Bf109 information, lighting a fuse and running for cover!

[ACE-OF-ACES]

Originally Posted by cheesehawk

That and the fact there aren't many viable airframes out there and the owners willing/able to test the real performances in the name of science. Some things are simply now passed to legend...

It is true that most of the warbirds around today are not in their original WWII configurations..

The good news is most WWII planes were tested and a lot of those test results still exist.. The bad news is not every field mod and or variant of a particular plane was re-tested..

The sim makers use these test results (outputs) as a sanity check of their FM.. That is to say the data from these test reports are not used as inputs to create the FM (unless your talking about a simple table based FM) just used as a check of the FM

Pretty simple, the FM results match the test data results or they don't.. So one would think that would be the end of the discussion, right?

Well sadly no

As noted you will be hard pressed to find test data for every variant of every plane in the game.. And even when you do find data for a particular variant in the game there will be people standing by to give it a thumbs up or a thumbs down.. For example, some will toss out the 'theory' that the Russian data was 'tweaked' to show the planes performed better than they actually did. The theory being they did that to keep uncle Joe from cutting off their heads.. Same argument is made with regards to some of the late war German data.. A similar argument is applied to US planes.. Especially with regards to test results from the manufacture.. The idea that the manufacture has tweak the results to show the plane performed better than they actually did to sell their plane.. Problem with that argument is USAAF also did acceptant testing that shows there was typically no tweaks made.. At least I have yet to see anyone post the results done by the manufacture that far exceeded what the USAAF was able to obtain.

Personally I tend to ignore all those who float those 'theories' especially the ones that will float the 'theory' for the planes they don't like and not even consider the possibility of the 'theory' for the planes they like (read hypocrites)

The only area of real world test data that I would consider to be suspect is that of the calculated/estimated type. That is to say data that was not from an actual flight test, just desk top calculated results based on what they expected to see if they actually did the test.. For example say they have a plane that they have already tested.. Than later figured out a way to increase the horse power.. Instead of re-doing the actually flight test, they would start with the flight test results from the previous test and simply increase the top speed and climb rate by an amount they 'calculated' it would increase by due to the increase in horse power. This is the kind of data that should be taken with a grain of salt imho, and on that note this is the kind of data the Germans did a lot of near the end of the war.

Long story short, even if you could find a WWII war plane with a WWII configuration and an owner willing to put it threw the paces of a test.. You will find someone who will try to find something wrong with the data.

[Al Schlageter]

Originally Posted by CaptainDoggles

Hmmm.

Well, I agree that the Luftwaffe were not always outnumbered 100% of the time.

But the whole point of Big Week was to exhaust, attrit and otherwise destroy the Luftwaffe in preparation for the D-Day landings and I'll maintain that Allied air superiority was the norm. Allied numbers were very very high during this period. For example, during one of the Berlin raids, they sent 800 escort fighters. While the Luftwaffe may have achieved local superiority in some cases, this would have been the exception, not the rule.

By February of 1944 the LW was feeling the effects of chronic fuel shortages, and the situation only got worse from there.

The only American fighters that could reach Berlin were the few P-51s and even less P-38s.

Feb 25 1944, Mission 235, final Big Week mission

- 268 B-17s are dispatched to aviation industry targets at Augsburg and the industrial area at Stuttgart, 196 hit Augsburg and targets of opportunity and 50 hit Stuttgart

- 267 of 290 B-17s hit aviation industry targets at Regensburg and targets of opportunity
At the end of May 1944, the Germans had ~400,000 metric tons of aviation fuel more than they did in Feb 1944.

- 172 of 196 B-24s hit aviation industry targets at Furth and targets of opportunity

- Escort is provided by 73 P-38s, 687 Eighth and Ninth Air Force P-47s and 139 Eighth and Ninth Air Force P-51s

These targets were beyond the range of the P-47s so only the 212 P-38s and P-51s could do the escorting and would be split among the 3 target areas.

At the end of May 1944, the Germans had ~400,000 metric tons of aviation fuel more than they did in Feb 1944.

[ACE-OF-ACES]

Originally Posted by cheesehawk

So true, and it seems the data we have from the war period doesn't cover everything we would think of now (i.e. roll rate progression, acceleration are some I've never seen referenced data on, although my research is mainly limited to what you can find on the internet),

True.. the standard acceptant testing consisted of a top speed per altitude test and a rate of climb test.. Which typically also produced a time to climb test.. Very few roll rate tests were done, and even fewer acceleration testing was done. It wasn't until just after the end of WWII that they switched to Ps testing for fighters

Originally Posted by cheesehawk

and funny hand drawn graphs that aren't posted at the Imperial War Museum or the Bundeswehr Military History Museum, leaves too much room for suspicion on accuracy.

Ya lost me there.. ?

Originally Posted by cheesehawk

Add to that the somewhat contradictory testimonies of the pilots, and no wonder we have wildly differing opinions on what each of our beloved aircraft should do.

Bingo!

I have an old saying.. For every Spitfire pilot that said he could easily out turn a Bf-109 there is a Bf-109 pilot that says he could easily out turn a Spitfire

Which only proves that combat reports by combat pilots are not something the FM results should be based on.. For many reasons, like they typically are one sided stories, typical preformed under none standard conditions, typically don't contain enough information to recreate the scenario..

In the end combat reports say more about the realitive pilot skills/luck than the planes performance

Originally Posted by Kurfürst

Rather badly researched and biased article I'd say with a large amount of clear errors, ie. the production number of Bf 109G, no Spitfire Mk V reached 400 mph, and he got it all wrong about the ailerons (109A-E had plain type ailerons, F-K had Frise type ailerons, and all Spits - maybe post-war versions didn't? - had Frise.)

The only really good point is about roll inertia, the 109 indeed seem to have been praised for brisk aileron control (that means, quick response, not neccessarily the same as maximum rate of roll) at low to medium speeds. And of course the 109 benefited from its high-lift devices on the wing in numerous ways, but the main thing about the 109-p51 climb rate difference was obviously that the latter was about a ton heavier.

I noticed that, too (roll performance). To continue in this vein, as the speed of the 109 picked up during development and the initial roll response dropped off due to less aileron deflection per pound force (at the stick) the guns were removed from the wings (F model) to bring the initial roll response (not to be confused with sustained roll) back up. No further action was taken on addressing high speed roll performance until server tabs were developed for the K (et al) but not uniformly applied and as a rule disabled when installed.

Do you know who developed the servo tabs?

[Kurfürst]

IMHO the main thing that effect roll response is the change in wing shape and aileron layout. The wing of the 109A-E was different from the 109F-K, and so was aileron layout. As noted, A-E had plain type of ailerons, and it seems from accounts it was brisker than the F-K. This may be down to the shape/size of aileron and its placement, as after all, what the ailerons do is changing the lift on the wings (increasing on one wing, decresing on the other, hence the roll).

The F-K had Frise type ailerons, which by their nature help to reduce aileron forces (Frise type ailerons have their hinge point moved slightly backwards, and the leading edge of the aileron protounds when deflected into the airstream, which helps a bit.)

As for the Flettners tabs on ailerons, these primary found on photographic evidence mounted on WNF (Wiener-Neustadt, near Vienna, Austria) produced Bf 109G-6/14 and G-10. I have some docs relating to this, trials showed that the effect was that 2/3s aileron deflection was possible at at around Mach 0,70+. WNF did not produce 109K however, only Mtt Regensburg did. The K was supposed to have them, but its difficult to find pictures with them. Perhaps it was mounted, but there are too few pictures of Ks sadly. What the K had however was increased gear ratio on the elevator (elevator deflection was reduced), hence stick forces in pitch decreased.

[xnomad]

Originally Posted by ACE-OF-ACES

It is also a bit of a myth that the USAAF allways had a altitude advantage.. The Lw would enter the area at a hight above that of the bombers.. Just ecanse the escorts picked them up prior to the B17s.. They knew the escorts hung out above the bombers..

Granted once the Lw got into position to attack the bombers.. they would dive down to the bombers giving up the alt advantage.. but at the same time trading alt for speed

Don't forget that the targets for the LW were the bombers. Near the end of the war there wasn't much fuel about so they only took off when the bombers were close enough to intercept directly. They didn't have the luxury of taking off early and climbing to a favourable position.

The allied fighters could be far ahead of the bombers and thus getting to the LW planes whilst they were still climbing. Also later in the war the order was given to actively seek and attack the Luftwaffe and her bases and not just fly escort. So the LW weren't even safe on the ground.

[Osprey]

Originally Posted by 5./JG27.Farber

Im not promoting it. I just wondered what people thought, especially the small percentile of Aeroengineers etc we have amongst us... Not the laymen such as I.

TBH the opening paragraph is just so unbelievable you realise that you are reading the equivalent of a religious website lol

I love the speculative sweeping statements though, such as "The P-51 used a NACA/NAA 45-100 laminar flow airfoil which had not been well tested ". In fact it's worth the read because it really is such utter nonsense it becomes funny.

[ACE-OF-ACES]

Originally Posted by xnomad

Don't forget that the targets for the LW were the bombers.

Which is why I said..

Originally Posted by ACE-OF-ACES

And it should also be noted that the Lw was not interested in shooting down the escorts.. They avoided them at all cost.. The goal was to get to the bombers.. Many a poor 109 was shot down while trying to line up the B17 as a P51 snuck up the 109s rear..

[Crumpp]

"The P-51 used a NACA/NAA 45-100 laminar flow airfoil which had not been well tested "

That is actually a fair statement. The P-51 series only achieved laminar flow under the ideal conditions of a wind tunnel when especially prepared.

In actual service condition, the aircraft did not achieve its design goal of laminar flow.

Thorough testing would have revealed this but wartime expediency did not. One of the consequences of designing an aircraft under such short notice.

[Uhu_BlueMax]

~S~ Alle

Interesting reading. I have only one gripe. Hispano Buchan. A Spit engine in a 109. It makes me cry.

I love the 109.

In my younger days, watching the film 'Battle of Britain', I kept looking at the 109 and thinking, somethings wrong, badly wrong. My Dad pointed out to me that they had Spitfire engines in them. Ouch! I thought!

I believe they did the same with the He 111 which was also used in the film.

Ta.
Happy Hunting