Author Topic: 109 Flaps  (Read 9254 times)

Offline Crumpp

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109 Flaps
« Reply #90 on: January 22, 2006, 11:09:56 AM »
Justin,

The Germans increased the dive limits in 1944 to 900kph.  I am not going to write out the whole table and the document has been posted in these forums by me before.

There was no variant of the Spitfire that could outdive it's contemprary German fighter opponent.

All the best,

Crumpp

Offline Big G

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109 Flaps
« Reply #91 on: January 22, 2006, 11:35:03 AM »
Quote
Originally posted by Crumpp
Justin,

The Germans increased the dive limits in 1944 to 900kph.  I am not going to write out the whole table and the document has been posted in these forums by me before.

There was no variant of the Spitfire that could outdive it's contemprary German fighter opponent.

All the best,

Crumpp

Yup, agrre with that crump:
One of the best tactics the LW used over the UK was to go into a turning dive, the spits couldn't keep up.
I'm just hoping that HT resolves the 109 issue, (not bothered about the flaps, just want the 109's to fly like 109's)

Offline Angus

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109 Flaps
« Reply #92 on: January 22, 2006, 08:22:51 PM »
So, are you saying that the Farnborough experiment was rubbish?

Oh, and Widewing, sorry, Welsh it was. The Pearl harbour guy ;)
It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline hogenbor

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109 Flaps
« Reply #93 on: January 23, 2006, 03:05:01 AM »
Fascinating story Widewing :aok

Offline Charge

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« Reply #94 on: January 23, 2006, 03:58:31 AM »
http://www.jazzitoria.dial.pipex.com/aspit-2.htm

Maybe somebody should inform the Spitfire society that they are grossly overestimating the performance of the 109.

-C+
"When you wish upon a falling star, your dreams can come true. Unless it's really a giant meteor hurtling to the earth which will destroy all life. Then you're pretty much screwed no matter what you wish for. Unless of course, it's death by meteorite."

Offline justin_g

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« Reply #95 on: January 23, 2006, 04:27:45 AM »
Quote
Originally posted by Crumpp
Justin,

The Germans increased the dive limits in 1944 to 900kph.  I am not going to write out the whole table and the document has been posted in these forums by me before.


I tried a search, but could not find the post you're talking about? The highest figure that I could find quoted here was 850km/h TAS, and the link to the scanned document was dead.

Offline Angus

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« Reply #96 on: January 23, 2006, 07:28:52 AM »
The experiment at Farnborough was a dive from max alt right?
I mean, we all know that the Spitfire was not a very fast diver, - 109's and 190's would leave it behind in a dive.
That said, they still needed to level out at perhaps lower speed.
I mean, a full power dive from ca 40K will build up a lot won't it?
It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Knegel

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« Reply #97 on: January 27, 2006, 03:18:43 PM »
Hi,

as far as i know the high estimated mach numbers while diving with a SpitIX was caused by wrong measurements due to turbulances in the pitot tube.
Same problem caused the 1000km/h claims of some german pilots.

The following graphic will explain why WWII planes wasnt able to reach mach0.9



As you can see, the planes run into a real wall at around mach0.75-0.8.

Even with max power in levelflight at sea level not many WWII planes did reach mach 0.6 (around 612km/h, up to this speed the drag coefficient is relative constant, above this the typical highspeed/supersonic problems did start).
Look to mach 0.75, how much the Cd already did increase(around 3 x as high as at mach 0.6).

Greetings, Knegel

Edit: i doubt that any prop driven plane ever did reach mach8.5, cause the propeller will act like a real airbreak at this speed, maybe the Me163 or 262 did reach 1050km/h (around mach0.85) close to sea level after a smooth dive.
« Last Edit: January 27, 2006, 03:54:51 PM by Knegel »

Offline Angus

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« Reply #98 on: January 27, 2006, 06:37:13 PM »
The pitout tube measures airspeed.
There is also a stopwatch and an altimeter.

So, did they only rely on the pitout tube?


As a sidenote, didn't they run the aircraft to it's max?
It was very interesting to carry out the flight trials at Rechlin with the Spitfire and the Hurricane. Both types are very simple to fly compared to our aircraft, and childishly easy to take-off and land. (Werner Mölders)

Offline Knegel

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« Reply #99 on: January 28, 2006, 02:18:44 AM »
Angus,

the vmax of the Me163 Komet was 960km/h(around mach0.8) in 3000m altitude, although the  rocket produce more thrust and the air get more thin in higher altitude the Komet wasnt able to fly faster in a level fligt in higher altitudes, cause the as colder the air get, as higher the machnumbers get.  The Me163 had max climbrate (tank almost empty) of around 150m/s, what mean, this is a vertical climb.
With other words, tha power of the Komet(almost empty tanks) was stronger than the gravity.  While a dive it couldnt get much faster, cause it simply dont was controllable anymore, although it had a advanced highspeed  wing construction(arrowed, very smal aspect ratio wings).

A propplane dont get any advantage out of its propeller at high machnumbers, cause the proppeller itself get earlyer into trouble than the plane, cause to produce thrust the propeller have to rotate faster than the plane fly. Actually the propeller will act much more early as airbreak, otherwise the engine simply would overdrive. In theory they could use a different reduction gear to overcome the engine max rpm problem, but still the blades would get supersonic problems and dont would be able to produce thrust.  Therfor propeller driven planes cant reach mach1 at all and much earlyer they cant produce thrust anymore, so the result base on a free fall, the engine is only needed for the initial acceleration.

To reach mach 0,85 in a free fall is not very credible, but maybe they did add two tonns weight to increade the dragload, but i doubt a pilot(plane) would have survived this.

A stopclock and altmeter dont would help, cause the max speed only could get reached for some sec, a to short timespan to measure it in this way.

In general the highest to expect speed will be at 2000-3000m, here the drag due to thick air and lower mach numbers result in a minimum of drag, but here a pilot dont had much time left to pull up(specialy in a typical WWII plane).

They made divetests with a P51B(from 28.000ft), with removed propeller but metal covered elevators, and did reach machnumbers of 0,755.  In a windtunnel they was able to reach mach 0,825(no propeller!!)
The P39N (much smaler wing aspect ratio) did reach max mach 0,8 while a powered dive from service selling(34.000ft), most trys was good below this(0,755 and 0,777).
Important to note is that they couldnt reach this speed with max rpm, they had to reduce the rpm, probably to avoid supersonic problems(increased drag) at the propellerbalades.
 
The resulting dragcoefficient at low machnumbers was a bit better in the P51(0,0215), as long as the P51 surface was clean, with a bit dust on it, it was worse than that of the P39(0,022) .

I doubt that a Spitfire was able to reach such numbers, it had a much worse dragload, what is most important. Maybe the heavy, late one, with clipped wings.

Greetings, Knegel

Offline justin_g

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« Reply #100 on: January 28, 2006, 04:21:52 AM »
The MTT dive trials with Me 109F were at 100% engine settings, and they reached Mach 0.8. Dive angle was 70-80º.

Drag is not the limiting factor, the wing design is. For typical WW2 fighter wing designs, thinner was better(measured as ratio of thickness:chord at the wing root) - Me 109 with 15% thickness had a limit of about 0.8M, which closely matches the dive speed limits in the pilots manual. P-51 had 16% thickness, and a dive limit of 0.75M per the POH. Spitfire wing was 13%. Pilots notes give a dive speed limit corresponding to 0.85M. This Spitfire dive table reports 0.891M reached.

Offline Crumpp

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« Reply #101 on: January 28, 2006, 11:07:42 AM »
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Drag is not the limiting factor


Drag is the limiting factor.

The insturmentation was not accurate enough in the transonic realm to definatively say what the Spitfire achieved in WWII.  Measuring speeds above Mach .8 was problematic at best.

In the 1950's they were still trying to overcome the margin of error.

http://naca.larc.nasa.gov/reports/1953/naca-report-1145/index.cgi?page0001.gif

http://naca.larc.nasa.gov/reports/1950/naca-tn-2046/index.cgi?page0002.gif

http://naca.larc.nasa.gov/reports/1950/naca-report-985/

Here is the results of the Mk IX dive trials:

 

Here is a Mk V that dove to an estimated 520mph.

http://www.potato.com/upload.php

So to claim such a high mach number for any wartime Spitfire is rather silly.  The test shows the results achieved with an unknown condition Spitfire using instrumentation with a large margin of error.

All the best,

Crumpp

Offline justin_g

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« Reply #102 on: January 28, 2006, 12:57:46 PM »
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Drag is the limiting factor.

Oh, I see. How could I not understand this before. It's all so clear now...

Offline Crumpp

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« Reply #103 on: January 28, 2006, 01:15:51 PM »
Quote
Oh, I see. How could I not understand this before. It's all so clear now...


Come on Justin!  You know this.  What are the four forces in flight and what happens those force vectors in a dive?

I should have made it clearer though that the speed measurement issues were seperate from the drag.  Sorry for the confusion.

All the best,

Crumpp

Offline Crumpp

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