On 21 January 2018, a McDonnell Douglas MD-83 (UR-CQC) being operated by Bukovyna Airlines on a domestic passenger flight from Mashhad to Isfahan for ATA Airlines as TBZ5704 and an ATR72-600 (EP-ITH) being operated by Iran Air on a scheduled domestic passenger flight from Ahwaz to Isfahan as IRA3366 came into conflict on runway 26L after the MD-83 entered the far end of the runway and began backtracking as the ATR72 was on short final to land on it. The ATR72 did not go around and was able to exit after landing before reaching the MD-83.
An Investigation was carried out by the Aircraft Accident Investigation Board (AAIB) of the Iran Civil Aviation Organisation (CAO). Both aircraft continued in service after the event and consequently relevant CVR and FDR data was overwritten and no equivalent data was available, however recorded ATC data was available.
It was noted that the 34 year-old Captain and the 30 year-old First Officer of the MD-83 were both Iranian nationals with their Iranian licences and type rating endorsed by the Ukrainian authorities as the State of Registry of the aircraft involved.
It was established that with the First Officer as PF, the MD-83 had landed normally on Isfahan's 4397 metre-long runway 26R and had almost immediately been instructed to vacate via taxiway ‘D’, a little over half way along it (see the illustration below) and then hold short of runway 26L. When it failed to make taxiway ‘D’, reportedly due to asymmetric reverse thrust during which the Captain had taken control, the controller subsequently asked the crew to report when clear and approved exit onto taxiway ‘J’ or ‘K’ but without repeating the “hold short of 26L” clearance limit previously given.
The runway and taxiway layout at Isfahan. [Reproduced from the Official Report]
The crew responded that they would be clear of the runway in 10 seconds and would exit via taxiway ‘K’. Following this exchange, the ATR72-600 on approach to runway 26L reported its position and was cleared to land.
The MD-83 then continued from taxiway ‘K’ onto taxiway ‘J’ and then proceeded to enter runway 26L contrary to the original instruction to hold short. The Captain stated that when he saw an aircraft on finals for runway 26L, he had reduced taxi speed and asked the First Officer to “confirm back track 26L”. This resulted in the First Officer transmitting that they were “backtracking on runway 26L” and the controller immediately repeating their original instruction to “hold short of runway 26L”. After then establishing the position of the MD-83, the controller passed this information to an ATR72-600 which had been cleared to land on runway 26L and which had been “just approaching to touch down” when the MD-83 first entered the far end of the runway. The ATR72 then landed on 26L “without receiving any instruction from ATC to go around” and subsequently exited the runway to the left onto taxiway ‘A’ before continuing onto the apron. As the ATR72 turned off, the MD-83 had almost reached the junction between taxiway ‘D’ and runway 26L,a separation of about 1350 metres.
The Investigation considered that the MD-83 crew had simply ‘forgotten’ their clearance limit and noted that they had not been cleared to enter runway 26L. The issue of post-landing taxi instructions very soon after touchdown (and then not reiterating the unchanged clearance limit when subsequently modifying the runway exit part of the clearance), was considered to have increased the chance of an incursion. However, it was also considered that the failure of the controller to instruct the ATR72 to go around once he became aware of the occupied runway had been contrary to standard procedures in such situations.
The Conclusions of the Investigation were as follows:
- After clearing runway 26R after its landing, the MD-83 was involved in a runway incursion by entering runway 26L during its subsequent taxiing despite being cleared to hold short of that runway. It is important to note that entering and back tracking on an active runway needs an explicit clearance from the TWR controller and shall be read back otherwise an aircraft must stop before the holding position markings until receiving further clearance to continue.
- Having observed the 26L incursion by the MD-83, the controller failed to instruct the ATR72 about to touch down on the same runway to go-around. It is important to note that the type, position and altitude of an aircraft approaching an occupied runway does not alter a controller's required response.
Four Safety Recommendations were made as a result of the Investigation as follows:
- that the State Aviation Administration of Ukraine revise the existing supervision of the flight operations of Ukrainian airlines which are operating on behalf of operators in Iran and agree the related coordination and agreement with the Iranian Civil Aviation Organization (CAO).
- that the Iranian Airport & Air Navigation Company require controllers to issue after-landing taxi clearances to arriving aircraft only after ensuring that an aircraft has reached taxi speed on the runway.
- that the Iranian Airport & Air Navigation Company emphasises the importance of controllers using a reasonable rate of speech and standard phraseology in their radiotelephony communications and of giving pilots an opportunity to read back clearances.
- that the Iranian Airport & Air Navigation Company establish or revise procedures for operation at airports which have parallel runways with centrelines less than 760 metres apart.
The Final Report of the Investigation was issued on 14 July 2018.