Spitfire engine cut out under negative G

[Wulf]

Does anyone know if the 'manner' in which a Spitfire's engine cuts out in the game, when subjected to negative G, is an accurate representation? Although I'm not an engineer or anything like it, I'd have thought that if the carb(s) are connected to the cylinders via some sort of inlet manifold (that may also incorporate a supercharger of some sort) wouldn't it be more likely that there's be some degree of stutter, splutter or coughing as fuel starvation occurs. It just seems so incredibly binary at present.

[Roblex]

I don't know the technicalities but I would expect the effect to be fairly immediate. When you shut the throttle the response to reduced fuel flow is immediate so surely stopping all fuel from entering an engine that is firing and exhausting 28000 times a minute would kill it very quickly. Remember, neg-g does not just stop fuel flowing to the float chamber, it removes it from the chamber so nothing is entering the cylinder.

Have a look at the first 30 seconds of the 'Battle Of Britain' film and watch the engine cut out immediately during a simple inversion. You will also see the black smoke caused by the engine flooding as he comes right way up again.

http://youtu.be/9BCl8RuME-M

[ATAG_Snapper]

Interesting question, Wulf. I tend to agree with Roblex for the reasons he gave.

I have an old carb-fed V-Twin Harley (yeah, I know, hardly a big supercharged V-12 water-cooled Merlin) that's been bored, stroked, cammed, ported, and a larger-throated, very old fashioned gravity-fed carb hung on it. At least the early Merlins and my old Harley don't have Miss Shilling's orifice installed, so that's ONE thing they have in common. LOL

While riding (no traffic -- empty road) I've reached down and deliberately closed the petcock to simulate an out-of-gas situation just to see what happens. (Figured it'd be good to know in case it does happen someday). After about 30 seconds the fuel in the bowl runs dry and the engine suddenly dies with no warning. No splutters, no coughing, no jerking. Just abruptly dead.

EDIT: I forgot to add: When I reopen the carb while still rolling with ignition remaining on there IS a bit of drama by way of some brief coughing, plus friends riding well behind reported puffs of black smoke from my exhausts for a brief second as the engine comes back to life. There is momentary surging of the engine which is left in gear to keep it turning. But recovery is very quick -- within a second or two.

I'd be the first to say I'm comparing apples to oranges, but it still made me say "huh!". I guess I expected a little more drama when the Hog got starved for fuel. Not even a snort -- until I fed it again!

[Talisman]

This has been covered very well in lengthy threads and investigations, on the banana forum if I remember correctly, and a lot of work has been put in to get this correct, or as near as possible. Better folks than me will be able to give you the gen, but it has been gone over and over. At one stage I think someone even managed to get some input from a current RAF BoB Memorial Flight pilot source as well.

My Clod Spit and Hurri cut out every time just like the film Roblex has posted when I pull that move. Sometimes I get the puff of engine smoke too (which looks good on a fly by (F3)), but I tend not to get the puff of smoke every time as I suppose it depends on my angle of dangle, LOL.

Talisman

[RAF74_Buzzsaw]

Salute

As has been mentioned above, the issue of Negative G cutout was examined in great detail by 1C themselves, and was one of the few elements in the game which the original development team got right.

Once we took over, Team Fusion went over the implementation of negative G in carbureted aircraft in some detail, compared to our own research, and came to the conclusion nothing should be changed.

[Wulf]

OK, thanks all. That sounds pretty conclusive.

[LG1.Farber]

Maybe TF will implement some of the damage features associated with negative gravity in the merlin engine...

Please cast your eyes on points 3 and 4.

2860

[ATAG_Bliss]

Hard to explain unless you understand engines. But any sort of negative G in CloD will fuel starve the engine immediately. So the only thing happening in neg g where oil could possibly get air in it is the engine free wheeling. That won't cause any damage at all to an engine. The oil, besides protecting/lubricating bearings, helps cool the pistons etc., while combustion occurs. In the same sentence, combustion (where the fuel/air mixture explosion slams the connecting rod down, violently turning the crankshaft, huge stress on main and rod bearings etc., doesn't happen when the engine is free wheeling or out of fuel like. So essentially combustion/heat pounds on the bearings, cylinder walls, etc., where lack of oil is a huge concern. Without combustion (essentially neg g) in cliffs of dover, there is nothing to worry about.

Those pilot notes make note of a problem that could occur if the engine was still running in a neg g situation. Perhaps something like the schilling orifice installed etc., where this is possible. But currently it isn't, so those pilot notes don't apply to anything in TF/vanilla clod right now.

[LG1.Farber]

A HA! The lesser spotted ATAG_Bliss! People were starting to invent rumours as to where you were.

Not so sure I understand your point. - So it can't be implemented yet? What your saying is that because the game mechanics wont cause the damage that the real life will not be emulated?

[ATAG_Bliss]

A HA! The lesser spotted ATAG_Bliss!

Not so sure I understand your point. - So it can't be implemented yet? What your saying is that because the game mechanics wont cause the damage that the real life will not be emulated?

Ok the short version in the hopes you understand.

During Neg G you DON'T have combustion.

Combustion is what can hurt the motor due to lack of oil.

Therefore in neg g you can not possibly hurt the motor as there is no combustion (AKA fuel / running engine) to allow it to be hurt.

The carb mod was to stop the neg g cutouts. Before the orifice was installed, the engine would lose combustion under neg g just like the current spit/hurri in CloD.

So again, what you are reading is what could occur if combustion is taking place during neg g, and more than likely applies to the later orifice that was installed to permit combustion (aka fuel / engine running) under neg g situations. What we have in Cliffs, as others have already stated in this thread, is correct for the planes in Cliffs.



And invent rumors? People do have real life jobs, at least I do, and real life hobbies that take up much of their time. I for one, in the summer, spend the majority of the time working on and drag racing my race cars. Most the people that know me, know this quite well. I'm not going to be stuck indoors playing a video game when it's nice outside. Noone should be.

[Osprey]

He was joking.

I would say that any RAF pilot loading up a series of neg g moves which add up to 'seconds' has bigger issues than worrying about engine damage. I'm sure I speak for practically all RAF pilots by saying that we may experience a blip when trying to get a few more rounds into that bunting 109 (whom does not get injured doing it) than a series of prolonged cuts which would simply knock the engine off completely anyway.

Welcome back.

[LG1.Farber]

Cool, winning any?

The damage comes from the CSP going to fine because it slows down. And when the engine gets fuel and the throttle is open there is a danger of over revving. See point 3, I didnt highlight in red the area.

[ATAG_Bliss]

Cool, winning any?

The damage comes from the CSP going to fine because it slows down. And when the engine gets fuel and the throttle is open there is a danger of over revving. See point 3, I didnt highlight in red the area.

It still can't happen unless the engine is running (aka combustion). That's like saying your freewheeling the engine with the starter motor and when it finally does fire somehow the engine will skyrocket to 4000rpms and somehow the oil will cavitate only in the CSP unit. Again, the revving up of the engine (combustion) is what creates oil supply, when in neg g since there's no combustion the freewheeling engine is doing the opposite and trying to quit turning. When its fired up again, the engine will reapply the oil immediately where it left off and control the CSP. Again, please read this time, the only way the engine will get damaged in neg g is if it is actually running.

You really need to look up the basics on a combustion engine. I've explained it in the simplest methods possible, but you just don't get it.

[LG1.Farber]

It still can't happen unless the engine is running (aka combustion). That's like saying your freewheeling the engine with the starter motor and when it finally does fire somehow the engine will skyrocket to 4000rpms and somehow the oil will cavitate only in the CSP unit. Again, the revving up of the engine (combustion) is what creates oil supply, when in neg g since there's no combustion the freewheeling engine is doing the opposite and trying to quit turning. When its fired up again, the engine will reapply the oil immediately where it left off and control the CSP. Again, please read this time, the only way the engine will get damaged in neg g is if it is actually running.

You really need to look up the basics on a combustion engine. I've explained it in the simplest methods possible, but you just don't get it.

Yes that is exactly what it says... That is exactly the problem.

There is combustion, are you reading point 3?



3. Danger of Overspeeding with a Constant Speed Propeller when the engine cuts.

Although the tendency to cut is less and recovery is quicker with the throttle well open, the pilot must close the throttle before power returns to avoid the risk of serious overspeeding of the engine; for as soon as power fades the propeller starts to fine its pitch and it is unable to readjust quickly enough to cope with a rapid return of high power. It is therefore, advisable to close the throttle when a cut has occurred from any cause and to reopen it carefully when power returns.

[Gromit]

The Spits and Hurri's in this game do not have a CSP, they have a variable pitch prop, the pilot selects the prop pitch and it wont change unless he changes it!

A constant speed prop has a governor which automatically adjusts the prop pitch against load and RPM, that did not become available until the mkIX, which did not suffer the neg cutout as they used SU or Bendix single point injector carbs!

so moot point either way!

secondly as long as the engine is turning, the oil pump is working, the engine is dry sumped and does not suffer oil starvation in a bunt, as oil flow to bearings , cams, etc is constant!

[LG1.Farber]

Wierd then that this document contradicts both of these things.

[Gromit]

depends on what you refer to as a CSP, if the prop pitch is automatically adjusted without the pilots changing it (as mkIX) that's usually referred to as an auto prop pitch, but some references refer to it as CSP, on the Spit1 and Hurri1 the pilot selected the pitch on a lever next to the throttle, setting the RPM against load manually! otherwise referred to as Variable pitch, but yet again some references refer to it as CSP, either way doing a bunt won't damage the engine, other wise pilots notes would forbid you to bunt, not unreasonably!

you seem to be implying the engine takes damage every time you apply any neg G, which of course is nonsense.

a quick perusal of the above notes -
the pilot must close the throttle before power returns to avoid the risk of serious overspeeding of the engine; for as soon as power fades the propeller starts to fine its pitch and it is unable to readjust quickly enough to cope with a rapid return of high power. It is therefore, advisable to close the throttle

the relevant passage being --as soon as power fades the propeller starts to fine its pitch , in other words it does not go immediately to fine pitch, just as it cant readjust quickly enough it obviously cant jump immediately to fine, so the notes advise not demand you shut the throttle, or put simply it's a matter of how long your engine has lost power!

unless your applying neg g for several seconds I fail to see how this will occur?

[RAF74_Buzzsaw]

Maybe TF will implement some of the damage features associated with negative gravity in the merlin engine...

Please cast your eyes on points 3 and 4.

2860

Firstly, the game's code does not have the capability to model oil starvation due to negative G. To add this element would require a re-write of the code at multiple levels, and would require an enormous amount of work.

Second, what is the source and date for the pages you posted? This material looks like it is either from a very early version of the Merlin, or another source. The Merlins were upgraded continually, with issues constantly being resolved with re-engineering. That included re-engineering to prevent oil starvation. The relief valves for the Merlin III Oil inlet system were a re-design from the valves for the Merlin II. And the Merlin XII also incorporated changes.

[LG1.Farber]

Gromit, I agree with you the Variable pitch propeller was probably a retrospective term to distinguish it from the CSP and as such we can only hazard a guess as to the meaning of it in a particular instance and that also the terms maybe interchangeable.

Who knows how long it would take to cause damage if it sent the RPM over the maximum it could cause a catastrophic engine failure. Like when the 109 U/pm goes beyond 3000.


Buzzsaw, If this feature is, at this time, too unrealistic a task in term of scope to implement then I can respect that and can understand other aspects of the great sim have priority and precedence over such trivial things. Please keep up the good work. The source of the material is I am told on good faith is "Spit II pilot notes" posted by NZtyphoon on 1c concerning the same issue as this thread:
http://forum.1cpublishing.eu/showthread.php?t=33942&highlight=spitfire+negative&page=22

[ATAG_Bliss]

Firstly, the game's code does not have the capability to model oil starvation due to negative G. To add this element would require a re-write of the code at multiple levels, and would require an enormous amount of work.

Second, what is the source and date for the pages you posted? This material looks like it is either from a very early version of the Merlin, or another source. The Merlins were upgraded continually, with issues constantly being resolved with re-engineering. That included re-engineering to prevent oil starvation. The relief valves for the Merlin III Oil inlet system were a re-design from the valves for the Merlin II. And the Merlin XII also incorporated changes.

The engine will never have oil starvation under negative g because its not running under negative g. So there's no need to model this unless we had field modded carburators.

Farber's comments are also misinformed or misunderstood. The big tell tale sign with his number 3 is it states as the engine loses power x can occur. The difference is cliffs doesn't lose power like an engine with a clogged fuel filter. It simply loses all fuel and shuts off. So there's no chance of the pitch changing adversely enough in freewheel to damage it in that fashion.

Sadly, I don't think he still gets it. Some people just come here to argue. I have no idea why.

[RAF74_Buzzsaw]

The source of the material is I am told on good faith is "Spit II pilot notes" posted by NZtyphoon on 1c concerning the same issue as this thread:
http://forum.1cpublishing.eu/showthread.php?t=33942&highlight=spitfire+negative&page=22

The thread you reference does not attribute this to Spit II pilot notes. The poster says "Here are the Pilot's Notes General comments about oil flow under negative-g:", no mention of Spit II. (the whole thread was about Merlins in general) And the two pilot manuals for the Spit II which I have do not include these pages, and those manuals include no reference to negative G concerns as referenced on the pages you linked. The pages are also not from the Spit I or Hurricane I manuals I have.

[ATAG_Bliss]

Wierd then that this document contradicts both of these things.

Not really. Tech documents are often written by writers and people that have 0 experience with what they are writing about. This sort of thing happens all the time. I could pick up almost any shop manual about a procedure or guideline and find it full of errors.

[RAF74_Buzzsaw]

Salute

Before people post material on these boards and request changes, they should know the source of the material, the date of the material and what aircraft/engine/tech the material is referenced to.

Team Fusion puts a great deal of effort into research and documentation. We base all our changes on clearly referenced sources. We are open to changes and new data, but we ask the material be presented with the appropriate references.

Thanks for your patience.

[LG1.Farber]

Not really. Tech documents are often written by writers and people that have 0 experience with what they are writing about. This sort of thing happens all the time. I could pick up almost any shop manual about a procedure or guideline and find it full of errors.

I guarantee you would.


Salute

Before people post material on these boards and request changes, they should know the source of the material, the date of the material and what aircraft/engine/tech the material is referenced to.

Team Fusion puts a great deal of effort into research and documentation. We base all our changes on clearly referenced sources. We are open to changes and new data, but we ask the material be presented with the appropriate references.

Thanks for your patience.

The only thing that made me think of that note reading this thread was the fact it was totally ignored and swept under the carpet when it was raised at the time. If more people were like you Buzzsaw and explained themselves in depth, with courtesy and clarity allot of this could be avoided. Of course the people reading must actually read...

S!

[ATAG_Bliss]

I guarantee you would.

Then why ask about it? I'm sure I'm not the only person that has been involved in project management where the tech writing division is tasked to write about a plethora of different things, procedures, guidelines etc. These are guys sitting at a PC their entire jobs writing about things such as overhauling a jet engine to things such as rebuilding weapons. Are the tech writers experts or knowledgeable in either? Highly doubt it. They mainly use notes and references from people that have. The ongoing problem is how they interpret these notes and references into their own style of writing.




The only thing that made me think of that note reading this thread was the fact it was totally ignored and swept under the carpet when it was raised at the time. If more people were like you Buzzsaw and explained themselves in depth, with courtesy and clarity allot of this could be avoided. Of course the people reading must actually read...

S!

This is a 2 way street. If more people would actually do their own research and learn about what is going on with regards to what is being said there wouldn't be the constant need to educate people like yourself. You are very dense. I almost feel like I'm talking to a brick wall when I respond to people like you. You may not like my tone. But common courtesy goes both ways. Next time have the courtesy to do you're own research. I responded several times with the why this won't happen, but instead of saying "ok Bliss, I understand how this wouldn't occur now, thanks". You instead take my response right over your head to hop into another section that deals with exactly the common principles I tried to tell you earlier of the combustion engine. That makes you either a troll or having a very low ability to learn.

I will gladly answer questions, but saying something should be x instead of y based on a piece of paper that isn't even sited to do with anything with regards to Cliffs of Dover is daft at best.

[buster_dee]

For what it's worth, from Graham White's "Allied Aircraft Piston Engines of WW2."

"An idiosyncrasy of the original SU carburetor was...rich 'cutout' caused by negative g. In fact...[it] was a two-stage event...fuel was forced to the top of the float chamber, which exposed the main jet to air. This caused the first, momentary, lean cutout. If a negative g condition continued, the floats...floated to the bottom of the float chamber. The needle valve opened wide, allowing...an excessively rich mixture...into the supercharger, causing the more serious rich cutout.

For a fighter pilot this could pose a severe limitation; if the stick was pushed forward a momentary loss of power or a complete cutout would result."

All I got from White's analysis is that black smoke can happen during the cutout (not only after), and that "momentary" was possible. Granting that "momentary" may need further defining, it seems reasonable that the in-game responses qualify as momentary (engine restarts as soon as negative-g is removed) or complete (engine reluctant to restart).

[Gromit]

[QUOTE=ATAG_Bliss;46357]The engine will never have oil starvation under negative g because its not running under negative g. So there's no need to model this unless we had field modded carburators.

Oil starvation has no connection to the carburation at all, the oil system on aircraft engine is "dry sump", this means the oil is not in a well at the bottom of the engine like a car, but contained in a tank, the engine oil pump is actually several pumps in a unit all running off a common shaft driven from the crankshaft, one or two will be pressure pumps taking oil from the tank and pumping it round the engine, the others will be scavenge pumps, removing the used oil from several locations on the engine and pumping it back into the tank, unless you empty the tank (impossible unless there is a massive oil leak as the volume in the tank is so great) you will always have oil pumping round the engine, if the crankshaft is rotating, whether that be under power or idling, then there is a constant feed of oil round the engine!

The overspeed of the prop is a separate matter, if the engine is allowed to cut out for extended periods the variable pitch unit will slowly change to the fine pitch position as the load comes off the engine as it splutters, then , if the power suddenly comes back on the engine will surge back up to power leaving the prop in fine pitch causing the engine to over rev as the variable pitch has not had time to revert back to coarse pitch!

The real issue there is how long it takes the pitch to change, if you bunt and cause a splutter cut out the pitch will not have time to go to fine before power is resumed, if you prolong the neg G for several seconds by pushing the nose down then the pitch will change causing the problem outlined above, put simply you would have to be under negative g for several seconds to cause that to happen, and when have you ever read of pilots complaining about engine failure after a bunt?

[Talisman]

[QUOTE=ATAG_Bliss;46357]The engine will never have oil starvation under negative g because its not running under negative g. So there's no need to model this unless we had field modded carburators.

Oil starvation has no connection to the carburation at all, the oil system on aircraft engine is "dry sump", this means the oil is not in a well at the bottom of the engine like a car, but contained in a tank, the engine oil pump is actually several pumps in a unit all running off a common shaft driven from the crankshaft, one or two will be pressure pumps taking oil from the tank and pumping it round the engine, the others will be scavenge pumps, removing the used oil from several locations on the engine and pumping it back into the tank, unless you empty the tank (impossible unless there is a massive oil leak as the volume in the tank is so great) you will always have oil pumping round the engine, if the crankshaft is rotating, whether that be under power or idling, then there is a constant feed of oil round the engine!

The overspeed of the prop is a separate matter, if the engine is allowed to cut out for extended periods the variable pitch unit will slowly change to the fine pitch position as the load comes off the engine as it splutters, then , if the power suddenly comes back on the engine will surge back up to power leaving the prop in fine pitch causing the engine to over rev as the variable pitch has not had time to revert back to coarse pitch!

The real issue there is how long it takes the pitch to change, if you bunt and cause a splutter cut out the pitch will not have time to go to fine before power is resumed, if you prolong the neg G for several seconds by pushing the nose down then the pitch will change causing the problem outlined above, put simply you would have to be under negative g for several seconds to cause that to happen, and when have you ever read of pilots complaining about engine failure after a bunt?

As understand though Gromit, the circumstance detailed in your last paragraph, above, will not apply to the CloD Spit and Hurry engines because the pilot sets the prop pitch and the prop will not go to fine setting on its own at all; correct?

[Gromit]

[QUOTE=Gromit;46418]

As understand though Gromit, the circumstance detailed in your last paragraph, above, will not apply to the CloD Spit and Hurry engines because the pilot sets the prop pitch and the prop will not go to fine setting on its own at all; correct?

It will change as the engine speed decays and it tries to maintain the rpm the pilot selected (it's load variable like an automatic gearbox on a hill), however you would have to keep the nose pushed down in neg G for several seconds for the pitch to get into fine, and that's the real issue here, for instance at the top of a vertical climb you get a neg g stall and the engine splutters , but that's only as long as it takes for the nose to drop and engine to pick up, if you bunt you get the splutter but again its momentary, if you tried an outside loop that's a different matter and would give the prop time to change to fine as the engine would be spluttering for a considerable time, and that's the defining parameter, time, how long in neg G, I don't think it's practical to try and define how long in neg g you could run without damage in a game as it's extremely complicated when you try to correlate RPM, load pitch and decay, it's not really applicable to what we do, unless you have some fetish for keeping your engine spluttering!

[ATAG_Bliss]

The engine will never have oil starvation under negative g because its not running under negative g. So there's no need to model this unless we had field modded carburators.

Oil starvation has no connection to the carburation at all, the oil system on aircraft engine is "dry sump", this means the oil is not in a well at the bottom of the engine like a car, but contained in a tank, the engine oil pump is actually several pumps in a unit all running off a common shaft driven from the crankshaft, one or two will be pressure pumps taking oil from the tank and pumping it round the engine, the others will be scavenge pumps, removing the used oil from several locations on the engine and pumping it back into the tank, unless you empty the tank (impossible unless there is a massive oil leak as the volume in the tank is so great) you will always have oil pumping round the engine, if the crankshaft is rotating, whether that be under power or idling, then there is a constant feed of oil round the engine!

The overspeed of the prop is a separate matter, if the engine is allowed to cut out for extended periods the variable pitch unit will slowly change to the fine pitch position as the load comes off the engine as it splutters, then , if the power suddenly comes back on the engine will surge back up to power leaving the prop in fine pitch causing the engine to over rev as the variable pitch has not had time to revert back to coarse pitch!

The real issue there is how long it takes the pitch to change, if you bunt and cause a splutter cut out the pitch will not have time to go to fine before power is resumed, if you prolong the neg G for several seconds by pushing the nose down then the pitch will change causing the problem outlined above, put simply you would have to be under negative g for several seconds to cause that to happen, and when have you ever read of pilots complaining about engine failure after a bunt?

I think you are missing the point as well or have a googled understanding of engines. Oil starvation in reference to the pilots notes means that you can oil starve the motor in neg g. So the engine running (fuel aka carb) compared to oil starvation is a direct correlation. The difference, as I've stated about 5 times now, is in ClOD, any neg g immediately kills the engine (takes away all the fuel). Therefore, during neg g the engine isn't attempting to run EVER. So under neg g, the engine is trying to come to a stop as it's simply free wheeling.

About dry sumps, I don't think you quite understand them. A dry sump (which I use in several of my race cars) is simply a different pump setup. A spitfire still has it's oil in the crankcase and has several scavenger pumps to help with oil starvation. But just like a race car, the crankcase (oil pan attached to the engine) is baffled so sudden changes in acceleration, g forces etc., won't allow that allow to splash all over the moving crankshaft, thus causing extreme foaming of the oil. This air in the oil is very bad for bearings. A dry sump can have extra supply oil in holding tanks etc., but the oil galleys and returns in any engine all drop that oil directly into the crankcase (exactly as a wet sump system). There are obviously advantages to a dry sump, but I think for clarity sake, I've said enough for you to understand it.

As far as the prop pitch and neg g in cliffs, it can't happen, again, because the engine is never running under neg g. It's not losing power. It's simply like an on/off switch. Those notes refer to an engine that is leaning out and running out of power during neg g. It's leaning out because it's running out of fuel. Because of this "lost power" in neg g, there's a chance that oil is cavitating (again, because oil is at the top of the baffles and not sitting in the bottom of the crankcase where the sump is, thus the possibility of the oil pumping air) and causing the pitch to change. Again, this is only going to happen if the engine is running, or has been running while losing oil pressure.

If you know anything about oil pumps, their job, 1st and foremost is to supply feed oil as quickly as possible. There's a reason why starting an engine, especially modern electronic fuel injected engines, don't have a need to crank over for 10 seconds to get oil pressure (pre lube) before they just take off. Since the earliest of combustion engines, oil pumps are designed around the amount of volume they need to move. That means, at idle, which is the lowest rpm of a basic running engine, they supply the proper moving parts with oil almost instantaneously. This also means, when upder load (high rpms, even ramping up rpms such as fast acceleration) that the oil pump opens (fuels the engine with oil faster) until the desired volume is reached. The relief valve then comes on to dump off the excess volume and pressure of oil. Oil supply is almost instantaneous, let alone with RPMs. If the relief was not there, and the pump was allowed to go to max and follow the RPM ramp, you would cut right through the bearings with the same oil in a matter of minutes.

What this all means, in flight, in Clod, is that there is no way possible to allow the prop to change at any time as the neg g causes an immediate killing of the engine. Even if there was a way to starve the engine for oil modeled in Cliffs, the only starving would happen when the engine is not running (free wheeling), which again means the engine is slowing down (not running) very quickly. So when fired back up, not only does the engine need to pick up the RPM it's lost to somehow get to an over rev, that time in doing so has long gained back any sort of oil lost to the csp unit (which is one of the main oil feeds from the crankcase).

Just to give you a little background. I've been building race cars for around 15 years now. I don't pay for anyone to do anything other than balance my rotating assembly (crank, rods, pistons) and block prep. In other words, in that time, I build the motors as well. These are engines that live on the edge and produce well north of 1000hp. I kinda know what I'm talking about when it comes to this stuff.

That paragraph in the pilots notes reminds me of the safety warnings that come with almost anything sold nowadays. "Plugging your hairdryer and dropping it in the bath tub can cause electrical shock". "When your engine is not running, starting it with the throttle all the way open can cause it to be damaged"

Both those instances are such a "no shit" or "Gee Mr. Obvious" things, that I can't believe people would spend this much time talking about them.

Now I've tried saying the same thing in an explanatory way, in a talking to a 5 year old way, and finally in another explanatory way.

If you people seriously don't understand what I have written, then go do some research or get some experience on an engine. If you were to post this sort of stuff in some of the forums I frequent, people would be laughing at you guys. I know that's sad, but armchair engine builders are kinda funny to poke at.

[Talisman]

[QUOTE=Talisman;46446]

It will change as the engine speed decays and it tries to maintain the rpm the pilot selected (it's load variable like an automatic gearbox on a hill), however you would have to keep the nose pushed down in neg G for several seconds for the pitch to get into fine, and that's the real issue here, for instance at the top of a vertical climb you get a neg g stall and the engine splutters , but that's only as long as it takes for the nose to drop and engine to pick up, if you bunt you get the splutter but again its momentary, if you tried an outside loop that's a different matter and would give the prop time to change to fine as the engine would be spluttering for a considerable time, and that's the defining parameter, time, how long in neg G, I don't think it's practical to try and define how long in neg g you could run without damage in a game as it's extremely complicated when you try to correlate RPM, load pitch and decay, it's not really applicable to what we do, unless you have some fetish for keeping your engine spluttering!

Now I am a somewhat confused mate, LOL. I thought you said in an earlier post, above, that in CloD we had a variable pitch prop and the pilot sets the prop pitch and it wont change unless the pilot changes it. If that is so, how is the prop pitch able, in theory, to change from a coarse setting to fine on its own. Sorry, but I think I am missing something here; I am a bit slow as I am just worn out after looking after our little grandson for 2 days on the trot (that's my excuse anyway, LOL).

Happy landings,

Talisman

[Gromit]

sorry mate, my fault, bit of confusion in terms, I am used to constant speed props being auto pitch as in autonomous , but it's a term used in different texts to mean different things!

in this context the CSP means the pitch compensating prop, variable prop whatever you want to call it, in other words the Rotol or DeHaviland, but basically it's like an automatic gearbox that keeps the rpm the same regardless of boost!

[Gromit]

[QUOTE=ATAG_Bliss;46465]I think you are missing the point as well or have a googled understanding of engines. Oil starvation in reference to the pilots notes means that you can oil starve the motor in neg g. So the engine running (fuel aka carb) compared to oil starvation is a direct correlation. The difference, as I've stated about 5 times now, is in ClOD, any neg g immediately kills the engine (takes away all the fuel). Therefore, during neg g the engine isn't attempting to run EVER. So under neg g, the engine is trying to come to a stop as it's simply free wheeling.

About dry sumps, I don't think you quite understand them. A dry sump (which I use in several of my race cars) is simply a different pump setup. A spitfire still has it's oil in the crankcase and has several scavenger pumps to help with oil starvation. But just like a race car, the crankcase (oil pan attached to the engine) is baffled so sudden changes in acceleration, g forces etc., won't allow that allow to splash all over the moving crankshaft, thus causing extreme foaming of the oil. This air in the oil is very bad for bearings. A dry sump can have extra supply oil in holding tanks etc., but the oil galleys and returns in any engine all drop that oil directly into the crankcase (exactly as a wet sump system). There are obviously advantages to a dry sump, but I think for clarity sake, I've said enough for you to understand it.
Now I've tried saying the same thing in an explanatory way, in a talking to a 5 year old way, and finally in another explanatory way.

No offence Bliss but this is incorrect, if you have an oil pan which collects and stores oil it's a wet sump, I also build race cars, single seat circuit cars, I install dry sumps on all my cars, the whole reason it's called a dry sump is there is no oil stored in the sump, below is a web site of a Spit being restored, the last photograph is I believe the oil tank for the Merlin engine, also shown installed below the engine, the oil tank is also mentioned in the restoration notes.

When the engine suffers fuel starvation it does not stop dead, it's still turning just like a misfiring car, if the engine is turning its still pumping oil as the pump is driven off the engine, I cannot understand how you would think the engine just stops dead?

[ATAG_Bliss]

I think you are missing the point as well or have a googled understanding of engines. Oil starvation in reference to the pilots notes means that you can oil starve the motor in neg g. So the engine running (fuel aka carb) compared to oil starvation is a direct correlation. The difference, as I've stated about 5 times now, is in ClOD, any neg g immediately kills the engine (takes away all the fuel). Therefore, during neg g the engine isn't attempting to run EVER. So under neg g, the engine is trying to come to a stop as it's simply free wheeling.

About dry sumps, I don't think you quite understand them. A dry sump (which I use in several of my race cars) is simply a different pump setup. A spitfire still has it's oil in the crankcase and has several scavenger pumps to help with oil starvation. But just like a race car, the crankcase (oil pan attached to the engine) is baffled so sudden changes in acceleration, g forces etc., won't allow that allow to splash all over the moving crankshaft, thus causing extreme foaming of the oil. This air in the oil is very bad for bearings. A dry sump can have extra supply oil in holding tanks etc., but the oil galleys and returns in any engine all drop that oil directly into the crankcase (exactly as a wet sump system). There are obviously advantages to a dry sump, but I think for clarity sake, I've said enough for you to understand it.
Now I've tried saying the same thing in an explanatory way, in a talking to a 5 year old way, and finally in another explanatory way.

No offence Bliss but this is incorrect, if you have an oil pan which collects and stores oil it's a wet sump, I also build race cars, single seat circuit cars, I install dry sumps on all my cars, the whole reason it's called a dry sump is there is no oil stored in the sump, below is a web site of a Spit being restored, the last photograph is I believe the oil tank for the Merlin engine, also shown installed below the engine, the oil tank is also mentioned in the restoration notes.

When the engine suffers fuel starvation it does not stop dead, it's still turning just like a misfiring car, if the engine is turning its still pumping oil as the pump is driven off the engine, I cannot understand how you would think the engine just stops dead?

Gromit,

This is taken directly from a spitfire merlin engine:
The lower crankcase serves as an oil sump, and also carries an oil pressure pump and three scavenge pumps, with provisions for an optional hydraulic pump. Baffles in the lower crankcase help reduce oil surge and improve oil control, particularly at unusual attitudes which can occur in flight. Each of the two primary scavenge pumps is equipped with removable oil screens; one scavenge pump collects oil via an extension pipe to a pickup at the propeller end of the engine, the other scavenges oil from the sump at the supercharger end of the engine. The third scavenge pump is the auxiliary scavenge pump used to collect oil from the supercharger impeller bearings -- it is located directly below the pressure pump.

The crankcase is essentially the oil pan. That's where the "sump" is located. I'm sorry, but I highly doubt you do anything with engines. What you are saying is that somehow oil supply is fed from an external source but yet when the oil drains into the crankcase (like every combustion engine's oiling system on the planet) that this oil somehow gets back to the external source like magic. The sump is and will always be part of the CRANKCASE. Again, the reason for any sort of external oil tanks is extra cooling and oil capacity. The job is still done via a "pick up" or "sump" that is directly underneath the engine where the oil flows back into (aka the crankcase)

And if you would read anything I said, I did not say the engine comes to a stop immediately. I said when an engine is not running, it tries to slow down. I've mentioned the word freewheeling about 30 times now. That is not stopped. The point being, that when the engine does finally fire back up, it has to not only gain all the RPM it's lost, but then add additional RPM to get to an over revving damage condition. In that short amount of time, the oil has long been resupplied and prop pitch control is already taken care of.

Holy shit man.. If I see one more ignorant thing in this thread I'm going to close it.

Here's a simple V8 dry sump oil pan. Notice the 2 Army/Navy (AN) fittings welded to the pan? These fittings are fed from the sump (which collects oil) which resupplies the external oil tank then to be resupplied back into the engine. I don't know how much more I can explain it. FFS a dry sump setup is just there as an external oil pump and instead of feeding or having to suck oil directly off the bottom of the oil pan. It has it's very own external tank mounted above the external pump so it doesn't have to pull. It pushes. But without the oil from the sump, this tank is never replenished. And in the same regards, if the oil in the dry sump tank and the oil in the bottom of the oil pan where at such an extreme negative g to where the oil sump (in the crankcase) and the oil in the external tank were both not being pumped (via air between them) cavitation will occur.

This bottom 2 fittings of this oil pan is the ONLY resupply oil feed on this instance of a dry sump.

http://www.jegs.com/images/photos/400/497/497-3044.jpg

[Gromit]

[QUOTE=ATAG_Bliss;46476]Gromit,

This is taken directly from a spitfire merlin engine:

The crankcase is essentially the oil pan. That's where the "sump" is located. I'm sorry, but I highly doubt you do anything with engines. What you are saying is that somehow oil supply is fed from an external source but yet when the oil drains into the crankcase (like every combustion engine's oiling system on the planet) that this oil somehow gets back to the external source like magic. The sump is and will always be part of the CRANKCASE. Again, the reason for any sort of external oil tanks is extra cooling and oil capacity. The job is still done via a "pick up" or "sump" that is directly underneath the engine where the oil flows back into (aka the crankcase)[Quote=ATAG_Bliss]


I assure you I have very detailed knowledge of engines and twenty years racing and competition experience, I submit a diagram of the engine installation of the spit mk1, here you will note it states "exposed oil tank" under the nose-

http://markonepartners.co.uk/sites/default/files/spitfire-poster-large.jpg

the lower cowling was re profiled on later spits to house a larger oil tank, giving it a more pronounced chin (not to be confused with the Vokes filter)

And yes the oil is fed from an external source, the oil tank, this is taken by the pressure pumps and pumped into the engine, where it drains into the sump and is removed back to the tank from the sump by the scavenge pumps.

descriptions of a dry sump system-

http://www.drysump.com/drysump.htm
http://www.motorauthority.com/news/1035909_video-2010-corvette-grand-sport-dry-sump-oil-system-explained
http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/question331.htm

No offense but you seem to be confusing wet and dry sump systems.

[ATAG_Bliss]

I assure you I have very detailed knowledge of engines and twenty years racing and competition experience, I submit a diagram of the engine installation of the spit mk1, here you will note it states "exposed oil tank" under the nose-

http://markonepartners.co.uk/sites/default/files/spitfire-poster-large.jpg

the lower cowling was re profiled on later spits to house a larger oil tank, giving it a more pronounced chin (not to be confused with the Vokes filter)

And yes the oil is fed from an external source, the oil tank, this is taken by the pressure pumps and pumped into the engine, where it drains into the sump and is removed back to the tank from the sump by the scavenge pumps.

descriptions of a dry sump system-

http://www.drysump.com/drysump.htm
http://www.motorauthority.com/news/1035909_video-2010-corvette-grand-sport-dry-sump-oil-system-explained
http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/question331.htm

No offense but you seem to be confusing wet and dry sump systems.

Did you read anything I said? I already know how a dry sump system works. The spitfire is no different than virtually any other dry sump setup. But you said that there is no oil in the sump of dry sump system. That's when I explained there was and further explained that the sump is the entire pick up point of the entire oil system in the 1st place. ALL the oil passes through the dry sump pickup.

No offense, but you need to google harder.

The point of this thread is to point out that under negative g, engine damage WON'T occur in Clod. Not a single person has shown a single shred of evidence that it will to my points that say it won't and the reasons why. Now the tangent is you trying to explain to a heads up drag racer how an engine works. I'm sorry but from what you've said earlier, you don't have very much of an understanding of combustion engines at all.

Like I said, you should've googled harder in the 1st place, so I'm not constantly having to correct all the misinformation you are typing. If you've done any engine building, then I'm superman.

And please learn how to use quotes. It's not that hard.

[LG1.Farber]

Gromit, I understand what your saying and your right however you should do something more constructive with your time. :thumbsup:


Once, a long time ago, there was a wise Zen master. People from far and near would seek his counsel and ask for his wisdom. Many would come and ask him to teach them, enlighten them in the way of Zen. He seldom turned any away.

One day an important man, a man used to command and obedience came to visit the master. I have come today to ask you to teach me about Zen. Open my mind to enlightenment. The tone of the important mans voice was one used to getting his own way.

The Zen master smiled and said that they should discuss the matter over a cup of tea. When the tea was served the master poured his visitor a cup. He poured and he poured and the tea rose to the rim and began to spill over the table and finally onto the robes of the wealthy man. Finally the visitor shouted, Enough. You are spilling the tea all over. Cant you see the cup is full?

The master stopped pouring and smiled at his guest. You are like this tea cup, so full that nothing more can be added. Come back to me when the cup is empty. Come back to me with an empty mind.

[ATAG_Bliss]

Yes - you are all right. That's why you can't respond to a single point I made about neg g cut in this thread. :thumbsup:

Thanks for the white flag.

[Robo.]

Maybe TF will implement some of the damage features associated with negative gravity in the merlin engine...

Please cast your eyes on points 3 and 4.

2860

Just to point out that this issue is not necessarily interconnected with the early Merlin neg-G cut out.

Oil pressure drop and possible damage associated with it was dangerous for any aircraft engine of the era, and many aircraft manuals do mention certain time limits for flying inverted or in neg-G maneuvers like continuous slow rolls. This has nothing to do with the fuel starvation in the neg-G maneuver that also occurs in this particular engines (Merlin II, III and XII), and the above document is equally applicable to later Merlin versions (with neg-G carb already resolved), and also for (m)any other aircraft.

[Gromit]

Gromit, I understand what your saying and your right however you should do something more constructive with your time. :thumbsup:

Wise man that Zen.:salute:

[ATAG_Bliss]

Just to point out that this issue is not necessarily interconnected with the early Merlin neg-G cut out.

Oil pressure drop and possible damage associated with it was dangerous for any aircraft engine of the era, and many aircraft manuals do mention certain time limits for flying inverted or in neg-G maneuvers like continuous slow rolls. This has nothing to do with the fuel starvation in the neg-G maneuver that also occurs in this particular engines (Merlin II, III and XII), and the above document is equally applicable to later Merlin versions (with neg-G carb already resolved), and also for (m)any other aircraft.

Yes - but the key here when referring to Clod RAF planes is this damage can't occur because the engine is not running anytime there is a possibility for oil starvation. For some reason this is lost on people in this thread.

[ATAG_Bliss]

Wise man that Zen.:salute:

Yes very wise. If only more people would heed to the advise, especially the open mind bit. :D

I always know when someone is upset about losing an argument. It's funny to watch specific points being made then to have those same posters completely change the subject when their points are shot down. It's sadly the real sign of defeat. As a competitive person, an engineer, and a drag racer, I love discussing power trains. The problem always comes in when people read about them actually honestly believe they understand them. This thread is just another example of armchair experts. I think that's the reason noone can refute anything I've said about the topic at hand. Some of what I speak of cant be googled and therefore the armchair guys can't refute any of it. So let's change the subject instead! lol

The zen piece is a nice touch that only further proves my point, further getting away from the topic at hand. I'd love to see some of these so called engine guys come over to my shop and try to put a $60k pro mod motor together. Sorry for the rant. I just really enjoy calling people out on their BS and watching them walk away with their tails between their legs. It's not really that I'm an ass. I just can't stand liars and bullshit artists.

Anyhow - it's obvious that noone can refute the points I've made and instead and gone way off topic in trying to save face. Therefore this thread is locked.