[Fireball]

Hi KC,

Unless my math is wrong, the TAS vs IAS numbers seem to be pretty close.

Let's take your first picture:

- The speedbar (which is IAS) shows 170 mph. It also shows you at 1000 ft.

- The digital readout in the center of airspeed gauge (which is TAS) shows 180 mph.

- The IAS/TAS conversion says that TAS increases 2 percent for every 1000 ft of altitude gain. Since you are at 1000 ft, your TAS should be 2 percent higher than your IAS. 2 percent of 170 mph is 3.4 mph.

- So...if you were going exactly 170 mph IAS at 1000 ft, your TAS should read 173 or so. But depending on what increments you have your speedbar set to, it may only increment every 10 mph. So when it reads 170 IAS, your actual IAS could be anywhere from 170 to 179. You can get a more accurate reading for testing this by setting your speedbar airspeed to increment every foot, instead of every 10 ft.

Hope some of that helps. Now MY head is spinning! hock:

Folks,

I'm not good at math.

Have installed the new HUD and well,.....things aren't adding up for me.

I'll let the pictures do the talking for me.

The first one is a page scan from Rod Machado's Private Pilot Handbook.

His instructions for computing TAS don't seem to jive with what I am seeing on screen.

I do note that he says "approximate".

Help !

My mind is spinning !

ps - I used "auto level or wing leveler (whatever its called)" and let the airplane fly for quite a distance over the ocean (MSL) so it settled down as far as speed goes.