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AT72, Copenhagen Denmark, 2013

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Summary
On 14 January 2013, selection of the power levers to ground idle after an ATR 72-200 touchdown at Copenhagen produced only one of the two expected low pitch indications. As the First Officer called 'one low pitch' in accordance with SOP, the Captain selected both engines into reverse. He was unable to prevent the resultant veer off the runway. After travelling approximately 350 metres on grass alongside the runway as groundspeed reduced, the runway was regained. A propeller control fault which would have prevented low pitch transition on the right engine was recorded but could not subsequently be replicated.
Event Details
When January 2013
Actual or Potential
Event Type
Airworthiness, Human Factors, Runway Excursion
Day/Night Day
Flight Conditions VMC
Flight Details
Aircraft ATR ATR-72-201
Operator Not Recorded
Type of Flight Public Transport (Passenger)
Origin Sarajevo
Intended Destination Copenhagen Airport, Kastrup
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Landing
LDG
Location - Airport
Airport Copenhagen Airport, Kastrup
General
Tag(s) Root Cause Not Determined
HF
Tag(s) Manual Handling,
Procedural non compliance,
Ineffective Monitoring - PIC as PF
RE
Tag(s) Directional Control,
Off side of Runway,
Ineffective Use of Retardation Methods,
Continued Landing Roll
AW
System(s) Propellers
Contributor(s) Component Fault in service
Outcome
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation,
Aircraft Technical
Safety Recommendation(s)
Group(s) None Made
Investigation Type
Type Independent

Description

On 14 January 2013, an ATR72-212 (E7-AAD) being operated on a passenger flight from Sarajevo to Copenhagen left the side of the runway at high speed shortly after touchdown on runway 22L at Copenhagen in day Visual Meteorological Conditions (VMC). After travelling on the grass and decelerating for approximately 350 metres, the aircraft regained the runway. After a visual inspection by the airport Rescue and Fire Fighting Services to confirm that no obvious damage had been sustained, the aircraft was taxied to the terminal. The aircraft was subsequently confirmed to be undamaged and there were no injuries to the 42 occupants.

The aircraft at speed on the grass (reproduced from the Official Report)


Investigation

An Investigation was carried out by the Danish AIB. It was noted that both pilots had similar and significant experience, almost all of it gained on the ATR-72 in both cases. The aircraft commander had been PF for the landing.

It was established that shortly after touchdown and in accordance with normal procedure, the PF had selected Power Levers to Ground Idle but that only the left engine had engaged as commanded and the aircraft began to veer to the left. This situation was clearly indicated by the absence of a 'LO PITCH' light for the right engine. However as the First Officer called out in accordance with routine procedure for this eventuality and twice in succession "one low pitch", the commander selected both power levers into reverse. As a consequence, and despite the prompt reversion from reverse to ground idle, the veer to the left had already increased and he was unable to prevent the aircraft departing the 45 metre wide runway onto the adjacent short grass about 1250 metres from the runway threshold. It continued on the grass for approximately 350 metres tracking up to 17.5 metres beyond the edge of the runway before control was regained and it re-entered it. It was then taxied slowly to a nearby taxiway and after an external visual inspection by the RFFS found no obvious damage, was taxied to the assigned gate for passenger disembarkation.

It was subsequently confirmed that the aircraft had sustained no damage and also that the excursion had not resulted in any damage to the runway edge lighting - both exit from and re-entry to the runway had occurred clear of these lights which had remained to the right of the aircraft as it travelled on the grass.

The ATR 72 Flight Crew Operating Manual (FCOM) was found to contain a clear procedure requiring confirmation of transition to low pitch after movement of the Power Levers from the Flight range to the Ground (Beta) range after landing and to also include a specific Caution that selection of reverse was "not allowed" if either 'LO PITCH' light is not illuminated.

Examination of the Propeller Electronic Computer (PEC) for the right engine found that it has recorded two fault codes. These both confirmed the indicated failure to the ground fine pitch system and would have appeared when the corresponding Power Lever had been moved below flight idle and the propeller blade pitch did not follow the command. Aircraft Maintenance Manual trouble shooting guidance was followed but no hard faults were found. The PEC failure codes were reset and an engine ground run confirmed that the operation of the propeller control system was normal.

The Conclusion of the Investigation was that:

"Upon landing the right hand PEC system failed. (With only one LO PITCH light illuminated, reverse pitch was selected contrary to SOP) and together with (a) left hand crosswind component of 16 knots, worsened the asymmetric forces to the left".

The Final Report of the Investigation was published without the inclusion of any Safety Recommendations .

Further reading