A very few words from R-R
Four days ago I concluded that there had been an oil fire in the incident on 4 November. I had not seen the press release of the previous day, Monday 8 November 2010. This is an extract.
“… Rolls-Royce has made progress in understanding the cause of the engine failure on the Trent 900 powered A380 Qantas flight QF32 on 4 November 2010. It is now clear this incident is specific to the Trent 900 engine.
As a result, a series of checks and inspections has been agreed with Airbus, with operators of the Trent 900 powered A380 and with the airworthiness authorities. These are being progressively completed which is allowing a resumption of operation of aircraft in full compliance with all safety standards. We are working in close cooperation with Airbus, our customers and the authorities, and as always safety remains our highest priority.
… The Trent 900 incident is the first of its kind to occur on a large civil Rolls-Royce engine since 1994. Since then Rolls-Royce has accumulated 142 million hours of flight on Trent and RB211 engines. …”
Then there was another press release yesterday, 12 November 2010 and this is an extract which is the only engineering statement.
“…. Immediately following this incident a regime of engine checks was introduced on the Trent 900s to understand the cause and to ensure safe operation. These have been conducted in parallel with a rigorous examination of all available evidence, including data from the damaged engine and its monitoring system, analysis of recovered material and interrogation of the fleet history.
These investigations have led Rolls-Royce to draw two key conclusions. First, as previously announced, the issue is specific to the Trent 900. Second, the failure was confined to a specific component in the turbine area of the engine. This caused an oil fire, which led to the release of the intermediate pressure turbine disc. …
Safety continues to be Rolls-Royce’s highest priority.”
Now those will be – I expect, the only and last words from the engineers to the general public.
Oil fires are a great fear of aircraft engineers. The oil is a more or less flammable liquid that is being pumped throughout the internals of the engine even close to the hottest parts. Here the failure of some component has resulted in the oil fire. The engineers probably had to look at and rule out or rule in over a hundred possible causes. As it is confined to the Trent 900 it seems less likely to have been an elastomeric oil seal than a failure of some component that contained oil. RR have said above that the fire ‘led to the release of the intermediate pressure turbine disc’
The word ‘release’ seems to be a very carefully chosen word that is, perhaps intentionally, slightly vague. The consequent fire may have destroyed and ‘released’ the highly stressed turbine disc into fragments. These could have burst centrifugally out of the engine and might have damaged the rest of the aircraft.
I think that there is a more likely alternative. That would have been the fire destroying by overheating the connection between the turbine and the compressor that it was driving. This could have resulted in relatively few fragments if any.