Flight Testing in CoD

[Viper2000]

Looking at the threads in this forum, it appears to me that a concerted and organised flight test effort will be required to work out exactly what is going on.

It isn't just a matter of posting (for example) a figure showing TAS vs altitude for a Spitfire I and then comparing it with the performance attained during a flight test in the sim.

The fact is that at the moment, we don't know what atmosphere model is used in the sim, we don't know what airframe and engine mod state is being simulated, we don't know whether the aircraft instruments read IAS, CAS or EAS, and we therefore don't know what corrections to apply. Therefore, we could have:

• Perfect simulation of the "wrong" aircraft
• Imperfect simulation of the "right" aircraft
• Non-standard ambient conditions
• Some combination of the above, across all components affecting kinematic performance

Because this simulation is considerably more complex than the original IL2, it follows that we're going to need to do an awful lot of work in order to properly understand what is going on so that we can make sensible comments to 1c. For example, the very fact that altimeters now have variable pressure settings implies that barometric pressure is a variable, and may well be a function of both geographical location and time.

I am therefore looking for volunteers to form a team to help me conduct some serious flight testing work.

Effort may usefully be divided into several strands across two departments:

History department
This half of the effort comprises the collection of historical data and its conversion into SI for comparison with data collected from the sim. Conversion work is particularly important because different flight testing organisations used different standards, and therefore it is not necessarily possible to immediately compare their data.

1. Data reduction standards (historical)
   • Atmosphere model
   • Constants & conversion factors
   • Other corrections
2. Aircraft performance data collection
   • Airframe drag estimation
   • Airframe lift estimation
   • Handling information
   • Airframe limits
   • Transonic behaviour
   • Failure modes
3. Engine performance data collection
   • Engine brake power map
   • Engine brake SFC map
   • Exhaust thrust map
   • Propeller map
   • Reliability data & failure modes
4. Conversion of the above to SI under a single set of data reduction assumptions for subsequent comparison with the simulation.

Simulation Department
This half of the effort comprises collecting data from the sim for comparison with the converted historical data collected by the History Department.

1. Atmosphere/weather testing
   • Temperature vs Altitude
   • Pressure vs Altitude
   • Density vs Altitude
   • Acceleration due to gravity
2. Aircraft & engine mod state derivation (in conjunction with history department)
3. Flight testing
   • Level speed
   • Rate of Climb
   • Turn performance
   • Cruise performance
   • Dive performance (including transonic behaviour)
   • Handling
   • Exceedances & failure modes
4. Data reduction & correction

It would obviously be extremely helpful to get authoritative information from 1c about modelling assumptions; as may be seen from the above, a substantial proportion of the effort envisaged at present is associated with deriving those assumptions rather than with testing the aeroplanes themselves.

N.B. The intention of this thread is to assemble a test team and discuss flight test methods & standards, not to get into a flamewar about the performance of aircraft A vs aircraft B.