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Winter operations / lowest temperature for starting / preheating methods (merged)

Ibra wrote:

Adding to the myths, does pointing an aircraft into wind make it start easily?

Can you start the engine by blowing at the propeller instead of hand turning it?

Yes, if you can blow hard enough to maintain a bit over 110kts (that number relates to a C152, other types may vary).

Fly safely
Various UK. Operate throughout Europe and Middle East, United Kingdom

dejwu wrote:

Can you start the engine by blowing at the propeller instead of hand turning it?

I don’t think that was the main benefit as the required speed will be along what Dave_Philipps mentioned, 30kts wind will not make that much difference while hand propping? Going to the gym does

Say on a 1m prop, 100% engine-prop-speed efficiency where the mags click at 1000rpm, you will need roughly 105kts (188km/h = 1000rpm*100%*1m*3.14*60), of course C172 mags may click at 500rpm but cruise prop efficiency is roughly 70%…

Besides the RPM, I don’t think 30kts wind straight into a SEP air intakes will give that much uplift in manifold pressure, the max will be 90mb or 2.5 inch of mercury

But that wind may make a huge difference on mixture as does a simple carburator choke?

Last Edited by Ibra at 18 Feb 12:24
ESSEX, United Kingdom

With another winter here, I came across this from Reiff preheaters.

They use mostly these bands which go around the non-finned part of the cylinders

but they also do a version which is quite similar to my “power resistor” idea above

The above one is only $200. It puts 200W into the engine. Based on my numbers “above” (112kJ/K) that will heat the engine up initially at around 6 degC per hour. Not sure if I got that calculation right…

If it wasn’t for the “hangar politics” I would buy this immediately.

Administrator
Shoreham EGKA, United Kingdom

We have this one and are really happy. I installed it myself under the supervision of my A&P. There is a band around each cylinder and two of the “power resistors” glued to the engine (with high temp epoxy). In total it puts 400W into the engine. We have installed a switch which can be operated by a text message via the phone. I’d say on a cold day it takes about 6 hours to throughly warm the engine. When we switch it on before we go to bed, we see about 75F the next morning, even on very cold days (however, Mannheim is not a very cold place).

EDFM (Mannheim), Germany

I use two regular “home electric heaters” 2KW each for my Seneca. In non heated hangar it takes one full hour to raise the engines from +1C to +24C. I take a temp reading by inserting a 20cm wire probe in the engine oil tube.
I have slim heaters and position them inside the cowling (through a cowflap) they blow directly into an oil sump and as the heat goes upwards – all cylinders become warm as well (90-120F on EDM). I think that placing the heater at the bottom of the engine is much better because of the convection.
Now it becomes interesting:
My probe measures temp and humidity. I use engine dehumidifier made by myself. Very simple. Air pump, air filter, box with silcagel, and plastic pipes connected to both crancase vent pipes. The idea is to slightly pressurise engines with dry air, which pushes away the moisture.
It works. The probe reads about 30-40% humidity after short time. But when I plan to go flying, after disconnecting dehumidifier when the preheating starts – the humidity inside begins to rise! To about 95-99%!
I guess it is the moisture diluted in the oil (although it looks perfectly clean!) and gets released to the crancase.
So I am against a constant heating device as it can do more damage than good.
I the engine manual it even says somewhere that preheating for more than 24 hours can do severe corrosion attack. I agree with that.
In my opinion after flying the engine should be cooled down and connected to a dehumidifier as after flight it is usually 100% humidity.
The colder the engine is – the longer it takes the oil to flow off the components.
At least in my Seneca which is designed to fly high where the cooling is hard and when flying low it is constantly below 170F oil – even with oil cooler fully covered.
The problem however comes outstation – when no electrical power is available to preheat.
I am using W100Plus and prefer do preheat below plus 15C.

Poland

Raven wrote:

I guess it is the moisture diluted in the oil (although it looks perfectly clean!) and gets released to the crancase.

I think there was a test done once by tanis or reiff. I don’t remember which one. The test did not recommend engine heaters to be left on all the time without a dehumidifier. Exactly in line with your findings, the heating would release moisture from the oil and all that moisture ends up condensing on the cold parts like crankshaft, cylinder walls etc.

I have a “homebuilt” heater in my hangar. It blows warm air through the front landing gear doors. I leave the cowling plugs on and cover the cowling with an emergency blanket (space blanket), gold side facing outwards. The space blanket is incredibly effective in reflecting the heat back into the cowling. With a 2000w heater, it only takes about 45-60min to raise CHT from 0C to about 18-20C.I prefer heating everything uniformly inside the cowling with hot air than using cylinder head and oil pan bands.

The problem is when travelling. I am quite religious about pre-heating but there is hardly any chance to preheat when you are far away parked somewhere in small airfield.

Switzerland

“In my opinion after flying the engine should be cooled down and connected to a dehumidifier as after flight it is usually 100% humidity.”

I believe you can improve the situation a lot by opening the refill cap and let the hot oil breathe out the vapor while doing all post flight tasks…

...
EDM_, Germany

ch.ess wrote:

I believe you can improve the situation a lot by opening the refill cap and let the hot oil breathe out the vapor while doing all post flight tasks…

I do it every time! :)
I leave it open for an hour or sometimes more immediately after flying.
You can see the steam flowing up from the oil refill. There are water droplets on the inner side of the caps.
Does’t help. Still 100% when I return next day or even after one or two weeks of inactivity.
Dehumidifier is the only solution I can see to reduce big amount of water in the crancase.
Before flying one hour of preheat.

Poland

Definitely steam comes out, but if one leaves the plane like that, unattended, the dipstick might get stolen

Administrator
Shoreham EGKA, United Kingdom
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