Hello All,

Recently I had a Hard Drive failure on my Game Computer which required a re installation of Combat Flight Simulator.
It was actually a bit of a chore to get the Sound Card and Joystick working again after the re installation and I was quite happy when I was finally able to fly ANY of the aeroplanes in the simulator again.
Although Programs were gone, much of the data was backed up, so restoring hundreds of aircraft was actually fairly simple.

My Development Computer also died at about the same time and needed some hardware (including a Sound Card) replaced in order to run again. There were enough things not working that I ended up re installing Combat Flight Simulator there as well.

When both machines were finally working, I noticed, when attempting to develop and test a new AIR file, that the Engine Power was at its maximum at Take-Off and was decreasing as the Aeroplane gained altitude.
Normally with a supercharged Engine, the power initially increases as the aircraft climbs.

it appeared that superchargers were not working any more.
This was happening on other aircraft as well and not just the one I was working on.

A day or so later, I tried another test.
I started the flight at 15,000 feet instead of from the ground and the Engine of my Aeroplane immediately cut.
This was interesting because although Engine Power decreased with altitude past the Critical Altitude, I had never seen an Engine completely cut.
Eventually I figured out that the Auto Mixture was turned off in Settings.
Restoring that setting restored the performance of various aeroplanes to where I had expected them to be.

This got me to thinking.

Most of the Flight Models for the Projects that I have worked on are based on the stock P51D.
I checked the behaviour of the stock P51D and it behaved the same way.
Engine power was restored as the Mixture was leaned as altitude increased.
The problem I ran into here was that the only easy way I could find to adjust mixture was to listen fo the changes in Engine Sound and that is not terribly precise.


With all the features of Combat Flight Simulator enabled, a Pilot actually has to constantly manage the Fuel Mixture with any changes in altitude which would get to be rather difficult in combat.
In reality, Combat Aircraft of this era often did have Mixture controls along with Propeller Pitch and Throttle, but except for extreme cases, Mixture was set to "automatic" and left there.

On American aircraft, this would have been
Auto-Rich for high power operation and
Auto-Lean for low power and cruise conditions.

This got me to thinking that perhaps enabling "Auto-Mixture" in Game Settings was not the best idea, but instead the setting should be in the AIR file. This is an option in Record 505.
That would allow aircraft that really only had manual mixture controls to behave as they should and allow the more modern aircraft to be configured for Auto-Mixture if appropriate.

There has to be some kind of cost to this.
From what I could tell with just limited testing, with Manual Mixture control disabled in the AIR file, Mixture is either automatic or at Idle-Cutoff. There are no intermediate steps.
Fine tuning Mixture would no longer be possible, but Engine management would more closely resemble typical combat aircraft.

I see this as an improvement to the accuracy of the simulation and will include it with new AIR files.

- Ivan.