Description

On 12 April 2013, an Airbus A319 (VT-SCL) being operated by Air India on a scheduled international passenger flight from Abu Dhabi to Mumbai as AI 944 landed without clearance on runway 27 in day VMC after failing to respond to a TWR instruction to go around because the runway had been temporarily closed for an unscheduled runway inspection after a suspected departing aircraft bird strike. Two vehicles on the runway carrying out the inspection cleared it after their drivers saw the approaching aircraft and the landing was uneventful.

Investigation

An Investigation was carried out by an Indian AAIB Committee of Inquiry. Data from the SSFDR was available but relevant data on the CVR had been overwritten because the crew did not file a corresponding 'Flight Safety Report' until 11 hours after the occurrence. The radio communications equipment of the aircraft was subsequently checked and found serviceable.

The Captain, who had been PM for the occurrence flight had accumulated "around 8,000 hours" total flying experience and had been an Air India Check Captain on A320 family aircraft for the previous four years. The First Officer had "around 2,800 hours" total flying experience, type experience unspecified.

It was established that after a departing aircraft had reported a suspected bird strike, a runway inspection had been initiated in accordance with prescribed procedures and an aircraft ahead of the one which subsequently continued to land without clearance had been instructed to go around and had done so. At this time the A319 was on the approach radar frequency and had been cleared to make an ILS approach to the runway. When the A319 was between 8 and 10 nm from touchdown, an instruction to change to TWR was given and correctly acknowledged but the aircraft did not thereafter check in with TWR or respond to the controllers calls, including several instructions to go around and landed just over four minutes after the crew had last spoken to approach radar to acknowledge their frequency change. The First Officer stated that having noticed after landing that the approach radar frequency was still active on COM1, the Captain had changed this to the GND frequency. On being asked by the GND controller the reason why they had landed without clearance, the crew response given was "communication failure".

Fortunately, the driver of one of the inspection vehicles, who had already recovered one bird carcass from the runway was continuing the inspection when they saw an aircraft on short final for the same runway and having alerted the driver of the other vehicle inspection vehicle on their discrete VHF frequency, both vehicles were able to clear the runway onto taxiway N5 before the aircraft touched down.

The A319 crew subsequently reported seeing the two vehicles on the runway as they passed 900 feet aal and that the Captain had then briefed the First Officer that if the two vehicles had not cleared the runway by DA (230 feet) a go around would be flown. They stated that as the vehicles then vacated the runway as the aircraft passed 500 feet agl, and there was no visual warning signal from ATC not to land, they continued. The First Officer added that their action in completing the approach and landing was in accordance with the applicable radio communication failure procedure. Despite the crew claiming to the contrary, FDR data showed there had been no attempt by either pilot to transmit on any frequency between the completion of the acknowledgement to approach radar to change frequency to TWR and their transmission to GND after landing. It was noted that the radio failure squawk 7600 had not been selected.

It was noted that Air India procedures for Airbus A320 series aircraft radio communication failure were examined and it was noted that COM 3 was required to be always selected to 121.5 MHz and monitored. It was also noted that the ATC Standard Operating Procedures (SOPs) for RTF involving vehicles carrying out a runway inspection included switching the runway edge lights on and off in quick succession to indicate that a quick vacation of the runway was required.

The Investigation noted - and the crew commented - that the flight concerned and the previous outbound sector to Abu Dhabi had been partially conducted during the Window of Circadian Low (WoCL). In the light of the available hard evidence and the statements made by both pilots, the Investigation considered that there had been two possible explanations for the loss of two-way communication between the aircraft and ATC, either the Captain failed to change the frequency on COM 1 after acknowledging the instruction to do so or he had inadvertently changed it to some other frequency. It was considered that "the first possibility is most probable".

It was further considered that whilst "nothing untoward happened in the present case", there had definitely been an "unsafe situation" and that there had been a number of ways in which this could have been addressed:

• The TWR controller could have handed the flight back to the radar frequency once the aircraft was not responding on the TWR frequency.
• The TWR controller could have selected 121.5 for communications once the aircraft was not responding to their repeated calls on the TWR frequency.
• ATC could have asked the inspection vehicles to vacate the runway much earlier than they did.
• Once it was established that the aircraft was not responding on the TWR frequency, an attempt could have been made to contact the aircraft on the radar frequency.
• Either pilot could have taken "appropriate RCF action" once there was no communication with ATC.

The Investigation considered the question of flight deck CRM and concluded that "in the absence of any recording of the conversation (between the two pilots) and relying on their statements and the sequence of events, it can be seen that there was a breakdown of CRM in the cockpit during the critical phase of flight" and that "excessive fatigue of the crew....might have contributed to this lack of desired level of airmanship and loss of situational awareness". In respect of all aspects of the performance of the two pilots, the potential effect of fatigue attributable to operating over the WoCL was reviewed and it was noted that "it is a well established fact that fatigued individuals are more prone to fixations, low situational awareness and poor decision making" and that this would have had the potential to compromise flight deck CRM.

In respect of the ATC response to the loss of communication, it was found that "both the Aerodrome Controllers were conversant with the Radio Communication Failure Procedures for the en-route phase of flight but were not aware of Radio Communication Failure Procedures of aircraft on final approach".

The Investigation determined that the Probable Cause of the Serious Incident was that "after being handed over to Tower, the flight crew did not communicate with the ATC on any of the frequencies and continued to land whereas it was instructed to go around by the Tower due ongoing runway inspection".

A Contributory Factor was also identified as "fatigue on the part of flight crew".

Three Safety Recommendations were made as follows:

• that the DGCA should develop a fatigue risk management policy under the Safety Management System, wherein Operators may be asked to:
  • Implement processes and procedures for evaluating information on fatigue-related incidents and evaluating their effects.
  • Develop procedures for reporting, investigating, and recording incidents in which fatigue was a factor.
  • Formalise education/awareness training programs.
  • Create a crew fatigue-reporting mechanism with associated feedback for monitoring fatigue levels.
• that the Airport Authority of India (AAI) (as ANSP) should lay special emphasis on Radio Communication Failure when an aircraft is on final approach track, during the refresher course.
• that Mumbai Airport should carry out a safety assessment of the risk associated with runway inspection with two jeeps in consultation with the Airport Authority of India (AAI).

The Final Report was completed on 30 April 2016, published in hard copy form on 6 September 2016 and released online on 27 July 2017.

Related Articles

• Landing without ATC Clearance
• Loss of Communication
• Communication Failure: Guidance for Controllers
• Cross-checking Process
• Crew Resource Management
• Circadian Rhythm
• Fatigue
• Safety Management System
• Fatigue Risk Management System (FRMS)