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a technical question Is it possible an aircraft with equal power and less total wet area than another plane to be slower?
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For people with proper judgement his work on his site speaks for itself.
a technical question Is it possible an aircraft with equal power and less total wet area than another plane to be slower?
I also had crossed swords with Kurfürst and I also be careful with his claims but his site is excellent and for ex in his 109K specs part he correctly points out that in the graphs the thick lines are results of calculations by Mtt for 109K with an experimental thin blade airscrew and that the most important graph is the thin line which is that of 109K-4 with standard airscrew and he also notices that the compression effect was ignored in the calculations.
Juha
On the page uploaded from Aozora
i'm not agree that DB 605 non offered better performance of DB 601, also w/o emergency power the DB 605 can use the 30 minutes setting that give aroun the same power of DB 601 in emrgency power so it's clear the DB 605 give better performance
Where he notices that the compression effect was ignored?
imho that curves not ignore the compression effect.
On the page uploaded from Aozora
i'm not agree that DB 605 non offered better performance of DB 601, also w/o emergency power the DB 605 can use the 30 minutes setting that give aroun the same power of DB 601 in emrgency power so it's clear the DB 605 give better performance
It is my interpretion of the fact that Mach effect wasn't taken into account.
Juha
As is well known i've not technician formation but i've the impression that mach effect and compressibility error are not the same, i hope some can give educated info.
My 2 cents:
DB-605 of 1944 was far more reliable than in 1943 or 1942. DB has made many of changes required that 605A functions well even in the confines of the small airframe, and we do not encounter any restrictions after late 1943, for the 605. Since the engine power was pushed to 2000 PS in 1945, the engine reliability seem okay. Despite the increasing difficulties for the German armament industry all together.
If the RLM was concerned over reliabilty of the DB-605A, that might apply for the time before late 1943?
Up about 2000 m altitude - no. Above - yes.
Tempest is about as fast as La 7, faster than Yak 3. Both run circles around it though..
It is all very well quoting test bed performance figures, but operational reliability under adverse conditions can be altogether different.
yes it can, Both Merlin and Sabre engines had very short lives in adverse conditions while the Merlin engines in bombers were rated at 360 hours in 1944 and in transports at 480 hours. Forward fighter fields can be very dusty/dirty places and without very good filters they can destroy engines in short order but that is a different sort of failure than burning piston crowns or valves or other signs of local overheating or operational problems (oil foaming)that will exist regardless of the amount of dirt the engine swallows.
While engine failure records are interesting, unless they breakdown the kind of failure or cause, they really don't tell us if the engine was reliable or not. A Merlin in 1939 in a fighter was supposed to be good for 240 hours flying from English sod airfields, Flying out of Malta or in NA engines many times didn't last 100 hours. It doesn't mean the 1941/42 Merlins were less reliable. It means the conditions were really adverse.
Mankau and Petrick seem to have seen records which led them to a different opinion.
Is there any evidence to show that the DB 605 of 1944 was more reliable, and, if so, what evidence? It is all very well quoting test bed performance figures, but operational reliability under adverse conditions can be altogether different.
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In view of the comments of Mankau and Petrick (who have read original documentation) I am trying to pin down whether the DB 605, especially the DB/DC series, had inherent design faults which were never fully resolved.
So far there has been nothing concrete showing that the final versions of the 605 could reliably develop the 2,000 PS, often cited, in operational service, especially when Allied bombing meant that there were shortages of all grades of avgas and a lack of methanol for MW50. Because of these factors I have serious doubts over whether the majority of K-4s in operational service could reach their full performance potential because they were more than likely restricted to using B4 grade fuel without the benefit of MW50.
By 'run circles around' do you meant the Soviet fighters could out-turn the Tempest, or that they comprehensively outclassed it?
Mankau and Petrick seem to have seen records which led them to a different opinion. Is there any evidence to show that the DB 605 of 1944 was more reliable, and, if so, what evidence? It is all very well quoting test bed performance figures, but operational reliability under adverse conditions can be altogether different.
So far there has been nothing concrete showing that the final versions of the 605 could reliably develop the 2,000 PS, often cited, in operational service, especially when Allied bombing meant that there were shortages of all grades of avgas and a lack of methanol for MW50. Because of these factors I have serious doubts over whether the majority of K-4s in operational service could reach their full performance potential because they were more than likely restricted to using B4 grade fuel without the benefit of MW50.
where did you hear this, there was never lack of Methanol in Germany during WW II..... there were shortages of all grades of avgas and a lack of methanol for MW50. Because of these factors I have serious doubts over whether the majority of K-4s in operational service could reach their full performance potential because they were more than likely restricted to using B4 grade fuel without the benefit of MW50.
You are guessworking... if you have data about showing reliability of these engines (or lack of it), please share them. Saying 'there is no evidence to the contrary of what I say' is logic flawed - if I read Mankau, they qoute German meetings, yes until about late 1943 there is lot of meetings about DB 605 reliability but afterwards I cannot really find. I suppose it has been fixed with lubrication system fixed.
And why were K-4s more likely restricted to fly with B-4 fuel? And why K-4 especially - because its best 109?There are plenty of examples of late war 109s flying C-3 on Kurfurst site, so you have bring some more concrete to this table.
Lack of methanol too?First hear. Where you read this? Also methanol was not absolutely required - it was anti freeze agent. Even pissing into the booster tank would do nicely for boosting...
Maybe you have some real information for your serious doubts. Sources, from which we can learn. I have seen most late war engines had very short practical life - 50 hours. Klimon, Merlin, Griffon Daimler, Sabre - doesnt really matter. Engines were pushed to extreme.