Carb Heat or No???

[Doug Rohrer]

I bought a flying RV-9A a little over a year ago. It has a 0-320 engine. The POH that came with the plane made no mention of using carb heat during landing. The training plane I used to get my PPL (C-172) has the same engine and called for carb heat when the engine speed was reduced below cruise power. Is there something different about the air box/filter on my RV-9A that would eliminate the need for carb heat, or did the builder just forget to include this in his POH? All comments appreciated.

Doug

[N941WR]

Doug,

That just means the guy who wrote the POH probably forgot about the crab heat.

In my RV-9, your results may be different, when I slow down to land w/o the carb heat, the decrease in air flow through the cowl will raise the carb temperature enough that carb ice is unlikely. However, I still have carb heat, should I need it.

[flyboy1963]

I am in the same situation ( bought flying -9a) and my training was to ALWAYS use carb heat.
Sure the lyc is not PRONE to it, but if the temp and dewpoint are within 4 ? degrees, unless you have a carb throat probe, I'd use heat.
The bonus is....the air is all filtered, so the only downside is a slightly richer mixture, which you can compensate for.

[David Paule]

If the engine has a Marvel Schebler carburetor, the ARP carb ice detector will show it if you've got it. It's installed on my Cessna 180 and it works great. Reliable.

http://www.aircraftspruce.com/catalo...icedetect2.php

No point using carb heat if there's no ice, and with this thing you'll learn when to expect it on that engine and that installation.

I'm not connected to the product, just a happy user of it.

[jsharkey]

....on my RV-6 (YO-360-A1A) using the Van's "tube over the exhaust cross pipe" system. The flap might prevent snow and ice from entering the filtered air box and restricting induction air but the amount of heated air that the heat exchanger provides isn't enough to cause an RPM drop during preflight run up checks. I'm skeptical but always use it when entering the pattern out of C-172 habit.

Jim Sharkey

[Ironflight]

I have generally gotten out of the habit of using Carb heat on every approach when I am flying with Lycomings - unless the POH tells me to, of course. When I owned both a J-3 (Continental) and a Yankee (Lycoming), I'd use carb heat in the Cub, but not in the Yankee. The carb heat is so minimal in the RV stock intake configuration (and even with the little tube from the exhaust pipe) that I really don't think it does much - which is good, since Lycs are much less prone to carb icing. (Note: I am NOT saying it doesn't happen - it just not very likely!).

Anyway, there are those of us you only use it if there is an indication of carb ice, and I haven't had such an indication yet in my -8.

Paul

[Sam Buchanan]

I came to my RV-6 via a Warrior with carbed O-320 and carb heat was never used on that plane. I don't know the difference in the induction system of the Warrior and C172 and why carb heat wasn't used in the Warrior but always used in the pattern with the 172. Could the 172 practice be a holdover from the older Continental-powered 172's? The Conti has the carb hanging under the engine instead of bolted to the hot sump of the Lyc.

In nearly eleven years of flying my O-320 RV-6, I've never used carb heat in flight. Two times carb ice has been experienced during an extended taxi and the following runup, but I've never used it inflight.

No doubt there are those who have flown an RV in conditions that dictated carb heat (snow), but as a general rule, the heat knob is only used during runup to make sure the heat door is closed.

By the way, my experience with the simple temp probes in the carb is that they are worthless. A sophisticated system such as referenced in an earlier post is necessary to have useful carb temp info.

[L.Adamson]

I am a "no" carb heat RV pilot. My friends are not either. Most RVs use Lycoming engines. The carb is bolted directly to the oil sump, which adds a bit of heat to the carb body. This is unlike older Cessnas that use to be Continental powered. The Continental does not pick up any heat from an oil sump. This is why older Cessnas always called for carb heat on the landing, while Lycoming powered Pipers did not. The Lycoming manual calls for carb heat, only if you think you need it. Since we fly out of high altitude mountain airports, the chance of leaving carb heat "on" during a go-around is not good. It robs the engine of takeoff power.

So..........in reality, you'll find a lot of former Cessna pilots putting carb heat in the checklist. And many former Piper pilots won't. And since I, as well as my friends fly these mountain areas with Lycomings, we don't either.

L.Adamson --- RV6A

[Garage Guy]

Originally Posted by jsharkey

.The flap might prevent snow and ice from entering the filtered air box and restricting induction air but the amount of heated air that the heat exchanger provides isn't enough to cause an RPM drop during preflight run up checks.

Similar situation with our RV-6 (O-360-A1A, standard FAB, Robbins Wings carb heat muff). We have a digital RPM gauge, and sometimes I can see a 10 or 20 RPM drop at runup, but not more than that.

And, while our POH says "carburetor heat as needed", the number of times it has been needed, in 640 hours, seems to be zero.

YMMV, but this appears to be pretty normal for these planes.

--Paul

[zilik]

I use my carb heat on every landing. It's there, why not use it. I installed it, I'm going to use it.