European air traffic control agency Eurocontrol has
confirmed that its records show that both aircraft involved in last night’s
collision over Germany were equipped with traffic alert and collision avoidance
systems (TCAS) and had altimetry systems compliant with reduced vertical
separation minima (RVSM) requirements.
By coincidence the Bashkirian Airlines Tupolev Tu-154 had for
the first time been verified as being RVSM-compliant by Eurocontrol when it
flew over the Linz height monitoring unit just 30min before the collision. The
DHL International Boeing 757-200PF was last monitored on 30 June.
In a statement, Eurocontrol says: “Based on the available
information, there is currently nothing to indicate that the introduction of RVSM
was in any way a factor in this accident.
“Both aircraft complied with technical and operational RVSM
requirements. The height-keeping performance of both aircraft had been recently
verified and shown to be well within limits.”
Information from Swiss ATC agency Skyguide suggests that the
aircraft collided after the Russian belatedly obeyed an ATC instruction to
descend to avoid the conflict and then struck the 757 which was obeying a TCAS ‘descend’
resolution advisory (RA) triggered by the Tupolev.
The result is that recovery and successful reading of the
Tu-154 cockpit voice recorder (CVR) is now crucial to the investigation in
order to determine firstly why the Russian crew was late obeying the ATC
instruction and secondly why its TCAS did not successfully prevent the
collision in any case.
The collision was the third major air transport collision
since the widespread introduction of TCAS from 1993 onwards, but the first in
which the two aircraft were TCAS-equipped.
In both the 12 November 1996 collision near Delhi of a Saudi
Arabian Airlines Boeing 747 and a Kazakh Ilyushin Il-76; and the 13 September
1997 collision of a Luftwaffe Tu-154 and a US Air Force Lockheed C-141
Starlifter, neither aircraft were TCAS-equipped.