Nacelle fins?
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Spinash,
It is all thoroughly good fun, is it not ?
At the moment I am only going on your brief description, although I will have a look at the nacelles when I get an opportunity. Until I see the size and position on the nacelle of the devices, I can only talk in very general terms.
One needs to keep in mind that there is a range of problems which these sorts of things are intended to minimise or otherwise control. For instance, it may be that this fix is simply one of effecting a clean separation to avoid Karman-type shed vortex excitation of the empennage structure. I don't incline to an OEI problem being involved. Ventral test fix fins usually are fitted to provide a defacto increase in the fin area to improve directional characteristics. Unless your devices are fitted underneath and are of a reasonable size, I wouldn't expect that this is their purpose.
And let us hope that QF grows the organisation into a significant longterm player in the Oz marketplace.
I presume, of course, that there is no specific detail in your engineering notes or AOM on the devices ? - ie you aren't just stirring the pot here, are you ?
Zeke,
We crossed paths. The AFM won't have any CG/stall variation - like most certification matters, the end document shows only the final data outcome, not the detail which contributed to it. The problem with rule status is that a current rule may be of no relevance to an older, existing type - so one has to be careful with reading something into an aircraft which might not be there - hence the need always to check the TCDS and dig out an appropriate archive copy of the rules - and even then, you can't be 100 percent sure that a variation deal wasn't done in respect of the particular matter of interest. So far as anciliary data is concerned, its importance lies in the regulator's accepting that set of interpretations so, to some extent, they become the defacto rules.
I suspect that we could have a most enjoyable and interesting beer some time ...... you sound like a stressman ?
[This message has been edited by john_tullamarine (edited 23 May 2001).]
It is all thoroughly good fun, is it not ?
At the moment I am only going on your brief description, although I will have a look at the nacelles when I get an opportunity. Until I see the size and position on the nacelle of the devices, I can only talk in very general terms.
One needs to keep in mind that there is a range of problems which these sorts of things are intended to minimise or otherwise control. For instance, it may be that this fix is simply one of effecting a clean separation to avoid Karman-type shed vortex excitation of the empennage structure. I don't incline to an OEI problem being involved. Ventral test fix fins usually are fitted to provide a defacto increase in the fin area to improve directional characteristics. Unless your devices are fitted underneath and are of a reasonable size, I wouldn't expect that this is their purpose.
And let us hope that QF grows the organisation into a significant longterm player in the Oz marketplace.
I presume, of course, that there is no specific detail in your engineering notes or AOM on the devices ? - ie you aren't just stirring the pot here, are you ?
Zeke,
We crossed paths. The AFM won't have any CG/stall variation - like most certification matters, the end document shows only the final data outcome, not the detail which contributed to it. The problem with rule status is that a current rule may be of no relevance to an older, existing type - so one has to be careful with reading something into an aircraft which might not be there - hence the need always to check the TCDS and dig out an appropriate archive copy of the rules - and even then, you can't be 100 percent sure that a variation deal wasn't done in respect of the particular matter of interest. So far as anciliary data is concerned, its importance lies in the regulator's accepting that set of interpretations so, to some extent, they become the defacto rules.
I suspect that we could have a most enjoyable and interesting beer some time ...... you sound like a stressman ?
[This message has been edited by john_tullamarine (edited 23 May 2001).]
Guest
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John,
No Sir, I am not just stirring the pot! The day that I had the VG missing was one of the last times I flew last week. Prior to this day I had never considered the effect of not having such a device. I have not been to work since and therefore have not had the opportunity to investigate further with our engineers (should they still be employed (I hope they are)). The FCOM's I have at home are so unbelievably vague, I am lucky to have them detail far more important items of the aircraft. I am beginning to wonder if they want us to know very much about the aircraft at all !!
I look forward to hearing more after you have had the opportunity to look at them.
Zeke, On the 1900, I was of the belief that the tailets (the small horizontal fins) were the reason for the wide CoG, not the much larger ventral fins (at least that’s what it said in the book) but I concede that they probably all work together to perform many different functions in controllability/CoG Range/aerodynamics etc.
If what john said was true about designers not knowing if their test aircraft would come back or not, I would not like to have been near the Raytheon factory when the stuck a B200 tail on the 1900 along with a bunch of other fancy looking devices, for the first time. Blind luck I reckon!!
Cheers
No Sir, I am not just stirring the pot! The day that I had the VG missing was one of the last times I flew last week. Prior to this day I had never considered the effect of not having such a device. I have not been to work since and therefore have not had the opportunity to investigate further with our engineers (should they still be employed (I hope they are)). The FCOM's I have at home are so unbelievably vague, I am lucky to have them detail far more important items of the aircraft. I am beginning to wonder if they want us to know very much about the aircraft at all !!
I look forward to hearing more after you have had the opportunity to look at them.
Zeke, On the 1900, I was of the belief that the tailets (the small horizontal fins) were the reason for the wide CoG, not the much larger ventral fins (at least that’s what it said in the book) but I concede that they probably all work together to perform many different functions in controllability/CoG Range/aerodynamics etc.
If what john said was true about designers not knowing if their test aircraft would come back or not, I would not like to have been near the Raytheon factory when the stuck a B200 tail on the 1900 along with a bunch of other fancy looking devices, for the first time. Blind luck I reckon!!
Cheers
Guest
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Spinash,
That's OK .. some people like to stir things up to see what reactions result.
The question of what significance is represented by missing VGs is a matter for the MMEL - only the manufacturer has the full story. Problems arise when airline personnel make invalid assumptions on these and other MEL issues and inadvertently expose the operation to unplanned risk. I made reference earlier to a missing nacelle VG - the aircraft concerned flew around your patch for some days before it was caught up with and the situation corrected. Caused the airworthiness chaps quite some considerable concern.
'Twas Zeke's comment. However, events sometimes do get out of hand if test and development programs are not fairly rigorous in their safety management and planning. I recall one flight test which rapidly ended in disaster (multiple fatalities and very serious injuries) following an ill considered mod intended to be a workaround for a particular problem. Probably a more conservative TP might have opted for a different recovery and possibly got away with it - guess we will never know.
Also it is prudent to treat some informative details in manufacturers' documents with a grain of salt on occasion. Often, a design deficiency workaround will be presented as a marketing advantage - true ...
That's OK .. some people like to stir things up to see what reactions result.
The question of what significance is represented by missing VGs is a matter for the MMEL - only the manufacturer has the full story. Problems arise when airline personnel make invalid assumptions on these and other MEL issues and inadvertently expose the operation to unplanned risk. I made reference earlier to a missing nacelle VG - the aircraft concerned flew around your patch for some days before it was caught up with and the situation corrected. Caused the airworthiness chaps quite some considerable concern.
'Twas Zeke's comment. However, events sometimes do get out of hand if test and development programs are not fairly rigorous in their safety management and planning. I recall one flight test which rapidly ended in disaster (multiple fatalities and very serious injuries) following an ill considered mod intended to be a workaround for a particular problem. Probably a more conservative TP might have opted for a different recovery and possibly got away with it - guess we will never know.
Also it is prudent to treat some informative details in manufacturers' documents with a grain of salt on occasion. Often, a design deficiency workaround will be presented as a marketing advantage - true ...
Guest
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Spinash,
Had a chance to look at the 717 nacelle devices. Their position is, I think, a little too low to provide just for clean separation. My guess is that they generate a vortex which curls up and around the nacelle to delay separation at higher alpha. It would take a response from someone at Douglas to put this one to bed.
Then again, with tongue in cheek ...perhaps they are there just to keep the rain off the ground engineers working under the nacelles ?
Had a chance to look at the 717 nacelle devices. Their position is, I think, a little too low to provide just for clean separation. My guess is that they generate a vortex which curls up and around the nacelle to delay separation at higher alpha. It would take a response from someone at Douglas to put this one to bed.
Then again, with tongue in cheek ...perhaps they are there just to keep the rain off the ground engineers working under the nacelles ?
Guest
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Gentlemen
Might I commend you to this link for a concise explanation of the naccelle chine.
http://www.smartcockpit.com/operatio...Generators.PDF
Might I commend you to this link for a concise explanation of the naccelle chine.
http://www.smartcockpit.com/operatio...Generators.PDF
Guest
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A great visible vortex peeling off a 777 nacelle chine:
http://www.airliners.net/open.file?id=155745
http://www.airliners.net/open.file?id=155745
Guest
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Just one point of clarification, as some readers may wonder how the vortex, apparently so tiny, can interact with the main flow so effectively.
The photographs (and aren't they rather lovely) only show the central core of the vortex. As the temperature drops with radially reducing pressure this results in dewpoint temperature occuring at some radius under the conditions in which the photos were taken. Within the resulting core, condensation is visible.
The actual vortex is somewhat larger in diameter than that apparently seen in the photos.
The photographs (and aren't they rather lovely) only show the central core of the vortex. As the temperature drops with radially reducing pressure this results in dewpoint temperature occuring at some radius under the conditions in which the photos were taken. Within the resulting core, condensation is visible.
The actual vortex is somewhat larger in diameter than that apparently seen in the photos.
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This might be a simplistic point of view.....but.....
I kind of like seeing vortex generators on an aeroplane. It gives me the feeling that it has been properly test flown and they've found a couple of small problems at the edge of the envelope and done something about it.
A330 has a very clean wing....don't like that.
Perhaps it's to do with having a teddy bear as a kid.
I kind of like seeing vortex generators on an aeroplane. It gives me the feeling that it has been properly test flown and they've found a couple of small problems at the edge of the envelope and done something about it.
A330 has a very clean wing....don't like that.
Perhaps it's to do with having a teddy bear as a kid.
