ATSB: Manufacturing problem potential factor in recent A380 engine failure

December 2, 2010

The ATSB has issued a safety recommendation about potential engine problems in some Airbus A380 aircraft.

The ATSB is investigating an occurrence involving a Qantas A380 aircraft that experienced engine failure over Batam Island, Indonesia on 4 November 2010. The aircraft landed safely in Singapore having returned with the aircraft’s No 2 engine shut down. There were no injuries.

The ATSB has now issued a safety recommendation (AO-2010-089-SR-012) about potential engine problems in some Airbus A380 aircraft.

The safety recommendation identifies a potential manufacturing defect with an oil tube connection to the high-pressure (HP)/intermediate-pressure (IP) bearing structure of the Trent 900 engine installed in some A380 aircraft.

The problem relates to the potential for misaligned oil pipe counter-boring, which could lead to fatigue cracking, oil leakage and potential engine failure from an oil fire within the HP/IP bearing buffer space.

In response to the recommendation Rolls Royce, affected airlines and safety regulators are taking action to ensure the continued safe operation of A380 aircraft. The action involves the close inspection of affected engines and the removal from service of any engine which displays the suspected counter-boring problem.

 

 


Report: A330 emergency descent due to bleed air system interruption (Taiwan)

August 30, 2010

The Aviation Safety Council (ASC) of Taiwan issued several safety recommendations as a result of their investigation into an  occurrence when an Airbus A330 made an emergency descent due to temporary interruption in the bleed air system supply.

On September 14, 2008 an Airbus A330-300, registered B-HLH, operated by Cathhay Pacific as regularly scheduled Flight CX521, took off from Tokyo-Narita Airport (NRT/RJAA), Japan on a flight to Hong Kong. Due to the presence of a typhoon the flight was rescheduled to Taipei-Taiwan Taoyuan International Airport (TPE/RCTP). There were 72 persons on board. The airplane was dispatched with the nr.1 engine bleed air system inoperative per MEL.

The aircraft encountered interruptions of the bleed air system supply at 38,544 ft during descent from flight level FL400. Flight crew members conducted an emergency descent and landed safely at Taipei international airport at approximately 19:29. The aircraft was not damaged and none of the 72 occupants were injured.

The investigators concluded:

Giving the de-activated status of the No.1 engine bleed air valve per MEL 36-11-02, the no.2 engine bleed air was the only one compressed air source for the two air conditioning systems.
The no.2 engine bleed air valve operated in a high demand status. During aircraft descent, the compressed air automatically bled from high pressure stage which provided the compressed air with higher pressure and higher temperature.
This led the pre-cooler downstream temperature air getting higher. Due to the THC’s grid filter contaminated from which to reduce the muscle air pressure to control fan air valve that resulted in the fan air valve could not open properly to provide sufficient cooling air to pre-cooler. The no.2 engine bleed air valve was shut down automatically due to bleed air overheat.
Both air conditioning systems lost the compressed air source and thereby aircraft lost its pressurization capability.

The Aviation Safety Council issued following 4 Safety Recommendations to Hong Kong CAD and Cathay Pacific Airways:

  1. require Cathay Pacific Airways to consider evaluating or revising the MEL procedure to reduce the depressurization risk under one engine bleed air fail, and recover the cabin pressurization capability with APU in a timely manner when the second engine bleed air system also failed;
  2. require Cathay Pacific Airways to consider evaluating the maintenance program for ThC shop-in service or overhaul interval before the new grid filter design or modification come to effect;
  3. require Cathay Pacific Airways to consider evaluating the MEL restriction regarding aircraft been dispatched from home base with an inoperative system to lower the dual bleed system failure risk;
  4. require Cathay Pacific Airways to review air dual bleed fault and emergency descent procedures and revise related inconsistent procedures accordingly; and require Cathay Pacific Airways cabin crew members to review cabin depressurization related procedures including: provide oxygen bottle side effect information, manually opening the oxygen cover panel to initiate oxygen flow; enhance cabin crew depressurization training.

Three safety recommendations were issued to the DGAC France to:

  1. require manufacturer to modify or redesign the ThC grid filter to reduce the risk of A330 dual bleed system failure;
  2. recommend the manufacturer to evaluate the maintenance program for ThC shop-in service or overhaul interval before the new design or modification come to effect and require manufacturer to review air dual bleed fault and emergency descent procedures and revise related inconsistent procedures accordingly; and
  3. require manufacturer considering to take the in-service fleet events and family fleet problem solving experiences into Product Safety Process account and form the problem solving task force in an earlier time as proactive risk mitigation measure.

The Aviation Safety Council issued  recommendations to CAA Taiwan as follows:

  1. require controller followed ATMP procedures;
  2. enhance controller emergency response and situation awareness when handling the distress aircraft in accordance with the ATMP procedure;
  3. enhance ATC internal coordination, communication during emergency situation includes the training, checking and handling of distress aircraft and carefully selected appropriate radio communication stations as backup system to avoid communication performance degrade; and
  4. to revise the TACC Guard frequency radio test inclusive at SALMI waypoint and review and revise the ATMP Chinese version 2-4-15 word meaning in accordance with the English version 1-2-1.

Safety recommendations following Japanese DHC-8 engine failure

August 30, 2010

The Japan Transport Safety Board (JTSB) issued safety recommendations to Transport Canada as a result of their investigation into a serious incident involving a DHC-8 engine failure.

On March 25, 2009 a DHC-8-402, registered JA847C, operated by Japan Air Commuter as regularly scheduled Flight 3760, took off from Tanegashima Airport (TNE). While the aircraft was climbing an abnormal noise emanated from the No. 1 engine and instrument indications showed the occurrence of engine failure. The engine was then shut down and the aircraft requested emergency landing clearance from the Kagoshima Radar Approach Control Facility. The aircraft landed safely at Kagoshima Airport.

JTSB concluded that it is highly probable that, while the aircraft was climbing after takeoff, the RGB helical input gearshaft of the No. 1 Pratt & Whitney Canada PW150A engine sustained fatigue fracture and was detached from its position; the fragments of the broken shaft then flew off, damaging the engine case and breaking the blades of the HPT and the blades and vanes of the LPT and PT at the downstream stages, and this resulted in breakdown of the engine. With regard to the fatigue fracture of the RGB helical input gearshaft, it is considered probable that fatigue cracks had started from the impurity inclusion present in the metal stock of the helical gear developed in the shaft, and after undergoing repetitive application of stress, the shaft was finally fractured.
In view of this serious incident, the Japan Transport Safety Board recommends that Transport Canada give careful consideration to the following and take necessary measures thereof:

(1) Considering the detrimental effect on safety brought about by the inclusion of impurities in the RGB helical input gearshaft of the engine involved in this serious incident, P&WC, the manufacturer of the engine, should make company-wide efforts including the management of the metal stock supplier and component manufacturer serving P&WC, towards improved quality control concerning the production of the RGB helical input
gear shaft.

(2) P&WC assigned a hazard severity of “Significant – Level 3” to this serious incident by considering only the occurrence of an IFSD as the basis for the risk level determination, but the actual conditions included the loss of all functions of the feathering system for the propeller of the shutdown engine in addition to the engine in IFSD.
The risk assessment of this serious incident should not be made only on the engine necessitating an IFSD, but instead the incident must be reassessed from the viewpoint of the safety of the entire aircraft, and safety improvement actions should be taken if the results of the reassessment indicate this to be necessary.


NTSB concerned about training for mechanics and inspectors

May 28, 2010

Based on preliminary findings from the investigation of a partial gear up landing of a CRJ200 in December 2008, as well as prior investigative findings, the U.S. NTSB voiced its concerns about training for mechanics and inspectors. Two safety recommendations were issued and three older recommendations were re-iterated.

On December 14, 2008, about 17:00 local time, Air Wisconsin Airlines flight 3919, a Canadair CL-600-2B19 (CRJ-200), N407AW, landed at Philadelphia International Airport, PA (PHL), with the left main landing gear in the retracted position. The aircraft was being flown as a repositioning flight from Norfolk International Airport, VA (ORF) to PHL. There were no injuries to the two flight crew and one flight attendant on board the aircraft.

The flight crew received indications of a left main landing gear problem prior to landing and stated that they completed the applicable Quick Reference Handbook (QRH) procedures, but were unable to lower the left main landing gear. They elected to land with the nose and right main landing gear in the down and locked position and the left main landing gear up.

Maintenance had been performed on both the left and right main landing gear systems prior to the incident flight. Post-incident inspection of the aircraft revealed that, the upper attachment bolt for the left main landing gear uplock assembly, which is designed to be attached to both the uplock mechanism and the structure, was attached to the airplane structure only.

The NTSB concludes that the incident mechanic was not properly trained or supervised when he replaced the uplock assembly on the incident airplane for the first time, which led to the error in installation. Further, the error was not detected by the inspector. The NTSB is concerned that the Federal Aviation Administration (FAA) does not currently require mechanics to receive on-the-job training (OJT) or be supervised while performing required inspection item (RII) tasks for the first time.

Problems with untrained or unsupervised mechanics performing maintenance tasks for the first time have also been found during the NTSB’s investigation of the January 8, 2003,  fatal accident involving a Beechctaft 1900D  which crashed shortly after takeoff at Charlotte-Douglas International Airport, NC. The accident airplane underwent a detail six maintenance check.  One of the mechanics assigned to check the elevator control cable tension was receiving OJT under the supervision of a quality assurance inspector who failed to adequately supervise and direct the mechanic.

Therefore, the NTSB recommends that the FAA:

Require that mechanics performing required inspection item and other critical tasks receive on-the-job training or supervision when completing the maintenance task until the mechanic demonstrates proficiency in the task. (A-10-96)

Require that required inspection item (RII) inspectors receive supervision or on-the-job training on the proper inspection of RII items until the inspector demonstrates proficiency in inspection. (A-10-97)



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