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1st of April 2011, Elevator Surface Disbonding, Blog #645

After all required (maintenance) checks had been carried out the crew of a Dornier 228-212 was getting ready for their flight from Schiphol Amsterdam Airport (the Netherlands). After the engines were started clearance was received to taxi to runway 22 at Schiphol for a flight over the North Sea. After getting airborne the aircraft turned on westerly heading with a speed of 180 knots, at an altitude of 1000 feet.

The elevator as found after landing (Source and © OVV)

While still over the airport a sound, similar to a cable, under tension, snapping was heard by the crew. Shortly afterwards a sharp and powerful nose-down movement occurred. The crew immediately stabilised the aircraft in level flight again, with strong vibrations being present in the control wheel. The crew suspected that the fabric covering of an elevator surface at been damaged. They reduced the speed to 150 knots after which they consulted a Flight Operations Bulletin published by the aircraft manufacturer. In this bulletin, the flight characteristics are described after disbonding of the elevator skin. It also advised on the procedures to follow to optimise the control characteristics of the aircraft after loss of elevator effectiveness. The aircraft remained fully controllable following the advice from the Flight Operations Bulletin and a return to the airport, from which they had just taken off, was initiated after informing ATC about the situation. The flight to and landing on runway 22, a short while later at Schiphol Airport, was uneventful. After parking the aircraft it became clear that the upper surface of the righthand elevator had come loose and was only attached to the lower side of the elevator trailing edge. The authorities were informed and an extensive investigation was launched.

It became apparent that 90% of the contact surface of the construction had a shiny appearance with little to no traces of the fabric, indicative of a lack of adhesion between elevator construction and fabric. On the areas without traces of glue, a clear unprotected metal surface of the structure was visible, there were no traces of the brown primer that should be there. On some parts of the elevator de fabric could easily be pulled from the structure. On a few small patches, there was proper adhesion.

Detail of the elevator, note the shiny appearance (Source and © OVV)

These findings lead to an investigation into the maintenance history of the elevator in question. During this part of the investigation, it became apparent that the elevator had been recovered in May 2004. The work had been performed per the Structural Repair Manual, part 5.

As a solvent methylethylketone (MEK) was used, as a replacement for the prescribed Toluene. A steel roller was used to press the fabric on the structure. Which tool to use and with what pressure the fabric should be pressed onto the structure was not described in the SRM. As a result of the investigation the Dutch Safety Investigation Board (De Onderzoeksraad Voor Veiligheid - OVV) concluded;

  • The elevator was not repaired in compliance with the prescribed procedure in the SRM, methylethylketone (MEK) was used as a solvent. Not the prescribed Toluene.

  • The SRM did not provide guidance on which tool to use and how much pressure to apply when pressing the fabric on the elevator structure.

  • The crew used the correct procedure during the emergency.


Several safety actions were taken as a result of this incident, amongst others;

  • The Flight Operations Bulletin has been included in the Emergency Procedures of the Aircraft

  • The aircraft manufacturer provides practical training for MRO's involved with repairs on Elevators and Rudder of the Dornier 228.


The investigation report (in Dutch) into this incident, which served as the source for this blog, is available by clicking on the .pdf file below;


01Apr2011 Do228 Fligth Control
.pdf
Download PDF • 229KB

** Editorial note **


V2 Aviation - Training & Maintenance has not been able to obtain an investigation report in English on this accident. This blog is therefore based on an interpretation of the report in Dutch. Should there be inconsistencies in the blog don't hesitate to get in touch with us. There are two possibilities to do that, via the comments function at the bottom of this page or the contact page of the website.

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