Spit/109 sea level speed comparisons in 1.08 beta patch

[Crumpp]

That is obviously wrong

Do the math....

[JtD]

The 12lb boost calculation done by the RAE is an absolutely reasonable extrapolation.

[Kurfürst]

Originally Posted by JtD

The 12lb boost calculation done by the RAE is an absolutely reasonable extrapolation.

I have my doubts about it having been made by RAE. It's an obvious farce.

[Crumpp]

The 12lb boost calculation done by the RAE is an absolutely reasonable extrapolation.

Well, then walk us through the explaination of how the engine data aligns with the graph. I would love to hear it.

Performance graph showing FTH of 11,000 ft:

http://www.spitfireperformance.com/s...-rae-12lbs.jpg

Engine data with RAM effect at max level speed showing FTH of 8,500 feet:

http://www.spitfireperformance.com/merlin3curve.jpg

[41Sqn_Banks]

Originally Posted by Crumpp

Well, then walk us through the explaination of how the engine data aligns with the graph. I would love to hear it.

Performance graph showing FTH of 11,000 ft:

http://www.spitfireperformance.com/s...-rae-12lbs.jpg

Engine data with RAM effect at max level speed showing FTH of 8,500 feet:

http://www.spitfireperformance.com/merlin3curve.jpg

Let's have a look at +6.25 boost ...

FTH at 17,000 ft (http://www.spitfireperformance.com/merlin3curve.jpg)
Max level speed at 19,000 ft (http://www.spitfireperformance.com/s...-rae-12lbs.jpg)

Looks like max level speed is achieved 2,000 feet above the FTH. Pretty much in line with the difference for +12 boost.

Edit: I want to make clear that this 2,000 ft difference between FTH and max speed must not be present in reality, it's more a systematical difference between the two charts that must be considered when they are compared.

[Crumpp]

That chart was not used because it does not align. The engine chart you linked already includes RAM effect at Vmax.


That means the FTH should match. Not be close or have the same margin of error, but match if that is the correct engine data.

I used the power figures as listed in the flight reports NOT a seperate engine curve that does not match the performance data.

[Crumpp]

[JtD]

Originally Posted by Crumpp

Engine data with RAM effect at max level speed showing FTH of 8,500 feet:

It's not with ram effect. That's painfully obvious from all the engine and plane data on 6.25lbs around. The power level generated by the engine on this chart has the designation "all out level" and that's all there is to it. Assuming otherwise is like assuming "combat" power is only available when the aircraft is in actual combat.

[41Sqn_Banks]

Originally Posted by JtD

It's not with ram effect. That's painfully obvious from all the engine and plane data on 6.25lbs around. The power level generated by the engine on this chart has the designation "all out level" and that's all there is to it. Assuming otherwise is like assuming "combat" power is only available when the aircraft is in actual combat.

You are right, e.g. AP 1590B states 890 bhp at sea level and 1030 bhp at 16,250 ft for +6.25 and 3,000 rpm. The chart is obviously without RAM effect.

[JtD]

Originally Posted by Kurfürst

I have my doubts about it having been made by RAE. It's an obvious farce.

I agree it looks simplistic, but technically it is sound and I see no reason it not being an original document. No reason for it being one either, but I will accept it on face value as I see no reason to mistrust Mr.Williams on this issue. If you have more than a gut feeling, I'm willing to re-evaluate my opinion.