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View Full Version : Wow, never noticed this about Spits!!



mortoma
08-06-2008, 10:11 AM
I hardly ever fly Spitfires. And it shows!! I never realized that only the Spit 5s allow you to change prop pitch! The 8 and 9 models disallow it.

And I can't figure out why, because the cockpit shows a prop control lever just like the Spit 5s have! I'm no Spitfire expert ( like we have many of here in the forums ) but I'd find it hard to believe that Spit 8s and 9s didn't have a constant speed prop that allowed for RPM changes!! A mistake on Oleg's part? You experts please tell me.

Also noticed the Spit 8 has a retractable tail wheel but the 9s revert back to the fixed! At least in the game. Why did the British do that? Seems a retractable is well worth the extra weight penalty as it offers a more streamlined aircraft.

JtD
08-06-2008, 10:17 AM
You can change prop pitch on all models, but you need to switch off auto-pitch first.

The Spit VIII is a later model than the IX, which is just a V with a new engine. So naturally it is more refined, for instance it has a retractable tail wheel.

SlickStick
08-06-2008, 10:17 AM
Originally posted by mortoma:
I hardly ever fly Spitfires. And it shows!! I never realized that only the Spit 5s allow you to change prop pitch! The 8 and 9 models disallow it.

And I can't figure out why, because the cockpit shows a prop control lever just like the Spit 5s have! I'm no Spitfire expert ( like we have many of here in the forums ) but I'd find it hard to believe that Spit 8s and 9s didn't have a constant speed prop that allowed for RPM changes!! A mistake on Oleg's part? You experts please tell me.

Also noticed the Spit 8 has a retractable tail wheel but the 9s revert back to the fixed! At least in the game. Why did the British do that? Seems a retractable is well worth the extra weight penalty as it offers a more streamlined aircraft.

1. You can change prop pitch in the Mk. VIIIs and Mk. IXs, too. You just have to toggle the Auto prop pitch setting.

2. The Mk. VIII came after the Mk. IX. Original Mk. IXs were converted Mk. Vs. The Mk. VIII was the first model to have the retractable tail wheel.

The Mk. IX we have in game is a later version, not a converted Mk. V airframe, as it has the pointed rudder and other updated features.

SeaFireLIV
08-06-2008, 10:24 AM
Shift+0 or (is it Ctrl+0?) will switch off auto-prop pitch and give you manual. I barely use it, but it`s useful sometimes.

gdfo
08-06-2008, 10:33 AM
I forgot about the retracable tail wheel on the late model spits.

It does retract with the other gear correct?

No need to assign a new key?

M_Gunz
08-06-2008, 11:31 AM
Are you talking about blade pitch or just the ability to command prop rpm?

It's easy enough to tell. If you set a fixed pitch and then speed up, your engine revs increase.

SlickStick
08-06-2008, 11:38 AM
Originally posted by gdfo:
It does retract with the other gear correct?


Yes.

mortoma
08-06-2008, 12:40 PM
Ok, I see....The later Spits are like the auto system on the 109 I guess. I tried using the auto prop toggle and it works like a Bf-109. So it's not a true constant speed prop like most allied planes have, including the Spit V. Strange I have been with this game from the demo days and never noticed that. Of course the Spits came in mid-way to late, starting with Ace Expansion Pack, IIRC.

mortoma
08-06-2008, 12:43 PM
Originally posted by JtD:
You can change prop pitch on all models, but you need to switch off auto-pitch first.

The Spit VIII is a later model than the IX, which is just a V with a new engine. So naturally it is more refined, for instance it has a retractable tail wheel. You don't have to do the auto pitch thing with the Vs.

SlickStick
08-06-2008, 12:53 PM
Gotta love those Mk. VIIIs. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

http://img357.imageshack.us/img357/8409/spitfiremt928topviewzg2.jpg

stathem
08-06-2008, 12:54 PM
Originally posted by mortoma:
Ok, I see....The later Spits are like the auto system on the 109 I guess. I tried using the auto prop toggle and it works like a Bf-109. So it's not a true constant speed prop like most allied planes have, including the Spit V. Strange I have been with this game from the demo days and never noticed that. Of course the Spits came in mid-way to late, starting with Ace Expansion Pack, IIRC.

No it is a CSP. In the IX and VIII the auto PP simulates the mechanical linkage of the throttle with PP lever. If you switch off the auto PP, you can fly it just the same as you would a P-51 or Tempest, if you're used to using the prop pitch.

I've only really become proficient at this since moving to the Tempest (and getting an X-52 with PP on the slider), but even back when I flew Spit IXs a lot, I would disco the Auto PP when slowing down for a landing at least (So you can zero the throttle but leave the prop at 100%), and sometimes in dives.

JtD
08-06-2008, 01:42 PM
Originally posted by mortoma:
You don't have to do the auto pitch thing with the Vs.

I know.

mortoma
08-06-2008, 02:26 PM
Originally posted by stathem:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by mortoma:
Ok, I see....The later Spits are like the auto system on the 109 I guess. I tried using the auto prop toggle and it works like a Bf-109. So it's not a true constant speed prop like most allied planes have, including the Spit V. Strange I have been with this game from the demo days and never noticed that. Of course the Spits came in mid-way to late, starting with Ace Expansion Pack, IIRC.

No it is a CSP. In the IX and VIII the auto PP simulates the mechanical linkage of the throttle with PP lever. If you switch off the auto PP, you can fly it just the same as you would a P-51 or Tempest, if you're used to using the prop pitch.

I've only really become proficient at this since moving to the Tempest (and getting an X-52 with PP on the slider), but even back when I flew Spit IXs a lot, I would disco the Auto PP when slowing down for a landing at least (So you can zero the throttle but leave the prop at 100%), and sometimes in dives. </div></BLOCKQUOTE>Ok, that makes a lot of sense. I totally understand how the system works now. Very interesting, and not like the auto pitch on the german planes. I use prop pitch to substantially speed up acceleration, so I'll just leave the Spit 8 and 9 on manual from now on. Reducing PP helps you pick up speed in a dive like gangbusters too.

M_Gunz
08-06-2008, 04:31 PM
In less than 100% power cruise to save on gas, reducing rpms gets you more speed than 100% rpm.

Reducing rpms even at 100% power will save on engine heat. Just figure the cylinders aren't
firing as often.

MB_Avro_UK
08-06-2008, 04:42 PM
Originally posted by SlickStick:
Gotta love those Mk. VIIIs. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

http://img357.imageshack.us/img357/8409/spitfiremt928topviewzg2.jpg

Superb pic http://forums.ubi.com/images/smilies/25.gif

http://www.youtube.com/watch?v=RaX3m7mMmxM

Best Regards,
MB_Avro.

SlickStick
08-08-2008, 09:59 AM
Originally posted by MB_Avro_UK:
Superb pic http://forums.ubi.com/images/smilies/25.gif

Best Regards,
MB_Avro.

Indeed, that is one of my favorite Spit pics. You can almost hear the growl of the engine as it performs that zoom climb. http://forums.ubi.com/images/smilies/25.gif

WOLFPLAYER2007
08-08-2008, 10:51 AM
Originally posted by M_Gunz:
In less than 100% power cruise to save on gas, reducing rpms gets you more speed than 100% rpm.

Reducing rpms even at 100% power will save on engine heat. Just figure the cylinders aren't
firing as often.

In real life, reducing prop pitch with the engine in full power cause major damage to the engine, according to a friend of mine that is private pilot...

I use a lot of prop pitch to easy on the engine too in il2.

M_Gunz
08-08-2008, 03:04 PM
It depends on how fast you are going, how much you reduce the rpms and possibly the plane as well.
But how fast you're going is critical, just not in IL2.

ADD: Oh and besides, full throttle is 110%, not 100%. I'm not lowering rpm at full throttle
when I run 100% throttle and less than 100%. 90% or 95% rpm at 100% throttle cools the engine.
Guess what % of 110 is 100? Try.... 91%. At say 450-500+ kph I feel safe enough at 100%-90%.

mortoma
08-08-2008, 08:39 PM
Originally posted by WOLFPLAYER2007:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
In less than 100% power cruise to save on gas, reducing rpms gets you more speed than 100% rpm.

Reducing rpms even at 100% power will save on engine heat. Just figure the cylinders aren't
firing as often.

In real life, reducing prop pitch with the engine in full power cause major damage to the engine, according to a friend of mine that is private pilot...

I use a lot of prop pitch to easy on the engine too in il2. </div></BLOCKQUOTE>A lot of private pilots think that but that's not necessarily true. You can reduce RPM a little without reducing MP but not a lot. If you reduce RPM much it will put undue stress and a heavy load on the engine. Most pilots to be safe reduce MP a little then RPM, then repeat the process until they get both RPM and MP where they want it. This is a safe way for doing it but it's a myth you have to reduce RPM first. As long as you don't over do anything and read the manual to see the recommendations of the manufacturer, you'll be alright. I still hold a PPL but am not an active pilot. My medical expires in September.

M_Gunz
08-09-2008, 02:57 AM
Consider the CSP prop blades as wings producing as much lift as they can for the power that is
being applied to them. Lift on the blades is thrust and the engine drives against the drag on
those blades which increases by speed squared before even considering compression.

A prop 3m in diameter, at 2500 rpm the tips move about 295 m/s just going around. If you're
flying TAS 720 kph then your forward speed is 200 m/s. The prop tips are going 356 m/s which
is 1281 kph... just over mach 1 at sea level. The rest of the blade moves slower but the
overall average spot is about 71% out from center and moving 249 m/s, to make 900 kph average,
not mach 1 at any standard atmosphere altitude used by WWII fighters but still damned fast.

Less rpm requires less power to deliver less thrust as well but consider:
if you set your desired prop rpm at maximum and at some high speed the drag catches up to the
engine. The engine is failing to supply enough power to turn the prop blades against the drag
of high forward speed and high rotational speed together.
We're in a power dive in IL2 at this point or we're not running near full throttle or under
limited power some way.

If the blades stay at the max rpm at this speed they have to have less drag. When the drag
gets more than the engine can power, rpm goes to drop and the CSP fines the blades a bit to
keep rpm at the desired, maximum rpm. The prop blades fine down some and provide less lift to
keep speed up simply because the engine is fighting extra drag.

Lowering engine rpm is a way to decrease drag on the prop by not turning the thing so fast, less rotational speed component which at high revs is much bigger source of drag than the
forward speed component. Some rpm will trade for more forward speed by ratio of the squares
of each speed. It's a matter of speed, in IRL you get compression too.

At max level speed the engine power is equal to engine drag from turning that prop. That's
about how fast at full power to start cutting back prop rpm to prevent your prop from driving
your prop and causing extra drag.

But most real pilots usually don't get into screaming dives that push them above level max,
do they? That's a bold pilot.