Update: Cathay Pacific Airbus A330 loss of thrust control during flight

by B. N. Sullivan

The Hong Kong Civil Aviation Department (CAD), Accident Investigation Division, has released preliminary factual information regarding its inquiry into the loss of engine thrust control during flight on a Cathay Pacific Airways Airbus A330-342 aircraft (registration B-HLL).  The crew experienced control problems with both of the aircraft's Rolls-Royce Trent 700 turbofan engines during the scheduled passenger flight from Surabaya, Indonesia to Hong Kong on April 13, 2010, resulting in a high-speed emergency landing at Hong Kong. During the high-energy braking, five tires on the aircraft's main landing gear burst, and fire broke out on the wheels.  Emergency evacuation of the aircraft on the runway caused injuries to 57 passengers, 10 of whom had to be hospitalized.

Engine Thrust Control Problems During Flight

In its first report on this accident [see link below], issued in May of 2010, the CAD revealed that the crew first noticed Engine Pressure Ratio (EPR) fluctuations during climb-out from Surabaya.  Twice during the cruise phase of the flight an ECAM (Electronic Centralized Aircraft Monitoring) message, ENG 2 CTL SYS FAULT was annunciated, and the crew dealt with the situation, following ECAM procedures, in consultation with Cathay Maintenance control.  All engine parameters remained normal, except for some EPR fluctuations.

During descent to FL230, at about 100 nm southeast of Hong Kong, the CAD report says "the ECAM messages ENG 1 CTL SYS FAULT and ENG 2 STALL annunciated within a short period of time. The flight crew completed the necessary ECAM actions with No. 2 thrust lever at idle position. No. 1 thrust lever was advanced to Maximum Continuous Thrust (MCT) position."  At this point, the crew declared PAN PAN, advised Hong Kong ATC that they had No. 2 engine at idle thrust, and requested track shortening and priority landing.

When the aircraft was about 45 nm from the airport and was about to level off at 8,000 ft AMSL, the ECAM message ENG 1 STALL was annunciated.  The crew carried out the ECAM procedures, and declared a MAYDAY.  According to the CAD report, "The commander then tested the engines by moving the thrust levers.  During these movements, the No. 1 engine speed increased to about 74% N1 while the No. 2 engine speed remained at about 17% N1."

"The commander flew the aircraft manually for a visual approach for runway 07L... During the final approach with both thrust levers at the idle position, No. 1 engine was stuck at about 74% N1, and decreased to about 70% N1 during touchdown, and No. 2 engine was stuck at about 17% N1 throughout the approach and landing."

The aircraft touched down at a ground speed of 230 knots.

On landing, the lower cowling of No. 1 engine contacted the runway surface briefly.  Spoilers were deployed automatically.  Only No. 1 engine thrust reverser deployed.  The commander applied maximum manual braking and the aircraft came to a complete stop on the runway.  The No. 1 engine was still running at 76–79% N1 with the No. 1 thrust lever at idle.  The flight crew shut down both engines."

Fuel Problems Discovered

In its second bulletin, issued last week [see link below], the CAD reported preliminary findings related to the accident aircraft's fuel, noting that the aircraft had been refueled at Surabaya prior to its departure for Hong Kong.  The report describes these anomalies:

The examination of engine fuel components revealed that the Main Metering Valves (MMV) of the Fuel Metering Units (FMU) of both engines were seized at positions consistent with the corresponding final engine power.  The Variable Stator Vane Controller (VSVC) of the No. 2 engine was also found seized. Fine spherical particles (spheres) were present in the FMU, the VSVC and the Variable Stator Vane Actuator (VSVA) of both engines.  No faults or failures have so far been observed with any of the removed components, other than those associated with the contamination by the spheres.  Examination and analysis indicated that those spheres could not have been generated from within the aircraft airframe or engine systems under normal operating conditions and environment.

The examination of fuel samples collected showed that there were also spheres in the fuel samples from the engine fuel system and the aircraft fuel tanks.  Traces of such spheres were also present in the monitor filters layers and the fuel samples collected downstream of those monitor filters in the dispenser used to uplift fuel to the aircraft.  These spheres appeared to be similar to those found in various aircraft engine fuel components examined.

The report also states that analysis of data from the Flight Data Recorder (FDR) and the Quick Access Recorder (QAR) revealed "no evidence of unusual command signal from the Electronic Engine Controls (EEC), the manual thrust and the auto thrust systems.  The abnormal engines performance during the flight was believed to have been caused by stiction and eventual seizure of the MMV."

The report goes on to say that work had been performed on the hydrant refueling circuit at Surabaya not long before the Cathay A330 had been refueled there.  The investigation "noted that some of the re-commissioning procedures of that hydrant extension work were not in line with the guidelines and practices commonly used by aviation fuel industry, and that the hydrant refuel system for Stands No. 5 to 10 was used for refuelling, including the subject aircraft, before the completion of the re-commissioning procedures."

The CAD has not yet determined the exact source and nature of the spheres found in the fuel samples and filters.  The investigation is continuing.

Links:

• Hong Kong CAD: Accident Bulletin 1/2010 - 5-page 'pdf' file
• Hong Kong CAD: Accident Bulletin 3/2010 - 4-page 'pdf' file

RELATED: Dramatic emergency landing by Cathay Pacific A330 at Hong Kong - Apr 14, 2010

Dramatic emergency landing by Cathay Pacific A330 at Hong Kong

by B. N. Sullivan

A Cathay Pacific Airbus A330-300 (registration B-HLL) made a dramatic high-speed emergency landing at Hong Kong International Airport on April 13, 2010 after both of its engines malfunctioned during approach. The aircraft, operating as Cathay Flight CX780 from Surabaya, Indonesia, touched down on Hong Kong's runway 07L at a speed of 230+ knots, and six tires deflated due to heat from the high energy braking that was required. All 309 passengers and 14 crew members evacuated the aircraft on the runway via emergency slides. A number of passengers suffered minor injuries in the evacuation.

Early media reports from the scene suggested that both of the aircraft's engines had failed or been shut down during approach -- one shut down while the aircraft was some distance from the airport, and the other during short final -- and that neither engine was functioning at the time the aircraft landed. Cathay Pacific claims this was not the case, stating that while the number one engine had indeed been shut down, the number two engine was functioning. The airline also confirmed that all four tires on the left main gear and two on the right had deflated.

Later it emerged that both of the Rolls-Royce Trent 700 engines had become frozen at 70% of N1 speed. Subsequently, one engine was shut down, while the other was left operating at that speed for the landing. Cathay Pacific gave this account of a press briefing by Dennis Hui, Manager of Maintenance Support at the airline’s Engineering Department, on April 14, 2010:

He said that after further investigation of the flight data from CX780 and having interviewed the crew, updated information had shown a clear picture of this aspect of the incident.

He said it had been determined that the number 2 (RH) engine was at idle power throughout the approach and landing at HKIA, and the Number 1(LH) engine was operating at 70 per cent of its maximum power, and frozen at that level.

Mr. Hui said: “This is a higher power setting than is required for a normal approach with a single operating engine. Consequently, this higher than normal power setting led to a higher than normal approach speed and incorrect flap configuration.

“The aircraft therefore touched down at approx 230 knots, as against a normal 135 knots at this aircraft’s operating weight.

“However, the aircraft touched down on the correct position on the runway, but due to its high speed had to brake hard and use reverse thrust from the operating engine to bring the aircraft to a halt.

“The high speed and high energy braking led to very hot brakes, tyre deflation and the report from the FSD outside the aircraft that it had observed flames and smoke on the landing gear,” he added.

Mr. Hui said details of what happened and what caused the engine malfunction are now the subject of CAD [Civil Aviation Department] investigations. Cathay Pacific was co-operating closely with the investigation, along with Airbus and Rolls Royce, the engine supplier.

At the same press briefing, Quince Chong, Cathay's Director Corporate Affairs, praised the crew of Flight CX780, saying, “The pilots and the 11 cabin crew all demonstrated professionalism of a highest order in handling a most testing situation. It was due to their training, professionalism, their judgment, and ability to perform multi-tasks under a highly intense situation that the injuries had been kept to a minimum.”

Ms. Chong mentioned that the evacuation had been accomplished in two minutes.

UPDATE Apr. 15, 2010: The Wall Street Journal is reporting that Cathay Pacific has stopped refueling its planes in Surabaya "as a precaution," suggesting that fuel quality is being looked at as a possible cause of the dual engine malfunction. For the time being, Cathay flights will instead make a refueling stop at Jakarta.

The Wall Street Journal also reported that Hong Kong's Civil Aviation Department has taken fuel samples from the Airbus A330 for tests, and also has retrieved the aircraft's flight data recorders for analysis.