DevNote Jan-05-2007
Wide

Modifying Zero Fighter (part 2)

Jan. 05, 2007

The instruments in A6M2 have been updated. Now she has altimeter and radio compass (ADF) but not only that. Most of the gauge faces have Japanese symbols as shown below. It looks better, doesn't it?

zero-panel-20070104.jpg SIZE:798x332(?KB)

The flight model for A6M2 has also been revised. This one is tough to tackle since YASim, a flight dynamics model in FlightGear, doesn't support many things that we want (such as both fixed-pitch and variable-pitch mode for propeller configuration). YASim also uses some estimate (or I should say guesstimate) models so I need to adjust some parameters even if it goes a bit far from the actual ones.

This also causes some instruments to be adjusted. The oil temperature should be around 80 to 90 degree Celsius but YASim outputs around 90 to 120 since it assumes the temperature should be around that range. I really hate this so I tried to use JSBSim, another Flight dynamics model in FlightGear, but JSBSim raises an exception (maybe because of improper parameters?) so I couldn't make it.

Moreover, the last version of A6M2 (that I wrote on Dec. 30) was a bit strange. The engine runs up to 1500 rpm without touching the throttle. This occurs due to the guestimate parameters in 'approach' configuration (YASim determine the engine characteristics by using two different control configurations - approach and cruise. Each configuration has a set of control parameters such as throttle, mixture, propeller pitch, and flap position). Therefore, I modified these parameters and the engines went more stable.

Another issue is the super-charger. There are two parameters in YASim - turbo-mul and wastegate-mp. After a few days of researches, I finally found what these parameter actually means. The former determines the maximum intake manifold pressure (Bar) and the latter determines the actual top-end of the manifold pressure (inHg). If turbo-mul is 1.3 and wastegate-mp is 37, the super charger tries to put compressed air into the engine up to 1.3 Bar (38.38inHg), but the waste gate will restricts the pressure at 1.25 Bar (37 inHg). The manifold pressure gauge shows 37 inHg as a result. In A6M2, there is a boost gauge instead of manifold pressure gauge so it shows +189.8mmHg.

As the super-charger installed in A6M2 compresses the intake air up to 1.33 Bar (+250mmHg), I set turbo-mul to 1.33 and wastegate-mp to 39.27 (1.33 Bar). I'm still wondering if I really need wastegate-mp in this case. Anyway, this modification enables boost gauge to show the accurate value without any adjustment.

I also changed the default values of both boost and propeller-pitch because you need the full power for taking off. Since keeping the full power all the time consumes pretty much gas, I recommend you adjust some parameters in cruising. I fly my A6M2 at 130kt with the following parameters:

  • mixture: 0.2 to 0.4 (pressing 'm' / 'M' can adjust this parameter)
  • propeller-pitch: 0.5 to 0.6 ('n' / 'N')
  • throttle: 0.2 to 0.4 This combination will make A6M2 consumes approx. 10 - 14 gallons per hour. A6M2 can fly up to 12 hours in this gas-flow, which is very close to the real A6M2.

You can download the latest files - A6M2-20070104. Choosing A6M2b will gives you have a test flight with my configuration and the modified panel.

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