Too cold for Pistons?

[mattedfred]

Everything is relative mattedfred, when you started in aviation it is obvious you may not have been exposed to flying in the north, therefore you would not be expected to know much about the environment or how to fly in same.

the farthest north i have flown is CYIV in twin turbines

the latitude isn't the same as many of the 'northern' airports that many of you have flown to but the remoteness and average daily temperature may be similar to some

perhaps not obvious to some however

[MichaelP]

Is that really a good idea? Most manufacturers recommend removing them above -7C -- Your CHTs must be through the roof! If anything's worse than running an engine at -35, it's probably constantly running it at the red-lines...

They are supposed to be removed above 12.5 degrees C, but experience shows that leaving them in at up to 20 degrees is OK.

We're caught between the devil and the deep blue sea on this one...
If we take the winterisation baffles out, the aeroplane sometimes comes back with worried renters because whereas on runup the oil temperature was fine, it dropped below the green arc in flight. The CHT never makes it anywhere near the green arc in these circumstances.

Here we often have an inversion and on climbout with the baffles in, the higher temperature outside can mean high oil temperature, and sometimes the aeroplane comes back with the oil temp above the green. The CHT in this circumstance is happily in the middle of the green!

At OATs between 20 and 25 degrees with the baffles forgotten in place, the engine will return to green/green in low power cruise.
In the climb the oil temp rises to the red line, while the CHT remains happily in the middle of the green arc if the baffles are not removed above 20 deg C.
Remove the baffles in this circumstance and the CHT will be below the green arc.

Diamond did not get the temperature control right with the IO-240.
Give me a Rotax any day; none of this nonsense!

[Cat Driver]

the farthest north i have flown is CYIV in twin turbines

Sorry I was not specific in my post matted fred.

So please allow me to correct the oversight.

Here it is :

Everything is relative mattedfred, when you started in aviation it is obvious you may not have been exposed to flying piston engine airplanes in the north,

the latitude isn't the same as many of the 'northern' airports that many of you have flown to but the remoteness and average daily temperature may be similar to some

Now I hope you and I don't get in a pissing match about turbine engines mattedfred.

perhaps not obvious to some however

True some of do not see the obvious...didn't you notice this thread is about piston engine airplanes?

[Double Wasp]

I have to agree with Doc on this. The farther you go below -35`the harder it gets to get stuff going, exponentially so it seems. I just remember that once you got to -40 stuff usually started breaking didn't matter if it was piston or turboprop, metal starts getting brittle, rubber freezes, oil doesn't lubricate, can't keep the windows clear etc. Better stay at home, have a cup of coffee and watch stuff emerge out of the ice fog.
One more little thing Cat. You may have got it running at -64`C, good on ya. The question is not really always if something can be done, sometimes it is if it should be done. But you know what they say on how long it takes to learn when to fly. LOL
DW

[mattedfred]

Cat Driver,

although i admittedly do not have any commercial experience in pistons i think my initial response has merit as i feel it should always apply

if the AFM or POH has a temperature restriction you are required to abide by it

i would tell your CP that you really want to go flying but the temperature is unfortunately below the aircraft temperature limit

[phillyfan]

Well, I would love to have flown every day in sandals and shorts but sadly i'm working North of 60. It can stay at -35 or better for weeks at a time. The invention of the turbo Otter has been a real help in parking the pistons during these stretches. Before that we had very few options. Parking airplanes for the better part of the winter was not an option. Now we have a cutoff of -55 for the Otter, -35 for the Cessna's and I won't touch the DHC-2 below -25. Sadly the Otter heat only works to about -15. Just kinda fly along bundled up with a window scraper in one hand.

Not tired of life yet Doc. I'm gettin there though. Damn water pipes in my place have frozen 3 times this winter already.

[C-FKLY]

They are supposed to be removed above 12.5 degrees C, but experience shows that leaving them in at up to 20 degrees is OK.

We're caught between the devil and the deep blue sea on this one...
If we take the winterisation baffles out, the aeroplane sometimes comes back with worried renters because whereas on runup the oil temperature was fine, it dropped below the green arc in flight. The CHT never makes it anywhere near the green arc in these circumstances.

Here we often have an inversion and on climbout with the baffles in, the higher temperature outside can mean high oil temperature, and sometimes the aeroplane comes back with the oil temp above the green. The CHT in this circumstance is happily in the middle of the green!

At OATs between 20 and 25 degrees with the baffles forgotten in place, the engine will return to green/green in low power cruise.
In the climb the oil temp rises to the red line, while the CHT remains happily in the middle of the green arc if the baffles are not removed above 20 deg C.
Remove the baffles in this circumstance and the CHT will be below the green arc.

Interesting -- I have very little experience on DA-20s (just the few flights I did to become checked-out on them when our club first bought them) -- I didn't know that they ran so cold. Most of my experience is on our 182, which tends to run quite hot -- on a summer's day, we need to keep the cowl flaps full open just to keep the CHTs under control, even at altitude. I went up a little while ago with winter fronts and -10C at altitude -- the only way I could keep the CHTs within our self-set range (below 400F) was to keep the power below 18 inches of manifold and cowl-flaps full open. Off they came! But I guess that's just DA-20 vs. 182 -- just kinda shocked me that you said you kept winter fronts on into the summer, whereas we'd be blowing temps if we did that.

[Cat Driver]

One more little thing Cat. You may have got it running at -64`C, good on ya. The question is not really always if something can be done, sometimes it is if it should be done. But you know what they say on how long it takes to learn when to fly. LOL
DW

Funny you should mention that Double Wasp because it was really interesting what did actually happen.

We were coming out of someplace I can't remember and needed fuel to continue on to Whitehorse...the weather forecast was iffy so we landed for fuel.

The temperature at our cruising altitude was somewhere in the minus twenties...can't recall the exact number but when we got the temp. on the ground we decided that we would dilute for xx minutes just prior to actually landing. We also diluted before shutdown.

We shut down and put the engine covers on and at the same time fueled up..took about twenty minutes.

Whipped the engine covers off and fired up the right engine..it started real easy...but just as I was about to flash up the left engine the FO said oh @#$! and pulled the right engine mixture to ICO.

What had happened was the oil cooler had blown and there was oil going everywhere.

By the time we got out of the airplane to have a look the oil had frozen on the landing gear so hard you could bounce a sledge hammer off it.

Anyhow a couple of days later we had a new oil cooler and changed it in our shirt sleeves under a parachute tent blown up by a Herman Nelson.

aaahh those were the days, there was still a working Radio Range station at Lac Labarge..I sure miss the Radio Range makes me weep just thinking about them.


Then there was the time we had an engine problem in Dawson City and after much checking by the company engineers they blessed it and gave the thumbs up and said it was safe to fly to Whitehorse.

When we turned around to take off low and behold if we haden't fogged in the runway while taxiing....waited until it cleared and down the runway we trundled and into the air we went.

At about a hundred feet there was this big fuckin bang as the cockpit filled with fog..the inverter had went tits up and the janitrol backfired turning all our windows white on the inside, no problem until just past the NDB in the turn up the valley the engine we were having trouble with quit....now we had a problem we were in a Douglas Racer on one engine in a valley and still below the mountain tops and couldn't see @#$! all outside because it was dark and our windows were iced up on the inside....in the next few minutes neither of us had time for any sexual thoughts because we were truly busy, not to mention terrified.....

[Doc]

I think there are a few variables. Type of airplane is one and the type of work your doing is another. On those real cold days you can generally climb up to a few thousand feet and have a temerature closer to minus 20. I would'nt consider doing any work that kept me down low. That being said our limits have been -40 on our C-185, C-206 and C-210 and I pushed to have them changed this winter (-35 point A to B) (-30 for low level survey work) I've flown the C-185 at -45 to -50 north of the tree line it's really not a good idea. If something does go wrong staying alive until help arrives is gonna be real tough.

I think you're nuts. Running around in a piston single at -50? You tired of life? Why would you even consider doing this?
Anything below -35 is a total waste of time and money. I've spent four hours getting a Racer fired up in -40, just to have it piss it's hydraulics all over the snow. All for pop and chips.
My absolute limit in any piston airplane would be -35. Have a problem with it? Keys are in it. Fill yer boots.

Whatever Doc, you were flying around in PAL at -65, through 4 ft of snow, on one engine and uphill both ways.... don't deny it.

Nope. Never even had a ride in PAL. Saw it a couple of times though. Pushing cold is just another form of pushing weather. You well might be able to get it running at -65, but why would you?

[Double Wasp]

Cat
I got a few of those "So there I was" stories myself. Looking back what a hell of a way to earn a living huh? Like to say I loved every minute of it, while I did enjoy most of it there were definitely some ass puckering moments along the way. I wouldn't trade in any of it though. The experience I gained has saved the same ass several times.
Nothing beats a Herman on a cold day. We used to preheat each engine for at least 40 min before the first start even after she was plugged in all night. You still got there 2 to 3 hours ahead of time cause if a breaker popped you could do chin ups on the prop. The only real thing that was handy was if you spilled some oil at that temp just leave it a few minutes then you could pick it up with your hands and put it back in the bucket.
We didn't use oil dilution, we were told that it washes the oil off the cylinder walls. If we went somewhere remote we brought our own gas powered herman with us, with an engineer for it to keep warm. Saved our skin several times.
DW

[Cat Driver]

Double Wasp, we could use up all Avcanadas bandwidth if we started relating all the problems we had during our career flying and wrenching aircraft in the north.

Sitting here thinking about that night even I don't believe how lucky we were, when we got to Whitehorse the weather had done what it does at low temps at that airport...zero zero in ice fog.

Thank Christ I had good teachers when I first started flying one of which forced me to practice zero zero landings until it was no big deal.

I had been flying out of Whitehorse all winter in that DC3, it was bright yellow with prop spinners on it, anyhow I had done some practice approaches using the radar altimeter as a primary flare aid and knew that there was a dip just before the runway so that was when to flare..had the FO read the radar altimeter as we got near the runway and when he called the dip I started to flare.

Thank Christ the approach lights and runway lights were lighting up the fog to tell us we were at the runway.....anyhow the fuckin thing made contact with the runway just like I could see where the runway was and I pounded on the brakes as hard as I dared and came to a stop still on the runway...had a devil of a time taxiing in.

Edmonton was sure happy when FSS called and said the 3 was on the runway somewhere, as they knew we were fucked on one engine with no other alternate we could reach.

The Airport Chalet made a lot of money that night selling us escape juice...

...aaahh the good old days.

[oldtimer]

I used to fly the old Norseman in -40 weather when I was young and stupid but our old chief pilot always watched over us so we stayed out of trouble..But one big concern in those days were passengers coming up from the south with stylish but impracticle clothing. The CP would always take those people off to one side and tell them that the pilots boots, parka, mitts and scarves belonged to the pilot and would not be shared.

[xsbank]

My first corporate job was on a Racer and we shut down at -40. I was supposed to be the FO but I spent so much time under an engine tent handing wrenches about and washing parts that I looked like a Douglas accessory. I think I could still do a creditable job of changing a jug and I was just a cheesy pilot!

My favourite was start-up - I used to take off the wing covers, take the electric heaters out of the cowlings then hook the right engine cover over the prop and walk it off (already walked 12 blades). As soon as it was clear the other pilot would start the right engine. I would drag the cover into the hangar and start pulling the left one. One lovely day the right engine started to cough and the captain took a stab at the primer. Well, he hit the left starter instead, picked me and the engine tent up and tossed us both ass over teakettle into an oily pile of snow! I grew a bruise that started at my knee and went straight up my chest and just missed me fiz. I was so mad I destroyed a barrel with a bung wrench before I realized how sore I was. I always wondered how he could get the wrong switch and turn it the wrong way....

Went home. When that job finished I refused to be a copilot for oh, 20 years after that. Now I only fly stuff you can get sucked into but I sure miss the Racer!

[C-FKLY]

Well, he hit the left starter instead, picked me and the engine tent up and tossed us both ass over teakettle into an oily pile of snow! I grew a bruise that started at my knee and went straight up my chest and just missed me fiz.

Oh God. One one side that sounds excruciatingly painful. But on the other it sounds kinda fun

[Hedley]

Regardless of what any paper (or anyone here) says,
you are looking for trouble if you fly a piston at temps
lower than the "pour point" of the oil that's in it. As
pointed out above, it can congeal in the oil cooler,
which is far more serious than when it congeals in
the prop hub.

Also, at extremely low temps, the density of the air
is going to be so much below sea level, that your
engine is going to be producing far more than rated
power, with a very lean mixture - the same amount
of fuel is going into it, but a whole lot more oxygen is
going in. Incredibly high EGTs and CHTs. Not good
for the engine life!

Not many people here would think it would be wise
to put an aftermarket uncertified "dry" nitrous system
on their aircraft engine - without even bumping up
the fuel flow! - but they're doing exactly the same
thing when they fly at very cold temps.

Who here bumps up the fuel flow of their piston
engines for winter ops? (sounds of crickets).

Didn't think so.

[Cat Driver]

Who here bumps up the fuel flow of their piston
engines for winter ops? (sounds of crickets).

If you examine the insides of a carb on a Douglas Racer you will find a unit that looks like a small dome in there, it is called an AMC ( automatic mixture control. ), it's purpose is to ensure the engine is getting the correct mixture.

However you are correct Hedley, excessively cold temps. can be very hard on piston engines.


What is your opinion on oil dilution Hedley?

[Ballsssssss]

Regardless of what any paper (or anyone here) says,
you are looking for trouble if you fly a piston at temps
lower than the "pour point" of the oil that's in it. As
pointed out above, it can congeal in the oil cooler,
which is far more serious than when it congeals in
the prop hub.

Also, at extremely low temps, the density of the air
is going to be so much below sea level, that your
engine is going to be producing far more than rated
power, with a very lean mixture - the same amount
of fuel is going into it, but a whole lot more oxygen is
going in. Incredibly high EGTs and CHTs. Not good
for the engine life!

Not many people here would think it would be wise
to put an aftermarket uncertified "dry" nitrous system
on their aircraft engine - without even bumping up
the fuel flow! - but they're doing exactly the same
thing when they fly at very cold temps.

Who here bumps up the fuel flow of their piston
engines for winter ops? (sounds of crickets).

Didn't think so.

Fuel injection systems have a bellows to compensate for variations in ambient pressure (air density)... though some require small seasonal adjustments sometimes.

The type of oil you use will determine the clouding temperature of your oil. Synthetic will cloud at far lower temperatures than straight mineral... did the experiments in College. But that being said, if you use engine preheat and oil cooler shutters, your oil shouldn't reach the clouding point.

[hydraulic fluid]

I remember flying for Johnny Midgett and there was no such thing as a day that too cold to fly....if we could get it going we were going flying.Always used dilution on the -3/-2.The weather does not seem to get that cold very often anymore.Where I am now we use -40 for the piston twins(fixed gear),and -35 for the 185.Will not do any ski flying unless its above -30 and then I want a ski strip smoothed out.

[Hedley]

For winter ops, you want to use a semi-synthetic multigrade
such as Aeroshell 15w50, which IIRC has a pour point of -42C.

Not sure anyone uses straight synthetics in piston engines any
more, after the disastrous Mobil One fiasco a few years back -
apparently no one knew back then, that purely synthetic oils
didn't suspend lead very well, which resulted in all sorts of
blocked oil passages and engine failures at the most inopportune
moments.

And, not everyone has shutters on their oil coolers. I seem
to recall seeing the wreckage of an older C310 which has
the oil coolers right up front in the nacelle air intakes - and
sure enough, the oil had congealed in both coolers, resulting
in a double engine failure, and destruction of the airframe.

P.S. I really like fuel totalizers, and I use them to glance at the
fuel flows on takeoff, of the piston engine aircraft that I fly -
you can fly without oil pressure for a while, but you won't
fly very long without fuel flow. And they all flow exactly the
same on takeoff at WOT, summer and winter.

There is no paper for this, but it would probably be a good
idea to bump up the WOT fuel flow 10% for very cold temp
ops. Say on your 300hp Lycoming, which should be flowing
around 30 gph on takeoff, it would probably like around 33gph
during very cold temps, for the roughly 330hp it is producing
at WOT.

[MrWings]

It is best in these situations when the head engineer is calling the shots, not the CP. There are many cowboys out there that will go out flying no matter what. But when things start to break because of the cold, AME's get mad. They will usually shut it down before that starts happening on a regular basis.

[iflyforpie]

For winter ops, you want to use a semi-synthetic multigrade
such as Aeroshell 15w50, which IIRC has a pour point of -42C.

Not sure anyone uses straight synthetics in piston engines any
more, after the disastrous Mobil One fiasco a few years back -
apparently no one knew back then, that purely synthetic oils
didn't suspend lead very well, which resulted in all sorts of
blocked oil passages and engine failures at the most inopportune
moments.

I don't think they even make synthetics for aviation any more (other than turbines). Still a big no-no.

And, not everyone has shutters on their oil coolers. I seem
to recall seeing the wreckage of an older C310 which has
the oil coolers right up front in the nacelle air intakes - and
sure enough, the oil had congealed in both coolers, resulting
in a double engine failure, and destruction of the airframe.

Probably one of the reasons why Continenal O-470/-520/-550 have non-congealing oil coolers which will bypass the oil at low temps. Shouldn't be a problem any more.

P.S. I really like fuel totalizers, and I use them to glance at the
fuel flows on takeoff, of the piston engine aircraft that I fly -
you can fly without oil pressure for a while, but you won't
fly very long without fuel flow. And they all flow exactly the
same on takeoff at WOT, summer and winter.

There is no paper for this, but it would probably be a good
idea to bump up the WOT fuel flow 10% for very cold temp
ops. Say on your 300hp Lycoming, which should be flowing
around 30 gph on takeoff, it would probably like around 33gph
during very cold temps, for the roughly 330hp it is producing
at WOT.

For the engines that have the altitude on the fuel flow gauge, it should be at or below the DA for the field at WOT. It will automatically compensate for PA.

[Adiabatic]

1830's at -40C I can keep at about +40C for about a day, with double tents and a heater in the cowl, along with other heaters keeping the oils liquid and accessory case at about +30C. This would be after running it of course. The heaters will never be able to catch up and get those kind of temps if you were to plug in a frozen engine. If the airplane is running every day, say a sked, the engines never really see below 20C.
It takes forever with those Frost Fighters at -40 to heat anything up. Just wish I had my hands on a Herman.

I wouldn't feel up to flying around without GPS, VOR's, just beacons like my experienced co-drivers back in the day whilst it being -40C. How much fuel did I put in again?

Hats off to you fellers.

[Navajo-dude]

Why does the AIM have section 9.17.1 explaining how the "Altitude Correction Chart" was calculated with that wild formula for calculating cold temp corrections? Did David Phillips write this part?

Anyone?