November 5, 2010

expert reaction to engine problems on two Qantas aircraft

An Airbus A380 was forced to land when its Rolls-Royce engine failed. This was closely followed by the precautionary grounding of a B747 after discovering problems with their engine.

Prof Nick Cumpsty, Emeritus Professor of Mechanical Engineering, Imperial College London, said:

“”Shutting down an engine in flight is uncommon, but it does happen occasionally and does not involve any significant risk to the aircraft or passengers. There is no reason to think there is any connection between the A380 event and the more recent one affecting the B747 except they are both Qantas and both have Rolls-Royce engines. This is a mixture of coincidence and the media being on the alert for events happening to both companies.””

Mr John Page, Senior Lecturer in Aerospace Engineering, University of New South Wales, said:

“”It’s not proper to turn this into a servicing issue without having the results of a full investigation. What’s much more significant is that this new aircraft was quite capable of coping with the failure – that’s why we have four engines, not one. The fact that it survived the damage is a credit to the design. Twenty years ago that would probably have taken the aircraft out of the sky. The big issue is the non-containment of the turbine blades – those blades should have been contained within the engine casing. The people leading the investigation are professional aerospace engineers rather than licensed aircraft maintenance engineers. The roles are often confused between the two.

“There’s very little world experience on A380 maintenance because they are only just starting to go in. Two years would be about the time you would expect with a long-haul aircraft between heavy maintenances.””

Dr Ranjan Vepa, Lecturer in Avionics, Queen Mary University of London, said:

“”It seems quite problematic to pinpoint the cause of the uncontained engine failure that took place on Qantas Flight QF32 after takeoff from Singapore’s Changi Airport en-route to Sydney. The aircraft turned back within 15 minutes. While the failure could have been triggered by one of three reasons, an external enabling event such as a bird strike, by improper maintenance or due to an engine failure, it does not appear to be related to the Indonesian volcano Mount Merapi’s eruptions over the island of Java. Yet one cannot discount the possibility of ash clouds travelling several hundreds of miles and being trapped in the atmosphere over the region south of Singapore and north of the Indonesian Batam island, and possibly triggering the uncontained engine failure. In fact the prevailing winds over Mount Merapi are currently North westerly and this has prompted Indonesian geologists to suggest that the volcanic ash could have reached Jakarta by November 3rd. Given that the southern tip of Batam Island is about the same distance from Mount Merapi as Jakarta, it is not impossible for the volcanic ash to have arrived at the point where the AIRBUS A380 turned back after experiencing the engine failure.

“The uncontained engine failure could also have been caused by a combination of circumstances which could have triggered a sequence of enabling events leading to the uncontained engine failure almost immediately after take-off. This naturally tends to make one suspect that the engine was probably hit by something that caused the engine inlet to be blocked which in turn could have triggered a sequence of events leading to the turbine trying to operate faster or even a “fire” within the combustion chamber.

“It is not entirely clear if the failure is related to the applicable Airworthiness Directive (AD) issued by European Aviation Safety Agency (EASA) (AD No.: 2010-0008R1 on Date: 04 August 2010). I feel it is best to await the verdict of the official investigators rather than try and quickly apportion the blame unfairly on AIRBUS, Rolls Royce or Qantas for snappy commercial reasons.”

This AD is detailed here:

Summary of the Airworthiness Directive
Source:
“In January, the European Aviation Safety Agency issued an airworthiness directive (AD) for the Trent 900 engine intermediate pressure (IP) shaft which, if not performed, could result in an uncontained engine failure similar to those that have affected a Trent 1000 Rolls Royce is developing for the Boeing 787. The AD says wear beyond normal limits had been identified on the abutment faces of the splines on the Trent 900 IP shaft rigid coupling on several engines during strip.
As the shaft-to-coupling spline interface provides the means of controlling the turbine axial setting, the wear through of the splines would permit the IP turbine to move rearward, the directive adds. This rearward movement would enable contact with static turbine components and would result in loss of engine performance with potential for in-flight shut down, oil migration and oil fire below the [low-pressure] turbine discs prior to sufficient indication resulting in loss of [low-pressure] turbine disc integrity.”

John Turton, Engineer, Institution of Engineering and Technology Aerospace Network, said:

“”From the initial reports it appears that this incident was caused by some kind of uncontained failure in the hot end of the engine. The underside cowling parts that were blown off are around the turbine area and there has been one piece of video looking out from the cabin that shows a radial puncture through the upper surface of the wing, apparently adjacent to the turbine section. This would indicate that there was considerable force involved in ejecting material from the engine in this location. A possible cause is an uncontained failure of a hot-end component. An authoritative answer will obviously need to await the manufacturer and airline investigations.””

Dr Thurai Rahulan, Lecturer in Aeronautics, University of Salford, said:

“”Detachment of the rear section of the nacelle and the damage to the wing should not have happened. Some of the scorch marks seem slightly upstream of the combustion chamber; if they are, that would be surprising and might indicate catastrophic failure in the compressor blade and/or casing. I am most impressed with the flight crew’s actions to recover back to Singapore and with passenger behaviour during deplaning.””

Jeff Jupp, Fellow of the Royal Academy of Engineering, Retired technical director of Airbus UK, said:

“”I would not want to speculate on what caused the engine failure on the information currently available. It is routine procedure to use or dump fuel until the aircraft weight is reduced to a safe value for landing (as long as there is no immediate danger) and all large passenger aircraft are certificated for safe operation following an engine failure.””

Stewart John, Fellow of the Royal Academy of Engineering, Former President of the Royal Aeronautical Society, said:

“”We will not have a proper idea of the cause of this incident until the damaged engine has been inspected – until then it’s all speculation. We do know that the engine has sustained severe damage but we need to establish whether it was an uncontained engine failure, which would be of great concern, or foreign object damage.

“The exact time at which this happened during the flight is of crucial importance to establishing the nature of the incident. Qantas have taken the correct precipitative action in grounding further flights until the cause is known.””

Science Media Centre Timeline: Airbus A380 1991 – Airbus begins talks with several international carriers about the possibility of developing a very large-capacity jumbo jet, originally as a response to Boeing’s 747, leading to the development of the A3XX project 1994 – official launch of the A3XX development programme; engineering and design begins 2000 – commercial launch of the A3XX project, later to become the A380. First orders placed. Airbus beings developing the huge infrastructure required to manufacture the planes January 2002 – aircraft begins production February 2004 – first engines delivered by Rolls-Royce to the Airbus factory in southern France April 2004 – major redevelopment begins at Heathrow to enable it to accommodate the A380 January 2005 – the first completed A380 is unveiled April 2005 – first test flight takes place from Blagnac Airport in Toulouse, in the south of France January 2006 – A380 makes its first transatlantic flight, to Medellin, Colombia September 2006 – first flight with passengers October 2007 – first completed A380 delivered to Singapore airlines. A380 enters commercial service with flight from Singapore to Sydney March 2008 – Singapore Airlines begins scheduled A380 flights between Singapore and London September 2008 – first A380 delivered to Qantas October 2008 – first Qantas A380 flight, from Melbourne to Los Angeles
Sources/further information Page on FlightGlobal.com, including overview, history and technical specifications http://www.flightglobal.com/articles/2007/02/27/205274/everything-about-the-airbus-a380.html#Overview How the Airbus A380 works – HowStuffWorks.com http://science.howstuffworks.com/transport/flight/modern/a380.htm Official Airbus A380 site http://www.airbus.com/en/aircraftfamilies/a380/ Timeline from BBC – only up to 2007 http://news.bbc.co.uk/1/hi/business/4182641.stm Factfile from BBC http://www.bbc.co.uk/news/uk-11693164 More detailed technical information at Aerospacetechnology.com – http://www.aerospace-technology.com/projects/a380/ This is a fact sheet issued by the Science Media Centre to provide background information on science topics relevant to breaking news stories. This is not intended as the ‘last word’ on a subject, but rather a summary of the basics and a pointer towards sources of more detailed information. These can be read as supplements to our ‘round-up’ press releases. For more information about our fact sheets, please contact Will Greenacre at the Science Media Centre on 0207 670 2933 or email wgreenacre@ri.ac.uk