Quote Originally Posted by Baffin View Post
Interesting! I understand the sea level IAS=TAS (at standard temperature), and this is important for players to know... that if you fly higher, the actual (True) speed through still air is higher than that presented on the Airspeed indicator. This is basic to navigation.

However, as a part of game programming, I found the statement that IAS=CAS (Airspeed corrected for installation/position error) to be worthy of a question. I have always treated IAS (A.S.I in the original RAF Pilots Notes) in our game to be exactly that... not corrected for installation error, simply a flight-tested value. During climb and cruise planning, I have sometimes applied the installation error listed in the Pilots Notes and it all seems to work correctly.

If I'm taking off at calibrated airspeed, I will be flying faster than what IAS should be indicating, and therefore rotating late and extending the takeoff run unnecessarily. For most of us, it makes no practical gaming difference (Probably less than 10 MPH in an RAF Plane), but it's a very peculiar thing to apply position error for takeoff and landing in an attempt to be technically accurate. In fact, if we apply the installation error to the IAS during a Spitfire no-flap approach, we will find ourselves dangerously close to the stall.

If IAS is programmed to equal CAS (in other words, position error is ignored) in a Spitfire cruising at more than 220 MPH IAS, the CAS will in fact be 8 MPH higher than it should be. In flight planning, this will proportionally increase the TAS according to the altitude flown and we will arrive at the destination early. It's not a big deal in our game... simply strange considering the high degree of technical accuracy found throughout our simulation.

The indicated airspeed in our game is what you've programmed it to be, but it certainly acts properly to me... just like uncorrected IAS when I fly RAF Planes.
Every real life aircraft had a different position for their airspeed pitot, and often there were different types of pitots used to measure speed. This meant there was a different position error for each type.

For that reason the original developers had the gauges show calibrated airspeed... and at this point it is simply not practical to change the readings to so they show each aircraft type's historical positional error.