Spit/109 sea level speed comparisons in 1.08 beta patch

[41Sqn_Banks]

I know that, I can read. You asked how the engine data align with the speed graph. They align with an consistent altitude difference of about of 2,000 ft.

The altitude difference between the FTH in the charts can be explained by a different level flight speed. E.g.
Hurricane I has a FTH of 17,750 ft at 316 mph.
Spitfire I has a FTH of 18,600 ft at 364 mph.

As we see the 50 mph speed difference results in a drop of 1000 ft for the FTH.

There is nothing contradicting in the charts ...

[Crumpp]

I know that, I can read.

Then what is the issue with the data not aligning?

The altitude difference between the FTH in the charts can be explained by a different level flight speed. E.g.

It will align. If you looked at other aircraft and not just confined yourself to one specific type, you would see this the case.

A speed difference is not going to account for a 2000 ft increase in FTH.

How do you explain the fact this chart comes from an investigation of performance with an experimental high altitude engine.

The chart exactly matches the one found in:

Messerschmitt Me. 109

Handling and Manoeuvrability Tests

BY

M. B. MORGAN, M.A. and D. E. MORRIS, B.SC.

COMMUNICATED BY THE PRINCIPAL DIRECTOR OF SCIENTIFIC RESEARC (AIR)

MINISTRY OF SUPPLY

__________________________________

Reports and Memoranda No. 2361

September 1940*

http://kurfurst.org/Tactical_trials/...ls/Morgan.html

[Crumpp]

Originally Posted by 41Sqn_Banks

I know that, I can read. You asked how the engine data align with the speed graph. They align with an consistent altitude difference of about of 2,000 ft.

The altitude difference between the FTH in the charts can be explained by a different level flight speed. E.g.
Hurricane I has a FTH of 17,750 ft at 316 mph.
Spitfire I has a FTH of 18,600 ft at 364 mph.

As we see the 50 mph speed difference results in a drop of 1000 ft for the FTH.

There is nothing contradicting in the charts ...

The data matches the same fan plot in another report on a Spitfire equipped with a Merlin XX engine.

AFAIK, the Spitfire Mk I was equipped with the Merlin III engine.

[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.