Cold starts
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Cold starts
Hi all,
I'd be grateful for your wisdom on cold starts, please?
Specifically, on a 172.
I've been told to turn the prop by hand (about 10 turns) as part of the pre-flight, to get the engine to start more easily in this very cold weather.
I think I understood this has something to do with evacuating (old, viscous) oil from the cylinders? Is that right, and just how does this work, exactly?
Also, is it dangerous? No, I've been told, as long as the mixture is fully set to lean.
Sorry if those are dumb questions, but I'd like to hear your thoughts/explanations.
I'd be grateful for your wisdom on cold starts, please?
Specifically, on a 172.I've been told to turn the prop by hand (about 10 turns) as part of the pre-flight, to get the engine to start more easily in this very cold weather.
I think I understood this has something to do with evacuating (old, viscous) oil from the cylinders? Is that right, and just how does this work, exactly?
Also, is it dangerous? No, I've been told, as long as the mixture is fully set to lean.
Sorry if those are dumb questions, but I'd like to hear your thoughts/explanations.
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Really, it would be wise to assure that the engine is warmed slowly and thoroughly before attempting to start it. This is best achieved with a plug in heater installed on the engine, and an engine blanket to insulate the engine while it warms. 2 to 3 hours should be the minimum plug in time before a start is attempted.
I am very reluctant to recommend the pulling the prop through first technique, because it can go really wrong. Mixture lean is no assurance that it will not start. Done with great care, and a correct technique, it can be helpful, but I treat it as a technique of desperation, not the "normal" way.
It's not "is it going to start cold?", but, is it well enough lubricated during the start? Cold oil gets thick, does not flow well, and thus lubricates poorly. Whether you pull it through by hand, or crank on the starter, you're still moving all the internal parts of the engine with less than ideal lubrication. The pistons/cylinders are really the most difficult to damage by cold starting, least of the worries, and the most easily replaced parts, if damage were to occur. In Lycoming engines, the camshaft and followers are particularly vulnerable to wear with poor lubrication, even briefly.
I suggest that you make an effort to have the engine preheated by an accepted method, before starting it. If, when you check the oil before start, it is nice and free flowing, the engine is ready to start. If it's thick and gooey, avoid turning the engine over at all until it's warmed up. Do not direct fire into the cowls, I have seen this go very wrong too!
There are other "tricks" to warm an engine, but all more complicated, less effective, and not looked well upon in an airport environment.
I am very reluctant to recommend the pulling the prop through first technique, because it can go really wrong. Mixture lean is no assurance that it will not start. Done with great care, and a correct technique, it can be helpful, but I treat it as a technique of desperation, not the "normal" way.
It's not "is it going to start cold?", but, is it well enough lubricated during the start? Cold oil gets thick, does not flow well, and thus lubricates poorly. Whether you pull it through by hand, or crank on the starter, you're still moving all the internal parts of the engine with less than ideal lubrication. The pistons/cylinders are really the most difficult to damage by cold starting, least of the worries, and the most easily replaced parts, if damage were to occur. In Lycoming engines, the camshaft and followers are particularly vulnerable to wear with poor lubrication, even briefly.
I suggest that you make an effort to have the engine preheated by an accepted method, before starting it. If, when you check the oil before start, it is nice and free flowing, the engine is ready to start. If it's thick and gooey, avoid turning the engine over at all until it's warmed up. Do not direct fire into the cowls, I have seen this go very wrong too!
There are other "tricks" to warm an engine, but all more complicated, less effective, and not looked well upon in an airport environment.
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Don't know about pulling the prop through! Does it get that cold in France?
One thing I have learned is that if the POH says 'Six pumps on the primer for a cold start' don't just pull it out and plunge away. You have to wait for the thing to fill up. Our 28 is a sod for that, it takes ages for the primer to get going, you can feel the extra pressure when you try and prime. Once I sussed that then cold starts are a breeze.
One thing I have learned is that if the POH says 'Six pumps on the primer for a cold start' don't just pull it out and plunge away. You have to wait for the thing to fill up. Our 28 is a sod for that, it takes ages for the primer to get going, you can feel the extra pressure when you try and prime. Once I sussed that then cold starts are a breeze.
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IMHO the old business of turning the engine by the prop X times is just stuff dating back to the old radial engines, which suffered from a hydraulic lock via oil leaking into the bottom cylinders.
If an engine in that condition was started, it could split the cylinder(s) because oil is virtually incompressible.
Hand turning does nothing for the flat-4 and flat-6 engines.
The weak point on a Lyco is that the camshaft gets lubed only by spray once the engine is running, so you can get a lot of wear at that point. Hand turning will not achieve anything there.
Preheating is obviously never a bad thing but it needs to be a lot colder than this
Multigrade oil is a must for year-round operation, too.
I want to know more The biggest issue with preheaters is the electrical supply needed, and the heater not getting stolen
If an engine in that condition was started, it could split the cylinder(s) because oil is virtually incompressible.
Hand turning does nothing for the flat-4 and flat-6 engines.
The weak point on a Lyco is that the camshaft gets lubed only by spray once the engine is running, so you can get a lot of wear at that point. Hand turning will not achieve anything there.
Preheating is obviously never a bad thing but it needs to be a lot colder than this
Multigrade oil is a must for year-round operation, too.
There are other "tricks" to warm an engine, but all more complicated, less effective, and not looked well upon in an airport environment.
The biggest issue with preheaters is the electrical supply needed, and the heater not getting stolen
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Normally in France it would not get cold enough to warrant engine warmers unless you are in the mountains. It will help if the aircraft is hangared and if you can do some sort of engine pre warming that would be good. Pulling the prop through may help slightly, but probably not a lot -IIRC this mainly came from older engines with cylinders at the bottom of the engine - especially radial or rotary engines. Another thing to watch out for is if you have electric flaps and the checklist has you running them up and down before start - leave it until after starting the engine, especially if the battery is slightly tired, cold weather is not great for batteries and anything you can do to help that is a benefit.
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Affordable heating for France.
Edit:
That's very true. Cold weather really kills batteries that are left idle for even a few weeks and I don't think the 172 charges very well on the ground either at 1200 rpm.
Edit:
Another thing to watch out for is if you have electric flaps and the checklist has you running them up and down before start - leave it until after starting the engine, especially if the battery is slightly tired, cold weather is not great for batteries and anything you can do to help that is a benefit.
Specifically for the Rotax 4-strokers: I was taught to do rotate them by hand for several turns before EVERY flight, not just in cold weather, for several reasons:
-) circulate some oil around all of the engine
-) circulate enough oil for the reservoir to burp, so oil level can be correctly checked
-) pump some fuel into the carb
-) circulate some oil around all of the engine
-) circulate enough oil for the reservoir to burp, so oil level can be correctly checked
-) pump some fuel into the carb
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Here we go.
In cold weather, preheat is another factor that must be considered
prior to starting the engine. There are specific guidelines in Lycoming service instructions which establish when preheat should be used, but how much, or the method of preheat is generally left to the good judgment of the pilot or maintenance person doing the preheating. Use of the heated dip stick is not recommended by Lycoming, although most other methods are considered to be satisfactory. For most Lycoming models, preheat should be applied anytime temperatures are at 10˚ F or lower. The exception to this rule is the 76 series models that include the O-320-H, and the O/LO-360-E. These engines should be preheated when temperatures are below 20˚ F. It is recommended that these guidelines be followed even when multi-viscosity oil is being used. In addition to hard starting, failure to preheat the entire engine and oil supply system as recommended may result in minor amounts of abnormal wear to internal engine parts, and eventually to reduced engine performance and shortened TBO time.
[my bold]
In cold weather, preheat is another factor that must be considered
prior to starting the engine. There are specific guidelines in Lycoming service instructions which establish when preheat should be used, but how much, or the method of preheat is generally left to the good judgment of the pilot or maintenance person doing the preheating. Use of the heated dip stick is not recommended by Lycoming, although most other methods are considered to be satisfactory. For most Lycoming models, preheat should be applied anytime temperatures are at 10˚ F or lower. The exception to this rule is the 76 series models that include the O-320-H, and the O/LO-360-E. These engines should be preheated when temperatures are below 20˚ F. It is recommended that these guidelines be followed even when multi-viscosity oil is being used. In addition to hard starting, failure to preheat the entire engine and oil supply system as recommended may result in minor amounts of abnormal wear to internal engine parts, and eventually to reduced engine performance and shortened TBO time.
[my bold]
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The Cessna 172M models I flew only primed two of the four cylinders and seemed to need more prime than usual when very cold. When it did start it would quickly stop again.
I would leave the primer out when starting. When the engine faltered I pushed the primer in and it would then usually keep running.
Pulling through after an initial prime should also help.
D.O.
I would leave the primer out when starting. When the engine faltered I pushed the primer in and it would then usually keep running.
Pulling through after an initial prime should also help.
D.O.
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Same experience with the 152s I've flown; found out about softly priming the coughing engine only recently. Mind you, below 25°F (and certainly below 20°F) I tend to spare the poor engine such a cold start, even though the planes are hangared and come to life without any issues after all (except for at least some Rotax-powered Katanas going on strike below 30°F).
Up until two winters ago we had a lot of problems starting our 0-200 and have no primer. Since then we have stuck to the following procedure and it has started instantly every time for the last two winters:
Place a fan heater under the cowl for at least 30 minutes (have a cup of coffee) Apart from slightly warming the oil this also warms the induction system. With the carburettor below the engine and a cold induction system, the fuel vapour tends to condense before it gets into the cylinders.
Remove fan heater and secure cowl.
Mixture to rich, fuel pump on and pump throttle six times (no primer)
manually turn propellor through 8 blades.
Pump throttle twice.
Start. It usually starts in less then one turn.
Place a fan heater under the cowl for at least 30 minutes (have a cup of coffee) Apart from slightly warming the oil this also warms the induction system. With the carburettor below the engine and a cold induction system, the fuel vapour tends to condense before it gets into the cylinders.
Remove fan heater and secure cowl.
Mixture to rich, fuel pump on and pump throttle six times (no primer)
manually turn propellor through 8 blades.
Pump throttle twice.
Start. It usually starts in less then one turn.
The Cessna 172M models I flew only primed two of the four cylinders and seemed to need more prime than usual when very cold. When it did start it would quickly stop again.
I would leave the primer out when starting. When the engine faltered I pushed the primer in and it would then usually keep running.
Pulling through after an initial prime should also help.
D.O.
I would leave the primer out when starting. When the engine faltered I pushed the primer in and it would then usually keep running.
Pulling through after an initial prime should also help.
D.O.
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We spent more than an hour this morning trying to get the Cirrus Major started on Auster Wobbler's J5G, but she just didn't want to know.
It's normally a good starter, the battery had been charged so it's reluctance to fire could only have been due to the intense cold
It's normally a good starter, the battery had been charged so it's reluctance to fire could only have been due to the intense cold
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more than an hour this morning trying to get the Cirrus Major started
If you've run a charged battery flat trying to start, the starter motor is going to need the same time to cool, as the battery will need to recharge.