Airspeed fsx indicator

C

Coola

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Hello

How come the speed indicator differs in cocpit of GPS and fs9.
Can I do something about it ???


Thanks.
 
GPS = Ground speed => actual speed
ASI = Indicated air speed => airspeed as influenced by air density
 
GPS is groundspeed as well, which will add or subtract any wind component. You could go to the cockpit display showing true airspeed, but I don't recommend that. There can de significant airspeed errors at high speed, but usually this only happens above 500 knots IAS and can be compensated in the .air file.

T
 
One other possibility is the calibration of the ASI in the airplane. A lot of older airplanes built in the USA will be calibrated in MPH rather than knots. In the reset do the world, KMH is common.

In short for all,of the above reasons, there is nothing to do, it's correct as is.

glenn
 
Another reason for a 'wrong' IAS is that you can build an installation error into the ASI in FSX. E.g. many high wing Cessnas indicate a way too low IAS at low speed. (e.g. even the default C208 uses this installation error)
This is an important item during FDE design if e.g. the actual stall speed is 55kts but the POH says 40kts IAS.
 
As mentioned earlier, low airspeed position error can be problematic, even in real planes. At higher AOA the resultant vector of airflow aligned with the pitot tube becomes less. For example, in my Supercub, during a low speed approach the airspeed actually goes off the low scale by a fair bit whilst in ground effect and a fair bit of power. At higher speeds it is quite accurate. This is also typically common in most aircraft. AOA indicators are the most accurate and becoming available for gen Av planes at a reasonable cost.

However your issue is one of groundspeed (GPS) vrs indicated or even true airspeed. The only time you could count on them being about the same would be at SL on an ISA day with no wind.

Regards: T
 
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