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rhinomonkey
11-13-2008, 03:07 AM
I've been flying the mod mk1 spit and the early hurricane alot lately and have a few questions. I know these planes had 2 stage or variable speed props in real life but in the sim the rmp seems to regulate itself at 3000rpm and i get best performance at 96% to 99% prop pitch. This has to be wrong no? or am i missing an option for full prop pitch management?

I understand the concept of gravity fed fuel and the problem of starving the engine in negative g manouvers. but surely the prop would not stop turning unless you were in a stall or if you feathered the prop? ive had the situation where ive dived, starved the engine of fuel and the prop has stopped fully resulting in having to restart the engine. i dont see how this would happen in a dive? especially as to get the best out of the plane you need to have prop pitch at 99%!

example: drive a car down hill then cut the engine. Do the wheels stop turning?


PS i love the mod mk1 spit! i know the cockpit is all wrong but it looks so good from the outside!

Jex_TE
11-13-2008, 03:17 AM
But if you put the car in gear, it stops doesn't it? Doesn't feathering the prop engage the "clutch"?

rhinomonkey
11-13-2008, 03:21 AM
feathering the prop makes the prop blades in line with the flow of air so they have least possible drag so the prop doesnt turn. Example: in real life in a twin engine plane if one engine fails the prop needs to be feathered on the failed engine or it will windmill and cause anough drag to render the plane unflyable. My critisism is that the spit and hurri engines fail to windmill!

Nicholaiovitch
11-13-2008, 03:28 AM
I think you are probably right IRL......

But, within the prog limitations the chaps have done a magnificent job with the Mk1 and I think what you are expecting, though maybe correct, would require many more mods to be achieved.

I have done some experimentation with changing pitch with the engine stopped on various types and I have to say that there appears to be little change in aerodynamic effect of selecting prop pitch to say 10% with the engine stopped. (does not extend glide etc.)

I'm sure some better qualified observers will add to this and open our eyes, but that is my current take.

Nicholaiovitch

Jex_TE
11-13-2008, 03:31 AM
Originally posted by rhinomonkey:
feathering the prop makes the prop blades in line with the flow of air so they have least possible drag so the prop doesnt turn. Example: in real life in a twin engine plane if one engine fails the prop needs to be feathered on the failed engine or it will windmill and cause anough drag to render the plane unflyable. My critisism is that the spit and hurri engines fail to windmill!

So do you mean that the airflow through the prop, if unfeathered causes it to spin and that the energy used to make it spin is what causes the drag (a bit like a chopper in auto-rotation) ?

So is the game has it wrong, it's a pretty big failure isn't it in the heat of battle say?

rhinomonkey
11-13-2008, 04:02 AM
[

So do you mean that the airflow through the prop, if unfeathered causes it to spin and that the energy used to make it spin is what causes the drag (a bit like a chopper in auto-rotation) ?

So is the game has it wrong, it's a pretty big failure isn't it in the heat of battle say?[/QUOTE]

Yes it's called windmilling and is a well known aspect of flying a prop a/c. Prop pitch is used to control speed in a dive and to lose speed on final approach.

if you were in a fuel injected plane like a 109 and you went into a dive and reduced throttle to 0% (simulating fuel starvation) would the prop stop turning?

GregGal
11-13-2008, 04:09 AM
Early Spits and Hurris had a 2 pitch propeller. Either fully coarse or fully fine. This latter was only used for takeoffs and landings. By the beginning of July 1940 most of the Spits recieved new, constant speed props. This is the one modelled by AAA (quite correctly).

The engine dying is another question. It is hardcoded by Oleg, and cannot (yet) changed by AAA. It's not realistic IMHO. I've read hundreds of accounts, but none of them mentionned such an occasion, while in Il2 it happens to me every 2 missions.

Xiolablu3
11-13-2008, 04:35 AM
I think it was only a few very early mk1's that had 'non--auto pitch' props wasnt it?

Around Dunkirk time?

rhinomonkey
11-13-2008, 04:44 AM
Originally posted by Xiolablu3:
I think it was only a few very early mk1's that had 'non--auto pitch' props wasnt it?

Around Dunkirk time?

I thought that no MK1 spits had auto pitch props. The very early ones had 2 stage props and they were replaced with variable speed props where the pilot would still have to adjust the pitch manually but had a sliding scale rather then two settings. The MK1 in IL2 seems to have a prop that automatically regulates the pitch. I'm no expert by the way!

JG53Frankyboy
11-13-2008, 05:15 AM
its a question how to call it http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

lets say it is a constant speed propeller.

the pilot it setting a wanted RPM , and the propeller is mantaining this wanted RPM by setting the propellerblade angels automaticly.

M_Gunz
11-13-2008, 06:23 AM
There were 2 and 3 speed props prior to the CSP's. P-40 used Curtiss Electric prop from the
start, btw.

I don't believe you could feather the props on most of the single engine fighters in IL2.
Feathering takes a bigger, heavier prop than non-feathering and once feathered they stay feathered
with few exceptions.

Years ago there was debate over prop torque that had some of us stopping engines in flight
in Spits and Yaks. It was a real chore to get the prop to stop, had to slow almost to stall
as you would IRL. If my speed on the subsequent glide got too high then the blades would
stop turning. But then it was an earlier patch and we had no mods.

Kurfurst__
11-13-2008, 07:02 AM
Originally posted by Xiolablu3:
I think it was only a few very early mk1's that had 'non--auto pitch' props wasnt it?

Around Dunkirk time?

The first 78 Spits produced had fixed pitch two-bladed propellors, ie. no possibility at all the change the pitch angle. From the 79th production aircraft this was changed to a two pictch 3 bladed prop which could be set to either fine or coarse. In late 1939, a few Spits and Hurris were fitted variable CSP props, but almost all retained the 2 pitch props and the early few still had the fixed pitch props.

In the end of June 1940 a crash programme was initiated to retrofit Spits and Hurris with CSP props; some 1000 had been retrofitted by mid-August 1940; IIRC all new production Spits and 2/3s of the new Hurris produced were fitted with CSP at the factory.

AllorNothing117
11-13-2008, 10:02 AM
Interestingly I'm reading a book called "Fighter boys" about pilots in the secod world war. And talks about the pilots setting the olds spits and hirris prop pitched to fine for landing and course whilst in the air. And if they didn't change it when the plane got airborn it got covered in oil!

M_Gunz
11-13-2008, 10:55 AM
Try taking off in a 109 with manual pitch and full power then not changing either once you're up.

Aaron_GT
11-13-2008, 11:29 AM
I've been flying the mod mk1 spit and the early hurricane alot lately and have a few questions. I know these planes had 2 stage or variable speed props in real life but in the sim the rmp seems to regulate itself at 3000rpm and i get best performance at 96% to 99% prop pitch. This has to be wrong no? or am i missing an option for full prop pitch management?

Spitfire Is started off with a two pitch prop. Replacement started from around May 1940 and was complete by the end of the Battle of Britain. Two types of replacement prop were used (hydraulic - de Havilland - a copy of the Hamilton Standard, or by Rotol - ROlls royce brisTOL). Both were constant speed units. Thus the pitch was varied continuously to give the set RPM. Thus the regulation of RPM you see is accurate. For constant speed units the 'prop pitch' control should be thought of as an 'rpm' control instead.

M_Gunz
11-14-2008, 01:59 PM
hehehe (http://www.spitfireperformance.com/spit1vrs109e.html)


Deliveries of Spitfires equipped with constant speed propellers began as early as November 1939. No. 19 Squadron recorded their first delivery of the improved Spitfire as follows: 9

No. 54 Squadron completely converted to "Rotol Spitfires" during December 1939. 10 The introduction of the constant speed propellers increased the Spitfire's climb rate by 730 ft/min. over that of the 2-pitch propeller equipped Spitfires.


9 and 10 above are scans of documents showing the changeovers, they don't 'quote' well though.