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Recording flight test data

Tom,

Thank you for the valuable insights, and your recommendations about altering the Aircraft.cfg!

Time to dive back into the technical data I have and try to pull some figures...

I guess my tinkering is more just to match what the Model looks like in the Sim.

Now that you and Paul (PRB) have enlightened me with regards to the C/S prop, once I set pitch and Mixture properly, everything works like a charm!

Thanks for all the help!
 
I use an EXCEL spreadsheet, set up to record in columns:

Altitude GW KIAS KTAS IMN Total Fuel Flow Notes

This is particularly significant for jet aircraft, since fuel consumption (fuel flow) decreases significantly as weight decreases. Also, the optimum altitude vs GW is significant. After a few tests, I can develop an optimum range profile. Of course you need to do some data collection regarding taxi fuel, takeoff and climb to altitude, enroute descent from a typical altitude, approach and taxi in fuel.

Using PAUSE you can easily record the desired data.

Looking on the web you can usually find valid comments regarding what the real plane actually burns. You can then adjust the aircraft.cfg file "fuel_flow_scalar=" factor to get close to the real thing if you have some credible cruise information.

I have a couple of freeware gauges for accurate fuel flow, ram and static temperature, and KTAS that I have put in a special flyout "Test Panel" window, which helps me out a lot
 
Interesting, Mike (welcome aboard, BTW). I've been using AFSD to record those, and a few other, numbers, but, to get an idea of maximum range I've been testing at various altitudes, filling up with gas, letting the speed stabilize, then start AFSD's logging feature. I wonder now if the "air range" and "true range" reported by AFSD takes into account the fuel flow changes that will result as the weight decreases, as fuel is burned off. It's really one of those problems that calculus was invented to solve: a formula that depends on variables that are not constant over time. I'm guessing my method is "adequate" but now I'm curious...
 
My interpretation of the AFSD fuel range data is that it is a quite simple point sample of fuel, speed and fuel consumption rate. The 747 FMC was slightly better including enroute winds and step climbs plus anticipated weight change. Supposedly we included approach etc but we always ended up a couple of tons short.

The fuel flow scalar is not the end all as the thrust curve is the most important as required thrust is the variable to achieve a set speed at altitude for a given weight. Fuel flow falls out from the thrust. A lot of time was spent to derive a reasonable EPR workaround for the Milviz 737-200 and get the thrust and fuel flow parameters pretty close. FS does not provide enough data points for many engine parameters to do more than get a best fit.

Cheers: Tom
 
I suspect you are correct, Tom. It has to be calculating, but how involved are those calculations? A good test would be to get to altitude, stabilize speed, fill up with gas, then write down what ASFD says your TTE, ETE, range, etc. is at that point. Then start the clock and see what the real numbers end up being when you run out. I'd be surprised if the TTE as calculated at “T0” ends up being accurate. Even the “FMC” in the FA-18, the real one, called FPAS (Flight Performance Advisory System) relies on lookup tables stored in the computer, which come from flight test data...
 
Did a test to see how accurate FS's range and TTE calculations are at the start of a run with full tanks. The results were surprising, but not where I expected:

Test Aircraft: Just Flight A6M2
Test Altitude: 10,000 FT

Predicted at T0 (full)
TTE: 3:47
RNG: 1054
FF: 67.71879

Actual at T1 (empty)
Elapsede time: 2:00
RNG: 1063
FF: 67.64984

So the fuel flow remained almost constant throughout the flight. Perhaps the difference would be greater if I tested a plane that carried more fuel... The range prediction was also pretty close to actual and was a little greater, probably because of slightly less fuel flow as time went on. What really surprised me was the calculation for "time until empty." Prediction at T0 was almost four hours, but in fact the Zeke's engine sputtered to a stop exactly 2 hours later! Something doesn't add up. Either the clock gauge is running fast, or the gauge I was using to predict TTE is off. I was running the sim at 16X time compression too. Wonder if that affected the test.
 
Ran the test again, without time compression, and this time the predicted TTE of 3:50 correlated perfectly with the elapsed timer. So, apparently, there is relativistic time strangeness in FS! :)
 
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