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Discussion in 'Maintenance Bay' started by JOhnH, Dec 3, 2017.
When its that cold, why is your battery still in your aircraft ?
Winter days are short. I’ve watched weather bearing down that would have had me grounded for days if I waited. Aborting the preheat early and getting out if Dodge makes sense sometimes. No big deal.
My Odyssey battery works perfectly well in cold temps. Being a small battery it doesn’t have a lot of cranking time to fart around with in any temperature.
How do you pre-heat on a lonely field in the middle of Alabama on a Sunday morning?
Lots of geniuses on this board criticizing my question. Why do so many of you think you know more than the people that wrote my POH?
This forum used to be much better when it was less "Facebookish" and had more people that actually knew what they were talking about, aviation-wise.
And how many of you would buy an engine pre-heater when you only see cold weather once or twice every few years?
Depends on how important it is to get airborne on those isolated cold mornings. And access to electricity.
With electricity available, a $50 quartz room heater and some ducting can solve the problem. Or even a hair dryer. Even a trouble lamp and some blankets can warm things up a bit.
No electricity? How practical would a small generator be?
I relayed my experience and stated that I used what is a low cost, easy to assemble, lightweight heater. You don't want to use one that is your business. Am I a genius? Did I criticize your question? Maybe I missed it but I didn't notice anyone criticizing you or your question. Perhaps you would be well served to simply follow what is written in your POH.
If a guy is convinced he knows all there is to know on a topic, why does he ask the question on an internet forum?
My POH instructs me to use oil dilution prior to shutting down if I expect a cold start. You know, pour fuel into the crankcase to literally thin the oil with gasoline. The things those really smart guys wrote in the POH, huh? My 1975 airplane had the silly oil dilution system removed very early in its life. Just because an old POH says it doesn’t always make it the best course of action.
If you plan to fly where temperatures are cooler than your normal? The single best thing you should do in preparation is to change oil to a grade that suits the operating temperatures. Current oil grade information should be easy to get from your engine manufacturer. If temps fall below 10* for a (typical) Lycoming or 20* for a Continental the engine manufactures will also prescribe pre heating prior to engine start.
Because it is that cold much of the time in northern regions and flying goes on anyway. And without crawling in the baggage compartment and removing/replacing the battery before/after every flight. I flew a C185 and Bellanca Scout on skiis for decades in Alaska; I removed batteries when they stopped taking a charge, otherwise I left them alone. It worked fine.
That might be true and apply to me, IF I thought I knew all there is about this. But I know I don't know much, so I read the POH. I still had a question about what it recommended, so I asked.
Your suggestion to change oil types for this one trip is valid.
But I asked WHY the POH said to rotate the prop in the opposite direction.
I think Eddie B was the only one that actually tried to answer my question.
Not sure if this has been mentioned upthread, but...
One other method is to drain the engine oil into a container and take it home, keep it in a warm place and pour it back in when ready to fly.
This can range from very easy (a ROTAX with a quick drain and only 3 qts of oil) to pretty difficult and messy (larger engine with no quick drain).
Just a thought.
Buy the proper pre-heater, When you know your are going to need the equipment, carry it.
I know several owners that carry a Honda generator, and a preheater.
I thought the opposite direction propping question was covered pretty well, so I didn't address it. It is less likely to get an inadvertent engine start.
But I assumed you were mostly interested in effective starting procedures for colder conditions, which is what I, and a few others were sharing our experiences about. I was trying to be helpful. I guess, to you, it was not useful info.
To you and all the others that tried to be helpful,
I apologize for snapping at you all.
I just thought that I made it clear that cold starting is a very rare event for me, so I am not going to buy generators or engine heaters. I just wanted to know why the POH said to turn the prop backwards, and what dangers might follow turning it the wrong way.
Now HOT starts are another issue, and I would be willing to spend a few AMUs if necessary for the best solution to that problem.
Do you take the battery out of your car that lives outside when it's that cold?
Most of us that live in the frozen north have had battery heaters at some point in our histories. AGM batteries make that unnecessary in modern times. On the other hand, I’m fixin to add oil cooler heaters to my Reiff system to complete the total system approach to pre heating my plane. And I use mult vis oil, too.
I’m surprised nobody advised to OP to drain his oil and take it indoors to keep it warm. That’s a persistent myth that warm weather fliers like to keep alive.
my Jeep doesn't stay out side, and we very seldom get cold enough to worry about it.
Every PA-18 owner I know in super cold weather bring their oil and batteries in where it is warm.
Yes I know it requires minus 70 degrees to freeze a fully charged battery.
Picking up planes stored in unheated t-hangars for maintenance in winter was not uncommon for me. Mostly, the owners didn't have them plugged in so after staring I let them idle for about five minutes to be sure oil was circulating and the pressure was in the green.
Hot starts on TCM engines were a piece of cake for me. Give the engine some fuel, push the throttle to wide open, start cranking while slowly retarding the throttle and when the mixture is right they start right up but you have to be quick to pull it back to idle when they do.
Injected Lycomings are a different ball game. It seems a teaspoon of fuel is enough to flood them when hot.
My Friend at Denali does, so do the two owners at Fairbanks.
Why? Don't they have pre-heaters?
I agree. This myth comes from bush flying exploits in the 1920's and 30's (maybe 40's and 50's, too) with pilots parking beside a tiny cabin on a lake at 30 below. Those guys didn't have red dragon heaters, high quality engine covers, multi-vis oil, or electric starters. The only heat source was the wood stove in the cabin. They pretty much had to drop the oil and take it inside by the stove.
... in my years of winter flying in Alaska, I never saw it done.
If investing in some ground equipment is not in the cards for the OP, then maybe just leave the plane parked until it is within normal operating ambient temps. Is the "mission" that critical? Or is investing in a good engine tent and even an interior car heater too much? They are the minimum equipment in southern Canada.
Yes, investing in special gear is not in the cards for something that will only be used a few times ever. Neither is carrying around the extra weight of extension cords, heaters or generators. If I lived in the far north, like North Carolina, I might consider it.
Leaving the plane sit in the sun until it is warm enough is something I have done, and will do again.
But what is wrong with following the POH recommendations, and what is wrong with asking a question about why it recommends that?
I did have an engine heater in my 172. It was always a pain and I gladly trashed it when my engine exploded at 1000 ft, while 4 miles from an airport and over the ocean and I had to replace the engine after landing on US 100.
From TCM Engine Tips Guide:
Thank you. That was very helpful.
I don't expect the weather to get below 20, and it should only be in the low 20s at night. And we have arranged to keep the plane in a hangar, even though I didn't know wind chill affected metal. At least I hope the hangar will keep ice from forming, since it might rain, or even snow.
I will also be keeping an eye on temps and icing at altitude too.
Preheating is a way of life here in Western Canada. If it gets close to 0C at night, the engine tent and heaters get used. My friend has a Cherokee with a full tanis system (cylinders and oil sump). I told him to use it as much as possible - cheap preventative maintenance.
If the OP is ok with the wear and tear he will be causing by not preheating, that is his decision.
As far as turning the engine backwards, that is probably a check to ensure that the engine's guts are able to rotate. No pre-heat + not being able to be rotated = $$$$!
Cold oil gets thick, and one of the biggest risks is that the pump won't be able to suck it out of the sump fast enough to keep the engine happy. Think really thick milkshake, the sort that's easier to eat than drink. I'm sure most of you can identify with that.
I used to prepare for an aircraft systems class by taking several grades of oil: W80 (SAE 40), W100 (SAE 50), and 15W50 (SAE 15-50). I would have a bottle of each on the desk, another of each in the fridge freezer, and a third of each simmering in hot water on the stove. All done in the student lounge. The students recognized the usual viscosity when I poured 15W50 or W100 at room temp, saw that the oils were all much runnier at 212°F (the 15W50 less so), and then were shocked when I tried to pour the cold ones out of the freezer. The 15W50 was thicker, W80 didn't want to move too fast, and W100 was like molasses: barely liquid. That freezer was at -10°C, around +14°F. I'd ask them just how much oil that pump would be able to suck from the sump at low temps, giving them the milkshake scenario, and they readily understood why preheating (or a heated hangar) was important. These engines use oil that's far thicker than the typical automobile uses now, so comparisons with cold-starting your car are irrelevant, and most people just don't realize how much oil viscosity changes with temperature. It's huge. If the pump can't suck it up, it can't push it to where it needs to go.
see if this works:
FWIW - The engine manufacturers seem to have established an upper viscosity limit of about 1500 SSU for starting.
Rats - it didn't. This was a chart of SSU viscosity of 4 common aviation oils vs temperature taken from an article I wrote for the Dec '86 "Sport Aviation".
I had a preheater when I was in a cold hangar. Now my hangar is heated (and I live in a much warmer climate).
I still remember a few years ago when I had left my plane at IAD overnight once for convenience (I lived right next to Dulles and had for years based it there, but had moved to a hangar at CJR 35 miles down the road). I called the line guys late in the evening and asked if it was possible that they could either pull my plane into their hangar or at least move it close to the building and plug in the Tannis heater. I came out for an early departure the next morning and found it in the middle of their hangar with the block heater going. Yeah, I left the guy a $20 tip.
But coincidentally I did buy a block heater and then moved to Mexico the next fall. :-(
Could there be microscopic ice crystals in the oil?
Or could that little bit of friction cause a slight change in the oil viscosity at the bearings?
Is that another way of saying it may prevent accidental engine starts?
I always figured there was frosty oil clinging to the cylinder walls. There's frost everywhere else when it's cold. Inside the engine would look like a frozen-over greenhouse.
Why'd you ask the question to begin with?
I wondered what the technical reason for turning the prop backwards was, and how much damage it could do if I turned it the normal direction. Last time I did that, I turned the prop in the normal direction, and nothing bad happened, and the engine started easily.
I feel like everyone thinks I am a jerk for asking why the POH recommends turning the prop backwards. I don't mean to be, but I thought it would be a simple question.
I figure the slow rotation smears a coat of oil on the rotating parts that take the reciprocating loads. Turning it backwards reduces the chance of a hot mag lighting the thing off...
It was a simple question and the answer is equally simple. The engine could fire and bite you in the normal direction, which is why the POH tells you to turn it backward.
Sure, nothing bad happened when you turned it in the normal direction. But that's no guarantee that it won't get you next time, or the time after that. Keep it up and your chances of getting maimed or killed go up, same as the guy who persists in buzzing his friends's houses.
On the other hand, you are unlikely to be maimed while propping in the normal direction as long as you treat the engine as if it will start on every pull. Many of us have started aircraft routinely that way, and for many years. The advantage is the oil pump and everything else is moving the right way.
JOhnH, Cleveland has a really nice little FBO and very helpful staff. Last time I Left my plane overnight, they put me in a brand new top notch set of hangars.
I’m in SE AL, and they are calling for some pretty nasty ice/winter mix tomorrow until early afternoon. I have a trip planned for tomorrow, but might have to put it off till Saturday AM.