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I was foolishly boasting on another thread on how fast my lowly C model is based on the TAS displayed on my new Aspen PFD, and then it occurred to me why I might be wrong. Rather than continue to divert that thread, I decided to start a new one. So the Aspen seems to calculate TAS in real time based on IAS, pressure altitude, and OAT data- I would think this would be pretty accurate. However, now that I think about it, I wonder if it has the CAS correction for the aircraft model programmed in? Does anyone know the answer to this? I could not find anything in the Aspen's manual. If not, this would be a significant source of error for the C model. At cruise speeds, power on, no flaps, the IAS is 4mph greater than CAS per the POH. This error should increasingly overestimate TAS with increasing altitude, and any such error would roughly approximate the amounts that I see above book value TAS. It should also get that very nice wind vector it calculates for you using TAS, GS, MH, and TC completely wrong in some situations. Another way to look at this might be that the Aspen PFD is a speed mod of sorts for the C model that flatters you with a high TAS and then explains the lack of commensurate GS increase by falsifying the wind data Does anyone know if I'm right or wrong on this? I think the large CAS error goes away in the newer planes, but i was wondering if anyone else who flys an Aspen in the vintage Mooneys has any thoughts, or if there are any Aspen reps lurking here who can weigh in. I'd be happy to learn that I'm wrong, but then you have to go back to hearing me go on and on about how fast my C is...