Cold starts

[FlyingLapinou]

Hi all,

I'd be grateful for your wisdom on cold starts, please? :ok: 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.

[Pilot DAR]

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.

[thing]

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.

[peterh337]

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.

There are other "tricks" to warm an engine, but all more complicated, less effective, and not looked well upon in an airport environment.

I want to know more :) The biggest issue with preheaters is the electrical supply needed, and the heater not getting stolen :)

[foxmoth]

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.

[The500man]

Affordable heating (http://www.herman-nelson.com/itemInfo.cfm?itemID=675) for France. :)

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.

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.

[Jan Olieslagers]

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

[peterh337]

Here we go (http://www.lycoming.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf).

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]

[Jan Olieslagers]

anytime temperatures are at 10˚ F or lower

That's how many hectopascals??

[dont overfil]

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.

[Armchairflyer]

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).

[mary meagher]

Join the Navy and keep it in a heated hangar (!)

[pulse1]

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.

[Jan Olieslagers]

Join the Navy and keep it in a heated hangar they no more build hangars that big

[Big Pistons Forever]

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.

This works well for most engines. Part of the problem with is people do not follow the POH direction. Specifically underpriming the engine. On cold days up to 6 strokes of prime may be required. The normal procedures section of the POH has a section on cold weather operation.

[Echo Romeo]

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:(

[Pilot DAR]

more than an hour this morning trying to get the Cirrus Major started

I have no idea what kind of starter would be involved in this, so I don't have a comment relative to this event. However, in refering to the duty cylces of many common stater motors, "an hour" of trying to start an engine would equate to about 3 total minutes (appropriately separated by cooling periods). More than that and you're probably cooking the starter motor.

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.

[peterh337]

There is something very wrong with the fuel system, or the starting procedure, IMHO. The UK is not that cold. -5C probably, in the middle of the night.

[diesel addict]

minus 11° C here last night - three miles from Kemble.

[Katamarino]

Parts of Holland hit -20 last night. Happily the PA28 started quickly this morning for a great day's flying over the snow.

[Pilot DAR]

Okay, I'll play.... -1C here last night, plugged the plane in for three hours, it started perfectly, and oil temp was +16C upon startup. It has not yet been cold enough here this winter to need the winter baffles on!

[FlyingLapinou]

Thanks very much for all your helpful replies - now I know a bit more about why I've been asked to pull the prop through, and just what's going on engine-side when I do, which is what I was after :ok: Thanks for the bedside reading, Peter :)

Good tips on priming and use of electric flaps in cold weather, too... what I tend to do is lower the electric flaps for the pre-flight check but only retract them once I've started the engine. I may modify that and not touch them at all in very cold weather until after the engine is running.

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.


With all I've read about the need for extreme care when handling a prop, I have to admit this is very much uppermost in my mind, but the instructor is adamant (I've nagged him about it twice) that the engine can't start with mixture set to lean. Always assuming, of course, one remembers to check the mixture before touching the prop. :eek:

Technique? Nope, haven't been shown that...

[peterh337]

that the engine can't start with mixture set to lean

It isn't going to run for long enough to fly somewhere :) but it can definitely ignite and turn for a few revs, enough to chop somebody's head off, just on residual fuel left in the fuel system from a previous shutdown which was not done by mixture cutoff.

[Crash one]

that the engine can't start with mixture set to lean.

Assertions like that scare the **** out if me. Famous last words!
The only assertion like that, that I might believe, is, "The engine won't start with all 8 plugs out".

[thing]

what I tend to do is lower the electric flaps for the pre-flight check but only retract them once I've started the engine. I may modify that and not touch them at all in very cold weather until after the engine is run

How are you going to check the flap runners then? Genuine question.

just on residual fuel left in the fuel system from a previous shutdown which was not done by mixture cutoff.

Aren't all shudowns done with mixture cut off?

[Katamarino]

Aren't all shudowns done with mixture cut off?

They are supposed to be. If you don't know 100% that it was done properly by the previous guy, would you bet your life on it?

[thing]

No, it wasn't a rhetorical question, having only flown the usual suspects I wondered if other types of a/c had different shutdown procedures.

[Katamarino]

Fair point; some do I think, but I am pretty sure all Lyco and Conti are mixture-lean.

[mikehallam]

Rotax including the 80 & 100 & 115 h.p flat fours have kill switches but no lean cut & even if the start/ 'ignition key' is off or removed/not inserted - not mentioned yet above - it could still fire if these are not shut !
So do their very useful two strokes.
Rotating the prop at hand speed turns the engine's crankshaft some 2 1/2+ time faster & energises the spark coils etc.
There is somewhere a report of a well experienced UK pilot accidentally starting a Rotax that way.

As written above, never trust a prop. - it's best to think of it always 'live'.
And on a tail wheel a/c though the top arc where one grabs it is away from you the six-a-clock position is a lot closer to your knees.
BTW One handed, if propping for a start, is the normal way, your other arm held firmly behind your back. Always train yourself to access the cockpit ignition/throttle controls by going round the wing tip, never lean straight across to reach inside, even if it hasn't fired - or one day it'll be your final move

Hand cranking is never the less a very normal pre-flight procedure to check compressions and that it turns freely. Rotax require it at least on the 80 h.p. model as it uses the crankcase blow by to return oil to the separate tank. Then one can do a proper oil level check on pre-flight.

Pulling the a/c out is also normal by pulling with both hands on the prop. close to the hub.

mike hallam.

[TCU]

1. Follow the POH....so many variations on a theme out there that one must be specific with each type
2. But for me the key issue (which is also reflected in pretty much every POH i've ever seen) is don't be in a hurry to go flying....let the engine warm up properly and then some too

It certainly adds a few more clicks of the hobbs this time of year to get everything nicely settled, but the pleasure of cruising in that crisp winter air always makes it worth while

[austerwobbler]

Quote:
more than an hour this morning trying to get the Cirrus Major started
I have no idea what kind of starter would be involved in this, so I don't have a comment relative to this event. However, in refering to the duty cylces of many common stater motors, "an hour" of trying to start an engine would equate to about 3 total minutes (appropriately separated by cooling periods). More than that and you're probably cooking the starter motor.

Yes I was trying to start my Cirrus for a hour but I wasn't cranking for all that time ! And no i didn't totally flatten the battery, the petrol tractor that I use as a tug would not start either it was to cold as well, with hind sight I suppose I should have put a electric fan blower heater blowing in to the engine bay for a while as W100 oil is like syrup when below freezing !

Austerwobbler

[Pilot DAR]

A few points....

Mixture to idle cut off is the proper stopping technique for all Continental and Lycoming engines. However, the idle cutoff valve in the carb is as inprefect as many other aspects of the aircraft, and can still allow some fuel to seep past after the engine is stopped. Primers and acellerator pumps can leak too. A person who asserts that it is "safe to pull a prop through because the mixture is lean is wrong: It's "probably safer" at best. If you're going to turn a prop by hand, do so as if that motion will cause the engine to start, and the plane to move if not restrained. If you have not prepared for both those possiblities, don't turn the prop.

On an aircraft which is presented to you as being airworthy, operating the flaps and checking the condition of the tracks is a "nice to do" not a "gotta do". If conservation of electricity is important, leave the flaps alone, until the engine is warming up, and the battery charged. On a Cessna single, you have a good enough view up the slots in the flaps to see anything which does not belong there. If anything is undone and going to fall off (which has happened to me in a 180) very unlikely you're going to see it even with the flaps extended. After that, cycle them before flight to be sure they're working.

While we're talking about conserving electricity, remind yourself that the original red flashing beacon on a Cessna draws as much as 7 Amps, which is more than half what the flap motor draws. Beacon flashing away for minutes before you start, va the flap motor running for seconds... the beacon is going to draw more. Yes, I know it's stylish to flash the beacon to indicate that your's is the plane that's about to spring to life (you hope), but that's your real electriciy consumer - not the brief use of the flap motor. Consider breaking with tradition, and instead conducting an extra good look around before you start, and yelling "clear" as though you really mean it! LED lights will make this a non issue....

I had the luxury of learning on a fleet of very well maintained Cessnas, which were always in working order, and warmed up before the first start of the day. A lot of things were taken for granted back then. It gives me shudders to think of the cold starts I did "out in the real world" before I learned how harmful it is to the engine!

[thing]

As usual DAR, a concise and very informative post Thank you.

Have you considered writing a book, maybe 'Things they don't teach you at flight school'?

[good finish]

Mikehallam
Interesting post.
I have been told by 2 rotax agents it is impossible to start a rotax by hand swinging the prop?
Regards

[gasax]

Some small Continentals O-200 and smaller have Stomberg carbs and they have no ICO. So this technique with those engines will result in surprises!

[Crash one]

Some small Continentals O-200 and smaller have Stomberg carbs and they have no ICO. So this technique with those engines will result in surprises!

Mine had one of those, since replaced with a Marvel Shebler with a real mixture control, I still shut down with the mag switches, at least it "proves" they work. It is my a/c so no-one else goes near it except the farm owner & he has enough sense to not "poke the cat".

[foxmoth]

No, it wasn't a rhetorical question, having only flown the usual suspects I wondered if other types of a/c had different shutdown procedures.


Certainly many older aircraft do not have a mixture cut off system, aircraft like the Tiger Moth are stopped by turning the mags off.

[Echo Romeo]

Certainly many older aircraft do not have a mixture cut off system, aircraft like the Tiger Moth are stopped by turning the mags off.

Austers too.

[gowaz]

O200 in J3cub today, nice and cold outside, mags off, prop rotated a couple of times, backwards. 4 full primes left mag on and handswing. Started first swing. Hop in and both mags on, apply a little throttle 600-700rpm. If it cuts out before I get in. Re-prime and go through same drill, slowly and carefully.

No mixture so always fixed.

Shut down: mags off, with throttle idle.

The only difference between my cold start and my winter start is that during summer I can get away with no primes and she starts after two blades.

Respect the prop.

Don't trust the mag switch, good to know it works on shut down,
If you shut down by closing fuel lever you will be surprised how long it continues to run for!

[MichaelJP59]

Any tips for starting a Rotax 912/914 in sub-zero conditions? My 914 is always fairly reluctant to start in those conditions and needs a tip-top battery to do so, not something I can guarantee in winter where weather can sometimes mean a 2+ week pause between flights. Is a fan heater to the cowling a good solution?

[gasax]

I have to say that after being gurgled my 912S starts near instantly with a bit of choke. If yours does not then the fan heater does really work. at -10 it was the only way I could get my old Gipsy going - it would fire but the oil was so viscous it just would not 'catch'. 20 to 30 minutes with the fan and there were no issues.

[Ultra long hauler]

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

Spot on!
That´s how I´ve been taught……….

###Ultra Long Hauler###

[Captain Smithy]

Interesting discussion and plenty of good info here. Just wanted to chuck in my tuppence, for all it's worth, which isn't much, but nonetheless.

Cold starts can be frustrating but if done properly are no worry. Someone earlier commented that we don't get exceptionally cold temps here in the UK, and that our "cold spell" lows of say -5C aren't that low. The truth is, as most car owners will know (especially those of us who have operated older ones), anything approaching freezing and below is enough to reduce the charge in the battery and thicken up the oil enough to make starting problematic.

A couple of winters back during a chilly spell not unlike the one we've just had, I took out a Tomahawk for a flight on a lovely clear crisp morning teh week before Christmas. the aircraft had sat unused for two weeks due to bad Wx and the temp had not been above -5C over the whole of that period, and the ambient that morning was at around about that temp. I knew that the battery would probably be flat as a pancake and the oil not exactly free-flowing. Gingerly pulled the prop thru a couple of rotations, could tell the sump was like jelly. Thought I'd give it a shot anyway but wasn't surprised when the prop lazily slopped round once, stopped, then twice, and stopped again. Gave up right there as I didn't want to knacker the starter and besides it was clear this lump wasn't going to want to wake up right away.

Ended up getting out the generator & heater & stuck it on, meanwhile removed the battery and trudged back to the club, stuck it on the trickle charger for an hour. After then, 6 primes and two attempts got it started nicely.

Have found through experience that leaving anything up to 30 seconds after priming before turning the starter gives enough time for the primer nozzles to fill. Each aircraft seems different but leaving the primer out while starting & pushing in when the engine fires seems to work every time.

At the end of the day flying's only as difficult as you make it, as with all else preparation's the key...

Smithy

[ChampChump]

Interesting thread. The Champ was reluctant recently in severe cold until it was suggesting priming each cylinder in turn. This, plus leaving the primer out while starting & pushing in when the engine fires which had also been suggested in the same manner as Cap'n Smithy's post, did the trick and today she started beautifully.

And as today was the first time I've ever flown off a decent covering of snow, it was especially rewarding. :ok: