Official Fulqrum Publishing forum - Spit/109 sea level speed comparisons in 1.08 beta patch

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- - Spit/109 sea level speed comparisons in 1.08 beta patch (http://forum.fulqrumpublishing.com/showthread.php?t=34115)

how was that patronising drivel?

that was just plain rude.

also on the ignore list, im ouita this conversation. leave to your 2 oversized ego's

I wish we were having this conversation in the pub, I woulda bashed you both out by now.

Quote:

Originally Posted by macro (Post 462174)

Oh crap, sorry......I somehow saw Crumpps avatar and your post, I honestly had no idea I replied to someone else, my most sincere appologies.....I think it's because it was quoting the same post by me.

Quote:

Originally Posted by Crumpp (Post 462163)

Now we have to teach people the basics.

Aircraft cannot sustain performance without excess thrust and the forces in balance.

Any airplane without excess thrust can use gravity and momentum to achieve instantenous performance.

A glider uses gravity to propel itself which is why we don't use them on transatlantic flights. They exist in a purely instantenous performance condition. They cannot sustain performance under the power of gravity alone and must constantly trade altitude for airspeed without an alternate form of energy.

Gliders seek an alternate form of energy in the form of rising air currents to stay aloft.

http://www.mansfieldct.org/Schools/M...ightglider.htm

Bongodriver, try to make a turn from maximum level speed in an airplane maintaining both airspeed and altitude.

Read macros reply to my post and learn how to actually process information.

Quote:

Originally Posted by Crumpp (Post 462182)

:confused:

Youre confused?....ok I'll take you through it carefully

Kurfurst said of the Spit in his scenario 'can hardly turn at all'......but why would the aircraft suddenly not be able to turn any more?......it in fact will continue to turn quite happily, what it won't do is sustain speed.

As my 6 year old would say, I am confused on who is whose friend, LOL.

:wink:

:-P

Quote:

Originally Posted by Crumpp (Post 462190)

As my 6 year old would say, I am confused on who is whose friend, LOL.

:wink:

:-P

:confused:

Quote:

Originally Posted by Crumpp (Post 462160)

It is a spreadsheet that calculates turn performance I made.

It is a sophisticated analytical tool that determines relative turn performance using standard incompressible flow theory. That was the predominate theory in use during WWII and is the same one used by the RAE.

By using EAS, all you have to adjust power production and you are in the ballpark for the Indicated Airspeed you should see performance.

I did it that way so it would be useful for the game. If you know the PEC, it is not hard to have the spreadsheet convert EAS to IAS directly.

It takes a little time but it can reworked for any aircraft.

But your graph Crumpp bears little resemblance to the RAE chart. Your chart gives the 109 a better sustained capability whilst the RAE chart gives the Spitfire a better sustained turn performance ?

RAE Chart from AVIA 6/2394

http://i40.photobucket.com/albums/e2...109susturn.jpg

Crumpp chart:
http://imageshack.us/a/img228/1949/s...bf109e3sus.jpg

Dont see any parameters/conditions/assumptions used on your chart either Crumpp

Who is right RAE or Crumpp ?

Quote:

But your graph Crumpp bears little resemblance to the RAE chart.

Do some math....

The RAE chart is at 12,000 feet and was taken off one data point. It did puzzle me as our radius and other data aligns. It puzzled me until I stated getting into the details of the chart.

According to that chart, the Spitfire Mk 1 is capable of reaching 340mph (+) at 12,000 feet on 1050 bhp.

The RAE graph found in AVIA 6/2394 is a performance estimate from September 1940.

A flight report from March 1940 gives the power at 12,000 feet:

Quote:

Normal B.H.P 950/990 at Rated Altitude 12,250 ft

And lists the Vmax for the type as 326 mph TAS.

http://www.spitfireperformance.com/n3171.html

The AVIA 6/2394 does not fit the only +12lbs estimate we have for level speeds.

http://www.spitfireperformance.com/s...-rae-12lbs.jpg

This estimate shows 359mph TAS at 12,000 feet.

That is over a 5% error from the speed found in AVIA 6/2394. It would be unusual for such a large estimate error in an established design.

I don't know what Spitfire data they used but I suspect it was for an improved high altitude version as we saw before in a similar report previously posted on these forums in which you were involved in the discussion.

All that can be said is we don't know the details and the ones we do know, do not fit any existing service model at the time.

When we plug in the data from the Spitfire Mk I serving in the RAF during the BoB, we get a different result.

Another anomaly is the CLmax. In order to get a CLmax of 1.87 on the Spitfire, you have to drop the stall speed far below what the Spitfire POH list's to a scant 62 knots.

At the 76mph Vs (69mph IAS Vs + 7mph PEC) found in the POH, we get a CLmax of 1.69 which is far below the 1.87 Gates uses in the report.

I am pretty sure Gates was not using a standard Spitfire Mk I for his base data in the estimate. It does not align with one.

Calculate Sea level CL max:

CL = Lift/(dynamic pressure * Reference Area)
Dynamic Pressure = density ratio * Velocity^2 / 295

Dynamic pressure = (1 * 66^2)/295 = 14.76610169psf

CL = 6050lbs / (14.76610169psf * 242sqft) = 1.693067034

Lift = CLqS

Lift = 1.87 * 14.76610169psf * 242sqft = 6682 lbs of Lift generated.

"I don't know what Spitfire data they used but I suspect it was for an improved high altitude version as we saw before in a similar report previously posted on these forums in which you were involved in the discussion.

All that can be said is we don't know the details and the ones we do know, do not fit any existing service model at the time."

"Normal B.H.P 950/990 at Rated Altitude 12,250 ft '

Garbage ! you are confusing rated power at 2600RPM with maximum power at 3000RPM. Here are 2 inspection test certificates for 2 different Spitfire MKI's one with a Merlin II the other with Merkin III. As you can see Max power is 1030hp at 16,250ft. at 6.25lbs boost 3000RPM.

The RAE chart references 1050hp at 6.25lbs Boost 3000RPM at 12,000ft.

http://i40.photobucket.com/albums/e2...ps5d31181a.jpg

http://i40.photobucket.com/albums/e2...ps805b515b.jpg

You are again trying to change history. You cover up your case by a smokescreen of Mathematical verbiage. RAE calculated that the Spitfire MKI had better sustained turn performance than the BF109E3. Pretty much every other report technical and general from either side of the conflict say the same. You on the other hand construct a graph that clearly shows the opposite.

Find another single independent reference that proves the BF109E3/4 had better sustained turn performance than a Spitfire MKI.

Whilst you are at it show us what this Mythical improved high altitude version that I supposedly referred to in another report and how this is supposedly used in the RAE turn chart