Compact Course: Airborne Physical Measurements
Basic Atmospheric Parameters
This course will give an introduction into airborne measurements of the wind vector and
temperature. The course aims to understand the basics of wind and temperature measurements and how both quantities are affected by the movement of the aircraft and related
dynamic effects. Corrections will be applied to account for these dynamic effects.
1.Laboratory
In the laboratory, two pitot tubes will be provided. Each is connected to a pressure sensor.
A) Pitot Tube - angular dependence
Use the wind tunnel and quantify the angular dependence of the individual tubes. Measure
static and total pressure for different orientations and calculate the wind velocity. Parameterize the angular dependence by use of a suitable function.
B) Two-Hole Probe
Build your own two-hole probe to measure wind speed and direction. Again measure static
and total pressure for different orientations. With help of the calibration obtained in (A),
calculate the angle of attack/sideslip.
C) Temperature
Calculate the potential difference between static air temperature and measured total temperature that can be expected for measurements in the wind tunnel.
2. Aircraft Data
On the LIM-webpage of this course a data set of airborne basic meteorology measurements
is provided (bahamas_data.zip). The data is from the HALO research aircraft obtained with the BAHAMAS system and was measured during the ACRIDICON campaign
2014 over Brazil. The HALO flight provides periods with different ambient conditions
(temperature, altitude, aircraft velocity) for which the performance of the measurements
can be studied.
A) True Air Speed and Temperature Correction
In the data set you will find measurements of an pitot tube (static and dynamic pressure)
and a Rosemount temperature sensor (total and static temperature). The static temperature
was already calculated for the data set. With help of the data:
• Calculate the true air speed of HALO and compare to the results given in the data
set.
• Calculate the static air temperature and compare to the results given in the data set.
Analyze your results by investigating I) the difference between total and static air temperature (dynamic air temperature) and II) the difference between total and static air pressure
(dynamic pressure) in dependence of:
• True air speed,
• Altitude.
By help of this analysis, what can you conclude for the aircraft performance; in particular
for the relation between true air speed, altitude and air density?
B) Wind direction in Earth fixed coordinates
Compare true air speed and ground speed of the aircraft. Explain the differences between
true air speed and ground speed by analyzing their dependence on the aircraft heading and
the direction of the horizontal wind.
Use the aircraft attitude and the measured true air speed and ground speed to calculate the
horizontal components of the wind vector u and v. Apply the simplified case given in the
lecture notes (Section 2.3.2).
• In a further approximation do not account for the angle of sideslip
• Compare to the results including the angle of sideslip.
• Compare the corrected wind components to the processes data given in the data set.
Explain the differences.