| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
On 11 April 2021, a flight examiner conducted an instrument proficiency check with a commercial pilot in a Vulcanair [1] P.68C aircraft, at an airport near Brisbane, Queensland. At 1000 Eastern Standard Time,[2] as the aircraft was taxied to the apron after the flight, the pilot had difficulty controlling the aircraft’s direction and advised that the rudder seemed jammed.
A post-flight inspection revealed that the top rudder hinge had failed (Figure 1).
Figure 1: Rudder with failed hinge, inset shows failed hinge
Source: Aircraft operator
Maintenance
The aircraft was being maintained in accordance with the Civil Aviation Safety Authority (CASA) maintenance schedule, which required that a periodic inspection be completed every 100 hours or 12 months, whichever came first. The last inspection had been conducted 26 flight hours prior to the occurrence.
The CASA maintenance schedule was detailed in Civil Aviation Advisory Publication (CAAP) 42B-1(1.1). This CAAP required that the flight control surfaces, including the hinge brackets, be inspected for ‘general condition’. It specified that inspection aids such as work stands, mirrors and torches should be used and that ‘surface cleaning of individual components may also be required’. Paragraph 6.7 specified that the procedures ‘prepared by the aeroplane manufacturer are to be used when performing an inspection required by this schedule’.
In 2015, Vulcanair released Service letter 23 revision 1[3] which has since been incorporated into the P.68C maintenance program. The service letter was an alert to all P.68C owners and operators, providing detailed instructions on how to inspect the hinges. In accordance with the manufacturer’s approved maintenance procedures, the inspection was to be completed every 200 flight hours or 1 year, whichever came first. As the Civil Aviation Safety Authority had not issued an airworthiness directive containing the information in Service letter 23, the service letter was not mandatory. The inspection detailed by Service letter 23 had not been completed on this aircraft.
Safety action
CASA’s Continued Operational Safety and Standards section has contacted the European Union Aviation Safety Authority (EASA) small aircraft section and advised them of the incident and two other defects of a similar nature.
The operator’s maintenance repair and overhaul company has submitted the service letter feedback to the aircraft type certificate holder.
CASA is progressing the project to reform the continuing airworthiness and maintenance regulations. This work is being managed under project SS05/01 and status updates are available on the CASA website. The proposed policies include significant improvements to the current regulations, including the rules involving the CASA maintenance schedule. Subject to priorities in CASA’s wider regulatory program, CASA anticipates making the new regulations in 2022.
The ATSB was informed that on the 21 October 2021, EASA released a Notification of a proposal to issue an airworthiness directive (PAD) 21-158: Stabilisers – Rudder hinges – inspection. This AD proposes to make an inspection of the upper rudder hinge mandatory, in accordance with Service letter 23, revision 2, dated 29 September 2021 and the associated aircraft maintenance manual.
Consultation on the PAD closed on 18 November 2021.
Safety message
The CASA maintenance schedule was intended for those aircraft listed in Civil Aviation Order 100.5 as having inadequate maintenance schedules. Although no Vulcanair aircraft were on that list, nothing precluded the aircraft being maintained in accordance with the schedule. For operators who maintain aircraft in accordance with the maintenance schedule, CASA’s Maintenance guide for owners/operators stated that:
Under [Civil Aviation Regulation] CAR 42V (1), because all maintenance is required to be carried out in accordance with the applicable approved data, you must still consult with the manufacturer’s maintenance manuals for the airframe, engine and propeller, as well as applicable literature such as service bulletins, for instructions on how to carry out inspections and corrective maintenance action.
A manufacturer may issue service information, such as a service letter, to advise operators about a problem and introduce or clarify an inspection, procedure or new part to prevent the problem recurring.
In 2011, the ATSB investigated a similar occurrence, AO-2011-115 Flight control system event involving Cessna 210N, VH-JHF, where the aircraft’s two horizontal stabiliser rear attachment brackets failed. During this investigation, the ATSB found that 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.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
__________