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Old 26th Feb 2009, 16:36
  #422 (permalink)  
Lost in Saigon
 
Join Date: Jul 2004
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Originally Posted by Magplug
Look at these pictures of the BA777 crash at LHR.
www.flightglobal.com

As you can see from the first picture the first stage turbine blades are sheared off at around half of the length of their radius. This was because they were rotating at some speed when the impact occurred. The engine nacelle was forced onto the rotating blades causing almost identical damage to all the blades as they turned and they have all fractured at a similar radial length. The engine therefore must have been rotating and producing at least some thrust on impact.

Look now at the second image of the other engine and you will see that the turbine blades are all intact even though the nacelle has hit the ground quite hard and scooped in a lot of dirt in the process. This engine was not rotating at impact and therefore could not have been producing any thrust.

As is also witnessed by the BA incident, a total loss of thrust below 1000' can be brought so a safe outcome given favourable terrain.
As I recall, both engines were operating, but they did not produce commanded thrust.

The article you linked to is very old and appears to be in error.

Initial report update, 24 January 2008

The engines did not shut down and both engines continued to produce thrust at an engine speed above flight idle, but less than the commanded thrust.

Last edited by Lost in Saigon; 26th Feb 2009 at 17:02.
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