rel4y

Oh I know Phil, I wasnt trying to say it isnt. I was just a bit surprised by the nonsense being propagated on the last page. Btw, would you consider adding a non MW50 109 in your missions, as the Luftwaffe without a Bf 109 in its rows is a bit offputting. The A-8 wasnt really deployed operationally as a dogfighter, it was used to counter heavy bomber formations (A-8/R6, R7, R8 ), hordes of IL-2s and as a fighter bomber as the factory ETC 501 installation shows. Would be nice if you could somehow still include the only purebred dogfighter the Luftwaffe had, even if it is not quite the correct model. The P-51D-25 also didnt see any operational use before around March 45. What would you say happens in terms of prop efficiency as Mach increases and the airflow around the prop is locally supersonic? What do you think provides pretty much all of the acceleration as these effects become more prominent? Why would you say props get torn off at about Mach 0.85, is it because their thrust is so immense that they simply evaporate? What do you think is more important for prop planes at high Mach, thrust/weight or drag/weight ratio? Where do you think the ratio of motor acceleration/gravitational acceleration is larger, at low Mach or at high Mach? :thumbup:

Pretty sure you are talking about the Spit XI not IX test. That one had substantially reinforced wings. Spitbombers (Mk IXs) were known to get wing skin wrinkling in the pullouts after bombing. At Mach 0.9 pretty much any prop plane would have its prop torn off by drag if not fully feathered. The prop drag would be equal to the flat plate area of the prop diameter. It is at high Mach numbers that engine power doesn't matter but only gravity and not the other way around.

I don't quite understand why people expect better elevator authority from trim tabs? They pretty much don't change anything at all in that respect, maybe the double sized trim tabs increased elevator area a bit, but that's it. They won't provide any advantage in pullouts or dogfights, neither will they mess up anything about the aircraft. Part of this discussion revolved exactly around that, because stab trim and trim tabs have pretty much the same effect at small deflections. All they do is trim the aircraft aka bias the elevator for a specific velocity. All that does is increase pilot comfort by increasing maximum nose down trim. What does help in a dogfight is that the elevator gearing factor changed on the K series (and G-10/U4 + some G-14 ASB/ ASC variants), which decreases stickforces. What we have established so far is: -K-4s had double sized trim tabs -stab trim was limited to +1°10` = ~1,15° on late models -stab trim was limited because double trim tabs set to nose down trim combined with high positive stab settings caused elevator force reversal* and goal was high speed pullout with the elevators only, at constant stab setting = basically safety reasons -trim tabs were only adjusted on the ground, by the aircraft mechanic after a testflight and were not constantly readjusted (except in some test series obviously) -we had a misconception of what cruise speed is supposed to be, Bf 109 Reisegeschwindigkeit corresponds to maximum continuous power *elevator force reversal meaning that one needs to pull the elevator to stop the aircraft from increasing its dive angle at high Mach numbers. So at lower angles stick pull the aircraft would still nose down. Based on this I would kindly ask ED to give us the option of elevator trim tabs in the menu or maybe trim the K-4 for a speed that more closely resembles Reisegeschwindigkeit. Based on the Soviet G-2 test about 3° elevator deflection nose heavy should be fine. But since we already have the one of a kind options in flight Sim history of trimming aileron and rudder tabs, I would be really happy about the addition of elevator trim tabs.

Actually that doesn't apply to the Spitfire or P-51 afaik, but may certainly be possible in some awkward way. Generally cruise is not equal to the economy setting and cruise and combat cruise can be used interchangeably. Economy setting means maximum range at minimal fuel consumption, while cruise means best range vs travel time. Anyway, in Luftwaffe terms aircraft were trimmed for Reisegeschwindigkeit, which translates simply to cruise and is flown at maximum continous power. Depending on the theater, common combat altitude differed, so trim may have been slightly different. I just introduced the term combat cruise to describe what it meant in practice. I think the confusion stems from G-2 documents. G-2 cruise was set to 1,15 ata as that was it's maximum continous power.

Did you see my above post? It addresses what cruise is. 109s don't have pilot adjustable aileron and rudder trim.

Ok, if it was ment like that I will apologize for being an asshole. His post before editing didnt make it sound like that to me though. I thought it is common knowledge that ground adjustable trim tabs are adjusted on the ground and cant be changed in flight? Noone ever made it sound that way either. The aircraft mechanic set the trim tabs after a testflight for combat cruise with an instrument called Gradwaage. I think our only difference here is what is considered cruise in German documentation. Combat cruise is used in contested airspace and always refers to Höchstzulässige Dauerleistung = maximum continous power. 1,15 ata is Sparleistung on the K-4 and only used if fuel is a problem. So let me address that quickly with a source. Cruise G-2 is 1,15 ata for 595 kph Cruise K-4 is 1,35 ata for 645 kph In the following doc you see that Höchstzulässige Dauerleistung aka maximum continous power outputs around 1030 PS (horsepower) at 1,35 ata at rated altitude 7,7 km. V-Reise = cruise = 645 kph at 1030 PS.

Hey Shagrat, I know you edited that part out by now, but I am glad you noticed that ground adjustable trim tabs are adjusted on the ground. I think I found the problem with your approach, you only read the first page. If I may suggest, it always helps reading the full report, understanding it and then drawing conclusions. Several times it is described how trim tabs were adjusted, let me quote myself from one page ago about one of these incidences. Bügelkante = trim tab bügeln = describes the act of adjusting the trim tab kopflastiger = more nose down attitude So you are an ED translater and your "interpretation" is that they never adjust the trim tabs during these tests? If this is the state of ED members and how they handle documentation I am starting to realize why we are having this discussion in the first place.

Guess you mean Pathos there, but dont worry I understood you anyway. Is having student pathos a bad thing btw? I would think the desire to learn and understand over our whole life span, is how it should be. Dont get angry Yo-Yo, just as I choose to be very stoic about this discussion by now. I am sure we will agree eventually. I saved it on the wayback machine because sometimes admins get rather trigger happy about deleting stuff, just a precaution to not loose all this valuable discussion. As far as I now the skunkworks development documents are still classified, even the -1 is still a national security asset. Are you saying you have access to them? Where did you get them from? Ok, so we are agreeing on this: So the most pressing question you had seemed to be the following and you said nobody answered that question in a satisfying manner. My answer was because it was done in real life and that it increases maximum nose down trim capability. That is also what the test report said. So we are in agreement now. Thats good progress I believe. So now you are not sure they pulled out the dive with 1,15° stab fixed? Mmm, but that was the whole reason of the second test series, to find a stab setting at which pullout was possible with elevator only. So they steadily decreased stab from +1,45° to +1,15° in idle dives until they were sure they have found a good setting and tested +1,15° several times in a full power dive. I will compile a bunch of quotes from the report which will make it more clear, ok?

Hey Yo-Yo, There is so much smoke screen up I dont even know what we are disagreeing on anymore. So from human to human, would you please give us (your customers, critics and fans) an honest answer? Where exactly do you disagree with us? We agree that the K gear ratio has changed, correct? Can we also agree that trim tabs and stab trim in real life are accompanied by slightly different effects, but the approximation you are using is perfectly valid for small deflections? The trim tabs were doubled in size on the K-4, correct? For doubling the trim tabs the high speed trial report gives insufficient dive angle at 100% power as a reason, agreed? After adding double trim tabs to get rid of elevator force reversal, the stab was limited to +1,15°. In that case the dive could be recovered with stab at constant +1,15° with elevator only, correct? In this test the engineers set the trim tabs nose heavy and the stab to +1,15° to gain nose down authority, yes? (Not sure if this was posted yet, but here is the section of the test report stating that.)

No they dont, in school academics you are free to use it as approximation for small angles. In the real world you get kicked in the ass. I cited the german report which speaks of Kraftumkehr im Höhenruder, that translates to elevator reversal. Thanks Curly. I have honestly lost patience by now. It is the same test and in the abstract both cases are summarized.

Yo-Yo please.. lets stop this nonsense. You asked me to name an engineering difference in effect between trim tab and stab. I gave you several. The question was are stab and tab effects the same, because that is what was said earlier in this thread. NO, they are not. Do you disagree? Then I gave two other pressing reasons why we need trim tabs on the 109. Did I not adress your question here? Do you honestly not see a reason to add trim tabs? My point is not what you put in my mouth but this! The second one is already addressed. Actually no, it was constant throughout the dive. There is even a graph about it and the passage in the text is three lines long. I would not mind translating the text for you if nobody has done yet. Nobody disputed that they set the stab different from 0° btw, just that it wasn't changed and elevator reversal doesn't occur at stab 1,15°. I can quote myself like six times stating exactly that. Btw they changed the grease in the stab mechanism. Can you tell me how trimming the stab at lets say + 1° and setting the tabs to deflect the elevator ~3° downwards is violating that? Because that would set cruise trim to around combat cruise and is actually what was done in real life. The only thing deeply wrong is your argumentation here. 109G wings were designed to withstand 10G + margin. I can show you a report where 10.5 Gs were reached. If the pilots violates that, its his own demise/death. I also remember earlier in this thread you said that it would have pretty much no effect at all. Why the sudden change of mind? I am really sorry how the tone of discussion changed, because Id like to get things done in a civilized matter. But I also wasnt the one to call others stupid in the first place. Now it is just a pi**ing match. Yo-Yo, Id like to ask you again very politely to think about what we are saying and I would be happy for a week straight if youd give us elevator trim tabs. I think this will be my last post in this topic. Btw, I saved this thread on the wayback machine, just in case somebody chooses to delete it for unknown reasons.

Sure, why not? First of all Mach effects. Above critical Mach subersonic flow at the front of the airfoil causes normal shock which leads to boundary layer seperation in the trailing region. This may cause trim tabs and the whole elevator to become useless while stab adjustment still works. In the transsonic region it becomes actually very different as you must know. Drag is different, you will not be able to reach the same trim at the same thrust. So different equilibrium speed. I could think of another thing due to different pressure distribution but we touched on that earlier. Also I kindly refer to what Curly said:

And I believe I gave a very valid answer, even detailed it into 3 seperate parts. I attached it again below for your enjoyment. I think by now three people tried to explain that stab trim and trim tabs act differently. You clearly have no engineering background whatsoever and yet you somehow have an opinion that is supposedly more correct & relevant than any proof presented. Then again you demand hard proof from everybody else. So me and others posted proof in form of documents, explained context, answered questions and you simply deny it based on: God, how could the laws of physics be so wrong!? Have they not heard the hearsay yet!? Mind blown. ...and... I could agree on your last post, that you should stay away of these discussion, that would have probably been better. Ok, I am just pulling your finger here. But please, just calm the nerves and have a think about what we are really saying.

Oh, come on.. See, thats the problem. Even though you guys know its wrong, the answer always is nothing to see here, please move on. Yes, I do also trust the sources. Thats why all my arguments are built around them. (Btw the same sources as Yo-Yo) And I trust YoYo in general, he seems to be a good & knowledgable engineer. Yet I know nobody is infallible. Even YoYo corrected several areas of the K-4 FM alone based on discussion/ documentation in the forums in the past Well, maybe you dont... I addressed it in one of my posts. Take the DCS K-4 to 4000m, MAC 23%, set the stab to 0°, turn the engine to idle, hit Ctrl + Z twice, observe. Finally compare to soviet test. Aaah, the famous hearsay. Does it even make sense to ask you for sources here? Someone in this forum said feel, opinions and hearsay dont count a penny, or something like that. Actually I did in all detail, you even quoted the post. Honestly, why are we even still discussing this? Everybody makes mistakes and thats not a problem as long as you dont act like it never happened and everybody else is stupid. The mistakes in drag, roll rate, level speed all were corrected eventuelly and everybody was grateful to ED afterwards. Why is this matter such a religion?

I actually feel kind of frustrated, because I am going full circle with my answers. But let me address it once again. That statement is untrue and I adressed it twice in this thread already. The 109 was not limited in trim ability because of safety reasons, at least not in the way you make it sound! In the configuration our DCS 109 is at the moment, it is not trimmed for any specific speed at all. It simply has the trim tabs set to neutral. To that, the DCS K-4 stab range is artifically increased to ~+1,5°. That configuration doesnt allow for any dangerous dive anyway, as the paper I have cited clearly states. And in the paper the test plane at least was trimmed to level flight in the first place, aka nose down. So what we have currently is a "trim setting" no pilot in WWII flew with, other than the soviet test pilot of the G-2 report, with a stab range no K-4 ever had. The horizontal stab was limited in positive incidence because elevator reversal could occur at high Mach with double trim tabs set nose down and at stab +1,15° this was no problem anymore. So at +1,15° stab the plane is safe and trimmable at any trim tab setting. So lets get to the answer why we would want trim tabs in addition to stab trim. First and most bluntly, because its historical. Thats simply how the 109 was constructed and used operationally. In the late models they were doubled in size because they were important features of longitudinal stability. Could they have redesigned the elevator mechanism to be more reasonable? Surely, but changing the production lines most likely wasnt feasable, so they improved on what they could work with. I mean, what are we simulating here, our own personal opinion how the 109 should have been designed & operated, or the real deal? Second, the effects of stab and trim tabs are not the same and I have already emphasized on this. I dont want to repeat myself, just take the fact that elevator reversal can occur at stab incidence of +1,45° with double trim tabs but not at stab +1,45° with single trim tabs, where even +2° is ok. Maybe the sim doesnt model these effects, but in real life the effects are not the same! To that you are suggesting that instead of trimming nose down by tabs, we should actually just use the stab at higher positive values for some unknown safety reason. This is the very setting that causes elevator reversal and makes the plane unsafe! Third, the maximum trim range clearly increases and it would be possible to trim the aircraft at combat cruise. In german manuals combat cruise (in contested airspace) was considered to be maximum permissible continous rating (1,35 ata for K-4) and not maximum fuel efficiency. In air combat patrols you would want to go as fast as your motor possibly allows, since at any moment a P-51 or Yak could jump you. And I am sure pilots would not have liked their aircraft to pitch up constantly because the lazy mechanic has not set the trim tabs to anything but neutral.

With your explanations the relevance of defining two neutral points at first didn’t quite occur to me, since at some elevator deflection the free stick NP must coincide with the fixed stick one anyway. After reading up in the literature I realized the free stick NP simply has the hinge moments defined as zero and is important in stability theory for response to perturbation. Well, perturbation response is not what I am interested in currently, I care about stick forces and trim. I think no one disputed your basics, but you seem to be placing them out of context. I am saying the tree is green and you are answering, no you dweeb, the sky is blue. “My wrong opinion” is actually a thing in Torenbeeks “Synthesis of subsonic aircraft design” in the context of plain flaps and how linear airfoil theory underpredicts pitching moments in comparison to empiric data. Now what is an elevator, but a plain flap located on the symmetric airfoil horizontal stab? With these deviation in pitching moments (dM/dalpha =/= 0), horizontal stab AC also moves around. You yourself said earlier that in praxis AC is not constant at quarter chord. This in turn would change the fixed stick NP from the calculated position as soon as the elevator incidence is different from 0. It was more of a thought experiment and like I said earlier will be marginal, but I don’t need to be called an idiot for it. Now lets get back to the real problematic: I think we all have realized by now, that the gear ratio indeed did change and the stickforces must with it. Looking at the formula we see that stick forces are proportional to hinge moment coefficient and gearing factor amongst other things. Since all we would like to change is gear ratio in the plot, we can for now consider everything but G and Fs as a constant. In the plot we can also see that the stickforces stay pretty much linear over the whole Mach range. At Mach 0,73 the Stickforce amounts to 32,5 kg for an elevator deflection of 2,8°. Corrected for the new gearing factor (x0.76) it amounts to 24,7 kg. That is less than I do one armed rows with. ;) I probably will get into more detail on the stickforces, elevator deflection and CoG in the future. Furthermore, the elevator deflection range in respect to 0° has changed a bit, lets look at stab +1,1°. In G models it was 31,3° upwards of 67° total, so 46,7% of total range. For K models it is 26° upwards out of 51° total, so 51% of total range. Upwards meaning pulling the stick. Ok, so far we have not addressed trimmed cruise flight. Above we have looked at the Stickforce Fs which is proportional to hinge moment coefficient. To get the stickforce to be zero, we must get the hinge moment coefficient to be zero. Let’s look how the hinge moment coefficient is defined. (b0 will be 0 for symmetric tailplanes) I think we will agree that elevator trim tabs will influence free stick neutral trim. Depending on how I bend/ deflect these trim tabs I can set the elevator angle with zero hinge moment at a specific stab incidence. By bending the trim tab aerodynamic forces exert a moment on the free floating elevator and deflect it. In the soviet tests the elevator deflection is 0° when the stick forces are zero. That means trim tabs are set to neutral and do absolutely nothing at all. If trim tabs were actually set to cruise trim, they would deflect the elevator by some degrees and for that elevator deflection the stick forces would be 0. Even if they were set to cruise speed of a G-2, G-2 optimum cruise is 595 kph at 1,0 ata and K-4 is 645 kph at 1,15 ata. That is a 50 kph difference. According to the soviet G-2 report it would only need 2° of elevator deflection to trim the aircraft at even 30% MAC with 1.3 ata, 2600 rpm, stab +1.5. So lets be generous and say about 3° for stab +1,1. From my experiences it is perfectly possible to deflect the elevator by about 3° with trim tabs. Now, for a second lets assume the Germans didn’t have too much material laying around and were totally bored at the aircraft factories in the final days of war. Why would they possibly add another workstep/ extra material to double the area of trim tabs? I wonder, could it possibly be because the single trim tab config did not create enough moment on the elevator to provide the necessary free stick elevator trim and nose down authority? Well the German test I quoted earlier says exactly that.

Well at least in theory it must, because it shortens the aerodynamic chord of the horizontal stabilizer and thus moves AC forward. If you assume AC at 25% of chord, then if the chord shortens the AC will move forward in respect to CG of the aircraft.

I completely misread what you said, to my defence I was in a shaky train writing on my phone. While I am familiar with AC, CP, CG, MAC etc, I honestly don’t quite grasp the difference of the two neutral points. Isnt the NP basically the AC of the whole aircraft? So at a fixed tailplane incidence wouldn’t the elevator angle (fixed stick) and stick forces needed for deflection (free stick) and therefore the NPs coincide? If I put the elevator at a positive angle, the elevator chord shortens thus its AC moves forward. This would shift the aircraft neutral point forward as well, wouldn’t it? I understand in contrast to asymmetric airfoils AC for symmetric airfoils is constant with AoA, but as soon as I move the elevator out of its 0 incidence I automatically change the AC forward regardless of AoA or Cl, right? Now I know this will be pretty much negligible, but it should be determinable. Well anyway, here is the plane view comparison of the Kp3 bellcrank. My understanding is as follows: The rods and cables are unchanged in length as the supply numbers are unchanged. The attachment point of the rod on Kp3 however is offset to the right by 10°. Since the cable mechanism functions in a parallel fashion the whole parellelogram is skewed to the left. This in turn pushes the elevator rod upwards and rotates the elevato. This shifts the elevator range to the nose heavier region.

I am not at home currently, but if you don't believe me just check the replacement part list. The part number changes if the part is changed. I don't believe I have an isometric blueprint of 109 G Kp2 equivalent. I have prepared a picture about the Kp3 changes, I will post it tomorrow. It shifts the elevator travel range to a more nosedown range. Makes sense to me, that the counterweight reacts to G forces. That's what I suspected. However, there is no way the bobweight stabilizes the stick aft at positive G, just check the force flow and you must realize it pushes the stick forward and the elevator downwards aka moves the control neutral point forward.

Yes, in principal it does mean exactly that. But although the elevator forces are decreased by about 25-30%, the aerodynamic effect on them is not linear. Dynamic pressure increases with velocity squared. Actually, there has to be a significant difference, let me explain why. But first I will post the elevator components. Between F and G-2 models the supply number did not change, which means that the parts were the same. The whole elevator transmission chain is basically unchanged except for two parts on the K-4. Inspecting these parts closely we will find that page 68 part 2 (=Kp2) and page 68 part 14 (=Kp3) were changed. The change in Kp2 will cause the difference in maximum deflection angle since the lever increased, while Kp3 will change the elevator zero incidence downwards at any given horizontal stab angle. Now one of the more interesting parts is page 70 part 1, the counterweight. Considering that the elevator horns balance it aerodynamically and weight in these horns mass balance the elevator in respect to the hinge, this is an interesting part. What is it for then? Well I tried to model the transmission chain in Solidworks and the effect is that it moves the stick forward in its neutral position with a higher mechanical lever than the elvator itself can. Considering that the stick is designed with more backwards travel than forward travel, it is pushing the stick in its upright neutral position at about 42% of stick travel. In effect and together with the double trim tabs this will cause an aerodynamic as well mechanical downforce of the elevator and will depress its neutral position in respect to the horizontal stabilizer. I am glad that finally people are listening, now it actually makes sense to calculate the stuff and correct it once and for all.

Yeah, that's from the front YoYo. Do you recognize the aileron axis to which the coat hanger bell crank is attached? Also the grip is rotated to the left for more comfort. You marked the sideways throw YoYo, the elevator is 38° and was never changed. I am in bed already, but I can provide you the pictures tomorrow.

Yoyo, are you sure you are not confusing the aileron stick travel with the elevator stick travel, because in my 109 K blueprints the aileron travel is 31° and the elevator travel is still 38°. As far as I know the basic stick mechanism was never changed in production lines. Only the second bellcrank was. And in my hinge moment calculations the difference is about 25% and the neutral position changed significantly.

Hey Yoyo, I see where you are coming from, but you are missing my point. I am saying two things: 1. The maximum deflection changed, thus in the simplified way you broke it down the lever is longer and the stick forces will decrease at the same elevator deflection angle. The stick throw stays the same 22° pulling and 16° pushing, but at 22° stick deflection I need less force to deflect my elevator to 27° than I would need to deflect it to 33°. = higher mechanical leverage 2. Neutral position of the elevator in comparison to the horizontal stabilizer changed, which also alters the elevator incidence at neutral stick. G-2 has 34° down and 33° up, K-4 has 24° down and 27° up. Since the elevator actuation is linear, the neutral stick elevator position must have changed. And in this case the neutral position will have changed to a more nose down attitude. I guess this is what you call elevator bias?

In German reports and also aeronautical engineering you talk about (Kraft-) Übersetzungsverhältnis which translates to gear ratio in English. This may be different in Russian, as my girlfriend tells me that in Russian rain walks instead of falls, but it is absolutely correct in German terminology. Since this Soviet report links stick forces to elevator deflection and the gear ratio between a G-2 and K-4 changed, would you mind telling me how exactly it is valid? I already posted in my first post in this topic that elevator travel at zero stabilizer incidence (0°) was decreased from 33° upward and 34° downward to 27° upward and 24° downward for late 109s such as K-4 and G-10. The maximum deflection angles at stab -6° are 30° up and 21° down and at stab +1,10° 26° up and 25° down. Do you want me to post the G-2 maximum deflections for comparison as well?

Because the elevator is modeled after a standard trim tab soviet tab G-2 report. You qouted YoYos post about this yourself. But contrary to when we provided him with information about the incorrect drag coefficient of the 109 due to wheel well covers, or provided the report on correct aileron forces he doesnt address elevator problematic. I have calculated the K-4 elevator hinge moments based on 109 blueprint documents (https://www.ebay.de/itm/WW2-German-Flugzeug-Bauplan-Blueprints-Me109-Fw190/391441687123?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649) and with these it is possible to correct the elevator. I have provided the drag curves for the Hispano cannons to YoYo before and wouldnt mind to give him this data as well if it only gets finally corrected.