1942: the best fighter

[Kryten]

are you guys confusing combat power with wep on the spit?
wep was limited to 5 mins and was only used in emergencies, to use it you had to break the lockout and then inform your ground crew chief on return, cant see the spits climb rate being calculated on wep?

 

[Vincenzo]

i've not confusing, there was not wep on thest of BS274 (called BF274), there were combat power, 5' set +15 lbs, and climb power, 60' set +12 lbs
you can read the test on spitfireperformance.com

 

[Juha]

For the Me 109G, inital "full throttle" and "climb" power were the same, the real full throttle - "emergency" in German terms - was not allowed initial.

The "climb and combat" power could be used for 30 minutes on DB 605A, and was equivalent of the British "Normal". "Start and Emergency", the actual German 5 min power, equivalent of British "Combat", also for 5 minutes, was initial disallowed on DB 605A. So terms are a bit confusing when translated to English, because combat power means different in the two countries - its more like US "Military power" in Germany, and US WEP in Britain.

In this case I think Vincenzos comparison is more or less valid, because if you wish to compare an intercept/time to altitude profile, it is done in both case (Kampf/Normal) at the rating official sanctioned for general climbing. For combat, of course Spitfire could use higher settings (and so could 109G from 1943, when "Notleistung" was clear for use)

I think Me 109G performance is pretty clear for 1942, the specification is on Kurfurst site. Specs were 637 km/h at 0m, 660 km/h a 7000m. Aircraftperformance site doesnt list the "good tests", only bad ones for German machines, not even Official specs, maybe people want to show how bad the Me 109 was compared to Spitfire this way, very possible. But everyone is biased to some extent.

Hello Tante Ju
I agree most, but firstly, usually I have seen the time limit for the "Start and Emergency" power for DB 605A/B as only 1 minute see for ex Mankau's and Petrick's Messerschmitt Bf 110/Me 210/ Me 410 and in a few other sources as 3 minutes. Different countries had different regulations which make the comparing a bit tricky.

Secondly, IMHO the better figure for max speed at the FTH for early Gs is the average reached in Erla tests, that of accepted a/c was 652km/h. IMHO we can leave out those failed ones. And you made a typo on the SL speed, it was 537km/h. But your point is valid, what is relevant is what the terms meant not the terms themselves, different countries had different terminologies.

JUha

 

[Siegfried]

Emergency Power in German is "Noteleistung" (emergency performance).
Sonder Noteleistung (special emergency power) would usually refer to ME 50 injection or some other special method such as rich mixture injection.
There was even erhoete sonder noteleistung (increased emergency power) which would involved say rich mixture injection plus MW50 on say a
Fw 190-D9.

I believe emergency power was effectively blocked on the Me 109G till 1943 due to the restriction to 1.3 ata so the aircraft could opperated at full power indefinetly temperature requipments aside.

 

[Juha]

Hello Siegfried
the time limit for German Climb and Combat Power was 30 minutes, which was completely adequate.

Juha

 

[Hop]

I believe emergency power was effectively blocked on the Me 109G till 1943 due to the restriction to 1.3 ata so the aircraft could opperated at full power indefinetly temperature requipments aside.

From the British translation of the German message banning the use of emergency power:

The take-off and emergency output with a boost pressure of 1.42 atm and 2800 revs may not at present be used. The climbing and combat output with 1.3 atm and 2600 revs may, in the case of the older engines (see work numbers below), be used only when operationally essential.

That makes sense, of course. If it was too dangerous to use 1.42 for even a few minutes, then using 1.3 ata for half an hour probably wasn't a good idea either. There was a similar practice with the 190, when emergency power was restricted the old climb and combat rating became the new emergency rating, usable for only a few minutes.

 

[Vincenzo]

"The pistons of older engines (before above-mentioned worksnumbers) will be replaced by reinforced pistons during the first partial overhaul.
Older engines mst be partially overhauled after 50 hours..."

 

[Vincenzo]

Juha have you a readable copy of graphs of 13 Erla 109 ? i can't read that on kurfurst site

 

[Juha]

Juha have you a readable copy of graphs of 13 Erla 109 ? i can't read that on kurfurst site

I think I got this from Kurfürst site

 

[Juha]

"The pistons of older engines (before above-mentioned worksnumbers) will be replaced by reinforced pistons during the first partial overhaul.
Older engines mst be partially overhauled after 50 hours..."

Contrary to German hopes that didn't solve the problems of 605A, IIRC they then tried new sparkplugs but the problems were finally solved with mods in the oil system which prevented foaming.

Juha

 

[Tante Ju]

From the British translation of the German message banning the use of emergency power:

That makes sense, of course. If it was too dangerous to use 1.42 for even a few minutes, then using 1.3 ata for half an hour probably wasn't a good idea either. There was a similar practice with the 190, when emergency power was restricted the old climb and combat rating became the new emergency rating, usable for only a few minutes.

Yes, but the 1,3ata "only when essential" limitation only refer to about those two dozen A-0 series preproduction engines which has serials listed in this order, A-1 series seems not to have such limitation for 1,3ata, the manual I see list it as 30-min. Unlike 190 manual, for example. Fw 190 limitation was due to entirely different issue (cooling).

Anyone know what was practical overhaul life of Merlin in 1942?

 

[Vincenzo]

Contrary to German hopes that didn't solve the problems of 605A, IIRC they then tried new sparkplugs but the problems were finally solved with mods in the oil system which prevented foaming.

Juha

what problem that that older engine can't go 1.3 ata? i'm talking referring to this

ty for the graph (i find only the copy of original in K site) as i thinked this a early 43 test, march, i'm not 100% sure but at time the production planes have not more the semi retracble tailwheel so the speed go down (this explain also because the max "official" for the test is 650 km/h)

 

[Shortround6]

Anyone know what was practical overhaul life of Merlin in 1942?

Not in 1942 but "nominal" overhaul life in 1939 was 240 hours for fighters and 300 hours for bombers. In 1944/45 this had increased to 300/360 hours for fighters, 360/420 hours for bombers and 480/500 hours for transports.

From 1942 on about 35% of the engines passing through repair organizations had reached their service live while the average hours of an engine going through the repair organizations was about 60% of rated life for type.

No numbers are given for engines going through repair facilities for reasons other than service life ( like battle damage or collision damage)

 

[Glider]

I do knonw that a large number of early merlins were refurbished, zero houred upgraded and reissued for service in Spit V. This caused a serious shortage as the Navy and Russia were after the older ones for use in MTB's but none were available.

 

[Juha]

what problem that that older engine can't go 1.3 ata? i'm talking referring to this

ty for the graph (i find only the copy of original in K site) as i thinked this a early 43 test, march, i'm not 100% sure but at time the production planes have not more the semi retracble tailwheel so the speed go down (this explain also because the max "official" for the test is 650 km/h)

According to the graph they were flown in April 43. What is interesting that the Finnish tests with very late G-2 MT-215 with fixed tailwheel gave the max speed of 636km/h after compression correction, without that correction the max speed was 652km/h. Some specialist here in Finland think that German figures are usually, not always, without the compression correction contrary to the British figures, which usually are compression corrected.

Juha

 

[Vincenzo]

is not that the trouble you can see here Kurfürst - Rechlin E`Stelle Erprobungsnummer 1586 the indicated speed for the german and you can see that finn test indicated speed was lower so in not a trouble with or not the compression correction

 

[Tante Ju]

According to the graph they were flown in April 43. What is interesting that the Finnish tests with very late G-2 MT-215 with fixed tailwheel gave the max speed of 636km/h after compression correction, without that correction the max speed was 652km/h. Some specialist here in Finland think that German figures are usually, not always, without the compression correction contrary to the British figures, which usually are compression corrected.

Juha

Maximum level Speed.

Juha, are you refer to that Finn test?

Kurfürst - Finnish Air Force Performance Trials on Messerschmitt Bf 109 G-2, WNr. 14 783 'MT-215'.

It is explained on kurfurst site:

"Maximum speed achieved at SL was 522 km/h, and 636 km/h at 6,3 km altitude, and 552 km/h at 10 km altitude.

During the tests, 1.3-1.32 ata and 2540 RPM was realized, though such small variations were within tolerance, the lower RPM and/or other factors appear to have somewhat impaired the supercharger`s performance, and thus may have reduced altitude performance, as seen from the performance curves : the rammed rated altitude of 6,3 km was considerably below not only the nominal value (of 7 km) of the DB 605 A, but also the typically obtained, avarage 6,6-6,7 km rated altitude. For this reason is it interesting to extrapolate the level speed curves of MT-215 to 7 km rated altitudes, which shows an extrapolated speed of ca. 650 km/h. The extrapolated values show matching result with those obtained on Bf 109G-4 WNr. 19 968, that was tested by the NII VVS in a very similiar configuration (ie. tailwheel was non-retractable in that case as well) in October 1943. This points to that the poor high altitude performance shown by MT-215 was likely to have been caused by a defective supercharger and/or lower supercharger speeds due to lower engine RPM."

I think such is normal - production quality was not same on all aircraft. aircraftperformance has trial of Spit 9, for example that is making 389 mph top speed (626 km/h). Nominal top speed was 404 mph.

http://www.spitfireperformance.com/jl165.html

In articles graphs however shown, the badly performing Spit is not shown, or Finn 109 (I believe because it climbs very well).

 

[Juha]

Hello Tante-Ju
the point is that the Finns themselves concluded that the speed test results were more accurate than the results of the climb test because Finns didn't have the luxury of being able to commit one of their few 109G-2s exlusively for testing, so the plane (MT-215) was one of ordinary factory new a/c which was used between tests in normal sqn service, so no full test instrumentation but good weather data was acquired from a weather balloon.

Juha

 

[Glider]

Looking at this debate re the Spit IX vs 109 I admit my opinion hasn't changed and I would take the SPit or 190 first, but I also believe that some people get a little excited over what performance chart is compared with another.

I can see the logic in taking the 30 min rating of the 109 and comparing it with the lower power of the Spitfire for the reason given, ie, that no one unless there was a dire emergency is going to flog a 5 min rating for 30 minutes while you climb to height. Equally I can also see the logic in comparing the higher 5 min rating of the Spit as once combat has begun then every ounce of power is needed.

Few combats went on for more than 5 mins so it isn't an issue. The 5 min limitation wasn't a fixed limit limited by special fuel such as the GM1 in later 109's, because there was nothing stopping you going for 7 or even 10 mins should a combat go on for that long. The engineers may well hate you for it and no doubt there would be an increased chance of it going very quiet very suddenly in the cockpit, but if you are going for home with a bunch of Me109's behind you, that's of secondary importance.

Its worth remembering that the Merlin 61 was tested for the increased power and the approval was based on the engine lasting (I think) 2 1/2 hours at the higher boost in five minute bursts allowing time for the engine to cool before the next burst.

I also believe its wrong to complain that Williams only shows the 'bad' tests, he does show a range of tests on his chart. If the climb chart was redone with both the higher and lower power ratings that would improve understanding

 

[Vincenzo]

Just for comparison
speed of climb BS274 test (combat power) and 109G-1 Datenblatt (w/o retractable tailwhell but this is not important for climb speed)
a 3048m 19.4 m/sec a 3000m 19.8 m/sec
a 6096m 14.9 m/sec a 6000m 15.2 m/sec
a 9144m 11.6 m/sec a 9000m 8.3 m/sec
a 12192m 3.5 m/sec a 12000m 1 m/sec

so in the low and midlle altitude gustav was in advantage both in speed and climb also in combat