Spit/109 sea level speed comparisons in 1.08 beta patch

[Crumpp]

Pstyle says:
Are you saying that, because we don;t know the AoB, we cannot therefore assume that their rotational velocity is equivalent

That is correct.

IvanK says:
Now lets look at this Clmax discussion which Crumpp claims the RAE cocked up.

Why don't you do the math IvanK? You have a better idea of how to interpret aircraft data. That is not being patronizing, it is just a fact. You can set emotion aside and let numbers fall where they may....

If you do the math, you will find the values for CLmax align with the NACA's!!

Spitfire Mk I:

Speeds Dynamic pressure CL
66 14.76610169 1.693067034




Once more, the RAE admits that operating a trailing static head is difficult as best. Do you know what you have to do? When installed, you have a tangle of tubes in the cockpit that the pilot must pinch off with an airtight seal on the correct lines at the right time. It is hard enough in cruise flight and would be extremely difficult to do accurately in a high performance fighter at the stall point.

That is why they labeled the values as "assumed values of CLmax".

[Crumpp]

IvanK says:
RAE methodolgy is slightly different to NACA's

Because of the difficulty in obtaining accurate measurements under certain conditions of flight.....

See above.

Glad you brought up all these points. You read my mind. .

You can use the NACA's values for some things on the Spitfire Mk V. The airfoil is the same. Airfoil selection is what determines Coefficient of lift.

If I would have posted it, some people would have just attacked it was from a different variant without understanding what is comparible and what is not.

[ATAG_Dutch]

Let me guess here.

The 'math' (or 'maths' as it's referred to over here) according to Crummp, shows something adverse to the documented real life performance of the Supermarine Spitfire relative to the performance of the Bf109.

There is a distinct pattern developing here.

I find it surprising that a man who purports to concern himself with the performance of 'real aircraft', does not spend his time debating these issues on a more appropriate forum involving comparisons between 'real world' aircraft.

Why would such an expert in his field waste his time on a forum geared to the analysis of a Battle of Britain based computer game? With most of his efforts geared toward the discrediting of the Supermarine Spitfire relative to the Messerschmidt Bf109?

It's a mystery to me, but maybe a psychologist could write a thesis.

[Crumpp]

shows something adverse to the documented real life performance

It is not documented real life performance.....

It is calculated from a single data point with assumed values for CLmax.

That single data point was measured from a trailing static head.

What do you think the spreadsheet is??? Try the same the exact thing...calculated performance from data.

I just have the advantage of being able to use Mtt data, Supermarine, and NACA data that did not exist in 1940.

[Crumpp]

they had the aircraft to test the results.

And we have 70 years of data including classified documents from the people who built, designed, and flew the airplane in service.

Sorry, but we have the information advantage.

[Glider]

Originally Posted by Crumpp

And we have 70 years of data including classified documents from the people who built, designed, and flew the airplane in service.

Sorry, but we have the information advantage.

Are you saying that having the real aircraft, most up to date test facilities at the time, the only trained test pilots in the world (at the time) is not an advantage when testing theory.

There is a reason why the premier Aviation University in the UK is at Cranfield (not Cambridge who do not teach Aeronautical engineering or theory) its because they have their own test flight of aircraft often passed down from the RAF research establishments.
You should tell them they don't need the aircraft, it would save them a ton of money

[Crumpp]

the only trained test pilots in the world

That is a good point. We are talking about the test pilots who felt the Bf-109 was "embarrassed" by the slats opening in the turn.

I would not be surprised if the pilots did not operate the propeller at its most efficient point at the single data point the RAE used. That would throw off all of Gates assumption for the entire envelope.

In order to reproduce the RAE results, I have to drop the propeller efficiency to below average and assume VDM could not properly design a propeller.

[Crumpp]

classified documents from Vickers-Supermarine

It is the ones from Mtt that the RAE did not have access too. Germany was at war with England at the time so they were not exactly sharing information.

Instead, a pilot with little experience with a selectable pitch propeller had to go up and operate it to record data using a very difficult method of gathering airspeed data.

My Spitfire analysis is in agreement with the RAE's analysis.

The relative performance is not in agreement, but that has to do with Bf-109 performance and not the Spitfire's.

[Glider]

Originally Posted by Crumpp

That is a good point. We are talking about the test pilots who felt the Bf-109 was "embarrassed" by the slats opening in the turn.

I would not be surprised if the pilots did not operate the propeller at its most efficient point at the single data point the RAE used. That would throw off all of Gates assumption for the entire envelope.

In order to reproduce the RAE results, I have to drop the propeller efficiency to below average and assume VDM could not properly design a propeller.

As it happens yes they are. The UK had the first and at that time only test pilot training school in the world. As for being embarrased yes the Me109E was embarased by the way the slots opened, which no doubt was why they were redesigned for the Me109F. Unless you have a better reason for the redesign.

As for you having to drop the propeller efficiency to get the same results, working on the basis that you are not a trained test pilot then I can only assume that your model is wrong. I know you believe that the test pilots are not important but if I had to pick between their hard earned experience and training, backed up be the science of the day and access to the real aircraft, against your maths and how you read documents, I would go for the experts.

[Glider]

Crumpp
You are reading something into the paper which isn't there and as a result are making an incorrect assumption.

Originally Posted by Crumpp

Once more, the RAE admits that operating a trailing static head is difficult as best. Do you know what you have to do? When installed, you have a tangle of tubes in the cockpit that the pilot must pinch off with an airtight seal on the correct lines at the right time. It is hard enough in cruise flight and would be extremely difficult to do accurately in a high performance fighter at the stall point.

That is why they labeled the values as "assumed values of CLmax".

You are right in some of what you say but have ignored other parts of the quote. The paragraph can be summerised as follows

a) An accurate calculation of the turn performance is dependent on an accurate measure of the CL max in level flight
b) The only way that the CLmax can be accurately measured is the use of the trailing static head.
c) It is difficult to do (this is the part which you highlight)
d) Despite it being difficult it has been successfully done on both the Spitfire and Me109
e) That the method used by the NACA is not as reliable and gave a misleading result

By ignoring the other relevent parts your assumption that the RAE had to calculate the results because they couldn't measure the CL max is fundamentally flawed.

Its because they were able to get an accurate measure of the CL max in a glide and max throttle that an accurate calculation of turn performance was possible

I should add that the RAE did exactly the same with the Me109 so these are by far the best calculations around.