Download - Aeronautics 1110x 2d-slides
Prof. dr. ir. Jacco Hoekstra
Geopoten'al & geometric al'tude
Introduc)on to Aeronau)cal Engineering
The hydrosta'c equa'on Geopoten'al al'tude Assump5on: g0 = constant
p + Δp
m· g0
p
Δh
Area A
dp = -‐ρg0dh
p + Δp
m· g
p
Δhg
Area A
dp = -‐ρgdhg
Geometric al'tude g varies
Geopoten'al & geometric al'tude
-‐ We use geopoten5al al5tude as default(easier)
-‐ Nota5on: h = geopoten'al al'tude (default but wrong) hg = geometric al5tude (real al5tude)
-‐ What is the difference? How to convert? -‐ Let’s derive the rela5on….
So what is the effect of our approxima'on?
eG
e G
Rh hR h
=+
6378 20
e
G
R kmh km=
=Let’s try with:
So what is the effect of our approxima'on?
eG
e G
Rh hR h
=+
6378 20
e
G
R kmh km=
=Let’s try with:
6378000 20000 19 937.56378000 20000
0.3%
h m
Error
= ⋅ =+
=
Geopoten'al & geometric al'tude