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turbulence include, among others, the three components of the wind, headwind profile, windshear hazard factor, and
turbulence intensity metrics such as turbulent kinetic energy (TKE) and eddy dissipation rate (EDR). This paper
describes the main features of the QAR data analysis software and illustrates its application in windshear and
turbulence studies.
2 Basic features of the algorithm ‘WINDSTURB’
2.1General
The aircraft types under consideration include, for the moment, A320, A330, B747 and B777. The parameters
measured on board the aircraft vary from type to type. Basically, the QAR data could be grouped into a number of
categori es, namely, inertial data (e.g. three components of accel eration in the body frame of reference, ground speed,
drift angle, latitude and longitude), attitude and angular rates data (e.g. pitch angle, roll angle, heading angle, and
their rates of change i f available), aerodynamic data (e.g. calibrated airspeed, true airspeed, Mach number, pressure
altitude, radio height, angle of attack, static air temperature and total air t emperature), cockpit control data (e.g.
control column deflection, control wheel defl ection, pedal deflection, throttle lever, flap lever and trims), control
surface data (e.g. ailerons, elevator, stabilator, spoilers, rudder, slats, flaps and flaperons), navigational data (e.g.
Distance Measuring Equipment (DME) distance and Instrument Landing System (ILS) glideslope), power engine
data (e.g. left and right Engine Pressure Radio (EPR) and miscellaneous dat a (e.g. wind speed, wind direction, gross
weight and time). The data sampling rates vary for the di fferent paramet ers and also depend on aircraft type.The
basis of all post-processing, filtering and calculations is a fixed sampling rate of 4 Hz. For this purpose, data
interpolation or reduction may be required for the various paramet ers.
2.2The heart of the algorithm
Detailed descriptions of the algorithm can be found in Ref. 1. Only a summary is given here. In the initial
processing of the QAR dat a, airspeed is computed from a variety of sources, viz. the true airspeed, the computed or
calibrated airspeed, Mach number and the total and/or static air temperature. The altitude is determined from the
available baro altimeter and radio height from a radio altimeter.
Basically, what is needed to determine the wind vector Vw is the inertial speed vector V and the aerodynamic
speed vector Va. The wind vector is “simply” obtained from the difference:
D
3
Vw V Va (1)
These vectors rel ate to one and the same reference frame. Three reference frames are important here, viz. the earthreferenced
frame (x,y,z) = (north, east and vertical), the runway reference frame (same as Earth frame, but with x
along the runway centerline, y to the right, and z vertical), and the body reference frame, with its origin in the
aircraft’s center of gravity, the x-axis pointing along the fuselage towards the nose, the y-axis pointing towards the
starboard wing tip, and the vertical Z-axis following the right-hand rule (i.e. “ downwards”). To discern into which
reference frame a particul ar vector refers, superscripts ‘b’, ‘r’ or ‘e’ will be used to refer to Body, Runway or Earth
frame. Thus, Eq. (1) could refer to either body, runway or earth axes.
The question to be resolved is how to obtain the various contributions that determine these vectors. For example,
the aerodynamic velocity vector is obtained in the Body reference frame, with the following components
b
Va
Va
Va
b
a
sin
cos sin
cos cos
V (2)
In order to “ know” the aerodynamic velocity vector one thus needs to know a) the aerodynamic speed Va, b) the
angle of attack and c) the sideslip angle . The aerodynamic speed is obtained using a combination of calibrated
airspeed, Mach number, true airspeed (i f recorded on the QAR), etc. A so-called “minimum-variance” estimate is
computed using as many of the speed components as are availabl e on the QAR. Calibrated airspeed is converted to
true airspeed using static temperature, which can be obtained from total air temperature and Mach number.
The “other” term in equation (1) is the “ inertial” velocity vector V, which in the Earth reference frame has as
components:
e
z
GS
GS
e
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Quick Access Recorder (QAR) Data Analysis Software(2)
