109 it fly wrong

[VO101_Isegrim]

Originally posted by gripen

Anyway, all this is pretty much just nittpicking, my point is just that 640 km/h TAS at 10km is pretty much impossible with a standard plane and standard settings.
 

Could be impossible, but it happened, Gripen. Refer to the TSAGI`s curves (1.42ata).

BTW, a sidenote to the Finn 109 G-2 being tested there. I think I found the clue why it performs well at low levels, but fails to obtain 7000m VDH, or why it performs badly at high altitude.

Look at it`s picture:



Notice something? Yep, the tailwheel is fully out in level flight . Bf 109G-2s had retractable tailwheel, unless of course the mechanism was disabled in individual cases. Late production aircraft would receive a stronger, but non-retractable tailwheel. There`s a picture in Prien-Rodeike, which shows three 109G-2s in transit flight. The foremost has n/r tailwheel, the other two have their tailwheels retracted.

This caused extra drag and considerable loss of speed : -12 km/h at SL as per German drag docs, and as a rule of thumb, 50% more at VDH, and even more at extreme altitudes like 10km.

The loss of obtainable maximum speed above static VDH would deprieve the plane from a lot of RAM and power, hence the lower speed and lower critical altitude obtained. It would hardly effect climb rates, though, since those being developed at low airspeed.

[HoHun]

Hi Isegrim,

>Refer to the TSAGI`s curves (1.42ata).

Hm, from the climb rates, I'd have thought the Tsagi curves are for 1.3 ata.

>Yep, the tailwheel is fully out in level flight .

From my estimates, I'd say the drag condition of the FAF aircraft was good. Accordingly, I don't think the tailwheel was out. Ram must have been lacking for some other reason.

Regards,

Henning (HoHun)

[VO101_Isegrim]

Originally posted by HoHun
Hi Isegrim,

>Refer to the TSAGI`s curves (1.42ata).

Hm, from the climb rates, I'd have thought the Tsagi curves are for 1.3 ata.

I believe so, too, I have drawn Rechlin`s, Tsagi`s and the Finn climb tests on the same paper, they match each other above 2000m to an extent of 0.1m/sec ! Simply it could be Tsagi climbed at the 30min setting, but speed runs were done at the 3 min setting - the latter being rather impractical for long climbs.

From my estimates, I'd say the drag condition of the FAF aircraft was good. Accordingly, I don't think the tailwheel was out. Ram must have been lacking for some other reason.

HoHun, look at the picture, it was posted by another member, and it`s the same MT 215 plane, just before in German service. And the tailwheel IS out.

Appearantly, one has only read the report itself, or see pictures of MT 215 in Finn service to be sure. But the tailwheel gives a good all around explanation. The other thing I can think of is perhaps different atmoshpheric conditions in the far North, Recling`s and Tsagi`s test would be done at least 1000 km more to the south...

[gripen]

Dear Isegrim,
As usual you mixing things to support your agenda. The DB 605 graph contains just one output curve  for about climb speed RAM effect, therefore the graph says static and dynamic RAM.This can be easily verified from the several clinb curves of the Bf 109G; at climb critical altitude is around 5800m. Basicly it's your word against the text in the document. and large amount of test data

Regarding the shape of the  speed curve,  the question is not about what happens below the first FTH  but what happens above the first FTH. When the plane reaches the first FTH, the second oil pump of the supercharger starts to work  keeping the MAP constant by increasing the RPM of the supercharger by readucing slip. This causes corner to the first FTH. Convex shape of the power curve between first and second FTH is caused by the relative efficiency of the hydraulic coupling which increases when the slip decreases. This is exactly what Hohun allready described above and again it can be verified easily from the performance curves of the DB 601E and the DB 605A as well as from the performance curves of the MT-215. Therefore it can be easily seen that the Russian performance curves are not correct between the first and second FTH. Basicly RTFM.

gripen

[thrila]

Originally posted by VO101_Isegrim
 The foremost has n/r tailwheel, the other two have their tailwheels retracted.
[/B]

errrmmm...  they all have their tail wheels out in that pic.

[VO101_Isegrim]

Originally posted by gripen
Dear Isegrim,
As usual you mixing things to support your agenda.

Yada-yada-yada...

The DB 605 graph contains just one output curve  for about climb speed RAM effect, therefore the graph says static and dynamic RAM.

As usual Gripen, you are dead wrong, and escape to primitively parrotting the same misconception of yours. The 605 graph shows the static outputs only, printed on a standard paper. Where`s the evidence that it includes ram effect? No-where. Just as we cannot find any evidence to any of your other claims, because you awfully bad at supporting your own statements (which may be related to the fact they can`t be supported).

This can be easily verified from the several clinb curves of the Bf 109G; at climb critical altitude is around 5800m. Basicly it's your word against the text in the document. and large amount of test data

Nope, sorry Grippy, it`s only you alone who invented that 'German power curves include a small dynamic head', now being changed to 'only the 605 curves include a small dynamic head'. Another spin in it... It`s unsupported, the document doesn`t show the any Staudruck at all, something very strange isn`t it?

Yeah of course, Grippy, any precise engineer would do a engine curve for dynamic output, and would say to you, 'Hey, here`s a graph I made, it gives you dynamic output somewhere between 1 kg/m2 and 5000 kg/m2, I will leave it to you to find out exactly'

But so far showed no evidence of it. It`s as usual, the case when Gripen wants to look like the local smartass who knows everything better than anybody, including the German engineers who drew those graphs. Then he goes into parrot mode, and keeps repeating it.

I will believe sooner that it`s a single man`s distorted idea, being invented to support his other distorted ideas.

Therefore it can be easily seen that the Russian performance curves are not correct between the first and second FTH. Basicly RTFM.

I perceive sadly that your lack the intellectual capacity to understand something very simple.

[VO101_Isegrim]

Originally posted by thrila
errrmmm...  they all have their tail wheels out in that pic.

If you noticed I referred to a picture in Prien-Rodeike`s book, not this picture of the finnish craft.

[Angus]

Hmmm, looking better into Isengrims comparisons:
(adding a few more lines)
The Spitfire Isengrim picked is the one I have very little info about, it is the Mk IX LF JL 165.

"Similiar joke comparisions can be made, let`s compare "

Mk VIII with 25 boost
Mk IXLF JL 165 at +18lbs and
Mk IX HF with 18 boost
vs.
Tsagi`s 109 G-2, shall we:

SL speed :
Mk VIII 582 km/h
109G-2 : 530 km/h
Mk IX LF : 515 km/h
Mk IX HF 524 km/h
at altitude :
Mk VIII 651 km/h at 6160. (also at 18 boost)
109 G-2 : 665 km/h at 7000 m.
Mk IX LF : 624 km/h 5900 m.
(the other LF fighter does 661 km at 6405 m)
Mk IX HF 664 km/h at 8113 m, or even 654 at 9150 m. The one with the Merlin 66 does 668 km at 8479 m.

Gee, aint that Spitfire Mk IX LF a good deal slower ? Let`s look at the really high altitude:

at 9100m :

109G-2 : 650 km/h
Mk IX LF : 611 km/h
Mk IX HF 654 km/h

Getting really high, 11895m, the Spitty still does 593 km/h

"Spit gets the low end of stick, as usual.  "

Well,the low end of the stick goes to your presentation of data Isengrim, because you handpicked the worst spitty.
It looks to me as the Spitties were good at the altitudes they were designed for, cruising well over stall at 43K as well.....

[gripen]

Dear Isegrim,
For the evidence please look at the DB 605  graph,  the text says directly that graph include static and dynamic RAM. It does not matter what ever paper it is printed. Look at the climb charts of the Bf 109G with the DB 605A (1,3ata 2600rpm) and the FTH in climb is allways around 5800m.Try to live with that.

The shape of the Bf 109G performance curve between first and second FTH is caused by power output of the engine, not by RAM effect. Try to live with that.

gripen

[VO101_Isegrim]

Dear Grippen,

if the DB 605A power curve includes the ram effect already, then it must be the case that SL power output was higher than we know, ie. 1475 PS. This is logical since ram reduces power output below FTH on fixed s/c speeds, as evidenced on the 601E curves which are w/o doubt show both dynamic and static positions.

So how much the DB 605A develops in static at SL? 1500-1550 PS ? Curious, why no mentioning of such figures in any document, nowhere! Also interesting, why the Germans would take an exception with the 605A, since by default all of their engine power output curves refer to static power. The DB 605A must have been a very, very special engine to be an exception from the rule...

Perhaps somebody is just wrong... in many things.

[gripen]

Dear Isegrim,
Ah,  now you are starting to understand. My quick and dirty estimate is that the DB 605A would produce around 1490hp sea level without dynamic RAM.

I don't know why the Germans invented output graphs with dynamic and static RAM.

HoHun,
I'm quoting directly the performance table which lists values:

h: 10000m
h cina: 10100m
density: 0,419kg/m3
IAS: 320km/h
Corrected: 566km/h
Comp. Cor: 552km/h
RPMi: 2580
RPM: 2540
MAP: 0,74ata

Regarding (about) 640km/h at 10km claim, I can't measure Russian chart any better, do you?

gripen

[VO101_Isegrim]

Originally posted by gripen
Dear Isegrim,
Ah,  now you are starting to understand. My quick and dirty estimate is that the DB 605A would produce around 1490hp sea level without dynamic RAM.

gripen

Great finding, Gripen. Now, you need to prove this. When you are done with that, prove also those half a dozen other claims you made here.

Until then, it remains an isolated opinion.

[HoHun]

Hi Isegrim,

>Simply it could be Tsagi climbed at the 30min setting, but speed runs were done at the 3 min setting - the latter being rather impractical for long climbs.

Hm. I'm not sure.

The Tsagi charts have several sets of numbers.

Pic. 1 Vmax: Me 109G-4, 650 km/h @ 7 km
Pic. 2 Vmax: Me 109G-2, 670 km/h @ 7 km
JPG15, Vmax: Me 109G-4, 650 km/h @ 7 km
1941 - 1943 Vmax: Me 109G-2 (tre...), 650 km/h @7 km

JPG21 Vmax: Me 109G-2 (tre...), 670 km/h @ 7 km

which seems to be a matching pair with

Pic.2 Vy: Me 109G-2 (tre ...), ca. 21 m/s peak climb rate

The Russian term in brackets which I'm unable to read might provide an explanation :-)

>HoHun, look at the picture, it was posted by another member, and it`s the same MT 215 plane, just before in German service. And the tailwheel IS out.

Oops, missed that it was the very same plane. How can you tell?

Regards,

Henning (HoHun)

[HoHun]

Hi Gripen,

>I'm quoting directly the performance table which lists values:

Roger that. I was using the FAF aircraft as a basis to calculate performance at 10 km for 6.6 km and 7 km full throttle height, getting 610 km/h and 625 km/h respectively. (Note that is for corrected engine rpm.)

>Regarding (about) 640km/h at 10km claim, I can't measure Russian chart any better, do you?

Ah, so the source was the Russian chart. Well, if that was for 2800 rpm, 640 km/h should be no problem. Maybe we can find someone to translate the Russian caption for us :-)

Regards,

Henning (HoHun)

[VooDoo]

Hope this help...



The Russian term in brackets which I'm unable to read might provide an explanation
Did you mean that (tre) ?