Cowl flaps in hot climate
A few years back I decided my aircraft was due a tidy up on the engine baffles, nothing bad just a few cracks here and there, stiff baffle rubbers the odd gap, you know they story. This is an updraft cooled pusher.
So in I went, it took about 3 times longer than I thought but I wanted it the best it could be.
Previously it was not unusual to see the coldest sitting on 310F and the hottest at 375F
I was more than a little pleased to see on the first flight that with mixture and throttle butterfly positioning I could achieve all 4 cylinders within 2F of each other and sitting around the 330 mark.
What really surprised me was the effect it had on the EGT spread, the O-200 is about as crude as they come and the EGT's were generally random but could be manipulated with throttle position, carb heat and mixture setting. Whilst there was a pattern it was complex and fluky to replicate.
Now with tidied up cooling a distinct repeatable pattern emerged, at WOT the front pair carried significantly higher CHT's than the back pair due to the front pair running much leaner. Cock the throttle butterfly a few degrees by coming off WOT and everything starts to even up. So much so it is nearly smooth enough to go over the hump to LOP. Makes me think this might be one engine that could actually see significant benefits from an internal induction flow straightener or at the other end of the spectrum a swirl plate eg. Hyclone device.
All from attention to detail on a engine baffles.
So in I went, it took about 3 times longer than I thought but I wanted it the best it could be.
Previously it was not unusual to see the coldest sitting on 310F and the hottest at 375F
I was more than a little pleased to see on the first flight that with mixture and throttle butterfly positioning I could achieve all 4 cylinders within 2F of each other and sitting around the 330 mark.
What really surprised me was the effect it had on the EGT spread, the O-200 is about as crude as they come and the EGT's were generally random but could be manipulated with throttle position, carb heat and mixture setting. Whilst there was a pattern it was complex and fluky to replicate.
Now with tidied up cooling a distinct repeatable pattern emerged, at WOT the front pair carried significantly higher CHT's than the back pair due to the front pair running much leaner. Cock the throttle butterfly a few degrees by coming off WOT and everything starts to even up. So much so it is nearly smooth enough to go over the hump to LOP. Makes me think this might be one engine that could actually see significant benefits from an internal induction flow straightener or at the other end of the spectrum a swirl plate eg. Hyclone device.
All from attention to detail on a engine baffles.
Last edited by Obidiah; 30th Mar 2015 at 23:30.
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Obi, too many variables here, but you have quoted me well out of context. And yes it is true that to explain things properly in an internet forum post is impossible. Heck we take 2.5 days to get people to the point where they have a good starting point of understanding.
Let me try to clarify things and maybe expand further.
** To explain the answer about power settings at the same altitude on the same day, let me copy a small extract from an article I wrote recently that is yet to hint the printers. This might make some sense.
Drop me a line if I am missing the mark or confusing the question. 
PM me for my phone number if you want.
Let me try to clarify things and maybe expand further.
Jabawocky,
"It is a commonly held belief that the higher the power higher the CHT. this is not true. In fact at 500 feet running WOT/2500 and 80dF LOP generating 82-84% power my CHT's are 30 or so degrees cooler than FL130 WOT/2400 and appropriately LOP."
That statement is likely trip off a whole new round of incorrect myth and confusion for some low time/experience pilots. (no more than the myths they get taught at flying schools all over the country
It is imperative to apply sound scientific principals in your above comparison and that means you must have exactly the same configuration bar one change, the power output. Same AoA same mixture same OAT same altitude same IAS same cooling configuration. No, not really. The statement was that I can have higher power being proceed and lower CHT, which given the higher density of cooling air and equally appropriate low ICP's is very real. However I will explain in more details below**
If you do that and increase power you will see greater heat loading and therefore a CHT rise. I point this out for the benefit of others as I have no doubt you know all this and it was just a somewhat rushed statement at the end of a long day. It was the next morning…but I was recovering from a long few days
Certainly using the full mixture spread capability you can do many things with temperature including increasing power whilst reducing CHT and EGT, but this is not the same as saying it is not true that the higher the power the higher the CHT.
Help me here, this does not make sense. How can I use mixture to increase power AND reduce CHT under the constant parameters of flight? The EGT absolute value is of no concern and not relevant
"It is a commonly held belief that the higher the power higher the CHT. this is not true. In fact at 500 feet running WOT/2500 and 80dF LOP generating 82-84% power my CHT's are 30 or so degrees cooler than FL130 WOT/2400 and appropriately LOP."
That statement is likely trip off a whole new round of incorrect myth and confusion for some low time/experience pilots. (no more than the myths they get taught at flying schools all over the country
It is imperative to apply sound scientific principals in your above comparison and that means you must have exactly the same configuration bar one change, the power output. Same AoA same mixture same OAT same altitude same IAS same cooling configuration. No, not really. The statement was that I can have higher power being proceed and lower CHT, which given the higher density of cooling air and equally appropriate low ICP's is very real. However I will explain in more details below**
If you do that and increase power you will see greater heat loading and therefore a CHT rise. I point this out for the benefit of others as I have no doubt you know all this and it was just a somewhat rushed statement at the end of a long day. It was the next morning…but I was recovering from a long few days
Certainly using the full mixture spread capability you can do many things with temperature including increasing power whilst reducing CHT and EGT, but this is not the same as saying it is not true that the higher the power the higher the CHT.
Help me here, this does not make sense. How can I use mixture to increase power AND reduce CHT under the constant parameters of flight? The EGT absolute value is of no concern and not relevant
So what did we get for our trouble? Sure we dropped a few knots, maybe 5% but we dropped about 43% in fuel flow. I know what some of you are thinking, but that’s not the same power, and while that is true, it is not much less and the simple test was to reduce the RPM or MP to achieve a few less sucking events per minute to around 26”/2400 rpm and a fuel flow of 78-80 LPH, so HP per HP that is a reduction of 33-35%. Still serious in terms of my wallet.
Interesting question comes to mind, how does this affect the engine stress? We know from science and data collection over the last 65-75 years that the relationship of internal cylinder pressure tracks accurately with CHT, and in fact it is the driving force literally for the CHT. If you are having trouble thinking about this think of your home garage air compressor. Just don’t add any fuel, to the intake, it might not end well.
So at low level and a nice dense air flow, what are the CHT’s typically on the RV10? When run rich of peak at the same 80% power they are typically in the range of 345 to 375 degrees F, and yet when run LOP for the same 80% power they are around 305-335 degrees F. How can this be?
Interesting question comes to mind, how does this affect the engine stress? We know from science and data collection over the last 65-75 years that the relationship of internal cylinder pressure tracks accurately with CHT, and in fact it is the driving force literally for the CHT. If you are having trouble thinking about this think of your home garage air compressor. Just don’t add any fuel, to the intake, it might not end well.
So at low level and a nice dense air flow, what are the CHT’s typically on the RV10? When run rich of peak at the same 80% power they are typically in the range of 345 to 375 degrees F, and yet when run LOP for the same 80% power they are around 305-335 degrees F. How can this be?
PM me for my phone number if you want.
Jabawocky,
I think we might be getting lost in the translation somewhat, please forgive me the quote function is U/S so I’ll use italics instead.
"That statement is likely trip off a whole new round of incorrect myth and confusion for some low time/experience pilots. (no more than the myths they get taught at flying schools all over the country"
Yeah yeah, but still not good to use others failings to justify yours, but I take the tongue in cheek delivery.
"It is imperative to apply sound scientific principals in your above comparison and that means you must have exactly the same configuration bar one change, the power output. Same AoA same mixture same OAT same altitude same IAS same cooling configuration. No, not really. The statement was that I can have higher power being proceed and lower CHT, which given the higher density of cooling air and equally appropriate low ICP's is very real. However I will explain in more details below**"
Well it certainly read that way, and here it is……….. "It is a commonly held belief that the higher the power higher the CHT. this is not true. I could forgive some newbie for taking that at face value because it is pretty much a standalone statement although later qualified by how you did it.
The point is if no other parameter changes except power is increased then a higher CHT will follow, these engines are after all heat engines by principal. Therefore it IS a correct belief in its purity.
“Certainly using the full mixture spread capability you can do many things with temperature including increasing power whilst reducing CHT and EGT, but this is not the same as saying it is not true that the higher the power the higher the CHT.
Help me here, this does not make sense. How can I use mixture to increase power AND reduce CHT under the constant parameters of flight? The EGT absolute value is of no concern and not relevant”
Perhaps I mislead you, I am not suggesting here that power was increased with mixture alone just that the full ROP/LOP spectrum was available, what I was eluding to was that with a throttle or RPM derived power increase you can then manipulate the mixture setting from a ROP setting to a LOP setting and achieve higher power with a reduced CHT. For example (and telling you nothing here) increase power by say 4” of MaP and from a setting of 25 ROP then reduce mixture to 35 LOP and you will likely be in the paddock of increased power and reduced CHT. The EGT inclusion was for illustrative purpose, of course it is irrelevant unless you are sitting on a highly strung turbo system.
The original point I was making was that yes it is possible to increase power AND see a reduced CHT, but I see this as vastly different to your opening statement claiming it is incorrect to believe that increasing power will increase CHT. It might be obvious to those in the know what the point is you are making but a new mind trying to unlearn and relearn the true principals of combustion needs to be handled carefully.
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In my POH (for an O-360) it clearly states that full power can be applied as soon as the throttle can be advanced without hesitation or rough running.
I dunno Porter, but I can tell you I am over pilots who want to warm up "till the oil is in the green". It is possibly pointless, unnecessary and not in any engine book I have looked at (which is not a huge amount). I guess it could be beneficial for anyone logging or charging on an oil pressure switch though.
So I guess this wraps up Cowl Flaps then?
Just because the POH states you "can" apply full power the moment the engine will do so without hesitation doesn't mean you should. It just said you can, nothing more nothing less.
I am pretty sure, but I am not going to try it, that all the flat engines particularly the fuel injected ones are more than capable of coming off the starter motor dead cold and straight through to full power without hesitation.
The only engines I have operated that will stumble on a cold morning are the 985, 1340 and 1820, (the entirety of my round engine experience) they seem to lean snuff out if you open the throttle to quick when they're cold and the air is really frosty and atomisation is quite poor.
Incidentally the 1340 I operated (Ag) used to be set to idle around 450 rpm from start up on a cold winter morning and there it would sit for up to 20 minutes until the 70w oil would reach 40c then you could open the throttle. Reason being the super charger bearing spinning at 10:1 of crank speed (4500 rpm at 450 rpm) could burn (coke) the oil onto the bearing races in the cold oil.
The hell you say.....but trying to spin a bearing in a thick medium at speed and an enormous amount of friction is created, the result of which is heat.
Well so the overhaul boys would tell me.
We did suffer the odd glazed cylinder from time to time though, no probs, pop it off hone it and good to go. Maybe that's were the notion of glazing cylinders by waiting for the oil to reach the green came from??
For those (Aussie Bob?) that are implying bad things will happen if you close the cowl flaps to assist with a warm up. Care to explain what those bad things might be or do we wish to leave that statement hanging so that those not in the know form their own opinion on what those things might be. I see a little bit of lee way here with regard to cowl flap ops in frosty conditions, but it is important to explain the why's.
My knowledge of the bad things comes from APS and John Schwanner (of the Skyranch Engineering Manual fame) but I'll let you explain to the masses why it can be bad in certain circumstances and the issues it creates.
I am pretty sure, but I am not going to try it, that all the flat engines particularly the fuel injected ones are more than capable of coming off the starter motor dead cold and straight through to full power without hesitation.
The only engines I have operated that will stumble on a cold morning are the 985, 1340 and 1820, (the entirety of my round engine experience) they seem to lean snuff out if you open the throttle to quick when they're cold and the air is really frosty and atomisation is quite poor.
Incidentally the 1340 I operated (Ag) used to be set to idle around 450 rpm from start up on a cold winter morning and there it would sit for up to 20 minutes until the 70w oil would reach 40c then you could open the throttle. Reason being the super charger bearing spinning at 10:1 of crank speed (4500 rpm at 450 rpm) could burn (coke) the oil onto the bearing races in the cold oil.
The hell you say.....but trying to spin a bearing in a thick medium at speed and an enormous amount of friction is created, the result of which is heat.
Well so the overhaul boys would tell me.
We did suffer the odd glazed cylinder from time to time though, no probs, pop it off hone it and good to go. Maybe that's were the notion of glazing cylinders by waiting for the oil to reach the green came from??
For those (Aussie Bob?) that are implying bad things will happen if you close the cowl flaps to assist with a warm up. Care to explain what those bad things might be or do we wish to leave that statement hanging so that those not in the know form their own opinion on what those things might be. I see a little bit of lee way here with regard to cowl flap ops in frosty conditions, but it is important to explain the why's.
My knowledge of the bad things comes from APS and John Schwanner (of the Skyranch Engineering Manual fame) but I'll let you explain to the masses why it can be bad in certain circumstances and the issues it creates.
Last edited by Obidiah; 1st Apr 2015 at 23:31.
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Obi,
Well said
I have always wondered how you would know….because you don't know until you try it. Yet another silly statement in POH's.
I think Aussie Bob's concern will be that the checklists may not contain a "check cole flap open" when it was previously done elsewhere in a checklist, and thus the pilot does not check because they do everything by rote and takeoff with them closed.
Not that it will kill anything, and if the alarms are set correctly (which all the certified glass is not) then a timely alert will sound or blink long before it becomes a problem. Of course those with the manufacturer alarm thresholds will just have to rely on noticing or wait till they over temp the engine. But they will know about it at least!
Well said
Just because the POH states you "can" apply full power the moment the engine will do so without hesitation doesn't mean you should.
I think Aussie Bob's concern will be that the checklists may not contain a "check cole flap open" when it was previously done elsewhere in a checklist, and thus the pilot does not check because they do everything by rote and takeoff with them closed.
Not that it will kill anything, and if the alarms are set correctly (which all the certified glass is not) then a timely alert will sound or blink long before it becomes a problem. Of course those with the manufacturer alarm thresholds will just have to rely on noticing or wait till they over temp the engine. But they will know about it at least!
Obi, I agree with everything you say and I add I have no experience with any radial other than the P&W 985.
I do not ever apply full power straight from a start up but I am also sure it could be done without hesitation. My engine book states that I can do it. I don't.
I believe the cowl flap closed to assist warm up is a waste of time and detrimental to flat engines because they are air cooled and closing the cowl flap with no real airflow through the engine (stationary) will result in uneven cooling. No data sorry, my plane only has ground adjustable cowl flaps. The pilots that I see advocating this are doing nothing more than guessing (if it is not in the POH) and if I recall correctly both the 206 and 185 POH's state cowl flaps open for all ground operations.
Here was yesterday courtesy of an engine monitor.
Start up at 10C
1000 RPM for 2 minutes while seat belt is fitted, oil temp 50F, CHT's through 150F
Power up to 1500 to get moving on long grass
Taxi 600 metres. CHT's now approaching 200F oil at 60F
Run up and cycle prop, CHT's now approaching 300, oil at 70F
Check idle then take off with CHT's around 300, oil at 77F (still below green arc)
At 500 feet, CHT's around 340 and oil suddenly at 120F (well into the green)
I suspect my oil temp sender is where the coldest oil is.
Most engine problems that occur before TBO relate to cylinders, induction systems and turbochargers. The bottom end of most aircraft engines is pretty bulletproof apart from the odd lemon like the 320 H2AD which had a propensity to gall camshafts. Other problems are from lack of use like rusted cams or cracked cases due to too many overhauls perhaps. It is my theory that a flat engine is ready for takeoff power once the cylinders are around 300F.
It is my aircraft, if I was operating yours I would do exactly as you wanted as opposed to "Aussie Bob theory" which is all it is. Works for me. I was going for an annual by the way, all cylinders were good and there was no metal in the filter.
I do not ever apply full power straight from a start up but I am also sure it could be done without hesitation. My engine book states that I can do it. I don't.
I believe the cowl flap closed to assist warm up is a waste of time and detrimental to flat engines because they are air cooled and closing the cowl flap with no real airflow through the engine (stationary) will result in uneven cooling. No data sorry, my plane only has ground adjustable cowl flaps. The pilots that I see advocating this are doing nothing more than guessing (if it is not in the POH) and if I recall correctly both the 206 and 185 POH's state cowl flaps open for all ground operations.
Here was yesterday courtesy of an engine monitor.
Start up at 10C
1000 RPM for 2 minutes while seat belt is fitted, oil temp 50F, CHT's through 150F
Power up to 1500 to get moving on long grass
Taxi 600 metres. CHT's now approaching 200F oil at 60F
Run up and cycle prop, CHT's now approaching 300, oil at 70F
Check idle then take off with CHT's around 300, oil at 77F (still below green arc)
At 500 feet, CHT's around 340 and oil suddenly at 120F (well into the green)
I suspect my oil temp sender is where the coldest oil is.
Most engine problems that occur before TBO relate to cylinders, induction systems and turbochargers. The bottom end of most aircraft engines is pretty bulletproof apart from the odd lemon like the 320 H2AD which had a propensity to gall camshafts. Other problems are from lack of use like rusted cams or cracked cases due to too many overhauls perhaps. It is my theory that a flat engine is ready for takeoff power once the cylinders are around 300F.
It is my aircraft, if I was operating yours I would do exactly as you wanted as opposed to "Aussie Bob theory" which is all it is. Works for me. I was going for an annual by the way, all cylinders were good and there was no metal in the filter.
No worries Bob.
Not sure where your oil temp is picked off from but suffice to say that sudden jump from an oil temp of 77 to 120 at T.O. is likely an indication that your vernatherm is doing its thing and recirculating oil and bypassing the cooler. I would not think the pick off is at the coldest point it is usually at the end point of its journey through the working internals.
For those wondering what this strange worded device the vernatherm is, it essentially a thermostat for your oil circulation system that regulates the flow through the oil cooler. I can't give you much more than that as I am not a mechanic.
Bob you mentioned no real airflow through the engine when the cowl flaps are closed on the ground. I disagree there is still considerable airflow just not enough for proper cooling in most normal conditions on the ground. My personal observation on some types, Shrike is one I recall is that with the cowl flap open on a frosty morning the oil temp can take an age to get to the minimum for take off (75f from memory).
My personal technique on the Shrike was close them up tight for the first 1 or 2 minutes then open to half after that and full open 1 or 2 minutes later. But this is for sub zero OAT starts. All other times open before start, that way I can hear their little electric motors running and get a feel on how they're doing out there. They have a tough life and get little to no attention, cowls were always parked closed after shutdown.
But closed can lead to issues during the warm up if not done with some thought and understanding.
Back in the late 90's early 2000's John Deakin (as I recall) equipped his Bonanza's cylinder barrels with some temp probes at various locations around the circumference. What he discovered, and this was only on his Bonza was that there was poor cooling airflow around the cylinders and a wide range of temps were recorded.
He also stated and again on his Bonza that the under cowl footage showed the cotton tufting flew best when run ups were done bum to wind. I would like to see a lot more on that before I bought in. I would strongly caution against this unless you own shares in a prop company or hate your boss and can blame another pilot for the fact the blade leading edges look like steak knives.
Over to John Schwanner's book The Sacramento Skyranch Engineering Manual which from memory has some photos of cylinder walls with 4 equally spaced vertical scoring marks attributed to strong differential temperatures around the cylinder barrel. The marks are a result of piston to cylinder contact due to warpage attributed to the cylinder base nut configuration under unneven temps. Note no present barrel temp instrumentation for this just one probe per head if your lucky. Once the cylinder/piston reaches operating temps the clearance tolerance fall into place, particularly as the top of the cylinder is choked (smaller). However when still cool the tolerances are tighter.
Have a look at your inter-cylinder baffling on your particular aircraft, on the Shrikes I flew the inlet opening of the wrap around cylinder baffle might be 30mm and the outlet 5 to 10mm. Almost nothing so a strong pressure gradient is required to get anything to pass through here and in light of the only airflow being from a prop creating the high and low pressure and the inherent gaps and design flaws in the baffling system we really are up against. Having said that the first 30 seconds you could near still hold your hand on the barrels so in icy conditions you are pretty safe for a few minutes, in fact the sooner you can get to operating temperature (with in reason) the better and the piston gets a head start on expanding as its alloy and at the coal face, the barrels lag being steel and not at the blast face.
The key to it is to not exacerbate the already crudely designed cooling system with poor cooling air distribution and pressure gradient unless there is good reason. Frosty mornings are the only good reason and it doesn't stay frosty for long under there.
I think it was John Scwanners book that stated you need 6" of water column pressure diferential to adequately cool a 300hp aircooled engine. It takes 160kph of airflow in the front and most importantly around the outlet lip to create that differential. A prop won't come close
As they say warm up fast cool down quick they do.
The above is all from my memory and posted on a forum for aviation nutters by another nutter who likewise likes the sound of our own opinions, seek clarification before adopting.
Not sure where your oil temp is picked off from but suffice to say that sudden jump from an oil temp of 77 to 120 at T.O. is likely an indication that your vernatherm is doing its thing and recirculating oil and bypassing the cooler. I would not think the pick off is at the coldest point it is usually at the end point of its journey through the working internals.
For those wondering what this strange worded device the vernatherm is, it essentially a thermostat for your oil circulation system that regulates the flow through the oil cooler. I can't give you much more than that as I am not a mechanic.
Bob you mentioned no real airflow through the engine when the cowl flaps are closed on the ground. I disagree there is still considerable airflow just not enough for proper cooling in most normal conditions on the ground. My personal observation on some types, Shrike is one I recall is that with the cowl flap open on a frosty morning the oil temp can take an age to get to the minimum for take off (75f from memory).
My personal technique on the Shrike was close them up tight for the first 1 or 2 minutes then open to half after that and full open 1 or 2 minutes later. But this is for sub zero OAT starts. All other times open before start, that way I can hear their little electric motors running and get a feel on how they're doing out there. They have a tough life and get little to no attention, cowls were always parked closed after shutdown.
But closed can lead to issues during the warm up if not done with some thought and understanding.
Back in the late 90's early 2000's John Deakin (as I recall) equipped his Bonanza's cylinder barrels with some temp probes at various locations around the circumference. What he discovered, and this was only on his Bonza was that there was poor cooling airflow around the cylinders and a wide range of temps were recorded.
He also stated and again on his Bonza that the under cowl footage showed the cotton tufting flew best when run ups were done bum to wind. I would like to see a lot more on that before I bought in. I would strongly caution against this unless you own shares in a prop company or hate your boss and can blame another pilot for the fact the blade leading edges look like steak knives.
Over to John Schwanner's book The Sacramento Skyranch Engineering Manual which from memory has some photos of cylinder walls with 4 equally spaced vertical scoring marks attributed to strong differential temperatures around the cylinder barrel. The marks are a result of piston to cylinder contact due to warpage attributed to the cylinder base nut configuration under unneven temps. Note no present barrel temp instrumentation for this just one probe per head if your lucky. Once the cylinder/piston reaches operating temps the clearance tolerance fall into place, particularly as the top of the cylinder is choked (smaller). However when still cool the tolerances are tighter.
Have a look at your inter-cylinder baffling on your particular aircraft, on the Shrikes I flew the inlet opening of the wrap around cylinder baffle might be 30mm and the outlet 5 to 10mm. Almost nothing so a strong pressure gradient is required to get anything to pass through here and in light of the only airflow being from a prop creating the high and low pressure and the inherent gaps and design flaws in the baffling system we really are up against. Having said that the first 30 seconds you could near still hold your hand on the barrels so in icy conditions you are pretty safe for a few minutes, in fact the sooner you can get to operating temperature (with in reason) the better and the piston gets a head start on expanding as its alloy and at the coal face, the barrels lag being steel and not at the blast face.
The key to it is to not exacerbate the already crudely designed cooling system with poor cooling air distribution and pressure gradient unless there is good reason. Frosty mornings are the only good reason and it doesn't stay frosty for long under there.
I think it was John Scwanners book that stated you need 6" of water column pressure diferential to adequately cool a 300hp aircooled engine. It takes 160kph of airflow in the front and most importantly around the outlet lip to create that differential. A prop won't come close
As they say warm up fast cool down quick they do.
The above is all from my memory and posted on a forum for aviation nutters by another nutter who likewise likes the sound of our own opinions, seek clarification before adopting.
Last edited by Obidiah; 2nd Apr 2015 at 06:42.
As they say warm up fast cool down quick they do
But it's the humble air cooled petrol driven aircraft donk that has my greatest respect. So well built, so hard working so well thought through.
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Aussie Bob, were you thinking of the R2800-R3350 etc when you say air cooled aero engine so well thought through, or the flat engines? Obviously they didn't think the induction / injection through on the latter - or did they? Is it true that they never bothered to balance the FA ratios because they had no say on the wide variety of airframes (induction systems) that the motors would be installed on. But then the early Malibu shows what can be done, so why wasn't this done all the time?
I would like to believe the modern flat engine is still a marvel of engineering but I am no engine connoisseur. If BSFC is the measure a TNIO-550 LOP is pretty impressive, but then a diesel is better again...
I would like to believe the modern flat engine is still a marvel of engineering but I am no engine connoisseur. If BSFC is the measure a TNIO-550 LOP is pretty impressive, but then a diesel is better again...
Lumps, this has been done to death already, use the following Google search or similar: "pprune lean of peak" and as I said previously, I have no experience on round engines except for the 985 and that was long ago.
Contact Jabawocky to do a great course on engine management, fuel air ratios, LOP ops and more. An eye opener.
Contact Jabawocky to do a great course on engine management, fuel air ratios, LOP ops and more. An eye opener.
Folks,
Unless I have missed something in this discussion, I haven't seen any reference to the type of oil engines are using.
Unlike motor oils, few aircraft oils are multi-grade, and when it comes to radials, much the consistency of treacle when cold.
Hence the widespread use of oil tank heaters to bring the oil up to a "flowable" temperature before pre-oiling and starting -- radials.
Likewise, sump or oil tank heaters (and sometimes pre-oilers) are commonly used in colder climates, such as parts of the USA and Canada, or in really cold conditions, heaters for the whole engine --- any type of piston engine.
I can't say I have looked recently (being largely involved with radials) but last time I took much of an interest, I didn't see any multi-grade oils around, and there were certainly none approved for my old IO-470Ms in Australia.
In USA, there are some excellent multi-grade aero engine oils available, but they have not often been approved by the manufacturer (or in the case of Curtis-Wright engines- no manufacturer exists to "approve" them). Of course, FAA being FAA, and not CASA, this is not a problem, the FAA accepts testing by the oil producers.
Bottom line --- how and why you warm up an engine is very dependent on the type and condition of the oil. No way would I use much more than idle rpm until the numbers are "in the green", and where relevant, the oil cooler thermostat is flowing oil through the cooler.
As for "warming up" causing cylinder glazing --- I simply do not believe that is real, and this is the first time I have heard that claim in my operation of piston engines over 50+ years on three continents -- including LOP since the 1960s.
Tootle pip!!
Unless I have missed something in this discussion, I haven't seen any reference to the type of oil engines are using.
Unlike motor oils, few aircraft oils are multi-grade, and when it comes to radials, much the consistency of treacle when cold.
Hence the widespread use of oil tank heaters to bring the oil up to a "flowable" temperature before pre-oiling and starting -- radials.
Likewise, sump or oil tank heaters (and sometimes pre-oilers) are commonly used in colder climates, such as parts of the USA and Canada, or in really cold conditions, heaters for the whole engine --- any type of piston engine.
I can't say I have looked recently (being largely involved with radials) but last time I took much of an interest, I didn't see any multi-grade oils around, and there were certainly none approved for my old IO-470Ms in Australia.
In USA, there are some excellent multi-grade aero engine oils available, but they have not often been approved by the manufacturer (or in the case of Curtis-Wright engines- no manufacturer exists to "approve" them). Of course, FAA being FAA, and not CASA, this is not a problem, the FAA accepts testing by the oil producers.
Bottom line --- how and why you warm up an engine is very dependent on the type and condition of the oil. No way would I use much more than idle rpm until the numbers are "in the green", and where relevant, the oil cooler thermostat is flowing oil through the cooler.
As for "warming up" causing cylinder glazing --- I simply do not believe that is real, and this is the first time I have heard that claim in my operation of piston engines over 50+ years on three continents -- including LOP since the 1960s.
Tootle pip!!
Phillips makes a 25 W 60 multigrade oil for radials. I use it in the 285 hp 9 Cylinder Husoi engine in my Nanchang Cj6A. You get almost instant oil pressure on start up even with cold oil but temps do not get too hot on hot days.
The only downside is it is not recommended for the bigger radials, that is bigger than a 985 because of reports of master rod bearing distress.
The only downside is it is not recommended for the bigger radials, that is bigger than a 985 because of reports of master rod bearing distress.