Kurfürst

The only close the rear permissable cg position (roughly 60-62 cm) on the 109 I could find was when it was mounting 4x50 kg bombs, but that was still within limits. All other conditions I checked (gondolas, 250 kger) well within the limits at 56-57. In other words, the loaded plane (clean fighter, gondies, 250 kg - the most common configurations) had as much rearward CG "reserve" as the whole allowable CG load margin of the Spit. From what I have seen, yes.

The truth is actually its much profane - there is simply no a test in which they run the thing at 46 minutes at +25 lbs, period. The 46 minute running a +25 is just a brainchild of a single spitfire fan guy, his own loosly based 'calculations' after the results of the cooling trials of JL 165. In the actual test which they climbed that plane with a rather cold engine for about 2-2.5 minutes with +25 lbs boost, on rather cold morning (6 Celsius or so). That is how internet myths are born, I am afraid.

Same is true to the Spitfire, they added a lot of weight elsewhere, after all the first Spitfire weighted something 5300 lbs and the XIV some 8500, the 21 some 9200 lbs. That's something like 3200 lbs difference, and about 10-15% of that went in the rear with the aux. tanks. So how is that all that weight going to the front in the form of heavier and heavier engines just couldn't balance out the things added to the rear on the Spitfire? The point is that if the aircraft has wide stability margins to start with, its easier to add things to the rear. A lot of things. Its really not all that complicated, really. No, I am not aware and it wasn't just as much of an 'issue'. Of course CoG limits have to be observed on all aircraft, but that's not necessarily an 'issue' if its easy to do in all load conditions. The issue is that some here want to put forth an arguement that CoG limits are just as much of an 'issue' on a plane that has 8.9 inches of margin for CG movement as the one which has a mere 3 inches... Certainly, it cannot go unchecked. It is true that the Messerschmitt guys were evidently a lot more successful in not having the CoG move about the aircraft randomly and unchecked compared to the Supermarine guys, that much is true. They still had to observe the CG limits of course but its a lot easier job to do when you have 2-3 times the CG limit to play with. That thing about the marginal stability on the 109G is just silly, JtD, and you know it.

Exactly. For what its worth, the Mk XIV's allowable CG margin: "Permissible C.G. range for all forms of flying...........from 3.5 inches to 6.5 inches aft of datum point." I don't think 3 inches (7.5 cm) can serve you well. ;)

Yet the claim remains unproven and an opinion piece that remains at odd with the facts, namely that it was done on the 109E and it did not have stability issues at all. There were no stability issues or deterioration of flight qualities or restrictions when 187 lbs worth of MW-50 liquid were added to the rear fuselage of the late 109G/K either, as opposed to the Mark IX which even with half empty rear fuselage tanks (cc 33 gallons remaining = cc. 250) lbs and hand-made elevators showed had serious stability issues and a tendency to tighten up in turns. Well, no reason at all, except physics and looking at loading sheets and actual stability margins. Apparently, aircraft with forward mounted fuel tanks (Spitfire, Hurricane, some Italian fighters like the Macchi 202) exhibited the narrowest longitudinal stability margins. A change in the... datum point... when the fuel tanks move. Would you kindly expand on this further, as I cannot fathom why that would be so? You do realize that this doesn't make much sense as the CG of an aircraft is, in fact, constantly changing during flight and depends on load condition and that there is not just one fixed point? That is why they bother to issue loading plans. It depends entirely on the allowed CG margins and not all fighter designs had such meager stability margins as the Spitfire, therefore, not all designs would react the same way to 300+ pounds in the rear. The 109, which you seem to be very fond to make a comparison with, added 485 pounds of fuel in the rear fuselage during its development without any trouble. Its really unfair to fault Crumpp if you cannot see the connection between these shape of these curves and instability, and "double handling" and the correct conclusion that it had rather narrow margins of stability.

That would be a very curious test report indeed, considering that the Merlin 66 had an hourly consumption rate of 197 imp. gallon / hour at +25 lbs/sq. inch boost and that the IXLF had a 85 gallon fuel tank... ... meaning that the thing would run its tanks dry at +25 lbs boost in a little under 26 minutes. So, one has to wonder about how in this allegedly existing test they managed to run the engine at +25 lbs for another 20 minutes after the fuel run out. ;)

Check the big 109K thread, I recall several knowledgeable poster have shed some light and some papers on this control modification.

There is no need to wonder, since such aircraft existed and was called Bf 109E - and reports also tell of its excellent control-ability near stall. The 109K topped that with another 25 gallons of fuel, or ca. 192 lbs, plus tankage. Of course the 109 had a lot of weight right there to start with -armor, the pilot and the fuel tank beneath him - so its not that much of a relative change in where the weight is placed in the airplane. I guess the crux of the matter is that the CoG change was far also more radical with the installment a extra tank (or any other weight for that matter) in the rear of Spitfire, as it originally had a very much forward placed CoG with a 85 gallons of fuel mounted forward, right behind the engine, than compared to a plane that had it in the wings or below/behind the pilot seat to start with. Perhaps that is very the low margin of stability of the Spitfire originates to. It can be stable at optimum CoG position, but apparently it was very sensitive to any changes in load with quickly occurring instability. Sensitive pitch control characteristics would only add to such troubles. This was noted from the earliest Marks on, see Rechlin's verdict on the issue: "Quick changes of the trajectory along the vertical axis cause especially with the Spitfire load changes around the cranial axis, coming from high longitudinal thrust momemtum, and significantly disturb the aiming. In summary, it can be said that all three enemy planes types are inferior to the German planes regarding the flying qualities. Especially the Spitfire has bad rudder and elevator stability on the target approach. In addition the wing-mounted weapons have the known shooting-technique disadvantages." Crumpp has been pretty consistently referring to a narrow margins of stability on the Spitfire, not that it was longitudinally unstable per se, alas it seems the difference in meanings had remained obscure.

What would be refreshing is if some (might I say - usual) of participants of this discussion would finally be able to present something, anything that would at least resamble like objective evidence, rather than just their limited pool of snide remarks. For example, I would like to see some evidence to the notion of the Mark IX had ample stability margins and that they managed to cure the failings of the previous Marks in this regard. So far the most 'serious' arguement put forth to this end is that 'hey, something was changed, so it must have been cured, completely'. But then I read the flying instructions for the later rear fuel tanks and I wonder... ;)

The 109K manual notes that the gearing (max. Elevator deflection) was changed to reduce elevator forces. But I recall there was a discussion on this Board on its testing. Unfortunately only snippets were available.

that single sheet of data shows the mean avarage of 125 serial production me 262s. In other words it is, by a very wide margin, the most reliable data of all WW2 fighters. Also note that the Me 262 climbed pretty well, but the main point is that it climbed at some 200 kph faster than propeller jobs.

I believe you can set the chance for these before flight.

I have no problem of pressing V and F respectively to simulate operating the flaps and that one of my hand is occupied in doing so, as in real life. I understand that for some maximum reality / cocpit builder users of the module would enjoy a different implementation, but IMO we should put first things first - lets have all the ordnance (bombs, cluster bombs, rockets and gunpods) and any possible FM bugs sorted out first, and prefarably multiple fuel choices (and not only for the K) which are long awaited, and then progress towards polishing control features.

Landing speeds are very, very heavily influenced by flaps... thus might not be a good basis for maneuvering comparison.

Very useful and enlightening thread, thanks for putting the effort in it!

Yeah, apparently someone in the Supermarine/Air Ministrz Designation Department figured out that he is only required to come up with random variations of Roman numbers and letters, not necessarily following any particular order, to get his paycheck. :lol: He surely had some distant relatives in the German and U.S. Ordnance Department though, who had also figured out that the job can be further simplified by just designating every piece of ordnance as '18' or 'M 1', respectively. :megalol:

The 'IXB' was kinda semi-official designation for the Mark IX L.F. the low altitude Merlin 66, to differentiate from the medium altitude Merlin 61/63 version, that came first. Still the 'B' had a 'C' wing of course.

Did anyone test the respective best turn times for them in DCS 1,5? I am curious.

Max. continous cruise is 1.35 ata / 2400 rpm (Höchtszulaessige Dauerleistung) economic cruise is 1.15 ata / 2000 rpm (Sparleistung) on the K-4 with DB 605DB/DC we have in the sim. See:

Well what gives, one of those days I actually agree with Milo on something. :thumbup:

The 5750 fpm climb figures best conform to the earliest RR trials with Mark IX L.F., serial no. JL 165 at +25 lbs and 160 grade fuel, albeit it should be noted that the RR trials were flown a considerably lower than normal (tested sans ammunition...?) takeoff weight 7234 lbs instead of the fully equipped takeoff weight of ca. 7450 lbs, and with the radiator shutters closed to their minimum drag position. This would significantly boost climb rate compared to normal conditions and was somewhat unusual, as the British testing standard at the time was to test the aircraft at full weight and with radiator shutter open for climb (and with 95% weight correction and closed radiators for speed runs). The combined effect of lowered weight and lowered drag was considerable on the results, as the same JL 165 was tested later in the standard condition, yielding 5080 fpm at +25 with full (normal) take off weight and open rads - albeit only to a couple of hundred feet high, since the supercharger really couldn't cope with maintaining this boost at altitude. They have also interpolated the +25 lbs results which would interpolate to about 4200 fpm @ +18 lbs boost.

Odd. Stick force gradient should be linear to very high mach numbers IMO, if we believe the stability curves posted in the other thread. Very odd. Slats disabled or what..? Odd in the extreme. If anything the 109 was known for high longitudal stability. If it would be wobbly in the horizontal axis, I wouldn't complain... Phew! At least HP/ton is still calculated the same...

Look really, really nice and quality model. Apparantly ED have found a way to have both clipped and normal wings. :thumbup:

Same question here.