Friday Update, February 10, 2012

[Kurfürst]

Originally Posted by Kwiatek

I really doubt Kurfust that any serial 109 E could do above 500 km/h at the deck - in such case it would be equal or faster then 109 F.

Well it did 498 km/h at 1,35 ata, or 1018 HP measured in test.. why do you think, that at WEP (W button, 1,45ata, which produced 1175 PS on the 601Aa), that the extra 150 HP would yield no more than 2 km/h? Math simply suggest that an extra 150 HP will yield around 520-525.

Yes I agree that being as fast as the early F on the deck seems strange at first, but when you think it over, the F has a different (smaller diameter prop), that can easily result in +/-10 km difference alone. The G-14/AS, as per the book, was something like 8 km/h slower on the deck than the G-14 with the same horsepower (on the deck), but with a different prop.

On the other hand, on the E the 1.45ata rating of 1175 PS was really a short one minute burst, presumably intended for bombers taking off at heavy loads (He 111P!), while the 109F it was a full 5-minute rating. And of course the 109F is much faster at altitude, probably partially down to the new prop..

And of course the Spit I was also faster at the deck at than the early Spit V, so, I guess its just normal that "newer" just doesnt translate to "better" in every performance aspect.

Most German data for serial 109 E Db 601 A at 1.3 Ata ( 1/4 radiator open) claim 460-467 km/h ( 5-minut combat power).

Are you referring the Emil tests of the 17xx serial no. airplanes? In those case the point of the trial was to measure the difference if the MG FFs are mounted/not mounted, and if the slats are filled/not filled. The only relevant data to the tests makers was the relative difference in perfomance, because it probably allowed them to asses the invididual drag of these items (which turned out to be marginal).

And, in both trials it is noted that the speeds are not corrected for the nominal engine outputs (which they are in the tests I have posted), so they may understate the actual speeds if the engine was not running at its rated power (which was the case in the test I posted, where the E-1 did 493/498 km/h due to being down in power)

I think it is very beliveable result (confirmed e.x. by Swiss test and other data).

I strongly believe that the Swiss test show operation of the engine at the high altitude supercharger speed (ie. 2nd speed, bad for low level). If you compare to the E-1 trial I posted, you will notice the Swiss got very similiar results as the Germans using the Hoehenlader (2nd supercharger speed). So the Swiss tests IMO underline the validity of the 2 German trials I posted (showing 498-500 km/h).

It makes sense since the Swiss test is not a performance trial, in a sense they wanting to know what are the specs of the plane, but a comparison of top speed with three completely different propellers. Same reasoning as just above.

Of course 109 E at 1-minut emergency power 1.4/1.45 Ata will be faster at about 15-20 km/h (with radiator closed little more).

I think its beyond doubt that the correct low level rating for the 109E at 1.35ata is 500 km/h. This is what we have without the W button at full throttle.

There is the German test showing this, and btw, this is what is the OFFICIAL german spec for the plane, 500 km/h at SL.

Of course individual planes may have been slower - or faster, hence the +/- 5 % tolerance. Of course Hurris and Spits are neither modelled after the worst flight tests results either, so why would be 109s? They should be modelled after the nominal specs, like Spits and Hurris.

The 1.45 Ata speeds can be pondered on, but it seems we agree that the extra speed is worth about 15 - 25 km/h. Its a pretty good guess, becuase the math ruling it is simple. This should be simply added to the figure we know for certain, 500 km/h.