# Does altitude affect how you interpret the attitude of the aircraft?

I understand that for any specific aircraft, at a constant power setting, you can use the aircraft's attitude as a proxy for airspeed.

For e.g. In aircraft X, when the dashboard is 1 inch below horizon, at power setting X, means the aircraft will be flying at around speed X.

My question is, if you are much higher in terms of altitude, won't your attitude based on visual reference e.g. How many inches away is your dashboard to the horizon, be different when you are much closer to ground?

• I would say not significantly, at least not in a small plane. The horizon is 60+ miles away, you are 1 to 2 miles above the ground (5000 to 10000 feet). Draw a right triangle and do the math, you will find the angle is pretty small. If you go higher, you may find you need more back pressure to hold altitude, but then you are compensating for loss of horsepower with altitude (unless the engine has a turbo to maintain sea level power, most small planes don't). The other thing you will find is that due to lower power at altitude, airspeed drops, but the thinner air lets ground speed go up. Feb 19 '20 at 17:17
• "... the thinner air lets ground speed go up." Unless you are facing a stronger headwind! ;) Feb 19 '20 at 20:37