Carb Ice --> Forced Landing

[Schinpop]

This was a first for me. I got carb ice so bad I had to land - on an interstate frontage road 30 miles north of Cheyenne. I've had carb ice on the ground that cleared instantly, but never in cruise. For background, I'm a CFI with about 730 hours, and a mission pilot with CAP.

I was in a 152 with a student doing a cross country. The engine roughness came on suddenly, but carb heat didn't solve the problem. Did the E-word thing and turned back towards CYS, but after about 10mins, the engine wasn't getting better and we were not holding altitude. I saw the arrow straight, plowed and dry frontage road and decided to put it down. Emergency over, Wyoming Highway Patrol called. It's all good - and, of course, the engine is running fine once we're on the ground.

I've discussed this experience with several CFIs - many of them CAP IPs - and would suggest the following steps beyond the checklist when carb ice is suspected:
1) Carb heat full (well, that one's on the checklist)
2) Aggressive leaning to keep EGTs (and therefore the exhaust) as warm as possible
3) Immediately slow down to Vy and or best glide. This would reduce the cooling air in the cowling and could possibly help. In the meantime, you might actually climb a bit, thus giving yourself more options.
4) You should be somewhat prepared to spend the night in the terrain you are flying over. We were about 4 miles east of I-25 when this happened, and my first move was to fly towards the interstate. Interstate means cars with heaters driving by and good cell phone coverage. 4 miles east of the interstate, you're landing in a snow covered field and you'll be on your own for a good while.
5) Always circle your landing spot if you can. We had to dodge a powerline at the last second - flew under it actually - been kicking myself for that one...
6) Don't be afraid to declare an emergency and get the help of anyone on the radio.

BTW, two days later the FAA called to close out the emergency. The guy said they've had quite a few carb ice episodes in Wyoming this year due to higher than usual humidity. OAT at the time was about 35F - just about perfect for carb ice.

All in all, no damage to equipment or personnel, so that's a plus. I sure am glad this happened during the day - would have been way more interesting at night...

[darrenf]

Good job, glad you made it ok.

[jynxyjoe]

hey wonder if getting higher (lower temp therefor lower moisture) woulda helped?

anyway nice job. get some equipment with a few more horsey's

[ctab5060X]

Glad you make it though with no major problems.

Originally Posted by jynxyjoe

hey wonder if getting higher (lower temp therefor lower moisture) woulda helped?

I was wondering the same thing...

get some equipment with a few more horsey's

Either that or something that is fuel injected!

[Murdoughnut]

Originally Posted by Schinpop

I'm a CFI with about 730 hours, and a mission pilot with CAP.

You would have established more credibility if you would have left out the second part.

Just joshing ya - glad you were ok.

[jynxyjoe]

Originally Posted by Murdoughnut

You would have established more credibility if you would have left out the second part.

Just joshing ya - glad you were ok.

[MikeOH58]

Good job man...Glad you got done safe.

I've been getting a ton of carb ice lately in the grumman here in Connecticut. Past couple flights, it seems when I pull back to 1800 RPM's, engine gets very course and rough...Pull the carb heat and it clears up instantly, but its definately something we al need to keep our eyes on.

Again, good job, and glad you made it done safely.

[Nihon_Ni]

Have you ever seen this chart?



Where were you on it?

[PGT]

Originally Posted by jynxyjoe

hey wonder if getting higher (lower temp therefor lower moisture) woulda helped?

well it's a 152 with 2 people in it at cruise alt. not sure how much higher he could have gone


Glad you were ok. how long were you exposed to the elements before help arrived?

[Schinpop]

Originally Posted by PGT

well it's a 152 with 2 people in it at cruise alt. not sure how much higher he could have gone


Glad you were ok. how long were you exposed to the elements before help arrived?

At the first sign of trouble, we turned toward the interstate (civilization), and contacted flight service on the closest RCO. They handed us off to Denver Center, so our location was known. Once down, a tractor rolled by about 15 minutes later, then a state snowplow. The first state trooper showed up about an hour after we landed. He was dispatched out of Cheyenne. It really wasn't that bad, but I was ready to sit in the trooper's warm car. Landing in a snow covered field and spending the night out there would have really sucked!

[Schinpop]

Originally Posted by Nihon_Ni

Have you ever seen this chart?



Where were you on it?

Short answer - I don't know.

Long answer - OAT was about 38F or so. The temp/dewpoint spread at CYS was 1/M13. We had a 30kt crosswind from the west, and the wind on the ground was calm. We were in a different airmass than what was on the ground which I suspect was more humid.

[Aero_Engineer]

Job well done , I am glad you are OK.

[aloft]

Originally Posted by Schinpop

I've discussed this experience with several CFIs - many of them CAP IPs - and would suggest the following steps beyond the checklist when carb ice is suspected:
1) Carb heat full (well, that one's on the checklist)
2) Aggressive leaning to keep EGTs (and therefore the exhaust) as warm as possible

The other application for aggressive leaning in such a situation is not so intuitive.

Carb icing restricts airflow to the intake manifold, resulting in an overly rich mixture which will likely cause the engine to quit. Immediately leaning the mixture when faced with a sputtering engine in conditions conducive to carb icing will at some point reach a combustible mixture, and presuming the prop hasn't stopped, the engine should come back online--at which point carb heat will start to to its thing.

Good job on handling the forced landing.

[athomeinthesky]

Good job, did they have to tow the plane or did they fly it out of there?

[mhcasey]

Originally Posted by jynxyjoe

hey wonder if getting higher (lower temp therefor lower moisture) woulda helped?

Not so convinced this is totally true. I guess dew point (aka moisture content) will typically decrease with altitude, but I'm not sure it always will. I'd be willing to bet that before your average warm front passes there will be higher moisture content aloft than at the surface. Lower temp does not equate to lower moisture...just lower moisture before the air becomes saturated.

[Schinpop]

Originally Posted by mhcasey

Not so convinced this is totally true. I guess dew point (aka moisture content) will typically decrease with altitude, but I'm not sure it always will. I'd be willing to bet that before your average warm front passes there will be higher moisture content aloft than at the surface. Lower temp does not equate to lower moisture...just lower moisture before the air becomes saturated.

Climbing or descending might put you in a different airmass with different conditions and could improve your situation. Staying at the same altitude leaves you where you know conditions favor carb icing - somewhat severe carb icing. If I were in the same situation again, I'd try to climb - or at least go to Vy to reduce the cooling air in the cowling and accept whatever climb I can get.

To answer another question - they flew it out the next day.