Carb Heat on landing?

[Palmpilot]

My question (which is admittedly a little off topic) is: Do they amend the POH when they issue an STC that might affect normal or emergency operating procedures?

I have seen STC documentation that contained modifications of information in the POH. A specific example was a 180 HP STC for a C172 that I used to be a partner in. I don't remember whether it modified procedures, or just performance data.

 

[Sac Arrow]

The POH on my ol' Cherokee used to say "carb heat as needed". Not much help to rule followers since one has to make an informed decision based on current conditions and circumstances.


Is this a pop quiz?
If so, my answer is "if you forgot to enrichen the mixture in the "decent descent", the engine became rough (overly lean) and by adding carb heat, you enrichened the mixture, thus fixing the symptom".
Now what did I win?

You win nothing, because had the engine been running excessively lean, the application of throttle would not have resulted in an increase of power, and the engine was responsive to throttle. And it continued to run smooth after I pulled the carb heat back out (although, after testing the condition, I put the carb heat back in until after landing, for obvious reasons.)

 

[brcase]

This is a bit dated but the NTSB seems to think many POH's don't cover the issue well enough.
Seems Like I recently saw a newer recommendation from the NTSB along the same lines.

http://www.ntsb.gov/safety/safety-recs/recletters/A89_140_142.pdf

Brian
CFIIG/ASEL

 

[Dan Thomas]

Once the engine has stopped; pulling carburetor heat didn’t have much effect.

In a glide, the exhaust system (the source of carb heat) cools off considerably. If the engine quits, it gets cold in a hurry. The metal in aircraft exhaust systems is thin and stores very little heat. Pulling the carb heat when starting a descent is to warm that carb body and keep it there so ice doesn't form. It's much harder to remove ice that has killed the engine.

 

[Kritchlow]

So, if you have modern day instrumentation that provides you with real-time information that wasn't provided when the plane was built and the POH written (i.e. a digital carb temp gauge on a '57 C172) then you should ignore that information and rotely do exactly as the POH/checklist states even if that action could be detrimental (i.e. cause severe engine stumbling at high density altitudes, plug fouling, etc.).

i.e. never use your ability to reason and think.

Got it!

Doing something different than the manual states will cause you much grief should a problem happen. That's my only point.

I'm not sure how your airplane manuals work, but ours had a section in the back for optional stuff. That section was a "mini AFM" and listed any procedural changes with that equipment installed.

 

[Palmpilot]

Doing something different than the manual states will cause you much grief should a problem happen. That's my only point.

If bug smasher manuals were as dependable as airliner manuals, then maybe we could afford to follow them slavishly. Instead, we have to use our best judgment based on our training and experience, in order to "survive long enough to attend the hearing."

 

[Lowflynjack]

I am located in Tampa, FL. I have been in training and have about 50 hours total. Mostly in Luscombes, J-3, Champs and other TW aircraft at first, until I decided to specialize over the last 6 months in low-wing PA-28 Pipers for my PPL. In the J-3, I would always be told to reduce power at end of numbers, perform the final orientation, add carb heat and bring her in.

Just trying to be safe and conscientious with my carb heat practices and rules of usage.

You mention flying a Luscombe... does it have wing tanks or a fuselage tank? If it has a fuselage tank only, you have to use carb heat for takeoff. They were climbing so steep during takeoff they would starve the fuel supply, so the solution was to pull carb heat on takeoff to limit power and keep the nose lower. One of the dumbest fixes I ever heard of, but it's a requirement!

Oh and btw, I use carb heat in my Cessna 140 every time I'm landing. I have a Stromberg carb and it's amazing how cold it will be right after landing. I actually had water dripping off of it the other day. I do turn the carb heat off right after touchdown on a grass/dirt strip to keep from sucking in too much junk.

 

[Kritchlow]

If bug smasher manuals were as dependable as airliner manuals, then maybe we could afford to follow them slavishly. Instead, we have to use our best judgment based on our training and experience, in order to "survive long enough to attend the hearing."

They don't update small airplane flight manuals?

 

[Kritchlow]

If bug smasher manuals were as dependable as airliner manuals, then maybe we could afford to follow them slavishly. Instead, we have to use our best judgment based on our training and experience, in order to "survive long enough to attend the hearing."

Regardless... My point is.... If you have an accident that kills someone, and it comes to light that you deviated from the nanufacturers published procedure, you will not fair very well in the legal process.

 

[Palmpilot]

They don't update small airplane flight manuals?

Not enough to make it safe to follow them slavishly.

 

[Palmpilot]

Regardless... My point is.... If you have an accident that kills someone, and it comes to light that you deviated from the nanufacturers published procedure, you will not fair very well in the legal process.

Which is more important, protecting ourselves from the legal process, or protecting our lives and the lives of our passengers?

 

[Kritchlow]

Which is more important, protecting ourselves from the legal process, or protecting our lives and the lives of our passengers?

Clearly you're correct on that point, but that doesn't fit the scenario. The scenario is pilot X deviated from published procedures and someone died.

Because you are correct with your above assertion, nobody is going to bother you if you deviate from procedures and nothing happens.

Likewise, if pilot X has an accident and someone dies but the pilot can show all published procedures were folllowed, I expect he will have a pretty easy legal time if it.

 

[Dr. O]

I'm too old and too dumb to change my ways.
All I can say is that I personally know two pilots who died from not using carb heat soon enough

I don't know any who died from using carb heat
Never read of any either!
I can tell you from long experience that in Fat Albert the Apache if you don't use carb heat on humid days you will soon be in a world of hurt
I am aware that the PA140 does not seem to need carb heat most of the time (shrug) but when I fly one it gets used

 

[Palmpilot]

Clearly you're correct on that point, but that doesn't fit the scenario. The scenario is pilot X deviated from published procedures and someone died.

Because you are correct with your above assertion, nobody is going to bother you if you deviate from procedures and nothing happens.

I thought we were talking about whether deviating from published procedures is ever justifiable. If you limit the discussion to cases in which a published procedure isn't followed and someone dies, that doesn't prove anything, because it becomes a circular argument.

A specific example I had in mind is that many of the manuals for planes I've flown instruct the pilot to take off with the mixture rich, with no mention of adjusting for field elevation or density altitude. They also don't say anything about leaning for taxi. Those can lead to poor climb performance and/or fouled plugs.

Likewise, if pilot X has an accident and someone dies but the pilot can show all published procedures were followed, I expect he will have a pretty easy legal time if it.

I'm not so sure about that. In naturally-aspirated airplanes, all of the instructors I've flown with advocate leaning for takeoff at high elevation airports, regardless of what the manuals say. What if opposing counsel asks whether the pilot deviated from what he was taught? And if something I do kills someone, having an easy legal time is not going to make me feel all that much better about it.