Spitfire RPM's

[icuucme37]

When flying the Spitfire without CEM on you can't get full RPM's out of the engine. The automatic engine controls pulls the prop pitch back to 0% and never mover it up to 100% so you can't get max RPM and speed from the engine.

[Viper2000]

Originally Posted by icuucme37

When flying the Spitfire without CEM on you can't get full RPM's out of the engine. The automatic engine controls pulls the prop pitch back to 0% and never mover it up to 100% so you can't get max RPM and speed from the engine.

That's what it's supposed to do.

Actually you'll get pretty much full rpm if you climb to operational altitude (ie about 16000-18000 feet).

The Spitfire was not designed to fight at sea level.

[Peril]

Originally Posted by Viper2000

That's what it's supposed to do.

Actually you'll get pretty much full rpm if you climb to operational altitude (ie about 16000-18000 feet).

The Spitfire was not designed to fight at sea level.

Viper, do you have any tested data we can see to verify the rpm v alt curve? This data would add support to any CoD FMs accuracy claims, be good to see it's close to the mark. I've not worked with 'fixed pitch' props in TW FMs, so not much data or first hand experience with simulated fixed props here.

[Viper2000]

Originally Posted by Peril

Viper, do you have any tested data we can see to verify the rpm v alt curve? This data would add support to any CoD FMs accuracy claims, be good to see it's close to the mark. I've not worked with 'fixed pitch' props in TW FMs, so not much data or first hand experience with simulated fixed props here.

Nothing beyond that available to everybody else online:

http://www.wwiiaircraftperformance.o...ane/l1547.html

And yes, I know this is data for a Hurricane. You'd get the same sort of results with a Spitfire, but unfortunately there doesn't seem to be good data immediately available; here is all the Spitfire I stuff:

http://www.spitfireperformance.com/spitfire-I.html

[Peril]

Thanks, that's indeed helpful.

I note that the lowest rpm shown is around 2650 rpm if you extrapolate the graph to SL. This is obviously the high pitch setting, I wonder how much rpm should we see from low pitch at SL? The planes in game currently show a lot lower rpm in fixed high pitch, for what ever reason? The issue that results is that hp is linked to rpm and thus the planes in game with fixed props may be under represented in this area if rpm is low.

Virtual props in Targetware were difficult animals to get functioning realistically, I imagine it is the same here in IL2 FMs.

Thanks again for the data.

[icuucme37]

It don't matter what altitude your at in the Spitfire with out CEM on, you can't get above 21-2200 RPM's.

So I know this is not right. You hit the auto-pilot and it turn 100% pitch and 2800-3100 rpms, airspeed picks up. turn off AP and watch airspeed and PRM's fall like a rock.

[Blackdog_kt]

I know this won't fix the actual issue, but why not fly the aircraft that have a two-position prop with CEM enabled in the meantime? I mean, the prop only has two positions, it's not exactly complicated to use.

Whenever your speed drops go to high RPM, as soon as you pick up enough speed go to low RPM and watch your airspeed increase even more. It's like driving a car with two gears, very simple and it will allow you to fly the aircraft better.

Contrary to popular belief, keeping the RPM at full does not equal full speed. Also, the airspeed affects the kind of RPM you'll get for a given pitch setting, so if you're not using CEM and you have trouble accelerating just point the nose down for a bit to pick up some sped.

It's just that since the prop only has two positions, it will only reach optimal RPM around a very narrow band of airspeeds.

To really solve this problem i see no other way than code an extra routine into the engine "auto-management" that will go to fine pitch whenever the RPM drops too much. I think it shouldn't be that hard, it's just an "IF RPM<2200 THEN pitch=fine" type of statement with a similar one that will force coarse pitch when the RPM picks up a bit, so i guess we'll see it in a patch. Until then, try with CEM enabled and see the aircraft transform from a dog to an actually enjoyable ride

[*Buzzsaw*]

Salute

Two position props were not in general use during the BoB as I have proven in a previous post.

http://forum.1cpublishing.eu/showthread.php?t=21066

All Spitfires I's were converted to Constant speed props starting in late June of 1940, conversions were a matter of a few weeks.

The only relevance for two position props is for scenarios set before the BoB, ie. Dunkirk, interceptions of early recon flights over Britain, etc.

[reflected]

Originally Posted by *Buzzsaw*

Salute

Two position props were not in general use during the BoB as I have proven in a previous post.

http://forum.1cpublishing.eu/showthread.php?t=21066

All Spitfires I's were converted to Constant speed props starting in late June of 1940, conversions were a matter of a few weeks.

The only relevance for two position props is for scenarios set before the BoB, ie. Dunkirk, interceptions of early recon flights over Britain, etc.

Precisely. Most Spitfire MKIa-s were 12 boost and had CS props.

[Blackdog_kt]

Originally Posted by *Buzzsaw*

Salute

Two position props were not in general use during the BoB as I have proven in a previous post.

http://forum.1cpublishing.eu/showthread.php?t=21066

All Spitfires I's were converted to Constant speed props starting in late June of 1940, conversions were a matter of a few weeks.

The only relevance for two position props is for scenarios set before the BoB, ie. Dunkirk, interceptions of early recon flights over Britain, etc.

That is true, but since we do have a constant speed prop Spit that is mostly similar in all other respects i don't think it's such a big issue. I mean, we have a correctly performing one for the time period in question, so that relegates the whole issue to a naming convention for the aircraft in the sim.

The easiest solution would be to add the extra variations (it should be easy since it would just need to take the prop from the Mk.II and bolt it on to the Mk.I 3d model) and then re-label the Spits according to the way it's done for the Hurricane. This way, we would have "Spit Mk.I, two-stage prop" and "Spit Mk.I, constant speed prop" and everything would be correctly labeled and accurate

At present, i find that applying fixes that can have an effect across the board is of a higher priority, like for example fixing the auto-mixture algorithms that would affect almost all of the fighters in the game. I'm not saying the Spit shouldn't get corrected, i'm just saying that it's the aircraft with the most variants and one of them performs close enough to real life data, so maybe it would be more prudent to focus on improving flyables that are further off the mark at this early stage.


As for the 100-octane fuel issue, it should definitely be fixed. However, i doubt it would be of much use in full switch flying for a very simple reason: it might prevent detonation and let us run the engine at higher ratings, but overheat is still there and it's the main limiting factor. The only real use would be in absolute emergencies (read: checking six and seeing a bunch of cannon muzzles light up with tracers streaming my way).

For normal flying and even during combat, i prefer to use a more conservative value with short bursts of full throttle with my radiator almost closed, instead of firewalling it for the whole dogfight and having to run the rads full open. Overheat forces radiator use and the resulting drag defeats the whole purpose of the added power. If i can run a cool engine with a low drag profile i'm not only maximizing my fuel usage, i'm also maximizing the effectiveness of my brief, full throttle bursts: the engine is cool enough that it can take max boost with the rads at about 30% for half a minute or so, which is usually all it takes to decide the outcome of a zoom-climb chase or an evasive attempt.

Long story short, even if we get +12lbs engines i don't expect to be able to use it for any length of time that would provide more than a token advantage at very extraordinary situations, it was after all labeled as an emergency power setting and not a continuous one.