Near Engine Failure Tonight

[steviedeviant]

That carb air temp system can't solve everything. Its sensor is near the throttle butterfly, and as long as the throttle is open for takeoff or cruise, the pressure drop is primarily in the venturi, upstream of the butterfly. The temp in the venturi might be, and probably is, lower than indicated. And when you close the throttle, the pressure drop in the venturi falls off but the drop around the edges of the butterfly goes way up, and ice forms there. It's a big pressure drop, which is why ice is much more likely at lower throttle settings.

The METAR gives you temp and dewpoint. Pay attention to those numbers. Make a habit of it. When the difference between them is small, ice is far more likely.

So the difference between the two was basically none, because a storm had just come through late afternoon sun was shining and clouds had moved on. So I think next time I will be more aware of this. Thanks though for the reminder.

To the OP - I wouldn't assume yet that your problem was carb heat/icing even though your mechanic etc has said so. The symptoms as you describe them in the first post don't all match carb ice.

Unfortunately I will never know for sure, but after reading all the post and looking back at the conditions, while I find it somewhat hard to believe, it just looks like the evidence is pointing to that. My still lack of experience doesn't give me a lot to go on. I will not be flying that particular plane for a while...so right now it is someone else's problem.

Did you notice a drop in RPM when you applied Carb Heat?
(I'm a little embarrassed I didn't think of this earlier)

The drop in RPM happened as I pulled back the throttle....yes I know that would cause it....what I mean is, that when I pulled back, the rpm dropped very quickly, engine ran rough, and rpm rebounded to about 1700. Giving it more throttle did nothing. Engine continued to run rough and I did apply carb heat and rpm dropped some more, as expected...but I never noticed anything showing it was cleared up. rpm would have dropped with application of carb heat. Engine continued to run rough all the way to landing. Not vibrating the plane rough, but rough none the less.

 

[ironnerd]

Carb Ice is a possibility, but kind of hard to prove a day later.
Notice anything when draining the tanks and gascolator? You mentioned a storm, there may have been some water in the fuel.

Next time you have a partial engine failure, record it on your phone so it's easier for us to figure out (seriously, don't... just fly the plane).

 

[steviedeviant]

Hey everyone, I wanted to post a couple of follow up questions to get some additional insight. So last week when I had the issues, the weather was very similar to what we are having here today. Below is the current and last couple of hours of today's METAR for the same airport. A storm has just come through, but there are no current clouds, weather is now VFR. Dew point and temperature are very close.

So not to beat this dead horse on carb heat, but you all with more hours than I have, do you fly with carb heat on when you have a similar situation? If you are going through an area with a storm or even light rain in the area, obviously moisture in the air, I assume carb heat should be turned on every now and then?

As you all know who are following this thread, the mechanic believes it was carb ice, and that is all I have to go by. Now I am trying to learn all I can about it because obviously I don't feel as comfortable with the subject as I should. Does the information below point out anything in particular that would have been concerning?

Data at: 2340 UTC 09 Aug 2017

KEET 092327Z AUTO 00000KT 9SM TS FEW029 SCT034 BKN070 26/25 A3009 RMK AO2 LTG DSNT SE-W TSB27 T02610250
KEET 092300Z AUTO 00000KT 10SM VCTS BKN029 26/24 A3009 RMK AO2 LTG DSNT SE-SW T02610244
KEET 092253Z AUTO 00000KT 10SM SCT029 SCT034 26/24 A3009 RMK AO2 LTG DSNT SE-SW RAB29E39 SLP183 P0000 T02610244
KEET 092153Z AUTO 00000KT 10SM BKN100 27/25 A3007 RMK AO2 RAE2055 SLP177 P0000 T02720250

 

[denverpilot]

The person saying it wasn't carb ice, has as much evidence as the person saying it wasn't.

Don't get hung up on it. Best to note that carb HEAT takes a little while, and if you need it, pull it on and leave it on. If that doesn't work, follow checklist for power loss... or, just like you did... if possible... land...

You did fine @steviedeviant ... move on... you have lots more to learn... Chalk it up to experience, and keep an eyeball on rentals that misbehave... if you see a pattern of rentals from the same place misbehaving... run away.

 

[steviedeviant]

The person saying it wasn't carb ice, has as much evidence as the person saying it wasn't.

Don't get hung up on it. Best to note that carb HEAT takes a little while, and if you need it, pull it on and leave it on. If that doesn't work, follow checklist for power loss... or, just like you did... if possible... land...

You did fine @steviedeviant ... move on... you have lots more to learn... Chalk it up to experience, and keep an eyeball on rentals that misbehave... if you see a pattern of rentals from the same place misbehaving... run away.

Thanks. I think that is a good way to end this thread. I am somewhat tired of thinking about it....

 

[denverpilot]

Thanks. I think that is a good way to end this thread. I am somewhat tired of thinking about it....

"So, other than that, Mrs Lincoln... how was the play?"

 

[Dan Thomas]

Hey everyone, I wanted to post a couple of follow up questions to get some additional insight. So last week when I had the issues, the weather was very similar to what we are having here today. Below is the current and last couple of hours of today's METAR for the same airport. A storm has just come through, but there are no current clouds, weather is now VFR. Dew point and temperature are very close.

So not to beat this dead horse on carb heat, but you all with more hours than I have, do you fly with carb heat on when you have a similar situation? If you are going through an area with a storm or even light rain in the area, obviously moisture in the air, I assume carb heat should be turned on every now and then?

As you all know who are following this thread, the mechanic believes it was carb ice, and that is all I have to go by. Now I am trying to learn all I can about it because obviously I don't feel as comfortable with the subject as I should. Does the information below point out anything in particular that would have been concerning?

Data at: 2340 UTC 09 Aug 2017

KEET 092327Z AUTO 00000KT 9SM TS FEW029 SCT034 BKN070 26/25 A3009 RMK AO2 LTG DSNT SE-W TSB27 T02610250
KEET 092300Z AUTO 00000KT 10SM VCTS BKN029 26/24 A3009 RMK AO2 LTG DSNT SE-SW T02610244
KEET 092253Z AUTO 00000KT 10SM SCT029 SCT034 26/24 A3009 RMK AO2 LTG DSNT SE-SW RAB29E39 SLP183 P0000 T02610244
KEET 092153Z AUTO 00000KT 10SM BKN100 27/25 A3007 RMK AO2 RAE2055 SLP177 P0000 T02720250

Those numbers present the real possibility of carb ice. Temps and dewpoints real close. Carb ice can happen all the way up to around 100°F (38°C) since the temperature drop in the carb can be as much as 70°F. Temperatures around 10°C seem to be about the worst. Remember that those are ground temperatures, and it will be cooler aloft.

No clouds would indicate a larger temp-dewpoint spread aloft. The spread can be close on the ground after a rain since the ground is wet and the sun is boiling the moisture off into the low-level air.

 

[steingar]

Like Nate said, carb heat takes a few minutes to do its thing. Get it in the pattern best thing is to just land. Never saw hide nor hair of it in my Cherokee, but it could happen. Got it once in my Cessna, and it took long enough to abate that I was on a long final to my nearest.

 

[PaulS]

I think the only thing to add to Nate's statement is that when you pull the carb heat, it might make the engine run WORSE before it gets better as the ice melts, be ready for that.