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#11
06-25-2011, 11:42 AM
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Quote:
I'm pretty certain that I've posted the RM1 rating from Harvey-Bailey several times now, which gives the rating at 1310 bhp at 9000', +12 psi. I really don't understand why you keep trying to "de-rate" the Merlin. There's no shortage of source material on the subject (you can cross check the power output of the Merlin III against figure 6 in Lovesey's paper for example), and in any case, given that we also have no shortage of data about the performance of the Spitfire & Hurricane, even if you managed to persuade 1c that the Merlin made less power than was actually the case, that would just mean that they had to artificially reduce airframe drag to match the known speed and climb performance. The result of that would be that the RAF would have an unrealistic advantage in shallow dives against the Luftwaffe. Frankly, if I was one of the "make my plane better irrespective of realism" crowd, I'd rather have less drag than more horsepower, because B&Z is a rather more effective strategy than T&B. It may well be that http://www.wwiiaircraftperformance.org/ doesn't post the best performance data for Axis aeroplanes, but I haven't seen any evidence to suggest that the source material it contains is fabricated. I might not necessarily agree with some of the interpretation, but that's irrelevant given that most people here just repost the source material and debate it, rather than reposting the gloss from the site. BTW, if anything, the +12 FTH of 9000' is an underestimate because it doesn't include intake ram AFAIK. If you cross-check the Merlin 66 horsepower chart which includes 400 mph intake ram against the RM10SM rating in Harvey-Bailey, you'll find that the MS gear +18 FTH from the rating is 5750', whereas the chart gives an FTH of over 9000'. Likewise, the rating specifies the FTH in FS gear as 16000', whereas the chart shows an FTH of about 20000'. You can cross-check the ram pressure rise against the FTH by using a standard atmosphere calculator like this one if you feel that way inclined. So actually the power comparison is unrealistic in as much as it's based upon the Merlin's static FTH. In reality, at about 300 mph you'd see an increase in FTH of a couple of thousand feet. You can easily cross-check this if you look at airframe speed vs altitude diagrams; max TAS is achieved at the rammed FTH for whatever boost they're using, and this is invariably higher than the FTH for the engine rating quoted in Harvey-Bailey. I don't know what the basis of the DB601 power curve is, so I can't comment on whether or not it includes intake ram. Reference: Harvey-Bailey, A. (1995) The Merlin in Perspective - the combat years. 4th edition. Derby: Rolls-Royce Heritage Trust. 
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