Lycoming O-540 cold start

[guillaume78150]

-20°temp on the KPNA airport early morning today.
I let the engine heater three days ago, so the oil temp was ok. Fuel pump on, I primed the engine 6 times.
I had to crank several times before the engine starts. Is it the right procedure when cold ?

[Scott - A2A]

Yes, as long as you have the engine heater installed, the temps should be good. The engine will reach it's max temp after about 8 hrs or so on the heater. But it may still be on the cold side in extreme temps, so extra cranking would be normal. 6 strokes of the primer is about right if the engine is just above freezing (could prime a bit more if in doubt).

Scott.

[guillaume78150]

Thanks Scott. Which brings the question how to start the engine without engine heater. I worry about the battery...

[Mustang]

I've yet to face such temperatures, but will eventually on my round-the-world trip. I never considered all the 'real time' aspects of this. The heater will, ideally, need engaging several hours before flying, real time? (Or leaving on after landing, before quitting the sim) Fascinating

I did notice how the Comanche's oil will still be warm if you shut down, quit FSX then immediately reload another flight, yet when I come back to the aircraft after a longer period of time the oil is seemingly at ambient temperature. I hadn't really thought about it but realise it must be based on the passage of real time since the last flight.

One question: When I load up the Comanche, if enough time has passed since the last flight, I expect the oil will always be at ambient temperature. With Active Sky Next loading in the weather just after the sim loads as far as I recall, will the oil be at standard-day ambient, or the temperature that ASN loads in? My default flight presumably has the "clear skies" theme with the ambient at 15-20°C, before ASN takes over and potentially changes it to -10°C. With the oil gauge's tooltip not showing the actual temperature until the needle starts to move (which is a great touch) it's hard to check it without timing how long it takes to warm up (assuming you're not using the heater & it actually starts, of course). Curious to know, but I can test myself if necessary when I find time. Hope I explained my question well enough!

If the oil temperature does always start at my default flight's ambient temperature, the only idea I have for a solution is to set the temperature in the 'free flight' weather menu before loading the flight, based on a METAR, so it's set in the sim before ASN takes over the weather generation. Of course, I know I can use the "C&D" button in the Comanche menu but I believe this resets all the switch positions in the cockpit too, so I avoid using it. Because I like all the aircraft 'persistence' I can get (but I welcome corrections, if I'm incorrect!)

Cheers,

Martyn

[EnDSchultz]

To my knowledge, the oil will cool to whatever the ambient temperature was at the time you last closed the aircraft. Thus, if it was -20C when you shut down, your oil's going to be -20C when you load the aircraft, even if the ambient temperature in the sim is different.

[mallcott]

Thanks Scott. Which brings the question how to start the engine without engine heater. I worry about the battery...

Change the oil first. Then it will be at a normal temperature.

[AKar]

Thanks Scott. Which brings the question how to start the engine without engine heater. I worry about the battery...

Well, if we speak of reality, it is mostly either pre-heat or hangar. Blankets are a must. I know that many Lycomings can start even cold-soaked well below freezing, but the amount of bangs and stutters really don't sound too healthy!

-Esa

[William Hughes]

I've cold started Lycoming O360's down to about -12 C or so. It is a bad idea as it wears various parts prematurely. My very great preference was to wrap the aircraft all up in blankets (including the fuselage around the cockpit) and then jam little ceramic space heaters into the engine compartment and under the instrument panel. I would leave them overnight - 8 to 10 hours.

The engine doesn't like it but the gyro's really seriously hate it. I worry about condensation under there more than anything - water in the electrics...

If the prop feels normal when you turn it over by hand you can start the engine. In cold weather we would prime the heck out of it, and then turn it over by hand several times to spread fuel and some oil over the bits. She would then usually fire up without to much complaining.

I've flown aircraft in -30C weather but we started them in a heated hanger. If they are outside at -20 then it is a terrible thing. Everything hurts when you touch it. Every moving part complains. Each time you move the controls there are mysterious noises. Stuff sticks and slips and it never seems to warm up. Plastic bits crack and fall off.

[AKar]

My very great preference was to wrap the aircraft all up in blankets (including the fuselage around the cockpit) and then jam little ceramic space heaters into the engine compartment and under the instrument panel.

One sees quite sophisticated approaches these days; in some instances there are separate engine and cabin heaters (obviously under insulating blankets) which can be monitored and controlled remotely. They can be set to keep up some base temperature of little above freezing, and when you know you are going to fly the airplane soon, they can be commanded to start the pre-heating by a text message. Rather nice stuff, it seems.

Obviously, the above requires electricity to be available. Some books and articles that describe war time aviation contain some really... chilling accounts of how it was attempted to keep or make the aircraft engines ready for scramble. The methods ranged from the ground crew running up the engines every few hours to keep them warm, to other putting a fire under the engine to warm it up, a method that was apparently in common use at eastern front.

-Esa

[mallcott]

My very great preference was to wrap the aircraft all up in blankets (including the fuselage around the cockpit) and then jam little ceramic space heaters into the engine compartment and under the instrument panel.

One sees quite sophisticated approaches these days; in some instances there are separate engine and cabin heaters (obviously under insulating blankets) which can be monitored and controlled remotely. They can be set to keep up some base temperature of little above freezing, and when you know you are going to fly the airplane soon, they can be commanded to start the pre-heating by a text message. Rather nice stuff, it seems.

Obviously, the above requires electricity to be available. Some books and articles that describe war time aviation contain some really... chilling accounts of how it was attempted to keep or make the aircraft engines ready for scramble. The methods ranged from the ground crew running up the engines every few hours to keep them warm, to other putting a fire under the engine to warm it up, a method that was apparently in common use at eastern front.

-Esa

Not to mention removing the oil from the aircraft while it was still viscous, carrying it indoors and leaving it by the fire until it was needed again, then pouring it back in.

Ah! simpler times...

[William Hughes]

Many years ago when I was a wee lad I went ice-fishing with my dad. We got to the lake in a scruffy Aeronca Chief on skis and spent the day fishing. It got a lot cooler and a lot windier as the day went on and when he decided to head home the engine would not turn. Now, that engine had no starter - hand propping!

So he started scrambling and built a big fire under the engine (on a platform of green logs cut with a chainsaw). We hung the blankets and spare jackets and everything imaginable that would work (including spruce boughs) around the engine compartment and I kept that fire going until the engine turned freely. Thankfully those are small engines. Hand propping an O-540 with a three-bladed prop is frightening but those little guys are easy.

Then we had to drag the fire out of the way and chuck all the stuff off the airframe so he could hand start it. I was the little guy in the cockpit with my cold hands on the throttle and mixture. No brakes on skis obviously.

We tore out of there right bang as it was getting on and we had an hour's flight to get home and had to get there before dark. Went back up the next day to clean everything up.

This sort of thing makes the lake trout taste better...

[AKar]

This sort of thing makes the lake trout taste better...

Love the story!

Not to mention removing the oil from the aircraft while it was still viscous, carrying it indoors and leaving it by the fire until it was needed again, then pouring it back in.

Ah! simpler times...

Or times before multi-grades! Today as proper oils are readily available, there is no place for most straight weight oils in winter flying IMO, at least when speaking of classic oils. While stuff like AeroShell 80/W80 (SAE 40 grade) has reasonably low pour point, it doesn't compare with their 15W-50 in that either, and has a much narrower viscosity index as well. On the paper, their W80 PLUS seems fairly impressive for an aircraft single-grade, but I don't have any knowledge of it really.

-Esa

[mallcott]

This sort of thing makes the lake trout taste better...

Love the story!

Not to mention removing the oil from the aircraft while it was still viscous, carrying it indoors and leaving it by the fire until it was needed again, then pouring it back in.

Ah! simpler times...

Or times before multi-grades! Today as proper oils are readily available, there is no place for most straight weight oils in winter flying IMO, at least when speaking of classic oils. While stuff like AeroShell 80/W80 (SAE 40 grade) has reasonably low pour point, it doesn't compare with their 15W-50 in that either, and has a much narrower viscosity index as well. On the paper, their W80 PLUS seems fairly impressive for an aircraft single-grade, but I don't have any knowledge of it really.

-Esa

I would have thought it would have to be an engine-specific requirement for single grade oils, I can't think of any other reason for using one in this day and age - but even multigrades can benefit from being off the bottom of the usable temperature scale before starting - shear strength advantage for lubricants with polymer additives as viscosity modifiers has decreasing effect at very low temperatures. The normal approved Viscosity Index range for ASTM-level testing only uses a dual temperature test of 40 °C and 100 °C. This is automotive industry practice and I am unaware of whether the aviation sector uses a different testing protocol to arrive at its multigrade conclusions (somehow, I doubt it!)

Consider the multigrade as `widening the operating range` - it doesn't obviate the smart aviator or engineer who can enhance that further with optimum choice and preparation. If that oil - however fancy-schmantzy - has NOT been tested and data acquired then its a gamble to start with really cold oil as there will be no guarantees.

As I understand it from recollection, and the reason for my advice above, the A2A oil change model places the `new` oil in the engine at a normalised room temperature rather than ambient air temperature, but that requires confirmation from the devteam. If it is the case then the simple expedient of changing the oil turns it from ambient cold-soaked to room temperature, EXACTLY the same as the winter engineer taking it out of the engine and keeping it by the fire. The clever cold-weather specialist is also doing the same thing with the battery.

[AKar]

I would have thought it would have to be an engine-specific requirement for single grade oils, I can't think of any other reason for using one in this day and age

I can't think of one either unless it came down to certain specific additives specific to some oil grades, but that's hard to buy. I do not know if there are any specific issues with the accessories in certain old engines, or rear end.

The main benefit of single grades, in practical talk that is, is the stability of them. The VI improvers can (and do) degrade in service, as the molecular structures giving this performance suffer both mechanical and thermal damage in use over time, in practice causing multi-grade oils typically to get thinner in service, and thereby losing certain of their lubricating properties. This applies especially to the oils of very wide viscosity indexes: I'd expect the modern wonder oils from automobile world such as 0W-40 to suffer this in particular, but as the topics about this seem rather religious, I only state that I'm lacking data.

It is true that not all the oils of wide viscosity index do too well in extreme cold, but this varies (depending, among the other things, of the base oil properties and the viscosity improvers used), and is something that indeed cannot directly be determined from the viscosity index alone, for instance. This is, when going beyond of their spec temps: if speaking aviation, most modern automotive oils are specified in rather extreme conditions.

Consider the multigrade as `widening the operating range` - it doesn't obviate the smart aviator or engineer who can enhance that further with optimum choice and preparation. If that oil - however fancy-schmantzy - has NOT been tested and data acquired then its a gamble to start with really cold oil as there will be no guarantees.

The specs as published do not really tell that much about the performance of aviation oil grades in extreme cold. But they do give some, the comparison of pour points perhaps being the most valid single comparison, if we are getting into coagulation range, so to speak. (Modern automotive oils typically quote some MRV values at, say, -40 instead.) This should order their minimum 'emergency operating temperatures' somewhat similarly. The aforementioned 15W-50 does better than any of the single grades from the same manufacturer, while in 'extreme cold', I'd expect none of the regular airplane engine oils really flowing too well at all.

-Esa

[mallcott]

Akar

Two factors to put into the equation in this most excellent technical discussion:
1: We need to be careful with too much cross-fertilisation of the design and construction of aviation versus. automotive oils. While there IS crossover, there is also considerable dissimilarity in the blends - even when the headline technical information would apparently indicate a high degree of commonality.
I used to be a tester for a large oil company on their motorcycle products and the technicians noted that for an equivalent 10W40 blend under the same branding, and identical SAE rating there was perhaps no more than 50-60% commonality. The pattern of use and individual characteristics of cars against motorcycle engines dictate that along with many other factors such as frequency of change, volume of oil against cylinder capacity and average revs, latent environment and much, much more.

2: Aviation oils will tend to work in a far greater range of temperatures than auto oils, and are surely compiled and manufactured to suit the specific requirements of the aviation industry. But there is a caveat: Modern aircraft engine oils and modern engines go together because they're designed that way. Aviation oils have to have high stability over long periods of non-use, but only for short periods IN use - 50-100 hour change intervals are still the norm, while your car might go 2 years between oil and filter changes, with near-daily use the norm.

The common theme in BOTH cases is that frequent oil changes are beneficial. Oil should ALWAYS be changed with the filter, unless the filter is designed to be cleanable. Caring for your oil is the same as caring for your engine and the clever owner does both.