Here or Maintenance? Engine quit on final.

[Shepherd]

Flew on Tuesday.
PA-17 C-85 engine.
28 F, high humidity.
Engine started fine after short preheat. (Armstrong starter, not electrical)
Normal run-up, carb heat works fine. Oil temperature at 110 degrees, but it never got much higher than that.
Flew for 40 minutes up to GBR.
On final, carb heat is on, I'm a little high and a little fast, with some power on (1,200 rpm) which is normal for me.
About 1/10th mile out I pull the throttle, and the engine went silent.
Landing was fine, no drama.

Flying back I kept 1,500 rpm until I was over the fence, pulled the throttle and it kept running.
Best landing of the day.

This is just the latest in a line of 65s and 85s that turn into gliders with power off in cold weather.
Anyone have any ideas?

Thanks

[tnowak]

Almost certainly carb icing...
I apply carb heat when turning base leg and keep it on after that.
TonyN

[Pacerfgoe]

I think in cold weather those engines do better with a plate in front of the air filter....spaced about 1/2" out from the filter.

[Steve Pierce]

This has helped others with the same issue.

http://www.bowersflybaby.com/tech/Cont_M64_6.pdf

[dgapilot]

Have you checked your idle mixture? With the denser colder air, you may need to richen the idle mixture some.


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[Shepherd]

Carb heat was on for the last few miles because I was flying through snow and haze.
Maybe the idle needs to be tweeked up a few rpm?

[cricko]

Carb heat was on for the last few miles because I was flying through snow and haze.
Maybe the idle needs to be tweeked up a few rpm?
Had the same issue with my Chief. Had the carb adjusted to run a bit richer. Problem solved.

[Subsonic]

I think you need more heat. Oil temp should get above 212 degrees F. The boiling point of water. Cover your oil cooler, if you have one. I don't know about these engines in these planes, but I know you need more heat. Sure, you can run richer, but if you run it rich at low combustion temp you're going to introduce carbon condensation and spark plug fowling next, if you don't have enough combustion heat. You need another 100 degrees more heat. That will fix most of your problem.

[rocket]

There is a " winter kit" for all the small continentals, a wrap like a diaper with snaps for around the oil tank and four snap on wraps for the intake tubes.

The bigger continentals have block off plates for the front of the cawl and an intake reduction plate, screws in front of the air filter, about a three inch hole which I always assumed caused a little more negative pressure in the induction system and caused the carb to draw a little more fuel which compensates for the cold air density.

Ive seen more then a few t-crates up here in AK with about half the cawl blocked off with duct tape, couple of Cubs too but the Lycs just don't need it regardless of the cold, well they do need the oil cooler block off plate.

Just some information that came up reading this thread.


Rocket

[rocket]

This has helped others with the same issue.

http://www.bowersflybaby.com/tech/Cont_M64_6.pdf



Steve,

wish I had seen this about 20 years ago. Had more then a few of these four jug contys come into the shop with bewildered pilots. I just told them to do all the usual winter tricks and not to bugger around at 1900rpm trying to save gas. Almost all of them actually iced up on the ramp going through their checklists etc or trying to "warm up the engine" idling at 700rpm at -10f.


Rocket

[Gilbert Pierce]

I think you need more heat. Oil temp should get above 212 degrees F. The boiling point of water. Cover your oil cooler, if you have one. I don't know about these engines in these planes, but I know you need more heat. Sure, you can run richer, but if you run it rich at low combustion temp you're going to introduce carbon condensation and spark plug fowling next, if you don't have enough combustion heat. You need another 100 degrees more heat. That will fix most of your problem.

If you had to get everything above the boiling point of water to vaporize it most things in our world would never dry. Especially in Florida in the summer.
Once you get the temperature above the dew point temperature water starts to evaporate. The greater the dew point spread between the dew point and the sensible temperature the faster the water vaporizes.

Ever seen ice evaporate without transitioning to water? It’s the temperature and pressure where water can exist as a liquid, solid and a gas simultaneously. It’s called the triple point and happens all the time in Wisconsin in the winter.

Granted it’s nice to have the oil temperature at 165F or more for rapid water vapor removal.

[Shepherd]

I had one of those weird, serendipitous moments when a random guy walked past my hanger today, stopped and said "You aren't flying that thing without covering at least part of the cowling openings, are you?"
So we chatted a bit. He has a Pacer (nope he's never heard of shortwing.org) and says he covers a little less than half of each opening with duct tape when the temperature drops below 30 degrees.
It's cheap and easy. When the weather clears, I'll give it a go.

[Subsonic]

if you had to get everything above the boiling point of water to vaporize nothing in our every gay world would ever dry.��

Agree! When exposed to normal atmospheric pressure in a free air - one atmosphere environment, you're absolutely correct. A partially vented engine crankcase is not that, however. It provides pressurization and containment that keeps water from easy escape to the atmosphere. Like a terrarium where you grow plants in a bottle. The water just keeps condensing at the top and recycling by raining or running down the walls of the crankcase back to the oil if you don't boil it off. That crankcase containment limits the evaporation of water out of the case at lower temperatures and pressures. The water condenses and drops back into the oil. Look at your tea kettle. How much venting of moisture happens below the boiling point. Very little, I think. It could take days or weeks to evaporate a tea kettle at 110 deg. F. I can do it in a half hour if I ignore the shrieking of the kettle once its boiling. I think his engine quit running when he chopped power on final because it wasn't very warm, and his carb froze the water in the venturi. His engine needs more heat everywhere.

[Jeff J]

During the cooler months I have to takeoff with carb heat in the Cub on or it stumbles real bad on takeoff roll. There are 2 fixes I have known about for a few years. The first is to seasonally adjust the idle mixture and the other is to install the plate over the intake filter. The Stromberg carbs are especially prone to ice and seasonal mixture issues. I should do both but I never think about it when I am in a position to do anything about it.

BTW, stock J3’s hardly ever get the oil hot enough. Even on he hottest summer day.

[brian heidt]

Flying in Michigan here with winter kit over oil cooler. 18 Fahrenheit outside and Oil temps stabilized at 150. I don’t have a CHT gage. Never worried about it until this thread. Should I tape part of the cowl inlets? If so what part. Top, bottom inside outside?? I like to do pattern work, so lots of low power settings. Am I damaging my engine ? -Brian in Owosso

[Subsonic]

Flying in Michigan here with winter kit over oil cooler. 18 Fahrenheit outside and Oil temps stabilized at 150. I don’t have a CHT gage. Never worried about it until this thread. Should I tape part of the cowl inlets? If so what part. Top, bottom inside outside?? I like to do pattern work, so lots of low power settings. Am I damaging my engine ? -Brian in Owosso

If you fly for an hour or more each time you light it off, you're probably getting rid of most of the water if you get your oil temps up around 200F or more.

I wouldn't recommend taping up your cowl inlets, but it's not a bad idea IMO. I'd use more RPM and fly the plane harder.

Your own engine has some level of blow-by that lets combustion products into the crankcase oil. That includes water. Older engines let more of those combustion products into the crankcase. And, more water. I have no proof of the rate of dissipation at temperature other than standard chemistry class heat of vaporization curves that every kid sees in high school chemistry.
https://chem.libretexts.org/@api/deki/files/61002/6c6b33a839c7613ad3305d597b687509.jpg?revision=1
150F is pretty low and you're driving off/vaporizing the water very slowly at that temperature. You're probably not going to get rid of all the H20 at that temp because the engine is generating it and pumping it into your crankcase as you fly it at low temp. If you do a cross country for several hours, you're probably doing your engine a big favor in driving off the water if the temps are that low, but I couldn't say for sure. 150 is too low. 110 is way too low.

I recommend more RPM in the pattern. Full power and climb at Vx. Climb harder, turn harder, leave your throttle wide open to increase heating. Run as lean as you can without causing icing. It makes pattern work fun.

Next,The most important piece of daily engine maintenance I do is this:
https://flyingsafer.com/2039

In fact, I'm upgrading soon to this:
https://flyingsafer.com/2065

Other than that, I change my oil every 25 hours and use CamGuard Oil additive.

[Gilbert Pierce]

Every gallon fuel you burn you generate a gallon of water. It’s all water vapor at that point and most of it exits the exhaust.
A small amount blows by the rings and most of that exits the crankcase vent. If this is cooled to the dew point it condenses into liquid water. I have my crankcase vent insulated to prevent condensation. The real problem happens when you shut down your engine. The residual water vapor in th he crankcase will condense out if your engine cools below the dew point of the water vapor in the crankcase. That is why I use CamGuard.

I installed new cylinders in January of 2019 so I couldn’t run CamGuard. Being concerned about water vapor condensing in the engine I built and installed a crankcase dehydrator. Immediately after shutdown I hooked a vacuum cleaner to the crankcase vent and removed the dipstick t allow ambient air to be pulled thru the crankcase removing the higher vapor content air while I closed up the hangar; about 10 minutes.
I then removed the vacuum cleaner and connected the suction side of the dehydrator to the crankcase vent and pulled the dehydrated air ok’ing out of the dehydrator in to the engine thru the dipstick hole sealed with a rubber cork. The timer was set for two hours which was more than adequate. Initially I measured the dew point of the air exiting the crankcase into the dehydrator to determine the two hours. I abandoned this process when the cylinders were broken in and went back to the cam guard.


Is all this necessary? Probably not, especially in the summer. In Memphis we can see some winter nights with dew points and sensible temperatures that are the same. That was my concern it would occur after a late afternoon flight.

[walt.buskey]

Thanks to both of you -- good info!

[Vagabondblues]

Flying in Michigan here with winter kit over oil cooler. 18 Fahrenheit outside and Oil temps stabilized at 150. I don’t have a CHT gage. Never worried about it until this thread. Should I tape part of the cowl inlets? If so what part. Top, bottom inside outside?? I like to do pattern work, so lots of low power settings. Am I damaging my engine ? -Brian in Owosso

Engine operating temperature is another item that is not usually given enough consideration in cold weather. We usually are very cautious about high oil temperature which we know is detrimental to good engine health, while a low oil temperature is easier to accept. The desired oil temperature range for Lycoming engines is from 165˚ to 220˚ F. If the aircraft has a winterization kit, it should be installed when operating in outside air temperatures (OAT) that are below the 40˚ to 45˚ F range. If no winterization kit is supplied and the engine is not equipped with a thermostatic bypass valve, it may be necessary to improvise a means of blocking off a portion of the airflow to the oil cooler. Keeping the oil temperature above the minimum recommended temperature is a factor in engine longevity. Low operating temperatures do not vaporize the moisture that collects in the oil as the engine breathes damp air for normal combustion. When minimum recommended oil temperatures are not maintained, oil should be changed more frequently than the normally recommended 50-hour change cycle. This is necessary in order to eliminate the moisture that collects and contaminates the oil.

[brian heidt]

Hi subsonic and others,
update. Have been flying longer and harder, today WOT for 30 min. 2600rpm indicated, 2800 ft. oAT 10 Fahrenheit. Oil temp never went above 165. Winterszation kit is in, oil cooler is covered. Using cam guard. Changing oil at 25 hours. Am I hurting this engine. Should I cover part of cowl inlet? Personally I don’t really like flying the pattern at 100 and landing no flaps. So not going to fly any harder. Ideas? Thanks Brian

[PACERGUY]

Every plane/engine is different. Covering or blocking off part of the oil cooler with metal tape is easy and you have a temp gauge to monitor what is happening. Covering cowl inlets can lead to problems if you do not have a 4 cylinder CHT gage to insure you are not getting your cylinders too hot. In general flying in the winter is good for your engine. Even blocking off my oil cooler I don't get over 160 so I just fly as much as possible, use Camguard and change at 25 hours/4 months. DENNY

[brian heidt]

Thanks Denny. If your temps are like mine that’s good enough for me. Just got worried from some of the discussion. Brian

[Gilbert Pierce]

With my oil cooler totally blocked I don’t get over 165 on a cold day.

[Subsonic]

Your best bet when temps are cold is to fly often. Block your cooler, and use thinner oil. Lycoming has the recommendations on oil viscosity vs. Temps. Sounds like you should be using 20 or 30 weight in those temps. Even if you can't get temps up, the frequent flying use (mechanical action) will tend to drive off water by evaporation and evacuation due to crankcase pressurization. That's the best you can do. Fly often, Correct oil viscosity, Slow warm up, then run it wide open for an hour or so. Smile, winter solstice was over a month ago. Spring is coming.

[Shepherd]

Weather has been consistently atrocious the last few months.
It's been so bad I went from 8 to 12 hours a month last winter to only 20 since the end of August.
And nothing but bad weather in the forecast for the next week.
sigh...........

[keith weber]

Only way a small continental will get 200 degree oil temp in winter is if it's on fire.