Serious Incident Review: Aerodrome Closed Due Works
Not all aviation incidents are accidents, but they are all learning opportunities. This serious incident involving a larger private aircraft at a relatively quiet regional aerodrome builds on some of the lessons from yesterday’s post and helps me build towards tomorrow’s discussion on Australian aerodrome works safety standards. So, let’s discuss the day a Merlin took off from a closed runway at Gunnedah.
The Timeline
There is a factor of bad timing in this event. While it doesn’t excuse a few of the lapses and mistakes in this situation, it is good to acknowledge the whole sequence of events.
The week before the incident and following a jet aircraft operating under a pavement concession, the Aerodrome Reporting Officer (ARO)* noticed some damaged pavement on the runway. The aerodrome operator organised for a repair crew to inspect the damage the following week. They said they could repair the damage the next day. The ARO identified that this work could be carried out as emergency works and raised a NOTAM closing the aerodrome the next day.
Meanwhile, on the same day the repair crew were on site and the NOTAM was raised, a privately-operated Fairchild Industries SA226-T was making their way north from Sydney. They flew to Mudgee and Dubbo in the morning and departed to Gunnedah that afternoon. They landed at the open aerodrome, with the investigation report noting that the pilot noticed the rough pavement while taxiing for the apron.
The following day, with the NOTAM starting at 0700 local, the repair crew got to work excavating and boxing out the damaged pavement sections. These sections were just west of the taxiway entrance to the runway, which sits about 160 metres from the eastern end of the runway, meaning that an aircraft taxiing for take-off from Runway 29 might miss them if they don’t scan the runway surface to the right of the intersection.
At 1200 local, the works crew, including their aerodrome works safety officer, left for lunch.
At 1225, the Merlin radioed ATC to advise that they were taxiing for a departure. The en-route controller, located in Brisbane, checked the aerodrome’s NOTAMs and attempted to contact the aircraft to advise of the closure. However, they were unable to get that information back to the pilot.
The pilot taxied for Runway 29, turning left at the intersection. While they reported seeing patches on the distant runway surface, the pilot commenced the take-off roll. Later, those patches resolved into large holes, and the pilot changed course to avoid them.
It was too late, and the left main gear fell into the hole and collapsed. The aircraft left the runway and came to “outside the flight strip”**.
The works crew came back from lunch and found the disabled aircraft.
The Investigation
The Australian Transport Safety Bureau (ATSB) investigated this event as a serious incident. They issued their report a little over a year after the event. There were three findings:
The pilot didn’t check NOTAMs
No works safety officer or insufficient markings/markers for the closed runway
Lack of awareness of new aerodrome standards and poor interpretation of previous standards
I’m not going to examine the first one in detail. However, given that the NOTAM system has and has had some issues, my opinion remains that a NOTAM is just one layer of a risk mitigation strategy. You are not doing enough if you rely on a NOTAM as a sole warning to pilots of changed or hazardous conditions on your aerodrome.
But let’s go into the other two.
The Structure of Aerodrome Standards Sucks
But there might be little we can do about it. Putting together standards covering physical requirements and operational processes takes a lot of work. In this scenario, we have the standards for unserviceability markings & markers in Part 139 Manual of Standards Chapter 8, and we have standards for managing aerodrome works in Chapters 13, 15 & 16. But sometimes, there are a few little crossovers.
The overall compliance, and in this case, safety performance, of the aerodrome operator’s management of aerodrome works safety falls short in one of two ways. But it is always good to trace the mindset of people involved in an incident to see if we can support them and similar operators in the future.
Firstly, the need for an on-site aerodrome works safety officer (WSO)*** during the project is raised. The aerodrome operator likely decided not to require the WSO to remain on site all day because Part 139 MOS Section 15.04 (3) says they don’t have to be when the aerodrome is closed. Section 15.01 covers a range of scenarios that result in the aerodrome operator having permission to close an aerodrome for emergency works via NOTAM without meeting the minimum notice period requirements.
Part 139 MOS Section 8 Division 9 lays out requirements for markings and markers associated with unserviceable portions of the movement area. They include cross markings and cone markers. Cross markings are required at each end of the runway and at set distances depending on the size of the cross used.
But then, in Section 8.107, the standards provide a range of dispensations that mean you don’t have to provide the cross markings. The investigation report lists them as follows:
the runway unserviceability is of less than 24 hours duration
the total works period is less than 5 days
a NOTAM has been issued
a works safety officer is present with a vehicle equipped with a radio that allows for emergency
2-way communication with aircraft
if the aerodrome has been closed: a total unserviceability signal is displayed in the signal area
(if it exists).
There are 195 pages of aerodrome standards between the standard that allows the WSO to be off-site and the standard that says if you don’t do crosses, the WSO needs to be on-site with a radio. It would be nice to have a cross-reference in there (someone should get on to that).
Filling the Gaps
There is an additional issue around cone markers related to the structure of the standards and my comments on the completeness of aerodrome standards from yesterday. The issue has three components:
The not-very-old standards (current until seven days before this incident) did not explicitly require cones to be placed across the entrance to a runway if it was closed;
The new standards did make it explicit;
Some confusion on the applicability of those standards remains.
As I said yesterday, I don’t think we should treat standards about marking works and unserviceabilities as exhaustive. As at Taipei, we use aerodrome facilities in various creative ways to maximise the benefit of our infrastructure. The standards can’t accommodate every circumstance, and aerodrome operators should fill in the gaps. For example, I included a reminder to close the entrance to the runway with cone markers in my training material back in 2008.
However, CASA closed that gap with the new standards. That being said, I think the comments in the report towards the aerodrome operator’s knowledge of the new standards are generous.
Some confusion may still be generated, though. The ATSB’s analysis states that the cone markers “would not have been required had a (WSO) been present.” I don’t see it this way.
The dispensations permitted under Part 139 MOS Section 8.107 relate to unserviceability (cross) markings. Section 8.108 details standards for unserviceability (cone) markers with no cross-reference to the previous section. Therefore, my interpretation is that a closed runway/aerodrome requires cone markers across the entrance to the runway regardless of the presence of the WSO.
The final sentence of that section, though, gets close to my original comment above as it hints at the need for “additional risk controls”.
* What we call airside safety officers in Australia.
** I’m not sure what the report is referring to here. In aerodrome standards, we use the term runway strip. I have heard of ATC using the term flight strip, but it hasn’t been clear to me whether they are the same thing.
*** Often the same person as the ARO but can be a dedicated officer with specific skills for larger projects.
