[{HVY-E}Jinxx]

What aviatorsneah said, but I personally think those speeds are actually ground speeds rather than true air speeds.

not true.

ground speed = true airspeed +/- tailwind/headwind component respectively.

so with no wind they are the same.

previous posts are correct with the superchargers...with some airplanes they are automatic.

Not true again.......

You are partially correct (TAS does differ according to windspeed/direction), but for a true representation of TAS vs. IAS you need to think in particles. The reason you are faster at alt vs. at sea level is air density (Thicker air).

Everything is made of particles (atoms), the more you have, the more weight, friction you have.

For our example, let's just work with friction.

- You fly along at sea level at 350mph.
- You fly along at 30,000ft at 430mph.

This is because the air is thinner and your plane has less drag (less friction due to air density) at that alt. Thus it is easier for the plane to slip through the air. The reason you can't get a proper reading on the gauges is due to particle density.

Think of the air like a bunch of balls. At sea level you have 200 balls all around you at any given time and need to have appx. 200 balls pass through the pitot tube in order to cause enough pressure and get a reading of 200mph. Easy to do because the air is denser (more balls) at sea level.

At 30,000ft. you still need the same number of balls to pass through the pitot tube, but there are only 175 balls around you at any given time, (thinner air = less dense), so you have to go faster to get the same reading in the pitot tube. You finally get fast enough to get the reading you're looking for, 200mph, but you've had to pass through all 175 balls and then back through 25 more again in order to get the same reading, so you are really going 25mph faster in order to get the same reading.

Hope I didn't confuse you too much.

S!