There are some simple changes you can make to the .xfm files in order to "create" different variants of the Spad, but you have to edit them by hand for each plane in the squadron or flight.
The simplest, but crudest type of change of course, is to change the top speed value. For instance, the current top speed of the Spad VII is 138 mph. (BTW this is too high IMO, for ANY variant of the Spad VII). Change this value from 138 to 119 for the 150 HP variant. Also, change the horsepower value from 180 to 150, of course. You can also fiddle with the speed values at different heights, but I'm not sure whether they have as much of an effect.
The main problem, of course, is that you have to do this all by hand for each aircraft for each mission. I don't know if you can use JJJ's mission editor to make the task easier, or not. I could probably come up with a mod to create a 150 HP variant, but it would still mostly be a 180 HP Spad with a few numbers changed around. OBD encrypted a lot of the FM files from WOFF 1 to WOFF UE, so not as many FM variables can be modded, unfortunately. Ah, well, c'est la vie, c'est la guerre!
Hi Buckeye,
One thing to keep in mind, is that when you see a top speed cited for an aircraft, you need to know the altitude that speed is referring to. And then it can get WAY more complicated than that.
But to keep it simple, the 119 mph top speed you see cited quite often for the 150hp SPAD VII was at 2000m (6562 ft) altitude, which would be the 2nd performance line entry, not the top one in the XDP file.
Take a look at the stock values for our SPAD VII 180. You'll see the top speed degrades by altitude. So using the same degradation curve (as we don't have historic values for all the different altitudes at hand for this exercise), to get 119mph in the 6562 ft alt position for a SPAD VII 150, it would look like this:
Sea Level (the first line) = 123.5 mph
6562 ft = 119 mph
9843 ft = 114.5 mph
13,123 ft = 112 mph
For instance, you'll see comments that our 220hp SPAD XIII is too fast at 143 mph at sea level. But I see lots of historic numbers for the 220hp SPAD XIII at 135 mph @ 6562 ft alt (give or take a mph or two). And if you check our 220hp SPAD XIII in WOFF, it is rated at 135 mph @ 6562 ft altitude...spot on perfect for a 220hp SPAD XIII from what I can tell.
At first I thought lots of the aircraft in WOFF were rated as too fast. But then when I looked at altitude, I realized they are mostly spot on. I have a few little quibbles here and there, but that's only a matter of who's "authoritative" numbers you believe. So its more about which historian to believe on the few I've changed (its not that I think the OBD number is wrong). I can see why Pol gets tired of answering questions about top speed in WOFF. So instead, I thought I would now ask for different engine models (I do enjoy the performance variation).
Anyway, I see what you're trying to achieve, so just thought I would help you get a tighter number for your mod based on the data you were using.
I made my wish request because I want OBD to eventually do all this and get them officially in the game, correct squadrons and time periods and all that!
But like you, in the mean time I've got some place holder mods!
Cheers!
