Nope; it's plotting BHP.

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.

Those are your words I posted Barbi. I don't see any original document in the link.

You are picking what suit better to your thesis and once again put a layer of complicated arguments to dissimulate this fact.

You are right there is the intake ram effect. Just like exhaust gazes propulsive effect ... and a lot of drag with the cooling system that did not take into account the boundary layer drag even at a late stage in the war.

It does not mean that you can add all the Power gains RR refer in its doc and then say that the merlin had the a total of BHP equal to the cumulative effect measured on the test bed.

Note that the intake ram effect went as a benefit only after a major redesign witch hve to be dated :rolleyes:

The diag you show is difficult to interpret as it it shown put out of any contest. And we are talking abt early war tech not late achieved Merlin boost. In 1944/45 the war for the Spit has switch from high alt air interception to low level mud fighting and interdiction witch favor over-boosting. (we also know that those level of boost proved unreliable and were lowered on the field - the griff engine being put forward has the 2K HP piston eng - Oh... and yes there is the Merlin Hornet but... wait is that not an evidence that DH has superior engineering capacities in term of aero when Supermarine despite strong gov support only produced contestable design ?)

In term of FM and drag for the spit, just catch the six of a 109 in the game and follow him in her maneuver for a min. If you are not laughing after 30 sec and still need to be convinced, pls take a similar ride in the Excellent Hurri we hve for now.

So no drag reduction! My humble opinion wld bend me in the direction of some change toward the set of modeling eq that might not apply to a 300mph fighters (in fact modelizing the Spit wing as a trapezoidal wing of similar wing surface/wing root chord and thickness wld lead to better accurate results without changing the overall FM engine). But this is pure guess as I don't know anything abt CoD FM engine :-P

So, to resume my self : you can't take a pce of this or that and build a convenient result

For example if you build your opinion on the spit only reading my posts here you'll conclude that the spit was an antique machine unsuitable for fighting even if this is not what I am thinking.

I repeat myself : The spit/Merlin were great design but with some major flaw that a simple look at history puts in perspective (search the web for a Elliptical winged B2 or floating carburetor PT6 turboprop or a Malcom Hooded BlackBird ;) )

Can't believe Kurfurst is still peddling out these BS arguments still? Ordinarily I wouldn't care a jot but he's doing his best to get what he wants and ruin any chance of a more realistic FM.

What could his agenda be?

History revisionism and or Historical Denialism!!

Viper,

It does not work that way.....

If you have flown an aircraft with individual Exhaust Gas Temperature Gauges and Cylinder Head Temperature gauges you would know their is a wide variance in the temperatures with any fuel metering system that introduces fuel to the intake.

100 degrees or more is considered normal variance........

Why? The fuel mixture is different for each of the cylinders.

There is no such thing as a direct injection aircraft engine in General Aviation. All fuel injection is single point injection much like the Allied designs of WWII.

In a direct injection engine, there is almost no variation in CHT or EGT between the cylinders.

It is that temperature variation that robs a single point fuel metering system of power.

http://www.costaricaaviation.com/fli...tions_rev1.pdf

Crumpp,

At first, thx for all the excellent references you are giving on many of your post.

I understand you point on DI vs SPI (single point injection). DI has clearly many advantage and was the panacea at the time.

Viper care much abt theory and given that you run at cte regime and that the ducting are of equal length after the s/c (what is not feasible) the SPI has clearly an edge in terms of practical answer.

DI however as you has pointed out offer much more advantage on reality grounds and this clearly can be seen in ehaust temp even in today cars (Ask GrandPa about engine backslash and loud bang with carburetor engined cars before the 80's GTI went out) ;)

Coming back on the BoB, I believed that RR had however an advantage with the s/c being inline with the engine witch simplified the routing of the air with a relative symmetry (the DB has some prob and a slight differences btw raws of left and right cylinder due to the s/c being on the port side ). This tend to makes the RR simpler ... and what is simpler is much easier to improve : a strong point for any strategical war item ;)

As a pilot, slick aircraft are problematic when it comes to maneuvering. They are good for cross country performance but poor in maneuverability. That is why you don't see many slick aerobatic platforms.

Drag with appropriate power gives a pilot precise speed control allowing him to reach and maintain his aircraft's design performance speeds quickly.

As a pilot, there is nothing worse than having too much speed and not being able to get rid of it when you need the airplane to maneuver or require maximum performance from it.

You are most welcome. Thanks for your contributions to the discussion too.

The technological advantage of DI allowed the German designs to be equal to despite strategic material shortages.

Maintaining equality with inferior materials came at a high cost though.

Exactly. The main drawback of Direct Injection is the expense and complexity. Germany is just a little smaller than the state of Montana in terms of square miles and had a strategic material shortage even before the war began.

For a resource poor country of that size to take on most of the civilized world in an all out war of attrition, complex and expensive is something to be avoided.