Spit Mk1 Boost?

[=XIII=Wedge]

Realism in IL2-Cliffs of Dover
"The flight sim we've built in Cliffs of Dover is much bigger than anything we've built before. We made it more realistic in every respect: graphics, plane models, physics, aerodynamics, weapons, customisability, and more."
Ilya Shevchenko - Pilot's Notes - Special Edition

The goal of greater realism is one the development team share.

For example, if the game currently modelled the Spitfire Mk 1A with 2 x 20 mm Hispano cannon, I would conclude that this was an genuine mistake on the part of the developer and raise it as a bug. If the developer then responded that this was by design then I would not be interested in using such a sim, they might might as well have modelled X-Wing fighters instead.

Also what would be the value in modlling different models of the same aircraft, not just the different marks, but even down to different propellors.

The fact is they wouldn't if they did not intend to strive for greater realism.

Whilst we can all discuss the merits of various sources regarding aircraft performance, ultimately it is down to the developers to decide on what parameters they want to use.

However if they did not want to strive for realism then it seems strange to spend time developing and engine to model so many features. If realism was not a goal then a simpler engine design would suffice saving time and money.

Whilst FM discussions are difficult, some elements can be modelled with a reasonable level of realism, hence...

Back to the Boost Cutout
So getting back on topic we end up with a couple of questions

Given a Spitfire Mk1A with with an unmodified Merlin III engine using 87 octane fuel.
When the boost cutout is engaged
Then what behaviour is expected? (as intended by the developers)
And how does this correspond with actual behaviour observed in the current version of the game.

Another question is what would the actual effect be on a real 1940's Spitfire?

The first question is easy for the developer to answer, the second is something that I am interested in from an understanding point of view.

[41Sqn_Banks]

AP 1590B Merlin II and III Aero-Engines:
"257A. In its unmodified condition, the boost control cut-out valve permitted the boost pressure to rise very considerably."

[TomcatViP]

Woaaaww... "Considerably" ?

@Wedge : can you consider that given the Spit FM are alrdy optimistic adding the extra boost cld hve proved so outraging that the devs might hve decided to lower this value on the Spit ?

[41Sqn_Banks]

Yes considerably ...

http://www.spitfireperformance.com/spit1-12lbs.jpg

full throttle would give about 17 lbs. sq.in.

If however I well understood, the boost cut out was put because this high pressure was damaging to the engine in the long run and therefore its use was limited to real emergency cases.

Could the fact that it is limited right now be linked to that perhaps?

[Osprey]

TomcatVIP, would you please stop posting if you aren't going to add anything other than hearsay to this. From reading the thread =XIII=Wedge has made some very interesting points - I for one am trying to understand the detail of this but clearly I'm a bit more stupid than other pilots. Understandably I don't really appreciate you throwing in undermining comments based on your own personal knowledge and trying to deride other posters arguments on the spurious suggestion that the length of registration on a forum somehow dictates your knowledge on the topic. Should Jeffrey Quill have registered today would you be telling him the same thing?

Frankly, if you are one of those people that doesn't believe that the RAF had the 100 octane in use on fighters thus achieving 12lbs boost then I'm afraid I don't think I'll be able to take anything you say seriously, ever. I'm confident that the development team aren't so unreasonable when it comes to looking at evidence.

=XIII=Wedge, please carry on.

[=XIII=Wedge]

Function of the Automatic Boost Control
My understanding was that the original reason for the throttle being design with an automatic boost control was to reduce the workload on the pilot and prevent over-boosting the engine.

It allowed them to set the desired boost pressure with the throttle lever and the ABC would ensure that that desired pressure setting was maintained up to the rated altitude.

Without it the pilot would constantly have to keep adjusting the throttle to maintain the same boost as the plane changed altitude.

Using the boost cutout disables this function.

@TomcatViP - It is possible, but it is more likely that pressure to release the product meant that development was scaled back.

There is clear evidence of this, due to having two variants of spitfire MK 1A that differ only by propellor. (DH-2S and Rotol-CS)

No problem with this it happens all the time, features are dropped to get a release to the market place.

However if you take these pressures out of the equation, a more realistic flight model is still a desirable attribute and is infact a major selling point.

Red vs Blue arguments don't really come into it.

Multiplayer is an important aspect of the game, but with out greater realism we might as well be playing Tom Clancy's H.A.W.X.

[Viper2000]

Originally Posted by 41Sqn_Stormcrow

If however I well understood, the boost cut out was put because this high pressure was damaging to the engine in the long run and therefore its use was limited to real emergency cases.

ABC was introduced in order to prevent pilots from breaking engines by overboosting them below FTH.

I suspect that the cutout was originally provided in case the ABC failed, so that the pilot would still have access to direct throttle control.

The cutout modification was basically a hack which allowed the cutout to function as a combat power detent without extensive modification to the rest of the cockpit.

Later Spitfires didn't have a boost control cutout, but were instead fitted with a gated throttle which allowed the independent setting of the various engine ratings, including the combat rating. They also had double-acting ABC instead of single acting ABC, which meant that the throttle behaviour was a bit different. This is explained in the relevant AP from the period (I forget the number now, but it's been linked to in quite extensively in this forum).