A Successful Failure

A2A simulations is building quite a reputation for themselves in the Flight Simulation community. Their attention to detail and focus on creating highly accurate models of important aircraft systems makes flying an A2A aircraft an immersive experience unlike anything else out there in the Flight Sim world. (Their B377 Stratocruiser, which I’ve written about before, is amazing!)

Recently, one of their developers was puzzled by a problem that had been reported when developing their P-40 fighter plane simulation. At high power, the engine would lose power — whereas actual P-40s would not, under the same conditions. There must be a fault in the simulation somewhere, right?

As it turned out, the simulation was working perfectly! In most simulated aircraft, the “engine” is really a straightforward set of equations relating fuel burn, manifold pressure, RPM, and torque/thrust. For simplicity, the internal workings of the engine are treated as a “black box.” On A2A aircraft with their “Accu-Sim” enhancements, though, engine systems are modeled much more accurately. Simulated fuel is pumped, a few cc at a time, into the carburetors, which mix it with air and feed the mixture to the simulated cylinders, which burn the fuel according to each cylinder’s timing, temperature, fuel/air mix, pressure, and other factors. If one of these parameters is incorrect, the cylinder will perform poorly — just as it would in a real engine. Cylinders can miss, for example, causing brief drops in RPM.

Troubleshooting the problem, A2A’s developer took the plane for a short test flight while keeping an eye on the engine instrumentation. He took off at reduced power, put the plane in a climb, then gradually added power. After the engine had been at full power for a while, he noticed the fuel pressure drop, after which the engine cut out.

It turned out that they had “installed” the wrong (simulated) fuel pump — which could not produce the needed fuel flow rate for the P-40’s (simulated) engine, starving it of fuel at high power settings. They’re working on correcting the problem (meaning, creating a higher-volume fuel pump simulation.)

You know you’re on the right track with your aircraft simulation, when diagnosing a failure comes up with a classic aircraft-engine problem, and the simulation gets the failure mode right!


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