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FAA Grounds Certain 777-200s Following Incident in Denver
Following yesterday's incident, where a United Airlines Boeing 777 suffered an engine failure after departure from Honolulu, the FAA declared that all Boeing 777s equipped with Pratt & Whitney PW4070 engines would be grounded until further notice. This would allow for a more thorough investigation in the matter whilst ensuring the safety of passengers on these aircraft. (theexplorerblog.com) Más...Sort type: [Top] [Newest]
The PW4000 series engine is used on many other aircraft: B747-400, B767, KC-46, MD-11, A300, A310 & A330. Why is the FAA only grounding B777s?
The 777 version of the engine has a unique blade design not shared with other variants of the engine.
What is/are the advantage(s) of hollow blades over solid blades ?
It seems to me that solid blades would be far more robust, easier to manufacture and visibly inspect than hollow blades. A solid blade with the same exterior dimensions as a hollow blade is more substantial. In a hollow blade a surface defect such as a crack might form on the inside void and thus not be detectable without sonic equipment but a similar surface defect would be visible on the exterior of a solid blade.
It seems to me that solid blades would be far more robust, easier to manufacture and visibly inspect than hollow blades. A solid blade with the same exterior dimensions as a hollow blade is more substantial. In a hollow blade a surface defect such as a crack might form on the inside void and thus not be detectable without sonic equipment but a similar surface defect would be visible on the exterior of a solid blade.
Weight. The hollow blades weigh over 30 pounds each. Heavier solid blades would put added stress on the root area of the blade and the blade attach area of the hub, which would then require those areas to be reinforced, which equals even more weight. Even solid blade can develop subsurface cracks which are not visually detectable.
Thanks. Reducing weight (Torsten Hoff said "mass", the same thing) seems to make a lot of sense especially to reduce the centrifugal force on the hub attachment. I hadn't realised the blades weighed as much as 30 lbs each.
Looking at the photographs it appeared that either a leading fan blade or an initial compressor stage blade had broken.
I initially thought the hollow blade was for cooling, and I could understand that for later stages where air was heated under compression or, more especially, for the turbine blades. But for the fan, or initial compressor blades, cooling didn't make sense to me. I felt that at the initial stages the airflow over the blades would be at ambient temperature and even after the air had passed the initial compression stages I can't imagine there would be so much of a heat increase as to require special cooling of the blade internals.
I could also imagine channels being designed in such a way as to induce uniform heat expansion of the blade material thus maintain the same blade profile. But again this would be more applicable to the later stages, especially the turbines.
So thanks both Torsten and Ffrcobra1 for taking the time to explain, I can well understand Mass/Weight reduction.
Looking at the photographs it appeared that either a leading fan blade or an initial compressor stage blade had broken.
I initially thought the hollow blade was for cooling, and I could understand that for later stages where air was heated under compression or, more especially, for the turbine blades. But for the fan, or initial compressor blades, cooling didn't make sense to me. I felt that at the initial stages the airflow over the blades would be at ambient temperature and even after the air had passed the initial compression stages I can't imagine there would be so much of a heat increase as to require special cooling of the blade internals.
I could also imagine channels being designed in such a way as to induce uniform heat expansion of the blade material thus maintain the same blade profile. But again this would be more applicable to the later stages, especially the turbines.
So thanks both Torsten and Ffrcobra1 for taking the time to explain, I can well understand Mass/Weight reduction.
Actually, weight and mass are not the same. Mass is the same regardless of gravity. Weight is the product of mass multiplied by the acceleration due to gravity.
I've never been able to grasp the difference until reading this. TYVM!
I believe there was a guy who postulated that mass multiplied by acceleration equals force.
Glad I had knowledge that was actually useful. That doesn’t happen often.
There has been mention of previous blade problems on this model engine. It is amazing that the pics of the front of the engine from the 2018 incident in Hawaii are almost indistinguishable from the pics of the plane in DEN yesterday. Here’s a link to the report and pics of the 2018 event. It’s like deja vu all over again.
https://data.ntsb.gov/Docket/?NTSBNumber=DCA18IA092
There has been mention of previous blade problems on this model engine. It is amazing that the pics of the front of the engine from the 2018 incident in Hawaii are almost indistinguishable from the pics of the plane in DEN yesterday. Here’s a link to the report and pics of the 2018 event. It’s like deja vu all over again.
https://data.ntsb.gov/Docket/?NTSBNumber=DCA18IA092
As stated elsewhere, concern is about the ones with hollow blades