally Posted by Koelemon68 View Post
I know we are not flying a Cherokee or a Cessna but the Piper says not to use carb heat for landing, where Cessna (Lycoming) says to use carb heat at lower power settings.
Is there a real downside of using carb heat on approach? If not, why not use it - its free and might keep your engine running one day.

I will say, carb ice is very, very rare in Lycomings. I've experienced it exactly once that I'm aware of.
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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Old 01-28-2022, 07:26 AM
Snowflake's Avatar
Snowflake Snowflake is offline
Join Date: Oct 2009
Location: Sidney, BC, Canada
Posts: 4,261

Originally Posted by Kyle Boatright View Post
I will say, carb ice is very, very rare in Lycomings. I've experienced it exactly once that I'm aware of.
This is highly dependent on your climate. Where you are in Georgia it may be warm and dry enough that you never see carb ice. Here in Canada I see carb ice conditions for about half of the year. I regularly find carb ice on the ground after a long taxi, and occasionally get a carb ice cough on descent. (O-320 E2D)

FWIW, the Robbinswings muff on my crossover pipes gives me a clear 40-50 rpm drop during runup. It's definitely adding heat to the system that wasn't there before. The stock "snorkel" carb heat never registered on the gauge at all.
Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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Old 01-28-2022, 09:09 AM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,253

Get an ARP carburetor ice detector. I have one on my Cessna and am installing one in the O-320-D2A on my RV-3B. They work very well.

It has a probe in the venturi that senses actual ice and turns on a light. In the Cessna, it's been reliable for years. When the light comes on, pull on some carb heat. No light, no heat. Don't bother with a carb air temp gauge, get one of these things.

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