Let’s talk pre-heating

[Ben2k9]

What are you all doing for pre-heating on the CT these days?  I currently have my CT in a hangar with no power supply, so trying to figure out some options for cold weather operations. 
 

 

[SportFlyer1]

Here in Arizona I do my pre-cooling with a portable AC ..... oh wait, that's not what we're talking about, lol.

[AGLyme]

I flew last winter in Connecticut... I merely plugged in the battery charger that came with the plane.  The Rotax starts right up 

[GrassStripFlyBoy]

Hey Ben,

Not having power certainly limits options.  I had my first 150 tied down outside a few years, and as crazy as this sounds, would hook a drier vent flexible tube up to the car dash center panel and route it out the window direct to the plane cowl parked 90 degrees to the prop.  My partner in plane and I both used it, and surprised us how well it worked, we'd give it 20 minutes or so and engine always started right up - but that was an old 0-200 without the oil temp / liquid cooling aspects of a 912.  I'd suggest a propane or kerosene forced air unit, with sufficient distance from airplane, I saw one with a 12V car battery and blower vent that was stand alone unit, on my local Craigslist for really cheap as used item.  Hunt around the web on this topic and you'll find some stand alone options.  I love winter ops, crisp smooth air and no humidity, CAVU days are few and far between - but no bugs to clean off after the flight, a great season.

[sandpiper]

It might not take long at +15F to get the cylinders warm enough to start. However, it takes a lot longer to heat up that glob of oil in the oil tank.

I don't know what temperature will be your cut off but at some point you will need to make sure the oil in the tank is properly warmed.

With the semi syn and full syn oils we are using I know this isn't as critical as if we had a lycoming or continental using AeroShell 65w but, still, something to keep in mind.

[MEH]

In the words of Mike Busch, "Its the clearance, Clarance."  The increased viscosity of the oil has little to do with cold start wear on the engine, its that the tight clearances get even smaller when things are cold.  Here are a few snippets from an article of his from AOPA Pilot magazine. 

A common misconception is that cold starts are bad for engines because the engine oil is thick and viscous and doesn’t flow well. Since it takes longer for oil pressure to come up when the oil is cold, the engine sustains excess wear in the early seconds after start because of inadequate lubrication.

While this may be true of single-weight oils, it’s not true of the modern multiviscosity oils that are universally used today for cold-weather operations. Multivis oils such as 15W-50 or 20W-50 flow extremely well even at 0 degrees F (minus 18 degrees C) or less. Pilots who use multivis oils see their oil pressure come up quickly after starting in cold weather, and figure that everything’s OK. Wrong.

It’s the clearance, Clarence

Actually, the biggest culprit in cold-start damage is that our engines are made of dissimilar metals with different expansion coefficients. The crankcase, pistons, and cylinder heads are made from aluminum alloy, while the crankshaft, connecting rods, piston pins, and cylinder barrels are made from steel. Aluminum expands about twice as much as steel when heated, and contracts about twice as much when cooled.

Consider your steel crankshaft, which is suspended by thin bearing shells supported by a cast aluminum crankcase. As the engine gets colder, all its parts shrink in size, but the aluminum crankcase shrinks twice as much as the steel crankshaft running through it. As temperature goes down, so does the clearance between the bearing shells and the crankshaft—and that clearance is where the oil goes to lubricate the bearings and prevent metal-to-metal contact. If there’s not enough clearance, then there’s no room for the oil, regardless of oil pressure.

Consider what happens to your pistons and cylinders when you cold start an engine. Here, instead of a steel crank inside an aluminum case, we have an aluminum piston inside of a steel cylinder barrel. The clearance situation is reversed: Piston-to-cylinder fit is loose when the engine is cold, and tightens up as the engine comes up to full operating temperature.

The piston has relatively low thermal mass, so it heats up quickly. The cylinder is massive and bristles with cooling fins bathed in frigid air, so it warms up slowly. The result is that the piston expands to its full operating dimension quickly after start, while the cylinder takes a lot more time to expand to its full operating diameter. The fit of the piston in the cylinder bore may become tighter than normal shortly after cold-starting when the piston has come up to temperature, but the cylinder still has a way to go. If it’s cold enough, the piston-to-cylinder clearance can go to zero, resulting in metal-to-metal scuffing between the piston and cylinder barrel.

[SlingPilot]

I installed Reiff’s heat system for the Rotax. A heating element band around the oil tank and a heat pad, epoxied to the bottom of the engine. The pigtail under the cowl is plugged into a Switchbox Control, remote cellular (T Mobile) switch. You text it on and off, cost about 10 cents a text. You can call it for free, but it won’t give you a confirmation text reply when you call it. 
 

ive used it twice in the past 2 weeks and I’m very satisfied. Of course, you need electricity with this setup. Previously I used force air heat, plugged the unit I;to my cars cig lighter for power. 

[FlyingMonkey]

I use a harbor freight heat gun on the low setting and a bit of high temp SCEET tube.    I put the tube in under the bottom rear opening of the cowling. also stick a hair dryer in the round cowling duct if it’s really cold.  I also wrap a blanket over the cowl and covering the radiator opening.  This usually gets things quite warm under the cowling in 45-60min.

[Ben2k9]

I'm thinking maybe this plus some ducting piped into the engine compartment would do the trick as a temporary solution until I get a hangar with electricity.  

 

[Tom Baker]

That takes an electrical plug in. 

[Ben2k9]

ahh yes...the fan.  maybe a little generator or battery pack.  How quickly do you think something like this could get temps up to a reasonable starting temperature?  

[Tom Baker]

I think a Tanis heater, and a small Honda or Yamaha generator to power it. That is until you get a hangar with power.

The Tanis heater for a 912 is a pretty straight forward installation, but you must follow the directions, especially when it says to run a tap through the holes. Make sure you have plenty of lubrication and go slow backing up often. I hand threaded a Tanis probe into a 912 cylinder head once, and it galled and got stuck. Yes, just hand tight. I twisted it off. Had to drill it out, then run a tap through to clean the threads. Twisted the tap off. Was able to remove the broken tap with a Walton tap extractor (I didn't know such things existed). It was a very slow process, but I eventually was able to properly install the Tanis probe on that cylinder.

[Ben2k9]

the trouble with Tanis/generator for this setup, is it says it takes 6 hours of preheating.  The hangar is too far to drive there to turn it on.  If I could do something that could somehow preheat in 30-60 minutes, then that would be more workable.  Wonder if the forced air propane heater solution would heat quicker... 

[AGLyme]

Does the Rotax require pre heating (as much as the other air cooled aero engines) ?  The Rotax legacy is snowmobile operations.  Never had an issue or slow turn starting in cold weather.  The one benefit is that the warmup period is shortened.

[Tom Baker]

2 hours ago, Ben2k9 said:

the trouble with Tanis/generator for this setup, is it says it takes 6 hours of preheating.  The hangar is too far to drive there to turn it on.  If I could do something that could somehow preheat in 30-60 minutes, then that would be more workable.  Wonder if the forced air propane heater solution would heat quicker... 

While they say 6 hours to get the full benefit. You will have a significant temperature increase in 1 hour.

[Tom Baker]

1 hour ago, AGLyme said:

Does the Rotax require pre heating (as much as the other air cooled aero engines) ?  The Rotax legacy is snowmobile operations.  Never had an issue or slow turn starting in cold weather.  The one benefit is that the warmup period is shortened.

I think the fuel injected engines start better in the cold. The carbureted engines don't like the cold so much. Many won't start when the temps are below freezing.

[AGLyme]

Got it, thank you Tom... 

[Ben2k9]

Reiff heater about a third of the cost of Tanis. Does anyone have any reason to think it would not do the job good enough?

[andyb]

1 hour ago, Tom Baker said:

I think the fuel injected engines start better in the cold. The carbureted engines don't like the cold so much. Many won't start when the temps are below freezing.

As one data point, I have the Tanis, in the fuel injected engine.  Actually installed by Tom.  Works beautifully.  Without the heater, if it was below freezing, the engine seemed very unhappy for the first few minutes after starting.

Andy

[John Vance]

4 hours ago, Ben2k9 said:

the trouble with Tanis/generator for this setup, is it says it takes 6 hours of preheating.  The hangar is too far to drive there to turn it on.  If I could do something that could somehow preheat in 30-60 minutes, then that would be more workable.  Wonder if the forced air propane heater solution would heat quicker... 

Maybe a power supply timer would work with the Tanis heater, depending on the amperage required.  You can get digital versions that can be programmed to turn on/off at least 7 days out. You’d have to set it to preheat for the next flight before you leave the hangar, so it’s not ideal, but it could be worth a look.

[Tom Baker]

1 hour ago, Ben2k9 said:

Reiff heater about a third of the cost of Tanis. Does anyone have any reason to think it would not do the job good enough?

I don't like the band around the oil tank. I have seen the carbon fiber holder for the oil tank scorched by the Reiff heating band.

[DHeal]

Back in the day flying students in frigid upstate NY we relied on Red Dragon propane-fired aircraft heaters.  They were portable, 12-volt battery-operated space heaters designed specifically for aircraft pre-heat use.  I have heard that they are no longer manufactured (?) but perhaps you can find a used one.  The backcountrypilot.org forum generally has a lot of information regarding engine pre-heating.

ps -- MEH's post regarding "clearances" is spot on.  You can get most any cold engine to "start" but what long-term internal damage have you inflicted in the process?

[Ben2k9]

16 hours ago, Tom Baker said:

I don't like the band around the oil tank. I have seen the carbon fiber holder for the oil tank scorched by the Reiff heating band.

Did they leave it on for long periods of time or something?

 

[Buckaroo]

I love this little heater!

[Tom Baker]

53 minutes ago, Ben2k9 said:

Did they leave it on for long periods of time or something?

 

I don't know. The Reiff strip clamp gets pretty hot ,and and it is captured between the tank and carbon fiber holder. The Tanis pad goes on the tank in the exposed area towards the engine compartment, so it is not touching the carbon fiber.