UdoR wrote:
Well then, looks like I’ll have to invest in some camera equipment to show you guys how to do it
LOL, a good phone will do these days.
Hey, I don’t think anyone wants to say you are talking garbage, certainly not me. I am more concerned that some indications may give you wrong information. And that can end up with unpleasant surprises.
Nobody has suggested that. What has been suggested is instrument error.
we could all go on a head to head race… during the next fly-in for instance 
Peter wrote:
What has been suggested is instrument error.
And I am fairly sure it is something like that too.
It’s bizarre. GPS groundspeed doesn’t lie, and it’s usually blindingly obvious when the IAS or derived TAS are in error.
In one aircraft I fly the ASI is obviously over-reading by a fair bit. I think it’s because the pitot head is (quite evidently, reads 20mph during power checks) in the propwash, but a co-owner is dismissive of such a notion on the basis that the pitot head is located where the manufacturer intended it.
On another aircraft I fly the 2x IAS indications are pretty much bang on and have an apparently-correct relationship to GPS groundspeed, but the calculated TAS value in the PFD is evidently excessive – I think the OAT input is over-reading.
On the third I’ve never seen an IAS value that appears inconsistent with GPS groundspeed, and it’s a traditional ASI where one sets the pressure altitude and OAT manually to derive TAS, which generally appears to be correct.
