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Old 9th Nov 2010, 10:22
  #42 (permalink)  
Bizman
 
Join Date: Mar 1999
Location: Australia
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Why is QF still grounded while LH & SQ are flying?

Derg:

"This engine is only used on the Qantas machines. So over the four units an extra 8,000lbs of thrust is available. Reason: 15 hr flight to Melbourne at max weights."

I get that, but surely this only applies for takeoff and the 25 minutes or so to climb to initial cruise altitude. Thereafter, won't almost the same thrust be required to maintain same LRC or higher as it would for SQ or LH with the 970 Trent?

Okay, a little higher weight, so a little more thrust required initially to maintain same altitude at same speed, but at cruise altitude, the thrust difference isn't 2,000 lbs per engine, more likely only 200 lbs per engine for the next 14 and half hours.

I understand the opportunity for harmonic vibration, both mechanical and aerodynamic through the engine, at higher thrust ratings, but again, I don't see how SQ could assume all these factors after the initial failure in QF32. Surely, initially, no-one knew why #2 in QF32 let go. So how come SQ was back in the air after 12 reluctant hours of checks, while QF was still grounded?

What is even more disturbing for me, is that SQ had already had one total IFSD of a Trent 900 on their A380 and is believed to have prematurely removed from wing and changed over a dozen engines on their fleet. They must know the engine is far from mature, particularly in the hot section, and there are still design issues in the hot section that are far from reaching the "bucket" level of a mature MTBF. Every new event like QF32's must surely be cause to sit back and ask yourself what is it that we don't know about what we don't know?
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