The ATSB is investigating the fatal aircraft accident involving a Dromader aircraft that occurred near Ulladulla, NSW on 24 October 2013. The aircraft was being used to conduct aerial work operations when at about 1000 local time, it collided with terrain. The pilot died in the accident.
Updated: 1 November 2013
For several days the accident site had been inaccessible due to rugged terrain, high winds, low cloud, and nearby bushfires. On 30 October 2013, due to the efforts of the Rural Fire Service, the NSW National Parks and Wildlife Service, and the NSW Police, a team of five ATSB investigators, including a materials specialist, examined the aircraft wreckage on site (Figure 1).
Figure 1: Part of the accident site
M18 Dromader aircraft have a cantilever wing; that is, it is anchored at one end with no mid-span supports. The wing consists of three sections; the central wing section, and the left and right outer wing sections (Figure 2). Between each outer wing section and the centre section there are three attachment points. At each of the main spar attachment points, a single lug on the outer wing is secured between two lugs on the centre wing by a through bolt and bush (Figure 3).
Figure 2: Overview of wing structure
Figure 3: Detail of left wing attachment points (centre wing section not shown)
The on-site examination found that the left wing had separated at the joint between the outer wing and the centre wing sections (Figure 4). The ATSB team examined the joints closely to determine the failure mode that resulted in the in-flight separation of the wing. Preliminary examination indicated that the left outer wing lower attachment lug (see arrow in Figure 4 and Figure 5) had fractured through an area of pre-existing fatigue cracking in the lug lower ligament. The fatigue cracking reduced the structural integrity of the fitting to the point where operational loads produced an overstress fracture of the remaining lug material.
Figure 4: Outer section of left wing (under side of wing visible)
Figure 5: Part of failed attachment lug
The ATSB’s on-site examination was completed on 31 October 2013. Several components were removed from the accident site for further examination at the ATSB’s Canberra facilities, including:
- both sections of the separated lower main spar lug and the remainder of the lower main spar attachment point (left wing)
- the entire upper main spar attachment point (left wing)
- part of the rear spar attachment point (left wing)
- the entire lower main spar attachment point (right wing).
Following M18 Dromader accidents that occurred in the United States involving in-flight wing separation, in September 2000, the United States Federal Aviation Administration issued Airworthiness Directive (AD) 2000‑18-12. This AD required repetitive inspections of the centre wing to outer wing attach joints for ‘cracks in the lugs, corrosion in the main holes, and ovalization of the main holes’. On 19 October 2000, the Australian Civil Aviation Safety Authority (CASA) issued AD/PZL/5 with the same basic inspection requirements.
In accordance with AD/PZL/5, inspections were required every 500 hours time in service or every 12 months, whichever came first. The wings of VH-TZJ were last inspected on 8 August 2013. Up to 17 October, the aircraft had accumulated about 110 hours time in service since the last wing inspection.
As of 24 October 2013, there were 30 M18 aircraft on the CASA aircraft register (including VH-TZJ).
The investigation is continuing and will include examination of the:
- wing inspection requirements
- inspection methods
- history of the aircraft’s operations and maintenance.
It is anticipated that a preliminary investigation report will be released to the public no later than 24 November 2013. Should any critical safety issues emerge in the course of the investigation, the ATSB will immediately bring those issues to the relevant authorities or organisations and publish them as required.
The information contained in this web update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.
Updated: 25 October 2013
The ATSB has been unable to gain access to the site of the accident due to the ruggedness of the terrain and an ongoing bushfire risk (Figure 1).
Figure 1: Terrain in the area of the wreckage
However, an initial low-level aerial survey has been carried out to understand the disposition of the wreckage. This showed that the left wing detached in flight (Figure 2), which was consistent with information provided to investigators by a witness to the accident.
Figure 2: Aerial view of the detached left wing (looking at the under surface of the wing)
Further updates will be provided as additional information comes to hand.