Three minutes twenty-four seconds.

When you're calling or listening on the radio, you aren't getting a METAR, you're directly accessing the ASOS/AWOS/etc.


True, but I believe the automated METARs are accessing data from the same system, and this introduces a little confusion about winds.

I was taught that METAR and TAF reports give wind in degrees true, whereas ASOS/AWOS give degrees magnetic. ("If it's written it's true," goes the saying) But this doesn't seem to be the case. I can look at my airport's METAR online while I'm listening to the AWOS and get the same number for wind direction. I'm guessing both are magnetic, but can't be 100% certain.

I really wish that METARs and TAFs would introduce the letter T or M to resolve any confusion, so wind direction would be written "270T" or "270M".

Better yet, just make all airport reporting in degrees magnetic. It makes sense to me that airport data should always be in degrees magnetic (TAF and METAR and AWOS/ASOS), since runway numbers are magnetic. I don't know why we'd ever give such in degrees true. For winds aloft, true makes more sense as the wind report might span different magnetic variation regions.
 
Fuel injection is considerably more expensive. It involves a header tank in the fuselage, usually a separate shutoff valve in addition to the selector valve, and sometimes a tandem selector valve to send returned fuel back to the tank it came from. There's an engine-driven pump, an electric boost pump in case the engine's pump fails, and that boost pump, in the Continental, has a system of resistors and switches to manage its pressure. There's a fuel servo and air throttle and flow divider and injector nozzles. Lots of stuff that all costs lots of money and needs maintenance. A carburetor is a rather simple thing that never gives trouble except for ice, as long as it's fed adequate, clean fuel, and the fuel injection system also needs adequate, clean fuel. Carbs cost a lot less. They are so reliable that we have ONE carb but TWO magnetos, as magnetos are more failure-prone. Both those mags need periodic disassembly and inspection and cleaning and new points and condenser and distributor parts, while that single carb is good for the whole TBO of the engine.

So. We learn to manage the carb, and that means managing carb ice, which means understanding it and knowing when it's likely. Yes, the Pipers are less prone to ice than the Cessna, and there's good reason for that. The Piper's exhaust system is a complicated thing that either surrounds the carb and radiates heat at it from all sides, or is below that carb. The Cessna has its exhaust up front, or at most, a muffler on each side. No piping all around everything. Just because the Piper doesn't ice up often does not mean that a Cessna, with basically the same engine and carb, is as forgiving. It's not. One still needs to know more about ice and its formation and management.

A long glide will ice up almost any carb, even with the heat on. The exhaust system is where that het comes from, and at idle, in the glide, it cools off. The piping is light and doesn't store heat for long at all. You need to open that throttle for ten seconds or so to warm the exhaust up, get some heat into that carb to clear any ice and warm the carb body, or the engine might not respond once you get to the lower altitude or on final if you're a bit low.
 
T
I was taught that METAR and TAF reports give wind in degrees true, whereas ASOS/AWOS give degrees magnetic. ("If it's written it's true," goes the saying) But this doesn't seem to be the case. I can look at my airport's METAR online while I'm listening to the AWOS and get the same number for wind direction. I'm guessing both are magnetic, but can't be 100% certain.
Your AIM, like our Canadian AIM, has all the details on that stuff.
 
Discussions like this make me wonder why fuel injection is not more common.
Maybe you need to make a video entitled “Three Minutes, Twenty-four Seconds to Live” to see if you can generate the level of panic that the “178 Seconds” video generates.
 
That's how long it took to make enough carb ice to kill the engine.
The C-85-8 makes more ice than a refrigerator/freezer. Seriously.
The manual for the C-85-8 says to keep the carb heat on at all times while sitting or taxiing when the conditions will create ice. I know this. I usually practice safe carb heat.
Today, I did my run-up and forgot to leave the carb heat on when I finished.
Add in a "Hold short for landing traffic."
When the tower released me I went out on the runway and started my takeoff roll.
And the engine stopped stone, cold, dead.
Three minutes and twenty-four seconds from run-up to dead engine.
I ended up dragging the plane off the side of the runway.
It restarted on the third pull. <edited for accuracy.
The entire embarrassing episode was caught on camera.
The rest of my 2.2 hour flight today was uneventful.
What were the conditions at the time?
 
What were the conditions at the time?

31F, 85+ percent humidity (the gotcha on this), CAVU and calm.
I have become VERY aware of humidity since I bought this plane. I will turn the carb heat on randomly even when in cruise.
It isn't as much of an issue in the Cherokee or Skyhawk.
 
31F, 85+ percent humidity (the gotcha on this), CAVU and calm.
I have become VERY aware of humidity since I bought this plane. I will turn the carb heat on randomly even when in cruise.
It isn't as much of an issue in the Cherokee or Skyhawk.
While not as much of an issue in my Archer2, having been burned by it, I too randomly turn on CH in cruise and routinely for a bit before landing.
 
31F, 85+ percent humidity (the gotcha on this), CAVU and calm.
I have become VERY aware of humidity since I bought this plane. I will turn the carb heat on randomly even when in cruise.
It isn't as much of an issue in the Cherokee or Skyhawk.
Those carb ice charts I posted show the relative humidity as related to temp and dewpoint. I never think about the RH, just that spread between temp and dewpoint, since that's what the METAR shows.
 
1930s technology.
Yup. But that very thing is what makes it possible for us to fly. The development and certification costs were paid off a very long time ago, and we benefit from the labors of people almost 100 years ago. Development of some of the stuff we use was paid for by the military.

When an engine manufacturer comes up with something better, it costs big salaries and and big development and testing costs and big certification costs, and the taxpayer isn't going to cover those for you. Lycoming responded to the demands for a modernized engine with their iE2, but pilots aren't buying it. It's expensive. Full FADEC, electronic ignition and fuel injection just like your car has. Starts instantly. Runs smoothly. Just one knob to push in and out. And only one airframe manufacturer buying it, for their twins.
https://www.lycoming.com/engines/ie2

Now, calling something 1930s technology does not make it obsolete. This is much older technology that we use everyday:

upload_2023-2-15_16-10-17.jpeg

The piston engine that we also use everyday was developed in 1862, and we still use that principle. We burn gasoline to make heat to expand gases to push a piston. 160 years later we're still using it. Not obsolete yet.
 
I've flown pa-28s with and w/o FI, here where it's almost always carb ice season. I prefer the carb because it's generally easier for me to start, and overall less of a PITA. Have had carb ice in cruise twice that I know of, not a big deal. Always use carb heat on descent into airport and until landing. Mechanical FI is a bit spooky, maybe just to me.

Cubs? They routinely made ice for me in cruise, but - knock on wood - so far no problems. I've had ice on the ground, but never enough to stop the engine. This story is one I'm taking to heart, to not be complacent about my success/luck so far.
 
Fuel injection is considerably more expensive. It involves a header tank in the fuselage, usually a separate shutoff valve in addition to the selector valve, and sometimes a tandem selector valve to send returned fuel back to the tank it came from. There's an engine-driven pump, an electric boost pump in case the engine's pump fails, and that boost pump, in the Continental, has a system of resistors and switches to manage its pressure.

No header tank in my plane. No separate shutoff valve. A number of aircraft return the fuel to only one tank. And low wing aircraft with a carb have a electric boost pump in case the engine driven pump fails.
 
I wouldn't fly a plane that has such a severe carb heat desig issue sell it or mod it
 
That's interesting...I would have imagined at 31F and 85%+ RH you wouldn't get CAVU conditions. But I'm no meteorologist.
85% RH is still clear. Maybe a bit of haze. 100% is fog.
 
While we all know the little Contis are ice machines and Lycomings aren't quite as bad...

What's the story on Rotaxes? I've never really heard of anyone talking about ice on those.


Identity crisis….

So there I was. Ft Walton Beach turn, MD-80, I’m a first officer. Fed shows to jump seat (read get home). I can’t find my plates… at all… arg… fed jumpseater, gotta fess up and go make copies at the gate house.

Hey boss, can’t find my plates.
“Did ya look under EGLIN AFB?”
D’oh…

Becomes obvious he can’t find them either… Fed chuckles. “You got anything to add here?” asks the Capt

“Ever wonder what VPS stands for?” Ya, meh…

VALPARISO!

Ooooooooh… always wondered where the heck that was! Geesh…

Seriously, THREE names?

The real Valparaiso is VPZ and much colder this time of year than Fort Walton Beach.
 
Last edited:
It is rare to get carb icing on Rotax engines …something about the underlying design that makes them significantly less susceptible but I don’t remember any details.
 
It is rare to get carb icing on Rotax engines …something about the underlying design that makes them significantly less susceptible but I don’t remember any details.
I flew a Tecnam for 6 years and never noticed any carb ice. BUT, I never pulled the throttle back towards idle without turning carb heat on.
 
I flew a Tecnam for 6 years and never noticed any carb ice. BUT, I never pulled the throttle back towards idle without turning carb heat on.

I don’t even have a carb heat knob on my plane … ( the plane has , according to manufacturer data, full time carb heat )
 

Attachments

  • 178F0161-DE1F-444F-AEDE-30F02C7F7395.jpeg
    178F0161-DE1F-444F-AEDE-30F02C7F7395.jpeg
    110.6 KB · Views: 9
I don’t even have a carb heat knob on my plane … ( the plane has , according to manufacturer data, full time carb heat )
What kind of plane is that?
 
I wouldn't fly a plane that has such a severe carb heat desig issue sell it or mod it
Learning to fly includes learning to manage the engine, and that includes managing carb ice. If all you can afford is an old airplane, you either learn to manage things or you can die. There are no mods to change anything, except for a few STCs for changing a carbed engine to a fuel-injected engine, something that can run $100K for some airplanes.
 
Harry Fenton mentions the following SB from Continental. Seems worth looking into.

I have also attached a copy of Continental Service Bulletin M64-6. This Bulletin specifically addresses idle problems when operating in cold weather. The solution is to make a baffle which is mounted in front of the air filter and prevents the intake from cooling too quickly.
 

Attachments

  • Cont_SB_idling_failures-1.pdf
    345.6 KB · Views: 2
Last edited:
Flew a 180hp 172 at 2,000 RPM, 1,000 AGL, 10 degrees flaps, about 90 knots, for multiple hours - making sure no one stole the Bay Bridge. When it was time to head home in the early evening I shoved the throttle and mixture forward and gave birth when it coughed, rattled, and gasped. Pulled to best glide, right into the Class B (I let ATC know). It was still making enough power to climb a little. Took a little while for me to: a) undo what I'd done, b) pull carb heat.

Our A&P and grizzled CFI asked me temp, dew point, and checklist. He didn't even slap me when I whined that the RPM was always (barely) in the green arc. He did tell me I was lucky I had the 172 that day - the 182 froze more water than a hotel ice machine.
 
Answer: Three minutes 24 seconds.

Question: How long did the honeymoon last until the bride became SWMBO.??
 
Back
Top