On 29 March 2014, an out of service Beech 1900D (C-GWGA) being taxied by two Air Georgian maintenance personnel at Calgary in normal ground visibility at night entered the upwind end of the active runway without clearance as a Boeing 737-700 was taking off. The 737 passed overhead the aircraft with safe clearance without the need for avoiding action.
An Investigation was carried out by the Canadian Transportation Safety Board. It was established that in the early hours of the day, arrangements were made with the airport operator to conduct an engine ground run on a Beech 1900D "at the holding bay of runway 29". An LAE and an apprentice completed preparations and started the engines before contacting TWR on the ground frequency and receiving taxi clearance to taxi from Apron 'V' to the Holding Bay of Runway 29 via Taxiway N and Runway 26 to hold short of Taxiway Y (see the diagram below which shows the cleared route in green). This clearance was read back correctly and no transponder code was issued by the controller.
The Airport Layout annotated with the cleared and actual taxi routes of the Beech 1900 (reproduced from the Official Report)
Contrary to its clearance and unnoticed by the controller, the aircraft then turned left out of Apron 'V' onto Taxiway M and then left again onto Taxiway 'Y' and onto Taxiway 'C' which leads to the Holding Point for Runway 35L. Whilst the aircraft was still taxing along Taxiway 'Y', the TWR controller, having "visually scanned Runway 17R...and then confirmed the scan by looking at the ASDE display", cleared a Boeing 737-700 to take off. The controller subsequently reported having "noticed a primary target on Taxiway Y near the intersection with Taxiway M, but concluded it was a vehicle heading for the access road that passes south of the threshold of Runway 35L".
The B1900 continued on Taxiway C and crossed the hold line at the threshold of Runway 35L as the 737 passed approximately 500 feet overhead, continuing onto the runway before calling on ground frequency to advise its position. The controller visually confirmed the aircraft was on the runway and immediately gave instructions to the aircraft to clear the runway and to taxi to the approved engine run location via Taxiway 'C', to hold short of Runway 26. The ground run was eventually completed and the aircraft was taxied back to Apron V without further event.
It was found that this had been the first time that the LAE involved had been cleared to the Runway 29 Holding Point for a ground run. However, it was also stated by the LAE "the Jeppesen airport diagram" had been consulted prior to requesting and receiving taxi clearance to the already-expected location. The controller stated that in their experience "maintenance personnel did not initiate taxiing as quickly as operational flight crews after receipt of instructions" and that they had therefore not expected the aircraft to begin taxiing so soon after being cleared to do so.
It was noted that Air Georgian was an Approved Maintenance Organisation with an SMS in place. However, it was found that an internal QA audit which had been conducted four months earlier had "found 62 (Air Georgian) individuals who had no current SMS training". The Investigation inspected the relevant personnel training files and found that the Company had provided only one of the six LMEs at its Calgary facility with the SMS training required by their SMS Manual.
It was found that Air Georgian held approval for ground running and taxi by engineers but that the process for approval of individuals did not specify the exercises required or performed. It was noted that there was a simulator program on taxiing designed for LAEs but completion of it was not required for an initial taxi authorisation to taxi aircraft although it was "expected to be completed within a year". It was found that the LAE involved had not received or been scheduled for this component of the training after having been authorised to taxi aircraft for almost 11 months; the only training he had received had consisted of "basic procedures to start and manoeuvre the aircraft". It was also found that he had "not received any initial or recurrent training from Air Georgian Limited in relation to company policy, procedures, technical, regulatory and human factors issues related to any work for which he was responsible". Although a 12 hour night shift was being worked at the time, "fatigue was not considered a factor" in respect of the performance of the LAE in the investigated event.
The ground surveillance provided by ASDE was found to be integrated with a Multilateration (MLAT) system which enabled all movements to be identified using their transponder codes. It was noted that although there was an ANSP and a Regulatory requirement for transponder usage when taxiing at Calgary as well as a local ATS requirement to assign code 1000 in the absence of any unit-specific code allocation, the controller had not done this and given that the Jeppesen publication consulted had only included the direction on transponder operation in the 'airport information' section, the LAE was not aware of it based on his consultation of only the Jeppesen airport diagram during preparation for the task allocated.
It was noted that although there was only limited provision of dedicated routes for vehicle operations at Calgary, vehicles approved to operate on the manoeuvring area were not required to obtain ATC clearance unless they wished to cross a runway or specified low RVR procedures were in force. It was considered that this had allowed the controller to discount the primary target seen prior to clearing the 737 for take off as a vehicle. It was also noted that the ASDE had a virtual stop bar feature which was not enabled because its use was not mandated in the prevailing visibility (greater than 5 nm). Had it been enabled, an alert at a position corresponding approximately to that of the runway entry stop bar would have been activated.
It was noted that the low volume of night traffic meant that ATC was staffed by two controllers, one of whom had been taking a break at the time of the event. The controller involved was working an 8 hour night shift but, in context, "fatigue was not considered a factor" in respect of his performance.
The formally stated Findings of the Investigation as to Causes and Contributory Factors were as follows:
- The company training received by the aircraft maintenance engineer (AME) was inadequate to prepare him for the complex nature of taxiing an aircraft around a large airport at night, and resulted in a runway incursion.
- C-GWGA was not assigned a transponder code as prescribed in the Calgary Tower Unit Operations Manual. This resulted in the controller not having a clear picture of where the aircraft was taxiing and, therefore, being unable to intervene prior to the aircraft crossing the hold line.
- Except for reduced/low visibility operations, the Calgary Airport Authority does not require positive control over vehicles operating on a taxiway. This resulted in the controller making an incorrect assumption that C-GWGA was a vehicle.
The formally stated Findings of the Investigation as to Risk were as follows:
- If the virtual stop bar feature on the ASDE is not enabled, there is an increased risk that the controller will not be alerted to an unauthorised movement across the runway hold line.
- If a company does not have a system to effectively control and record training requirements, there is a risk that employees may be assigned to perform tasks for which they are not trained.
Safety Action taken as a result of the occurrence was recorded as including the following:
- Calgary Airport Authority ceased recognising the holding of an LAE licence as sufficient authorisation to tow or taxi an aircraft and determined that all such operations must be undertaken by holders of an 'Airside Vehicle Operator' Permit' issued by the Authority. It also issued a requirement that all vehicles operating on the manoeuvring area must be equipped with an "MLAT-compliant unique transponder".
- Air Georgian has comprehensively revised its maintenance taxi procedures and comprehensively improved the corresponding training provision. Personnel have been restricted from taxiing aircraft until they have completed training.
The Final Report was authorised for release on 22 April 2015 and officially released on 28 April 2015. No Safety Recommendations were made as a result of the Investigation.