DCS Spitfire Mk IX performance

looks like a close match to me :)

In the airspeed graph the dark blue line is the DCS Spitfire Mk IX? There is no legend. Thanks.

seem's so because it's the average value of all other lines

looks perfect for me :thumbup:

I CAN'T WAIT

Thanks for sharing this information Yo-Yo :thumbup:

Happy landings,

Talisman

Looking good: Thanks Yo-Yo :thumbup:

As a reference, Mk IX BS. 543 was used for level speed and climb rate, Mk IX MA. 648 was used for level speed.

Extremely poor choice IMO since subsequent reports (see report BS 310 w. M70) and the BS 543 curves make it clear that the engine of the prototpye BS 543 was operating on too rich mixture, therefore it had an abnormally high full throttle height and improved low/medium performance at low medium altitude. Very higher altitude performance suffered somewhat.

BS 543 also had an experimental propeller that was never serialized and achieved performance far in excess of ALL other Spitfire IXs/VIIIs tested.

Take a look of climb curves of BS 543 at higher altitude, there is a break in the climb curve - apparently the mixture that was getting too rich there.

MA 648 is an even poorer choice since its representative only of an experimental plane with a type of injection carburetor that never saw service in the end (all Merlin 66s were produced with the Bendix Stromberg injection carburator, not the SU type carb), hence the much higher altitude performance than normal. That plane never existed in service.

IMHO BS 310 results should be best choice as reference, since this one was a control flight for the odd results with BS 543s and the results obtained (404 mph - still pretty much on the high side considering no other serial production Mark IX with the Merlin ever seem to have been capable of reaching or exceeding 400 mph) were, in the end, accepted as the official reference specifications for the Merlin 66 Spitfire IX by the British Air Ministry.

Also of interest is the results obtained with serial production Merlin aircraft in reality - 397 mph, 389 mph (IX LF JL 165), 385 mph (Soviet Mk IX LF), 394 mph (RAAF Mk VIII LF JF 934 - extended w. tips though)

Of course there is nothing wrong with using BS 543 and MA 648 as reference if you do not name Spitfire Mk IX. Name it a "an experimental Spitfire with an experimental propeller and and experimental carburetor with too rich mixture that gives you abnormally high powers at low and medium altitudes". ;)

So it is 18lbs boost... Well, prepare your self Spitfire pilots. You are up for a ride.

Very nice Yoyo.

One question if I may ask, so Spitfire will be running only +18 lbs boost ? Not +25 ?

So it is 18lbs boost... Well, prepare your self Spitfire pilots. You are up for a ride.

It will run circles around anything anyway. So IMO it would kinda add some spice to the current mixture.

I believe he is just using those charts as a comparison for this example, I dont think he is using data from those aircraft for the FM, if that makes sense.

Thanks for the clarification SiTh: as with the other FMs, and with access to properly restored Spitfire IXs, Yo-Yo has access to far more data than can be found on the internet. :thumbup:

The big question in my mind, directed at Yo-Yo as he's flying it:

Is it as hard to fly for us desktop simmers as you expected? I remember you warning us quite a while back that it's going to require silk hands :)

Mmm... the Spitfire at 18 lb has equal energy with 109K with MW50. Will you feel good as you know that at 25 lb you have superiority over your opponent? :)

Another 1943 allied plane up against 1945 rivals? Pass.

Mmm... the Spitfire at 18 lb has equal energy with 109K with MW50. Will you feel good as you know that at 25 lb you have superiority over your opponent? :)

The spitfire at 25lbs boost will have equal climb with the k4 but much inferior in speed.

Another 1943 allied plane up against 1945 rivals? Pass.

another?

There is no other as of now.

The Mustang is a late 44/early 45 model.

And BTW, it is not the machine that makes the superiority, but the pilot. At least within these performance ranges. It sounds trivial, but a better tactic and knowledge of aerial combat will get you much further than those extra 30 or 100 HP, IMHO.

Also, I found this website for anyone who is interested.

edit: It seems like every permutation of the Mk.IX is covered, incl. the Merlin 61,66 and 70.

Cheers

If you take a look at the curves you will see that all that "very experimental" reference planes have almost coinciding lines within the constant MP range. It means that the difference between engine power with Bendix-Stromberg pressure losses or with reduced losses for MA.648 as well as for BS.543 propeller are negligible.

Both BS 543 and MA 648 were experimental setups, never serialized. That's a fact. And its not a particular surprise that their results are similar, since both plane had setup/modification of carburrator that gave them much higher full throttle heights than normal planes as you have probably realized yourself. That is the problem if they are reference values, these factors had to be taken into account.

For example MA 648's report specifically states:

"These results compare favorably with those of other Spitfire LF Mk. IX aircraft, which fact is attributed cheifly to the higher full throttle height obtained with the S.U. pump."

So MA 648 had a new SU carburrator, it gave the plane higher FTH than normal planes, which gave it of course better altitude performance.

But this will get even more funny when you realize that BS 543, the prototype IX LF with the normal Bendix carburetor (but set to too high engine mixture) had even higher full throttle height (cc. 22k ft) than the experimental MA 648 (21k ft by ca. 1000 feet)...!

In fact the BS 543 report clearly points the reasons for that out:

"The powers of the RM-9SM and the Merlin 66 engines in F.S. gear should be identical, since the high speed supercharger gear ratio is the same. It will be seen that on the climb, the performance and boost pressures were similar, within the limits of experimental error, but in level flight above the full throttle height the Merlin 66 engine was developing about 1 lb/sq.inch higher boost pressure than the 9 SM engine, with a consequent higher full throttle height and improved performance. This discrepancy must be due to variations in the manufacture of the engines and possibly of the air intakes, but it should be borne in mind that any small differences in performance of a high compression ratio supercharger or of the intake will be more noticeable at high speeds because of the increase in the dynamic head."

These results obtained by BS 543 were by 2500 ft higher ft than any of the serial production M66 aircraft tested, which all but these two gave FTHs of about 19 500 feet - which btw matches RR's own engine curves and full throttle heights given for 400 mph rammed conditions (20k ft).

And evidently the current DCS model has even even higher FTH than the better-then-even-experimental-carburattor-plane, by another 1000 feet. In fact 3500 feet higher full throttle height than what is normal, explainable and consistent with real life tests...

So in the end we can conclude that the evidence points to that current DCS "Experimental Spitfire" model overstates greatly the FTH and thus high altitude performance, even though the real aircraft's peculiarity was that it was produced with an an engine optimized for low altitude performance and had a relatively low full throttle height and reduced supercharger gear ratios (5.79 to 1 & 7.06 to 1).

This is not "nitpicking on 1-2%" (although I do mention that if we have 1-2% lower specs for one plane, 1-2% higher specs for another, it adds up and gets significant). Due to the various errors in measurement, but also ignoring the peculiarities of the tested planes, each adding to a systematic error margin of higher FTHs than should be stack up and in the end result, in the DCS model s a full kilometer different (better) full throttle height than it realistically should be and corresponding effects on altitude performance.

This is not 1-2% error, its 18% in FTH... but hey, no biggie, right? So lets just have a K-4 with a 9000 meter full throttle height (18% error) instead of 7500m in the specs, OK? Nobody fights there, as in not that that altitude regime would be the place where the P-47 or later VEAO XIV would enjoy better altitude performance. ;) I mean, yeah, it would effect top speed a bit too, as in increase it to about 740 km/h at this new, somewhat flawed FTH that's only 18% greater than it should be. :)

Of course if all the data is derived only from select prototypes and experimental planes that had better full throttle heights than the normal planes (and understandably such "representative" trials are attractive for Spitfire fans ;) ) and all the serial production results are ignored and not crossed check, such flaws are bound to happen.

See the modified chart I attached which includes serial production Mk IX LF aircraft for comparison with DCS model and "reference" figures for the prototype and experimental machines... its very easily seen that both the serial production BS 310 and JL 165 (despite difference in speeds, which is probably down to drag difference betwen individual planes, but lets ignore that as normal serial production variation) both resulted in practically the same full throttle heights slightly under 20 000 feet.

P.S. For some reason the Brits had the annoying habit of correcting level speed tests to 95% take off weight - this woudl, very rougly correspond to half fuel / ammo load on the Spitfire. For example BS 543s trials notes:

All results given in this report have been corrected to standard atmospheric conditions by the methods of report No. A.& A.A.E.E./Res/170 (which incorporates A.& A.E.E. Memorandum dated 27.8.42). The level and speed results have been corrected to 95% of the take-off weights by the method of the same report."

In practice this means very little in speed in low altitudes, but with altitude it gets significant because a lighter plane needs less angle of attack to maintain altitude, thus has less drag and is faster. Bottom line - if British trials are used, the level speed results, particularly the high altitude results cannot be used directly for 100% take off weight model, but need to be adjusted accordingly.

I believe this might also attribute to the abnormal high altitude results in the current "Experimental Spitfire" model. ;)

But I could be wrong, but then please explain how an engine (Merlin 66) with 16 000 feet static FTH (4876 m) gets a rammed FTH of 23 000 + feet (7000+ meter). And why go all the fuss with high altitude engines at all when a low altitude engine can do both! :)

another?

There is no other as of now.

The Mustang is a late 44/early 45 model.

Yeah, except it doesn't have the engine power of a late 44/early 45 Mustang.

another?

There is no other as of now.

The Mustang is a late 44/early 45 model.

 

And BTW, it is not the machine that makes the superiority, but the pilot. At least within these performance ranges. It sounds trivial, but a better tactic and knowledge of aerial combat will get you much further than those extra 30 or 100 HP, IMHO.

 

 

Cheers

1. It has an early 1944 setting.

2. That is one of the worst points to ever make that "it is the pilot not the plane that counts". When you listen to real WW2 pilots they always talk about how their airplane made them better or their airplane was not enough to be able to combat the enemy. Airplane is just as important as the pilot that uses it.

Please let us not open this debate again. This has been discussed many times before and it always leads to insults and nonsense