Russian authorities have withdrawn the airworthiness certificate of a UTAir Tupolev Tu-154M and suspended its crew following an airprox incident last month which also involved a Transaero Boeing 767-300.
Both aircraft had been following the same airway on 24 April, the Tu-154 operating Moscow Vnukovo-Samara and the 767 flying Moscow Domodedovo-Vladivostok.
Moscow air traffic centre had instructed the Tu-154 to climb to 9,100m (29,850ft). At the time it was operating about 600-800m above, and 2nm (4km) ahead of the 767, which had been authorised to climb to 7,500m.
But according to air traffic authority Rosaeronavigatsia the Tu-154 had not retracted its undercarriage and, as a result, started losing both airspeed and altitude.
In a statement the Moscow air traffic centre says the aircraft "unexpectedly stopped climbing, stayed at level flight for some time, then began descending" as it headed out of Moscow airspace. The descent, unauthorised by air traffic controllers, threatened to bring the tri-jet into conflict with the 767.
"The distance between the conflicting aircraft rapidly decreased and a real threat of a dangerous convergence was created," says the centre's statement.
One controller, it adds, urgently began warning the 767 of a potential collision, ordering it to level at 7,200m and turn right to 110°. He also made "repeated, persistent" attempts to alert the Tu-154's pilots to the presence of the other aircraft, and confirm their altitude, before directing them to turn left heading 050°.
The Tu-154 descended through the 767's flight level with the two aircraft diverging and laterally separated by about 2nm.
Rosaviatsia has not clarified whether either the Tu-154 or 767 had an operational collision-avoidance system, but it has grounded the Tu-154 - registered RA-85069 - citing airworthiness reasons.
It has also notably issued a statement on the level of collision-avoidance system carriage in the Russian fleet, stating that 81% of aircraft are equipped - and emphasising that all aircraft operating international routes are fitted, while pointing out that traffic intensity in domestic airspace is relatively low.
Lessor Avializing delivered RA-85069 to UTAir on 23 June 2007 and, in a statement at the time, said it had undergone modernisation at Moscow Vnukovo's VARZ-400 plant including the fitting of a collision-avoidance system.
Investigators are examining the incident, including the reasons for the non-retracted undercarriage of the Tu-154 and the actions of its crew.
Source: Air Transport Intelligence news
