Spitfire Mk IIa performance tests - Patch 1.07.18301

[klem]

Originally Posted by bongodriver

it's difficult to tell if the game models density altitude well, to be honest we would need the game to give us more control over atmospheric variables, we know they have used a standard adiabatic lapse rate and the atmosphere is more or less ISA + 10, so we know that the density altitude should be approx 1200 feet more than pressure altitude.
so the tests should be done using 1013 on the altimeter to give pressure altitude and then for each altitude band you test at you know that ISA + 10 means your density altitude is 1200 feet more
i.e 2000 foot pressure altitude at ISA + 10 = 3200 density altitude

the density altitude is what the game test data should be being compared against real life data, if things start to match up then we have an indication of wether the FM's and atmosphere modelling is correct.

Thanks for that info bongodriver, I believe I have made the mistake of plotting my Hurricane results against indicated altitude instead of bringing them to a common playing field of Density Alltitude.

Apologies to you Felipe for diverting your Thread onto "Principles of Performance Measurement" but it may prove useful to you for gathering data for the Spitfire IIa once I have straightened out the script in my Performance.mis.

So, bongodiver, just to be sure I have got this:

1. I believe my TAS calculations (formulas in earlier post) will still be correct as they use indicated altitude and altimeter setting to arrive at Pressure Altitude and then OAT to arrive at Density Altitude?
2. I the take calculated Density Altitudes and plot TAS against those?

If Yes to both that actually makes the performance figures worse because on my Hurricane chart with DA being higher than Indicated Altitude (SL temp was 16.9C) the results get pushed to the right. Again apologies to Felipe but I'm attaching those Hurricane results (Indicated Alt and DA) as an excercise in my understanding of performance measurement.

I will re-run the tests using 1013mB setting and see how that turns out but I think the results should be the same as the DA chart attached. Then I'll correct my Hurricane Thread post.