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Carb Heat in IMC
- Thread starter NYCPilot
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Thanks for clarifying that. The next obvious question is how fast you exited icing conditions after noting the structural icing. It's time to stop holding at to get out of ice...especially if you're not equipped for known ice.
As far as the RPM drop to be seen on the runup...you should be seeing the book value that the manufacturer specifies. The actual amount of loss is going to be somewhat dependent on the outside air temparture and ambient conditions, but you should still see close to the book loss. If you're not getting that loss, you may have a problem in the carb air box. Common problems include improperly adjusted linkage, and damage to the carb air butterfly, or it's seal material. This can be serious; if the seal material is damaged it can come off and enter your induction and cause an engine failure or blockage in the carburetor. Carb air boxes crack...they're notorious for it. Once the box begins to flex, the carb heat control doesn't work the same.
In many installations, your induction air filter attaches through the cowling, and also attaches to the carb air box. The motion of the cowling against the motion of the carb air box can cause cracking. It also can mean your air filter isn't secure, and can lead to cracking in the cowl, too. Your carb air box is bolted to the carburetor, in most cases.
If you're performing engine runs and not getting the manufacturer-specified results, then maintenance should be performed to find out why.
As far as the RPM drop to be seen on the runup...you should be seeing the book value that the manufacturer specifies. The actual amount of loss is going to be somewhat dependent on the outside air temparture and ambient conditions, but you should still see close to the book loss. If you're not getting that loss, you may have a problem in the carb air box. Common problems include improperly adjusted linkage, and damage to the carb air butterfly, or it's seal material. This can be serious; if the seal material is damaged it can come off and enter your induction and cause an engine failure or blockage in the carburetor. Carb air boxes crack...they're notorious for it. Once the box begins to flex, the carb heat control doesn't work the same.
In many installations, your induction air filter attaches through the cowling, and also attaches to the carb air box. The motion of the cowling against the motion of the carb air box can cause cracking. It also can mean your air filter isn't secure, and can lead to cracking in the cowl, too. Your carb air box is bolted to the carburetor, in most cases.
If you're performing engine runs and not getting the manufacturer-specified results, then maintenance should be performed to find out why.
avbug said:
No problem. Yeah it was immediate. The examiner and I agreed without speaking that the hold was satisfactory and we were inbound on the approach.
Funny how stuff works like that isn't it?
I don't mess with ice. My first experience (then) freaked me out. If I'm gonna fly in it, I want an aircraft capable of handling it until I can get out of it.
...anywho...(structural) ice discussion over.
-mini
gkrangers said:Man..all you guys with your fancy ice experience...I'm instrument rated and don't even have any real legitimate actual.
While I love my actual time (reeeeeeally love actual for some sick reason), I do not like actual when it's even close to icing conditions...I can't tell you how many trips I cancelled because the freezing level was at 4000' (MEA 3000'), etc...
Now if you're in something like a Malibu...well...have at it!
-mini
Yes the approaches need to be done in instrument conditions (actual or simulated), and must be flown to minimums. That's really the heart of the matter, anyway...the requirement is for proficiency, and getting and staying proficient isn't likely if you aren't flying it by reference to instruments, and flying it all the way down.
Even where you don't have a safey pilot, however, you're doing the right thing by picking up the approach and flying it anyway. Even though you didn't have a hood, you're still gaining some valueable experience in the proceedure.
What I used to do was fly the approach at every airport I visited, even when coming back VFR. And when flying in mountainous country, I flew the approaches in the day so that I was familiar with them at night, and always flew them at night regardless of the weather, for terrain. When the time came to fly the same approach in instrument conditions, I was already familiar, and a lot more confident being close to the terrain.
By flying them on your own visually, you can correlate what's going on on the panel to what's going on outside, and you can use this information to your benifit when flying an approach in instrument conditions. For legality, you will either need to fly the approach in the cloud or with a safety pilot and a view limiting device...but you can get useful experience either way. If you fly somewhere, try to arrive by flying the approach visual or otherwise. It's always good practice.
Even where you don't have a safey pilot, however, you're doing the right thing by picking up the approach and flying it anyway. Even though you didn't have a hood, you're still gaining some valueable experience in the proceedure.
What I used to do was fly the approach at every airport I visited, even when coming back VFR. And when flying in mountainous country, I flew the approaches in the day so that I was familiar with them at night, and always flew them at night regardless of the weather, for terrain. When the time came to fly the same approach in instrument conditions, I was already familiar, and a lot more confident being close to the terrain.
By flying them on your own visually, you can correlate what's going on on the panel to what's going on outside, and you can use this information to your benifit when flying an approach in instrument conditions. For legality, you will either need to fly the approach in the cloud or with a safety pilot and a view limiting device...but you can get useful experience either way. If you fly somewhere, try to arrive by flying the approach visual or otherwise. It's always good practice.
A Squared
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jafo20 said:
Horse$hit
chriskcmo said:
More Horse$hit. the idea that brand X is more or less suceptible to icing than brand Y is pure fantasy. Both manufacturers use various models of carburetors form the same 2 manufacturers....mostly Marvel Schebler but both manufacturers use a few Bendix Stromberg Carbs.
I've owned a C-180 with a 0-470-R engine for over 10 years, and have only had carb ice on one occasion, and that was while taxiing on a river one cold wet October morning whth the temp hovering right around freezing. By contrast I have an acquaintence with a 0-470-R equipped C-180 (actually a converted early model 182) who gets carb ice practically on a continuous basis. The only difference between his and mine? The intake system, everything from there on down is identical.
A friend of mine has a modified PA-12 with an O-320. He flew it for decades and never had Carb ice. He had some major work done and one of the changes was a "new and improved" induction system, now it makes carb ice at the drop of a hat, with the same original engine and carburetor.
It's a little more involved than "lycoming engines don't get carb ice and continentals do"
Here's the deal about situational awareness when you're single engine IMC:
I'm one of those guys who thinks single engine IMC is more risky than multi engine IMC. Still, I did it for a living. If you're going to do it, it's better to know where you are and what's around you than not. It's better to have a mental picture of your surroundings rather than just have "38.9NM on 137 radial from ABC" stuck in your head.
This isn't so you can go flying with one engine over the Rockies with an intricate plan to let down to a field that's fogged in. The idea is that you can get below a 1000 foot cieling to land visually without hitting a hillside, tower, etc. The idea is that you can turn away from the Smoky Mountains to buy yourself some more time dead-stick into Knoxville.
I must not have made my points sufficiently clear in my first posts.
When it's foggy on the ground or the cielings are too low, your options are limited. That's what I mean about aiming for the best terrain nearby. The idea is that one engine, low IMC leaves you vulnerable, and your best options still aren't that great.
Of course, vacuum pumps and alternators are things to think about, and I didn't address them in my previous posts. If you're engine is windmilling, you may or may not have enough RPM to get either of spin either of your vac pumps enough to keep the instruments erect.
I'm one of those guys who thinks single engine IMC is more risky than multi engine IMC. Still, I did it for a living. If you're going to do it, it's better to know where you are and what's around you than not. It's better to have a mental picture of your surroundings rather than just have "38.9NM on 137 radial from ABC" stuck in your head.
This isn't so you can go flying with one engine over the Rockies with an intricate plan to let down to a field that's fogged in. The idea is that you can get below a 1000 foot cieling to land visually without hitting a hillside, tower, etc. The idea is that you can turn away from the Smoky Mountains to buy yourself some more time dead-stick into Knoxville.
I must not have made my points sufficiently clear in my first posts.
When it's foggy on the ground or the cielings are too low, your options are limited. That's what I mean about aiming for the best terrain nearby. The idea is that one engine, low IMC leaves you vulnerable, and your best options still aren't that great.
Of course, vacuum pumps and alternators are things to think about, and I didn't address them in my previous posts. If you're engine is windmilling, you may or may not have enough RPM to get either of spin either of your vac pumps enough to keep the instruments erect.
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