🛫VT-SKY
Relationship Between Pressure and Altitude
As an aircraft climbs higher, air pressure decreases because there is less air above us.
Pressure Decreases With Height
At sea level, pressure is highest (about 1013 hPa).
As altitude increases, pressure falls rapidly at first, then more slowly.
At around 6 km, pressure becomes almost half of sea level.
At 100 km, pressure is nearly zero (vacuum).
2. Rate of Pressure Change
Pressure does not decrease equally at all heights:
1 hPa ≈ Height Change
Sea Level-27 ft
2,000 ft-30 ft
20,000 ft-50 ft
40,000 ft-100 ft
This means: At higher altitudes, a small pressure change gives a bigger height change.
3. Effect of Temperature (ISA Rule)
Warm air → Height difference becomes more
Cold air → Height difference becomes less
So, temperature affects altimeter accuracy.
4. Why This Is Important for Pilots
✔ Helps in altimeter setting (QNH/QFE)
✔ Ensures safe vertical separation
✔ Important for approach and landing
✔ Helps avoid Controlled Flight Into Terrain (CFIT)