Spit/109 sea level speed comparisons in 1.08 beta patch

[Glider]

I have put in a request to the Rolls Royce Heritage Trust part of Rolls Royce to see what they say. The NA don't seem to have anything that would satisfy everybodies requirements. I wouldn't hold your breath as it might take forever but should at least deliver a definitive reply.

[Crumpp]

I shall do the math to prove that 400kph was the cruise speed

Do you know where cruise speeds are located on the Power and thrust curves?

Need me to show you.....????

[Crumpp]

Spitfire III, AFAIK only the prototype was built.

[Seadog]

Originally Posted by Crumpp

Spitfire III, AFAIK only the prototype was built.

The 2nd (lower) page is not a Spitfire III. Spitfire III had a wingspan of 30 ft 6 in (9.3 m) and wing area of 220 square feet and for 6000lb that gives a wing loading of 27.3lb.

[Robo.]

Originally Posted by Crumpp

Spitfire III, AFAIK only the prototype was built.

Yes, I know, only few built. My point was that the original data linked by Banks were of Merlin III powered Spitfire.

Even your image is not an Mk.III, just the 1st page.

[Osprey]

Originally Posted by Crumpp

Spitfire III, AFAIK only the prototype was built.

That was built for the Griffon engine but they had a ton of problems and dropped it. The Merlin XX wasn't used in the Spitfire, that's why Robo is rightly taking the mick out of you.

[NZtyphoon]

Originally Posted by Osprey

That was built for the Griffon engine but they had a ton of problems and dropped it. The Merlin XX wasn't used in the Spitfire, that's why Robo is rightly taking the mick out of you.

In this case Crumpp is right, just for once - the Spitfire III prototype was built with the Merlin XX, which had a single-stage two speed supercharger - it also had clipped wings, a revised undercarriage which was raked forward by 2 inches, and a revised windscreen with two straight side pieces and flat windscreen with internal glass (the undercarriage and windscreen were later used on the Spitfire VC) . When it was decided to reserve the XX for Hurricane IIs the Mk III was adapted to take the first Merlin 60 series engine, becoming a Mk IX prototype. The Mk IV was very similar to the Mk III but had the Griffon engine.

[Osprey]

OK so I may be a version out here lol Either way it's another case of running with it because there's a war on, not exactly the engineers style planning he expects in theory. Of course it's theory that engineers plan because where I work, which is a very successful global engineering firm, the engineers have virtually zero planning, all prototyping and wing their projects (plastering it with documentation on the fly). It's in software, my dept, which has far more planning than the engineers.

[Robo.]

Originally Posted by NZtyphoon

In this case Crumpp is right, just for once - the Spitfire III prototype was built with the Merlin XX, which had a single-stage two speed supercharger - it also had clipped wings, a revised undercarriage which was raked forward by 2 inches, and a revised windscreen with two straight side pieces and flat windscreen with internal glass (the undercarriage and windscreen were later used on the Spitfire VC) . When it was decided to reserve the XX for Hurricane IIs the Mk III was adapted to take the first Merlin 60 series engine, becoming a Mk IX prototype. The Mk IV was very similar to the Mk III but had the Griffon engine.

Very true, thanks for the details NZtyphoon. The key is the different (clipped) wings and therefore different wing load than the one we see at the top right corner of the above sheet.

Crumpp came up with the Merlin XX theory only to prove that the fan plot posted was for different engine with 2 stage supercharger. That is wrong just as was wrong his assumption that the chart posted previously by Banks (post 345) already included RAM effect.

No matter how I look at it, the post 345 makes perfect sense.

[Crumpp]

All I said was that you were wrong in your statement that 400kph fixed trim setting was due to the 'good speed for dogfight' reason

Again, robo...

I asked you if you know how to determine the cruise speeds for an airplane. These are not random figures, pulled from a hat.

They are specific points on the power required and thrust required curves. The cruise speeds points of the thrust required and power required curves are fixed by the design and completely independent of engine settings.

Do you need me to talk you through how to determine them?

It is very easy to proved I am not wrong if you understand how the physics works.