EASA issues Emergency AD on ATR-72 flight controls

April 1, 2010

EASA issued an emergency airworthiness directive (EAD 2010-0063-E) regarding ATR-72 flight controls.

During flight control checks prior to take-off (cockpit pre-flight preparations), abnormal motion of the rudder pedal was observed in two ATR72-212A aeroplanes, the affected pedal staying stuck on its stop end position. Subsequent inspection showed that in both cases, one of the rudder pedal rods, Part Number (P/N) S2728116400000, was broken.

Further investigation revealed that an error has occurred during the manufacturing process of the affected rods. As a result, some of the rods (which have been identified as belonging to production batch numbers CC 2109699 and
CC 2118930) may have an outer diameter which is smaller than the minimum value as specified in the original design drawings.

The rods belonging to these batches were installed in the rudder pedal assemblies of certain aeroplanes. Most of the related rods have been checked and found to be in conformity with acceptable dimensions; those that were not
have been replaced while still on the production line, prior to delivery of the affected aeroplanes. However, seven (7) aeroplanes already in service have been identified that are likely to have the affected rods installed.

This condition, if not corrected, could lead to failure of the rudder pedal rod, possibly resulting in reduced control of the aeroplane. In combination with an engine failure or during a landing or take-off under crosswind conditions, such a failure could lead to loss of control of the aeroplane.

For the reasons described above, this Emergency AD requires inspection of the four rudder pedal rods, to detect a lower than acceptable outer diameter at each rod end, and replacement of any rods that fail the inspection criteria.

Emergency AD: A330 main fuel pump system

March 15, 2010

The European Aviation Safety Agency (EASA) issued an emergency airworthiness directive EAD 2010-0042-E regarding the main fuel pump system and water scavenge system on certain Airbus A330 aircraft.
During a recent in-service event the flight crew of a Trent 700 powered A330 aircraft reported a temporary Engine Pressure Ratio (EPR) shortfall on engine 2 during the take-off phase of the flight. The ENG STALL warning was set. The flight crew followed the standard procedures which included reducing throttle to idle. The engine recovered and provided the demanded thrust level for the remainder of the flight.
Data analysis confirmed a temporary fuel flow restriction and subsequent recovery, and indicated that also engine 1 experienced a temporary fuel flow restriction shortly after the initial event on engine 2, again followed by a full recovery. The engine 1 EPR shortfall was insufficient to trigger any associated warning and was only noted through analysis of the flight data.
No flight crew action was necessary to recover normal performance on this engine. The remainder of the flight was uneventful.
Based on previous industry-wide experience, the investigation of the event has focused on the possibility for ice to temporarily restrict the fuel flow.
While no direct fuel system fault has been identified, the operation of the water scavenge system at Rib 3 cannot be excluded as being a contributory factor.
Testing and analysis are continuing to identify the root cause of the event.
The scenario of ice being shed and causing a temporary blockage in the engine fuel system may lead to a temporary fuel flow restriction to the engine. This may result in a possible engine surge or stall condition, and in the engine not being able to provide the commanded thrust.
Therefore, as a precautionary measure to reduce the possibility of ingesting ice into the engine fuel feed system, this AD requires to:
– deactivate the automatic Standby Fuel Pump Scavenge System, which operates during Taxi and Take-off by removing relays
Functional Item Numbers (FIN) 80QA1 and 80QA2 (this will not affect normal standby pump operation) for aeroplanes identified in the applicability section of this AD and on which this deactivation has not been performed in production through the modification 200801, and
– Prohibit the dispatch with one MAIN Fuel Pump inoperative on all aeroplanes identified in the applicability section of this AD.

Emergency AD: 737NG elevator tab controls

March 13, 2010

The U.S. FAA issued an Emergency airworthiness directive (AD) 2010-06-51 to all owners and operators of  Boeing 737-600, -700, -700C, -800, -900, and -900ER series airplanes.

The FAA received a report of failure of the aft attach lugs on the left elevator tab control mechanism, which resulted in severe elevator vibration. The flightcrew diverted from the intended route and made an uneventful landing. Subsequent investigation revealed extensive damage to the elevator tab control system. Severe vibration in this attach point is suspected of allowing rapid wear of the joint, and resulted in failure of the attach lugs. This condition, if not corrected, could result in a loss of aircraft control and structural integrity.

Therefore, the FAA issuing this AD on March 12, 2010 to detect and correct a loose bearing in the aft lug of the elevator tab control mechanism, which could result in unwanted elevator and tab vibration. The AD requires accomplishing the actions specified in Boeing Alert Service Bulletin 737-27A1296, with some exceptions.

Boeing 737 elevator

Location of the left hand elevator tab on a Boeing 737-800 (File photo ASN)

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