In determining the location where the missile exploded plus determining the angle of the missile relative to the aircraft it is important to understand the position of the aircraft relative to the missile at the time of the explosion.
The modeling of the damage pattern and matching the location of the missile was performed by TNO. TNO however failed to include the drift angle of the aircraft. This does have an effect on the modeling.
There are four important terms to understand:
- displayed heading of aircraft
- Magnetic declination at position
- drift angle of aircraft
- track course of aircraft
Displayed heading (aka magnetic heading)
DSB describes the displayed heading as “Angle in degrees between the longitudinal axis (where the aircraft is pointed) and magnetic north
as displayed on the primary flight display (1 x per sec).
The Flight Data recorder showed a displayed heading of 115 degrees.
Magnetic declination or variation is the angle on the horizontal plane between magnetic north (the direction the north end of a compass needle points, corresponding to the direction of the Earth’s magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole). This angle varies depending on position on the Earth’s surface, and changes over time.
Magnetic declination in Torez is 8 degrees.
The difference between the track and heading is called ‘drift angle’. Drift angle is caused by wind.
The drift angle of MH17 because of the South/southwesterly wind at 10km alititude was 4 degrees.
Drift angle according DSB final report was – 4 degrees. The table below was taken from the DSB final report page 111 of 279.
Almaz Antey showed the drift angle of 4 degrees in their presentation as shown below.
The track course is the actual ‘heading’ of the aircraft relative to the meridian of a map.
The track course of MH17 was 115 + 8 -4 = 119 degrees.
No drift angle used for TNO missile azimuth calculation
The remarkable fact is that TNO, who did the modelling of the warhead damage, did not use the drift angle of the aircraft in the calculations. Split X software was used to model the damage pattern. If parameters in Split X matched damage to MH17, the location, azimuth and elevation was determined.
Page 13 of Appendix Y written by TNO clearly states:a possible roll angle, angle of attack and drift angle of the airplane have been assumed to be negligible.
TNO was informed by Dutch NLR via an email dated January 28 2015 that there was no need to use drift angle in the calculations.
Dutch NRC on April 16 published an article about the angle the BUK missile hit the aircraft. NRC concluded there was a large difference between the expected angle (azimuth) from a launch near Snizhne compared to the calculated azimuth of 27 degrees. NRC did use the drift angle in the calculations.
Modelling on software only
One of the most remarkble facts of the DSB investigation is the lack of a full scale, complete reconstruction of the cockpit and business class section during the investigation. The 3D model we saw at the October 13 presentation of the final report was made for that purpose.
NLR and TNO had to use the limited number of wreckage which was attached to a temporary wooden construction. Read this pressrelease for more information.