Spit/109 sea level speed comparisons in 1.08 beta patch

[Glider]

Originally Posted by Osprey

All that extra power from 12 fewer litres. According to some of the logic here I conclude, mathematically, that the DB601 was rubbish.

I don't know about rubbish, that is a bit strong, but its worth remembering that it was soon changed for the DB 605 and the Germans wouldn't have done that without a reason. I can only assume that it lacked development potential

[IvanK]

I guess RAE were clueless ... and you have superior knowledge Crumpp... trouble is your graph reflects the opposite of pretty much every known record,chart,computation or actual flight test or pilots account of the facts !



One more from the RAE clearly showing better turn performance of the Spitfire in all regimes.

[Crumpp]

Originally Posted by IvanK

I guess RAE were clueless ... and you have superior knowledge Crumpp... trouble is your graph reflects the opposite of pretty much every known record,chart,computation or actual flight test or pilots account of the facts !



One more from the RAE clearly showing better turn performance of the Spitfire in all regimes.

The RAE shows better turn radius in this chart. The Spitfire always has a better turn radius than the Bf-109.

Radius being just one parameter of turn performance and not the most important either.

Pstyle says:
Crummp, when the RAE refer to "normal bhp", do you know what the term "normal" refers to.

Not specifically. It appears to be RAM power because the chart list's power in flight.

Pstyle says:
At least then we are all able to work to the same assumptions and review each others work. It's be good to see how the manipulation of one or more of the variables influences tge overall outputs.

Exactly, once the parameters are input, the math does it's magic.

[Kurfürst]

Originally Posted by Crumpp

The RAE shows better turn radius in this chart. The Spitfire always has a better turn radius than the Bf-109.

Flaps...

[pstyle]

Originally Posted by Crumpp

The RAE shows better turn radius in this chart. The Spitfire always has a better turn radius than the Bf-109.

Radius being just one parameter of turn performance and not the most important either.

True, if the aircraft are BOTH at the same speed (according to that chart) , the spitfire will have less distance to travel, and thus will turn faster, in every case.

I think I can convert the figures to turn rate fairly easily... Then we can see, using that very ddata, the combinations of speeds at which the two have varying turn speeds right?
See here, http://s13.postimage.org/4fo4e806f/turns_comparison.jpg

According to that, Provided the sptfire remains between 200kph and 370kph TAS, the 109 can never out turn it.

[bongodriver]

Wow....maths really is magic........it made Crumpp dissapear.

[TomcatViP]

"Normal" shld stand for standard atmospheric value. The HP being a function of the air density, the Power have to be converted to the reference to be absolutely rigorous.

Note that standards varies (and still does) from one country to another.

ISO being 0°C and 1013mbar - CFM around 15°C etc..

Note also that if this is the case, there might be some error in the the conversion.

[Crumpp]

True, if the aircraft are BOTH at the same speed (according to that chart) , the spitfire will have less distance to travel, and thus will turn faster, in every case.

They are not at the same speed or angle of bank!

I'm not Ivan but they are obviously power on clmax.

They don't match CLmax power on for either type. In otherwords, a bad assumption.

Only one flight was made, as operating a suspended static head from a single-seater aircraft with a rather cramped cockpit is difficult.

http://kurfurst.org/Tactical_trials/...ls/Morgan.html

[IvanK]

Originally Posted by Crumpp

The RAE shows better turn radius in this chart. The Spitfire always has a better turn radius than the Bf-109.

Radius being just one parameter of turn performance and not the most important either.



Not specifically. It appears to be RAM power because the chart list's power in flight.



Exactly, once the parameters are input, the math does it's magic.

Er the chart above also shows Sustained G for any given IAS....at pretty much any IAS the Spitfire can sustain somewhere around 0.5G more than the BF109 ..... (not hard to determine turn rate here either)

The Blue RAE chart (from the same document) also shows sustained G, Turn times for 360 and also provides a means to determine Ps for bleeding turns ..... So we have turn radius, turn rate, sustained G (Ps=0) and a means to determine -Ve Ps values for energy bleed .... what more is there to turn performance ...... give us a break !

So far you have admitted to a weight error in your calculation. We know you made an error on the Spitfire power as well using 950/990BHP whilst RAE used 1050Hp at 12,500ft .... and we also know that a Merlin II power rating at Combat power was 1030hp at 16,500ft as detailed in the 2 seperate Inspection and test certificates.... shown earlier. And in Post 209 with respect Spitfire BHP you said "I suspect it was for an improved high altitude version".... when we know it wasn't and that RAE used standard Combat Power ratings.

[Crumpp]

Ivank says:
Its the a similar but more detailed chart

It is not a more detailed chart. It is the same thing.

Only difference is the CLmax estimates. The RAE used a trailing rake to measure speed.

Those are very accurate when properly operated but are complex to operate. They measured the CLmax in flight. I see a problem with operating such a system at the edge of the envelope trying to stall a high performance fighter.

As for the weight of the Bf-109, my original estimate just used the one the RAE used for the test. Using the ladeplan does not change the relative performance significantly.

The all-up weight was 5,580 lb. with the C.G. 24.8 in. aft of the leading edge at the root (h = 0.302). This loading agrees well with the value of 5,600 lb. quoted for the all-up weight by the Germans.

http://kurfurst.org/Tactical_trials/...ls/Morgan.html

My calculated CLmax agrees with the RAE measurements for the Bf-109.

Speeds Dynamic pressure CL
82 22.79322034 1.433906325




My Spitfire CLmax agrees with the NACA findings and the calculations were made using standard data on the type with the weights and stall speed listed in the Operating Notes.

Kurfust says:
RAE's calculation also using estimated/guessworked stall speeds, Clmax and rather questionable power values for both the Spit and 109 (the latter probably understood with the effect of engine thrust). That's the problem with these charts in general - there's such a margin of error with the base values, that the results are all over the place. (estimated) Propeller effiency can vary results by 5-10% alone, drag values are unknown, the wing's oswald effiency factor is unknown (directly shifts the results, since its a multiplier in the equation), Cl max is unknown.

That was my first thought. Gates was using high angle of attack theory to determine turn performance. High angle of attack theory is good for estimation but has to be based on measured data otherwise it is a complete crapshoot and guesswork.

The stumbling block to the assumption that Gates used high angle of attack theory is the fact he clearly list's the 1G stall CLmax for both aircraft.

That listed CLmax is clearly labeled on the chart as "assumed values of CLmax":

Spitfire 1G CLmax = 1.87

Bf-109E-3 1G CLmax = 1.95

The only way either aircraft can achieve such a CLmax at 1G is in landing configuration with full flaps and gear down.

The CLmax Gates used matches both aircraft in landing configuration.

It is definate proof Gates used the landing configuration CLmax for his estimate.