Big Zeppelin Engines
Hello Aleatorylamp,
First of all, let me state ahead of time that many things I post here are just opinions from having tweaked CFS Flight models for a while. I often state opinions about things I have never tried but seem consistent based on things I HAVE tried and how I believe things work.
First of all, your 3% power loss per 1000 feet is for decreasing engine power with increasing altitude because of decreasing air pressure / density.
Thus 267 HP at 4300 feet corrected to 307 HP at SL sounds correct.
This is a bit of a rehash of an earlier thread called "War Emergency Power" but here goes.
My understanding of the operation of Aero engines is that they have generally three or four ratings we should be concerned about:
1. Economy Cruise - The engine should be able to run at this power rating pretty much as long as there is fuel and oil. In reality this may be two ratings. One might be for lowest rate of fuel consumption and the other would be for greatest range.
2. Maximum Continuous - The engine should be able to run at this power rating as long as there is fuel and oil. This is the highest power rating that may be used without time limit. It may not be very economical in fuel use.
3. Military or Rated Power - This is a higher power level that will certainly have a time limit. This may be a "Climb" rating. Typically this rating is around 30 minutes.
4. War Emergency / Emergency / Take-Off Power - This rating is only permitted for very short term use. Typically the time limits are either 1 minute (Take-Off Only), 5 Minute (as we see in the stock P-51D), 10 Minute as we see in other aircraft. It may be longer, but CFS only offers 5 Minute or 10 Minute enforced limits. This power level may require the use of an anti-detonant such as Water, Water & Methanol, or even Additional Fuel.
CFS also has a non-anti-detonant "Supercharger" WEP that allows for increased boost for 5 Minutes 10 Seconds of cumulative use before severe engine damage.
The reason I bring up the subject of WEP is that I believe your engine power ratings / settings are not consistent.
The 267 HP / 1450 RPM @ 4300 feet appears to be a full power rating. It probably does not require a anti-detonant, but does appear from the discussion to be restricted use because of possible engine damage. Can this be considered a WEP rating?
There appears to be a much lower power rating at sea level and for take-off. The question is what throttle RPM settings are used and what the power output should be. Is that a Military or Emergency rating?
Note that the four ratings I listed may often have different names and exact restrictions depending on nationality and sometimes even on the branch of service. Some of these are pretty hard limits in that the engine really may self destruct with prolonged use and some of these limits may be pretty much ignored with no real consequence. They are written in the aircraft manuals but often are the choice of the engine manufacturer who is trying to guarantee a certain Time Between Overhauls.
Some of these limits are because of heat rejection limitations of the cooling system or because service manuals require things like spark plug replacement after each use. Perhaps the Oil Filters need to be checked for pieces of Engine Bearings? You may make enemies in the ground crew if you use them without cause.
The big question here is what exactly are the sea level maximum power ratings and what the limitations are. Is it a procedural / operating manual limitation, or is it one of engine damage. How do you wish to enforce the limit?
I typically (in recent releases) put in some engine operating instructions in the Aircraft Check List along with other little useful bits one might find in the Pilot's Manual, but except for WEP, the virtual pilot is free to ignore those limits.
Regarding Record 512, I did a few calculations with the Horse Power, RPM, Propeller Diameter, and Reduction Gear Ratios on the stock CFS flyable aircraft and put them in a spreadsheet. By this method, I could select a Record 512 from the stock aircraft with a Propeller Power Coefficient as close as possible to the aircraft I was building.
Sometimes this won't work though because the range between the flyables isn't really all that great. I found for example that the Junkers JuMo 213 engine for the FW 190D had a much greater Power Coefficient than any of the stockers and some other stuff such as the Nakajima Sakae engine for the Mitsubishi Type Zero is much lower.
Unfortunately, these spreadsheets and notes are all on my now deceased laptop and currently not accessible.
My suggestion here is to take the 512 Record from something like the Hurricane and shift all the columns in the spreadsheet over by one.
I personally haven't tried this, but I think it should work well enough for your purpose here.
Test things our with a Constant Speed Propeller and see what angle the simulator wants to use based on your engine / propeller combination.
Hope this helps.
- Ivan.
