On 12 September 2011 at about 1000, the pilot of a Cessna 210N aircraft, registered VH-JHF, was conducting low-level aerial survey operations near Bourke Aerodrome, New South Wales. After encountering a brief turbulence event, the pilot had difficulty in making elevator control inputs and in maintaining height. The aircraft subsequently landed safely. There were no injuries.
What the ATSB found
The ATSB found that the reported elevator control input difficulties resulted directly from the fracture of the aircraft’s two horizontal stabiliser rear attachment brackets. The forward spar of the horizontal stabiliser was also extensively cracked. The fractures and cracking were all consistent with metal fatigue and, as such, were typical of the damage sustained by aircraft as they age and move beyond the manufacturer’s originally intended design life. Many manufacturers have addressed the growing potential for this type of damage by introducing supplemental inspections to the principal aircraft maintenance requirements.
The Australian Civil Aviation Regulations 1988 (CAR) were being misinterpreted by some class B aircraft registration holders, to the extent that they believed that their aircraft was exempt from the manufacturer’s supplemental inspections when their aircraft was maintained using the CASA maintenance schedule. While the CASA maintenance schedule did not make any specific reference to the incorporation of the manufacturer’s supplemental inspections, it was a CAR requirement that all aircraft be maintained in accordance with approved maintenance data that, by definition, included those inspections.
What's been done as a result
As a result of this occurrence, on 19 September 2011 the Civil Aviation Safety Authority (CASA) issued Airworthiness Bulletin AWB 55-001 issue 2; highlighting the failure of horizontal stabilisers on Cessna 200 series aircraft. The AWB made recommendations on the maintenance schedule and inspection of the stabiliser in order to ensure the structural integrity of the area.
CASA also published a series of Discussion Papers in December 2012, detailing a range of options for developing updated continuing airworthiness regulations for all aircraft not used in regular public transport operations. This included options for reform of maintenance program requirements for non-RPT aircraft – to bring the regulations up to date with modern technology and current international standards and practice.
The outcomes from the discussion papers were unresolved at the time of writing and therefore the Australian Transport Safety Bureau has recommended that CASA proceed with its program of regulatory reform to ensure that all aircraft involved in general aviation operations are maintained using the most appropriate maintenance schedule for the aircraft type, and to also ensure that the provisions of CAR Schedule 5 are clarified in relation to the incorporation of all relevant supplemental inspections specified for the aircraft type.
This occurrence highlights the importance of comprehensive, periodic maintenance inspections and the role of supplemental inspections in maintaining ageing airframes. The ATSB strongly encourages registration holders of class B aircraft to review their aircraft’s maintenance schedule to determine if it is the most appropriate for their aircraft and to ensure that it adequately provides for the continuing airworthiness of the aircraft.