Spit/109 sea level speed comparisons in 1.08 beta patch

[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.

[Kurfürst]

Originally Posted by Glider

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

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 Nope it was not done on the 109
e) That the method used by the NACA is not as reliable and gave a misleading result According to RAE...

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.

No, it's correct, RAE admits that it has estimated Bf 109 Clmax values from earlier Spitfire flights, and did not measure them.

The " stall boundary " depends on an estimate of CL max at full throttle. In the case of the Spitfire this has been measured in flight, while the Me.109 figures were based on the Spitfire results; tables of the assumed values of CL max are given in Fig. 17. CL max falls off as g is increased, because the stalling speed increases as g gets larger, thus lessening the slipstream effect.

In contrast, RAE only measured Clmax in throttled back conditions:

Only one flight was made, as operating a suspended static head from a single-seater aircraft with a rather cramped cockpit is difficult.[b] Stalling speeds with engine throttled right back were measured/b] with flaps and undercarriage up and down, and the speed at which the slots opened were also noted ; in every case both slots opened almost simultaneously.

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

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.

Nope. What RAE did can be best described as a reasonably close estimate based on guessworked Clmax, with wrong weight, and with wrong power. REA did not measure full throttle Clmax on the 109, they have estimated that from results with the Spitfire... so who's quoting out of context now, David?

The most accurate calculations for the Me 109 turn capability are those done by Messerschmitt A.G., for obvious reasons.

[Glider]

Originally Posted by Kurfürst

No, it's correct, RAE admits that it has estimated Bf 109 Clmax values from earlier Spitfire flights, and did not measure them.

This paper clearly states that these measurements had been successfully done on the Me109. and it is clear that they had been measured on the Spitfire, Me109, Buffalo and Whirlwind.

Only one flight was made, as operating a suspended static head from a single-seater aircraft with a rather cramped cockpit is difficult.[b]

So you agree that they were measured

Stalling speeds with engine throttled right back were measured/b] with flaps and undercarriage up and down, and the speed at which the slots opened were also noted ; in every case both slots opened almost simultaneously.

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

And you agree that they were measured in landing configuration (flaps and gear down), plus gliding config (with flaps and gear up).

It should be noted that this section in the paper is titled
Stalling Tests 4.4 4.41 determination of CL max
Would you really expect them to comment on the CL max at full throttle during stalling tests?

However, you are corect when you say that the CL max at full throttle was based on the SPit figures but the RAE did have the accurate figs on the Stall and Gliding configs which is half the battle so would be a good estimate

Nope. What RAE did can be best described as a reasonably close estimate based on guessworked Clmax, with wrong weight, and with wrong power.

Let me reword this for you
What RAE did can be best described as a close estimate of CL max at full throttle based on known Clmax for Gliding config.

so who's quoting out of context now, David?

I would say both of us missed something. However Crumpp when commenting on the RAE reply on the NACA tests missed a heck of a lot.

One obvious point which no one including me has mentioned, is that the RAE did have the 109. If their calculations said that one was better than the other at something, they had the aircraft to test the results. A luxury that we would love to have

PS - By the way, I have no problem you using my real name but can I ask what yours is?

[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.

[SlipBall]

Originally Posted by Crumpp

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.

It's great that some of the information survived all these years, I've often wondered. Here in the States much of our early mechanical history, can be found in the library of Congress.

[Crumpp]

Here in the States much of our early mechanical history, can be found in the library of Congress.

You can find all the patent information and applications in the National Archives. The Smithsonian has a bunch too.

Even foreign patents, I got all of BMW and Focke Wulfs on one of my visits.

[bongodriver]

So we can all look forward to you sharing this data so we can all draw our own conclusions? or are we just going to get your assurance you've seen it and done the maths and we can take your word for it?