Elevator In-flight Failure
During climb out through 5000 feet, the flight crew began feeling elevator vibration and then heard a loud bang followed by mild elevator oscillations. Immediately following the bang, the pilot flying (captain) commenced a level off flight and reduced power to maintain at or below 120 knots. The aeroplane was easily controllable and it was found that the elevator oscillations, approximately 2.54-5.08 centimeters (cm) (1-2 inches) of uncommanded elevator travel, diminished further at 120 knots speed.
Air Traffic Control (ATC) was advised that they were troubleshooting a flight control problem and that they would proceed in a holding pattern. The crew carried out a controllability check by extending the landing gear while maintaining 120 knots and no abnormal control tendencies were noted.
The crew declared an emergency and intentions with ATC, along with their pertinent details of fuel, souls on board, and dangerous cargo. They then conducted a no flap approach to maintain 120 knots until touchdown and landed without incident where they were met by maintenance at the ramp.
Upon maintenance inspection, it was found that a substantial portion of the right-hand elevator fabric skin had come loose. The elevator fabric failed through delamination and separated from the structure of the control surface, causing the airframe buffeting and uncommanded elevator oscillations.
The horizontal stabilizer, elevator control system, and empennage of the aeroplane, were all inspected and found serviceable. The right-hand elevator was removed and a serviceable elevator was installed and the aeroplane was returned to service.
Transport Canada Comments:
It is essential that fabric covered aeroplane surfaces, and in particular to this incident, polyester fabric flight control surfaces, are to be kept in a water tight and secure condition.
Any form of imperfection with a fabric surface will promote the possibility of contamination and delamination damage.
Dornier Aircraft Maintenance Manual 51-70-20 provides the inspection and repair requirements to prevent possible icidents such as this.
Electrical Failure With Single Engine Operation
After take-off, the first officer attempted to select gear up but could not due to the gear handle release solenoid. Shortly thereafter, the captain’s Electronic Flight Instrument System (EFIS) screens went blank. The captain initiated a visual circuit and landing. The first officer’s screens went blank and they noticed the Crew Alert Warning System (CAWS) panel indicated “gen 1 off”, non-essential bus. The crew had lost the radios, screens and other components were beginning to dim. Fortunately, the pilots were able to perform a safe landing.
During troubleshooting it was discovered that the starter relay had engaged as soon as they took off and drained the battery. It was found that the auto start system (starter timer) had failed and powered the starter relay in flight. This disengaged “gen 1” thus running off battery power only. (Auto start is an internal feature of the Engine Instrument System (EIS) screen on the pc-12/47.) The EIS screen and starter solenoid was replaced.
Transport Canada Comments:
This condition is potentially dangerous. Operators and maintainers need to be aware of the possibility of total electrical system failure.
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