cold temp flying

[gliderman]

Hi all
need some advice from you folks in Alaska who fly in cold temps like me.I went to go flying this morning: temp was-22C and the dew point was -26c. just outside my little rule of a 3 degree spread minimum on temp- dew point to fly.
still had icing problems on taxi- the engine quit! Got a little freaked out and went and put away the A/C. so I now taxi with the carb heat on. still a little worried about takeoff though.

your thoughts

shane

[MN_flyer1]

I am very interested in the responses also. I don't have much cold weather experience. Yesterday I was pulling on the carb heat about once a minute just to make sure nothing was freezing up at idle. I don't like leaving it on in case it would freeze up in the on position. On approach I will pull it on during downwind leg. On final I will push it in and pull it back out just to know it will be there on a go around.

[bigjohnnie]

I too am interested in the rsponses of those experienced in cold weather flying. It gets pretty cold here in the Ohio valley as well.

[Troy Hamon]

Well, I'm still a newbie so more experienced folks will be along. But...you say you had icing problems on taxi. Do you mean carb icing? Are you sure it was carb icing? All sorts of things are different when it's cold. Sometimes the perfectly calibrated throttle and mixture really don't give the same results when the cables are cold, the engine can be more prone to dying for any number of reasons until it is really nice and warm. So if you are sure it was carb icing is my first question, solely because you haven't actually provided much information to explain what happened.

Second, the other PA-22 operator out here has his carb heat on during ground operations almost religiously. I do not keep carb heat on because I don't want to be trying to remember to do it one way on pavement and another on dirt. So I make sure the airplane is preheated. That makes more of a difference than anything else, in my opinion. The couple times I plugged the generator in and got it started, left it to preheat, and the generator turned itself off so that airplane wasn't really that warm and I flew anyway...took a really long ground run to make the airplane operate happily. Preheat, preheat, preheat.

As for carb heat, I make an extra point to put carb heat on for a long couple of clicks when I'm doing a runup. Mag check is pretty quick, but the carb heat is a longer one because I want to see if it drops and then rebounds, as that would indicate I am building ice. The building of ice is not the primary concern, the carb will do that, I just want to know so I can be ready to deal with it. I've had carb icing three times. Twice on takeoff during climb. Both times between 70 and 85 degrees, near 100% humidity. Once during cruise, cool temps probably 20s after flying for an hour and a half. If you have a way to install a temperature gauge in your carb like they used to do (Beavers have them) you can prevent ice by managing the temperature. My replacement for that is that I pull on carb heat every 5 or 10 minutes briefly. The flight where I forgot was the one where I got icing in cruise. I haven't forgotten it again since.

So...taxi with the carb heat on is fine. My version is I clear the carb immediately before takeoff with the runup. But any sign of reduction of engine power, carb heat should be an almost automatic response, right there with changing tanks and jamming the throttle full forward (in case it isn't already there). Just make sure the carb heat is off when you go to takeoff. I have twice taken off with carb heat on, and it is not the sort of mistake you want to make when you are dealing with anything short or tight, so if you can taxi with carb heat on without running that risk, fine. If your operations flow might result in missing that item...change something to make it so it won't happen.

I'd be really curious to know if there are any experiences of carb icing below 20F (-7C) in cruise. It seems like it is mostly a ground phenomenon at those temperatures, but I don't trust it, so I always clear carb occasionally regardless. Hope this soliloquy is useful.

[gliderman]

Hi Troy
it was definitly carb icing. took FUWA out of her nice warm hangar into -22C( 3F) weather. started her up and waited for the oil temp to start rising. began to taxi to the active runway(16)and it started to backfire. got to the runup area and did the run up. upon throttling down to idle after the mag check etc.. she quit. started her up again was backfiring so I turned around and went back to the hangar. I then ran over to my engine guy and got snickered at. he came overand checked things out and told me to taxi with the carb heat on." refrigeraton" was his comment. I wonder if going from a nice warm place to a cold one had something to do with it.I have only rented this warm hangar for a couple of months to do some flight training( night endorsement)as FUWA is generally kept in a unheated hangar.....
yesterday I went flying with our local freelance instructor and told him what was happening and he had a C182 do the same thing that day.he took me to situations that I hadn't been to since flight training 25 years ago. We did things in a Pa22 that I didn't think was possible. Slow flight at >50 mph indicated? 60 degree turns?He definitely put me though my paces and opened up the flight envelope. best 80 bucks I ever spent.
thoughts
Shane

[Troy Hamon]

The other thing I do that I failed to ask about...how lean is your mixture on the ground? I lean aggressively during ground operations. Less fuel to vaporize should reduce the temperature drop in the carb. It also prevents plug fouling, which is why I do it. I'm jealous of the nice warm hangar...

If you did a runup, what about pulling on carb heat during runup? What happened there? Normal no-icing for my plane, the rpm drops about 75 and remains there. Carb icing, it will drop more, get rougher, then start to climb after being left there for a few seconds, which is how I know it was icing up. Runup can build ice quickly, as can takeoff, in part due to operating with a full rich mixture, so I make sure to check the carb heat response carefully as it warns me about takeoff and climb behavior.

There are people that will authoritatively tell you that carb ice is most likely to happen during low power operations. As posted above, I've had it three times in flight, all high power flight phases. The more fuel is going through the carb the more it vaporizes and the more the temperature will drop, so high power settings are much more vulnerable to icing. I say this to say...if you can get carb icing make sure you are consciously prepared for dealing with it during takeoff. Carb heat application on descent is a good habit because it clears the carb for the application of high power if needed. A partially obstructed carb can produce normal engine behavior at low power, so the icing problem can be masked until you try to add power and your engine quits...so carb heat during approach to landing is most likely to pay off if there is a need to do a go-around.

As I said, I know people that have carb heat on during ground operations all the time. I don't, but I lean heavily.

[gliderman]

Hi Troy
I too lean the mixture. Red Deer is 3000 ASL so it is a matter "having to". your right about plug fouling- if I don't lean you sure can notice it on run up- a 300 mag drop isn't cool.
On the day in question i didn't use any carb heat until cycling it on run up.I probaly didn't leave on long enough and as the engine was farting around on taxi to the run up area- I thought it was plug fouling:( I probably didn't notice any great change as the engine wasn't running optimitally. it died soon after i pushed the carb heat in after going to idle...

[Troy Hamon]

Well, maybe take this as an opportunity to add a little more emphasis to how you look at the carb heat check during runup. And liberal use of carb heat during ground operations as well. Asked another local pilot about carb icing today, and he said when his airplane was susceptible, he mostly noticed it at lower or reduced power settings. He made a bunch of changes in his induction system and doesn't know which one fixed it, but he can't seem to make ice anymore. I do know third hand of a guy that had trouble with carb icing so he flew with carb heat on all the time. He was strongly chastised for that by a bazillion hour pilot (Herman Ruess if I recall correctly) because...what happens if you are running carb heat and you get carb icing? Without proper gauges to check the temperature in the carb, there's no way to moderate the application of carb heat and be sure you still have some heat in reserve.

Just saying that because if you have a problem that persists or that can't be addressed with ground application of carb heat and/or more attention to carb heat during runup, there is at least one thought that running carb heat all the time (we're talking in flight here) isn't the answer.

[skydogk]

Gliderman, you mentioned the narrow difference between temp and dewpoint. That is why your carb iced up so easily. During cold temp operations where temp/dewpoint spread is close, or when flying in visible moisture (cold rain, or snow) it is advisable keep a close eye on carb heat and use it often.

The reasons to not use carb heat (either on the ground while taxing or continuous in the air) are as follows. Using carb heat is allowing raw / unfiltered air into the carburator then into the cylinders. While in the air, this is not a big deal, but for taxi operations, may be hazardous due to rocks and dirt being picked up by the prop the introduced into your engine. If the taxiway is snowcovered, or ice covered don't worry about this as the snow and ice prevent dirt etc. from getting into the engine, so I advise in this situation to keep carb heat on during warm-up and taxi.

Now, about taking off with carb heat. Carb heat, as the name implies, introduces warm air into the carburator. This does two things, it changes the fuel / air mixture and changes the density of the air in the carburator. Both these phenomenoms decrease the power that the engine will produce. However, because we can change the mixture in our carburators, that can be dealt with simply by pulling a little on the mixture knob untill you notice peak RPM, then richen it slightly (during cruise just leave it at peak RPM).

About the density problem, during cold weather ops, lack of horsepower and lift is much less a problem than during summer ops. Why, remember ground school and the density altitude thing. Yup, that cold air is helping your wings, prop, and engine. So, all things remaining the same (still using wheels etc.) using carb heat may decrease your engine performance compared without it for the same temp, but I bet you carb heat on a cold day is still more horse power than no carb heat on a hot day. This density thing on cold days isn't really an issue either.

My opinion is when the temps are cold and the ground is covered, use carb heat espicially for warm-up and taxi. If the moisture content is high (ie. close temp/dewpoint spread or visible moisture) I use carb heat constantly during cruise and adjust my mixture accordingly. On take-off, I usually don't use it just because the mixture is difficult to get right because braking action is limited and full power takes different mixture than idle / warm up. I don't like to be adjusting mixture while on my takeoff roll.

This is only my pilot / mechanic opinion. I hope it helps.

skydogk

[nicka]

Something to keep in mind in really cold temps your engine will tend run a little lean, and if you make quick advances on the throttle the engine will want to stumble/miss. In cold temps sometimes it is hard to get the fuel to emulsify well. I usually taxi w/ carb heat on(depending on strip conditions) and push the throttle in all the way for take off power( carb heat will enrich the mix) and then take the carb heat off. I also anytme at low power setting put the carb heat on. At cruise I watch RPM and if I notice any loss of RPM I run the carb heat, pull it out a little at a time just in case there is ice, so a chunk does not come loose at once and ease the heat on to full for a couple of minutes at a time and see if the engine smooths out. I also reduce power slowly and usually do not pull it all off, and fly a shallower descent w/ power, when able. I had a O-200 just quit on me once pulling the power out fast on a cold day, right at the runway. I like winter time flying but w/ short days and preheating, shoveling etc, it gets tough, Also just getting enough heat in the airplane gets to be tough. And then there is huge Pac Boots on the rudder pedals.

[gliderman]

Hi all
thanks for the insights . They were helpfull.Went flying yesterday and used carb heat on the ground( runways were nice and clear) and at lower power settings- no problems :) dew point was 4 degrees different.
having a heated hangar sure is nice -it's gonna be hard to move out next month and back to preheating etc. I use a ceramic heater with a tip over safety switch in the cockpit- it works great.
shane

[nicka]

I like the Northern companion, fairly portable little unit.

[Zac Weidner]

Since it has gotten cold (below 40 F), I have been running with the cover over the oil cooler. I still cannot get a reading of oil temperature above about 170 degrees. Isn't it pretty important to get above that boiling point?

Another thing, I noticed at Rural King the other day that they sell oil heaters that go in place of the dipstick. It seems like it would be a great way to preheat the oil overnight and not kill the electric bill. It said it only uses 90 watts. Seems like the most effective way since the same principle is used on diesels and works, generally well, to about 20 below.

[gliderman]

Hi Zac
I use a heating pad stuck to the bottom of the oil pan.To save the light bill I use an outdoor timer set to come on abot 5-6 am and turn off about 3pm. daylight is scarce in these parts come dec-jan.
My oil temp runs about 180 with the oil cooler partly covered. OAT on Sunday morning was-26c.

shane

[Troy Hamon]

I have heating pads on the pan like you, but no power available. So I have a generator I have to haul out to the airport to preheat.

Karl, thanks for weighing in. I always learn something helpful.

[Curly]

Guys - I will never ever complain about doing a preflight on a cold windy morning again! :frown:

[nicka]

Here's a link to the Northern Companion http://www.stoddardairparts.com/northcompheater.JPG

[Troy Hamon]

Guys - I will never ever complain about doing a preflight on a cold windy morning again! :frown:

What is a cold day down under, anyway? 5C?

[nicka]

Hey Troy, I was just in King Salmon the other day I was going to see if I could say HI but I didn't get a chance.

[smcnutt]

Another thing, I noticed at Rural King the other day that they sell oil heaters that go in place of the dipstick. It seems like it would be a great way to preheat the oil overnight and not kill the electric bill. It said it only uses 90 watts. Seems like the most effective way since the same principle is used on diesels and works, generally well, to about 20 below.

I've heard these are bad for the oil as they have such a small heating surface that in order to get all the oil to temp they are too hot and can scorch the oil. Where as an oil pan heater heats over a larger surface and therefore doesn't need to get quite as hot.

[Zac Weidner]

That makes sense. Diesel heaters use a heater that circulates the coolant through it, so it might not do the same damage at the dipstick could if it were used for oil. I think they might even have it as an option to get an oil heater on some of the new tractors. Do those apparatuses stick to the pan permanently or are they removed before each flight?

Pre-heating is not a huge problem because it's in a heated hangar and we can just turn the heat up overnight, but my concern is mostly that the oil never gets warm enough in flight to boil out moisture. I flew for an hour and ten minutes the other day on the way home from a pancake breakfast with OAT's in the mid 30's and it never got above 170.

[Curly]

Troy - for me it depends on the wind chill - 5c would be considered cold but OK on a still frosty morning but if it was blowing hard from the south and 5c, I would need a real serious reason to fly!

Our weather is fairly benign in the southern states, hot and dry in the centre and tropical in the north so your definition of cold depends on where your from. My brother on the mid coast of West Australia rarely sees temps under 20c overnight and usually 40c+ during the day, so when he comes to visit he freezes his you know what's off at 10c.:rolleyes:

[gliderman]

Hi Zac
mine is stuck to the bottom of the pan permanatly. wiped the bottom of the pan with mek and stuck it on with hi temp silicone. stuck like goosep--p to a blanket.the pad was about 100 bucks CDN

shane

[gliderman]

hi Zac

here is a page from the lycoming operations manual. reading this tells me that the oil temp that you want depends on the ambiant air. if you got 170 degrees you should be in the limits. on the low side.....
I put a piece of aluminun tape on the cooler on each side vertically so that only the centre is open. my oil temp in - 20c OAT is above 180.

http://picasaweb.google.com/markawbolton/Lycoming0290OperatorManual#5327783339284164370

hope this helps
my two cents
shane

[Troy Hamon]

Hey Troy, I was just in King Salmon the other day I was going to see if I could say HI but I didn't get a chance.

Sorry to have missed you! Are you out of Bethel? Was it business or pleasure?

[nicka]

Sorry to have missed you! Are you out of Bethel? Was it business or pleasure?

I am out of Palmer, I was picking up a stranded airplane.

[Troy Hamon]

We usually fly in and out of Wasilla, but I have been over to Palmer once. I'll try to send you a pm before I head in next time, see if we can meet.

[Treetop_Flyer]

Do those apparatuses stick to the pan permanently or are they removed before each flight?

Pre-heating is not a huge problem because it's in a heated hangar and we can just turn the heat up overnight, but my concern is mostly that the oil never gets warm enough in flight to boil out moisture. I flew for an hour and ten minutes the other day on the way home from a pancake breakfast with OAT's in the mid 30's and it never got above 170.

Zac:

Check out the Safe-Heet line. Inexpensive and seems to work well.

http://www.aircraftspruce.com/catalog/eppages/safeheetengineheaters.php

Another option would be Reiff if you want something a little more fancy (http://www.reiffpreheat.com/).

Give me a heads-up if you're ever going to be in the La Crosse area. I'm up at 36WI and would love to see your TriPacer.

-Dave