JAS grounds planes
Few Cloudy
I fail to see any linkage with your mixed facts and postulations.
The SAS certainly was not a cold soaked fuel problem since it was the first flight of the day following freezing precip overnight.
I can see no linkage between your soft/ice/slush SB and nicks and scractches in a compressor.
As I understand the JAS situation it was not a fleet wide grounding involving non-suspect aircraft but only limited to aircraft that had a specfic mainetnance history (parts and SBs).
I fail to see any linkage with your mixed facts and postulations.
The SAS certainly was not a cold soaked fuel problem since it was the first flight of the day following freezing precip overnight.
I can see no linkage between your soft/ice/slush SB and nicks and scractches in a compressor.
As I understand the JAS situation it was not a fleet wide grounding involving non-suspect aircraft but only limited to aircraft that had a specfic mainetnance history (parts and SBs).
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Specifics
Hello lomapaseo,
If the whole fleet hasn't been "grounded" - the word used in the title to this thread - that is a good thing.
The linkage you say that you can't understand isn't mine. The technical cause and effect of compressor damage - catastrophic or ongoing on PW engines at the back end of MD-80 series aircraft - including the "soft ice" problem, is documented in MDC and PW bulletins over the past years.
You maybe right about the cause of the ice on the SAS machine not being cold soak related. Nevertheless, deicing in the morning failed to shift the surface layer of ice and it is well possible that it formed as a result of cold soak (I don't know where the flight originated the evening before) and was subsequently disguised by later ppn.
It doesn't matter why the ice formed, of course - main thing is to make sure it is off the wing before TO. Fuel tank surface ice is the classic - well illustrated in a Finnair photo of a huge thick cake of ice being removed from an MD-80 after it had been on the ground for several hours and moved into a hangar if memory serves right.
Overnight icing can clearly be due to many causes including the freezing PPN you refer to on the night in question. Winter ops does occur in FUK on occasion. It is not dealt with as efficiently there, as in the north, where it regularly occurs. But I don't want to speculate - same thing happens when you get snow in Rome, compared to Copenhagen.
Other FOD ingestion is also a blade damager. The engines are right behind the mainwheels on the MD-80 and experience in one European airline shows that regular flights to poorly maintained runways or taxyways often show up in blade nicking. The field in question was Tirana in Albania a while back but it has also showed up at "good" airfields where work was in progress and debris not properly cleared, as well as Scandinavian fields where runway surface ice has cracked loose. The cautious use of reverse (not above idle unless needed) also reduces the static circulation effect at lower speeds - a known cause of MD-80 FOD ingestion. It is why the reverse buckets were "canted" in the evolution from the DC-9 series.
It's just background info. however. Let us see what the boffins find out...
If the whole fleet hasn't been "grounded" - the word used in the title to this thread - that is a good thing.
The linkage you say that you can't understand isn't mine. The technical cause and effect of compressor damage - catastrophic or ongoing on PW engines at the back end of MD-80 series aircraft - including the "soft ice" problem, is documented in MDC and PW bulletins over the past years.
You maybe right about the cause of the ice on the SAS machine not being cold soak related. Nevertheless, deicing in the morning failed to shift the surface layer of ice and it is well possible that it formed as a result of cold soak (I don't know where the flight originated the evening before) and was subsequently disguised by later ppn.
It doesn't matter why the ice formed, of course - main thing is to make sure it is off the wing before TO. Fuel tank surface ice is the classic - well illustrated in a Finnair photo of a huge thick cake of ice being removed from an MD-80 after it had been on the ground for several hours and moved into a hangar if memory serves right.
Overnight icing can clearly be due to many causes including the freezing PPN you refer to on the night in question. Winter ops does occur in FUK on occasion. It is not dealt with as efficiently there, as in the north, where it regularly occurs. But I don't want to speculate - same thing happens when you get snow in Rome, compared to Copenhagen.
Other FOD ingestion is also a blade damager. The engines are right behind the mainwheels on the MD-80 and experience in one European airline shows that regular flights to poorly maintained runways or taxyways often show up in blade nicking. The field in question was Tirana in Albania a while back but it has also showed up at "good" airfields where work was in progress and debris not properly cleared, as well as Scandinavian fields where runway surface ice has cracked loose. The cautious use of reverse (not above idle unless needed) also reduces the static circulation effect at lower speeds - a known cause of MD-80 FOD ingestion. It is why the reverse buckets were "canted" in the evolution from the DC-9 series.
It's just background info. however. Let us see what the boffins find out...
Last edited by Few Cloudy; 4th Feb 2004 at 23:31.
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Update
Ministry of Land, Infrastructure and Transport of Japan has made an announcement regarding JAS MD-81/87 engine incident. The announcement indicated that only those engines which received a maintenance repair on stator fins showed cracks on stator fins.
Stator fins are welded onto a metal plate in a compressor. However, on JT8D-217A/C engines it is possible to develop a gap between a metal plate and a stator fin after about four years of use. The manual written by Pratt & Whitney indicates that a stator fin parts to be replaced with a new one or repaired after certain time interval. JAS contracts this specific stator fin maintenance to a subsidiary company of Pratt & Whitney in Singapore.
The investigation so far showed that only those engines which received a stator fin maintenance at Singapore showed cracks on a stator fin.
Ministry of Land, Infrastructure and Transport of Japan has made an announcement regarding JAS MD-81/87 engine incident. The announcement indicated that only those engines which received a maintenance repair on stator fins showed cracks on stator fins.
Stator fins are welded onto a metal plate in a compressor. However, on JT8D-217A/C engines it is possible to develop a gap between a metal plate and a stator fin after about four years of use. The manual written by Pratt & Whitney indicates that a stator fin parts to be replaced with a new one or repaired after certain time interval. JAS contracts this specific stator fin maintenance to a subsidiary company of Pratt & Whitney in Singapore.
The investigation so far showed that only those engines which received a stator fin maintenance at Singapore showed cracks on a stator fin.
