Spit IIa

[IvanK]

""Another problem is with the test itself, when compared to a Spitfire. Overall the accuracy of the test suffers from the fact that it was flown with a crash landed plane wirh a worn, several years old engine producing less power than usual. It was then flown against a brand new Spitfire with a 1940 engine. As shown by the test data, the turns were made in the 120mph range which is too slow for the 109 slats to be deployed, which doesn't compare the maximum turning abilities of each aircraft."

Of course the old clapped out engine theory will be presented. The data is the best available and is presented as is. I am not sure about the clapped out bit either. that is a readers assumption, and is not reflected in the report which is very thorough.

as to the slat comment ... The original author shows a fundamental lack of basic aerodynamic knowledge. Slat deployment is a function of AOA. The Slats deploy at a specific AOA every time not at an IAS. The AOA remains the same and IAS at which the slats deploy will vary as a function of G .... BUT ALWAYS AT THE SAME AOA. But the corker is the bit " the turns were made in the 120mph range which is too slow for the 109 slats to be deployed" ... you are not serious surely ! Think about it Slats are High AOA slow speed regime devices they are more likely to deploy at the slower speed (i.e. higher AOA).

For the record here are the 1G slat deployment speeds as found by the RAE in AVIA 6/2394 Messerschmitt Me.109 Handling and Manoeuvrability Tests. Its worth noting a 9Mph diff between the ASI reading and the trailing static source.

[Kurfürst]

Hmm, Werknummer 1034s engine problems (seems lubrication related) are documented in both French trial reports and RR reports. Its noteworthy that already in French trials the plane was loosing boost at altitude for some reason - I suspect French lubricants did not go well with the DB engines hydraulic supercharger clutch. But that's besides the point, because the British did not measure turn times for the 109E in flight tests, nor they did measure times for the Spitfire either.

The doghouse charts you presented are inidrectly based on stall speed measurements of the Spitfire. Now, those long enough to remember Ubi there were a number of threads discussing the difficulties of defining and measuring stall speeds, so there is a degree of potential inaccuracy with this base data already. From the established stall speeds of the Spitifre, they estimated its lift coefficient; they used this estimate to guesstimate the 109's lift coefficient. These guesstimates were used to calculate the doghouse charts you presented, using known power curves.

In short, they are calculated estimates with a bit shaky base data.

As to Bf 109E turn times, these are known from German/Mtt calculations, and are given as 18.92 secs for a sustained turn at 0m altitude using 990 PS or 1.3ata output of the DB 601A. (note British guesstimate is for 12k feet so the figures are not directly comparable).

As to Bf 109E(-1, -3, -4) performane in the sim, I note that in the early versions of COD the 109E just can't go past around 460 using 1.35ata, whereas the actual specifications for the type gives top speed as 500 kph at SL and 570 kph at critical altitude, with plus/minus 5% tolerance on production aircraft (so actual production aircraft fell between ca. 545 - 595 kph). Can it now reach its specs in the new beta patch?

The aileron up/down travel angle for the 109E is very interesting though - it seems the F-K increased the travel angle a lot (and changed to Frise type ailerons), though I wonder why. Better control response times, even though the E was already noted as brisk for aileron control response?

Anyway for a reality check with a new patch I always use to try if I can break the Spitty in two by madly pulling back the stick, something that would be suicidal in the real one with a stick force of a mere 4 lbs / G. It isn't possible in the sim. In fact, I did nto manage to break any aircraft in the sim, no wonder what stupid maneuvers I tried.

The increased aileron travel for the F to K series might be at least partially to counter the increased roll inertia and roll drag with the curved wingtips (hence longer wingspan).

But interesting post, Kurfurst.

I dunno about the doghouse chart and how they produced it but don't you think that they at least verified their method by test flying the Spit?

Has anyone made a test about turn times as implemented in game?

[Crumpp]

I can break the Spitty in two by madly pulling back the stick, something that would be suicidal in the real one with a stick force of a mere 4 lbs / G.

If the unacceptable stability and control characteristics of the Spitfire are not modeled, then you will never have a simulation of the relative dog-fighting capabilities of these airplanes.

Aerodynamically the Spitfire could easily out-turn a Bf-109E series. A pilot dealing with the real world stability and control issues would leave the contest much closer than the aerodynamic analysis on paper.

The stability and control characteristics of the BF-109 were acceptable and actually conformed to a set standard based on Robert R. Gilruth's findings on flying qualities. Germany was ahead of most of the world in adopting such as standard. Japan was also on an acceptable control standard. None of this was known to the Allies until after the war.

It is interesting to note that the NACA adopted a unified stability and control in 1942 but it was not until 1945 that the USAAF (R-1815-A)and USN (SR 119A) printed their own standards using the NACA findings. The first fighter the NACA tested was a Spitfire Mk V. The aircraft failed miserably and was replaced in USAAF service as soon as possible.

[IvanK]

Originally Posted by Crumpp

If the unacceptable stability and control characteristics of the Spitfire are not modeled, then you will never have a simulation of the relative dog-fighting capabilities of these airplanes.

Unacceptable to Who ? A NACA methodology formalised 4 or so years after the aircraft first flew. Didnt a number of US units actually switch from from MKV's to MK VIII's.

As to NACA's evaulation of the MKV the RAE in Technical note No.Aero 1106 made a bit of a rebuttal on the NACA findings. This includes some criticisms in the way NACA carried out its tests. I guess both reports should be read to draw a balanced view. The RAE document refers to NACA reports ARC 6423 and ARC 6422.

Here is the Summary or conclusions of the Langley evaluation of the Spitfire MKVA "Measurements of the Flying Qualties of A Supermarine Spitfire VA Airplane" ... not all exactly bad


Here are the conclusions from the second Langley report "Stalling charcteristics of the Supermarine Spitfire VA Airplane again not all bad:

[Crumpp]

Unacceptable to Who ?

Any stability and control engineer in existence. Remember there was no such person when the Spitfire was designed.

There is a reason why the RAE added bob-weights to correct the stick force gradient. This fixed the control force issue but did not correct the instability itself.

As to NACA's evaulation of the MKV the RAE in Technical note No.Aero 1106 made a bit of a rebuttal on the NACA findings. This includes some criticisms in the way NACA carried out its tests. I guess both reports should be read to draw a balanced view. The RAE document refers to NACA reports ARC 6423 and ARC 6422.

I am aware of the RAE rebuttal. Keep in mind the British were one of the last to adopt any kind of standard on stability and control.

Of course they thought it was fine, there was no established basis for what was acceptable and what was not. A few fatalities later though, the RAE did something about the Spitfire's longitudinal instability. Again, it made it easier to control but did not eliminate the cause of the instability.

[Crumpp]

It is right there.

You know what stick fixed stability is right?

Originally Posted by Crumpp

Aerodynamically the Spitfire could easily out-turn a Bf-109E series. A pilot dealing with the real world stability and control issues would leave the contest much closer than the aerodynamic analysis on paper.

I agree that the fighter pilots would have driven their kites closer to the limits than tought at flight school. As you indicate yourself by your phrase, aerodynamic calculations are never as accurate as to predict reproducable stall speeds. But this may go both ways that is that calculations are either pessimistic (stall would occur later than calculated) or also optimistic (stall would occur sooner than calculated). So it may be the way you stated it (the pilots drove their plane closer to the limits than what calculations would have predicted) but it may also be the other way around.

Principally I would guess that stall speeds taught to the cadets were obtained experimentally. And keep in mind that pilots appreciated when they got a feedback from the plane (e.g. buffeting) when they got close to the stall limit.

[Kurfürst]

I wonder, is there a clear definition of stall at all...?

[CaptainDoggles]

Originally Posted by Kurfürst

I wonder, is there a clear definition of stall at all...?

Stall is defined as the point where the airfoil's critical angle of attack is exceeded.