Sikorsky S-92: From Design to Operations
There was a recent test programme to expand the envelope, but for various reasons it was felt safer to leave it at 45 kts. Have the Coast Guard boys invested in a large moveable wall yet?
To Nicklappos re Air-stair Door redesign
Nick:
I hear from someone who participates in the weekly Sikorsky video brief that they are working on a complete redesign of the Air-stair door
- perhaps they can move the suspension cable and support bar to the FWD side of the door vs. the aft. The darn support bar is always banging the passenger in the fwd right hand seat in the knee when you close the door.
This is especially true if an overenthusiastic HLO is "helping". Small thing, perhaps, but why not do it right. I can not see it being overly difficult but could well be wrong, I often am. Would chain be better than cable?
Also slightly more powerful pistons on the upper section would be nice. When doing a rotors running turn around the down force on the door is enough to partially overpower the pistons. Crosswinds from the Starbord side do not help. Not a big problem for we "tall, strong and stupid" types but a difficulty for the vertically challenged.
Anyone else have comments on the air-stair door?
Thanks by the way Nick for all your commentary and insight.
I hear from someone who participates in the weekly Sikorsky video brief that they are working on a complete redesign of the Air-stair door
- perhaps they can move the suspension cable and support bar to the FWD side of the door vs. the aft. The darn support bar is always banging the passenger in the fwd right hand seat in the knee when you close the door.This is especially true if an overenthusiastic HLO is "helping". Small thing, perhaps, but why not do it right. I can not see it being overly difficult but could well be wrong, I often am. Would chain be better than cable?
Also slightly more powerful pistons on the upper section would be nice. When doing a rotors running turn around the down force on the door is enough to partially overpower the pistons. Crosswinds from the Starbord side do not help. Not a big problem for we "tall, strong and stupid" types but a difficulty for the vertically challenged.
Anyone else have comments on the air-stair door?
Thanks by the way Nick for all your commentary and insight.
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Rich?
Yeah in many ways 
.........
In the east richness comes in many different varieties not just those so highly valued in the western hemisphere.
Never mind!
So if a company was to make an investment in machines and manpower and needed to spend a little under 90 mill USD on 5 helicopters which craft would Albatross and Doc tend the company towards? And for what reasons? Is the type of support that would be required from the manufacturer beyond the usual type courses / ground school and spares packages taken into consideration? There is indeed a difference on what is on offer regarding further training / sim and continued background and front line support between the 3 main manufacturers. Again need to look more carefully to the future for other reasons as not everything can be forecast from the past.
Anyway back to the speculation (which used carefully can decide important issues not least character).
Doc, is this correct? "It is inevitable that one will see many of these cautions during the course of normal flight schedules."
I would not be blessed to have such a helicopter! Is it really normal to have so many of these cautions?
I have read all the pages dealing with the S92, EC225, and AW139 and find so many differences, not least all the technical problems on each type and how the pilots enjoy or not flying each helicopter.
So if you want to take my richness Mr's A & D is there a new problem this time? Or is it one that has occured in the previous pages?
Oh Doc, I find you also very entertaining, but so I shall await further real facts that are so lightly dispersed from the non-entertainers. Maybe I should be waiting on the street?
.........In the east richness comes in many different varieties not just those so highly valued in the western hemisphere.
Never mind!
So if a company was to make an investment in machines and manpower and needed to spend a little under 90 mill USD on 5 helicopters which craft would Albatross and Doc tend the company towards? And for what reasons? Is the type of support that would be required from the manufacturer beyond the usual type courses / ground school and spares packages taken into consideration? There is indeed a difference on what is on offer regarding further training / sim and continued background and front line support between the 3 main manufacturers. Again need to look more carefully to the future for other reasons as not everything can be forecast from the past.
Anyway back to the speculation (which used carefully can decide important issues not least character).
Doc, is this correct? "It is inevitable that one will see many of these cautions during the course of normal flight schedules."
I would not be blessed to have such a helicopter! Is it really normal to have so many of these cautions?
I have read all the pages dealing with the S92, EC225, and AW139 and find so many differences, not least all the technical problems on each type and how the pilots enjoy or not flying each helicopter.
So if you want to take my richness Mr's A & D is there a new problem this time? Or is it one that has occured in the previous pages?
Oh Doc, I find you also very entertaining, but so I shall await further real facts that are so lightly dispersed from the non-entertainers. Maybe I should be waiting on the street?
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Albatross,
I know that Sikorsky have been investigating Air-stair door mods. We have had a couple crack (on the Fwd shoulder of the Fwd hinge). There is speculation that this may be cycle related, as we do many short hops rather than long sectors. Better engineers than I have suggested there should be another dampened strut on the aft end of the door, to even out the loads during opening. We have the sliding upper door, so no problem with the downwash buffeting that you experience (though I did see that problem whilst flying the CHC 92 in Abz).
Fat,
I accept any currency, even spiritual ones!
Egads - you ask too many questions in one go!
As to the first:
I could opt for the older types that I have flown and loved, but I guess one has to move with the times... If you're limiting it to 90 mil, maybe the 225 will be out of the question, although the 225, S92 and 139 would be the only realistic options. I would obviously prefer a hybrid of the three - taking the best of each, they all have their own winning features and Achilles heel. As I have only flown the 92 from the list, I am not best placed to compare.
As for Cautions: It is almost inevitable that one will see a 'AFCS degrade' caution on most flights - though a Caution, it (mostly) does not have huge implications and is normally easily reset. There are some others of an almost equally benign nature, benign because of the high level of redundancy.
To the last: the factual information contained in a few earlier posts, are just that; the best information at present. The relevant components will be stripped and tested. An open and honest finding will be released by a very competent team of investigators/engineers.
Cheers,
Doc
I know that Sikorsky have been investigating Air-stair door mods. We have had a couple crack (on the Fwd shoulder of the Fwd hinge). There is speculation that this may be cycle related, as we do many short hops rather than long sectors. Better engineers than I have suggested there should be another dampened strut on the aft end of the door, to even out the loads during opening. We have the sliding upper door, so no problem with the downwash buffeting that you experience (though I did see that problem whilst flying the CHC 92 in Abz).
Fat,
I accept any currency, even spiritual ones!
Egads - you ask too many questions in one go!
As to the first:
So if a company was to make an investment in machines and manpower and needed to spend a little under 90 mill USD on 5 helicopters which craft would Albatross and Doc tend the company towards?
As for Cautions: It is almost inevitable that one will see a 'AFCS degrade' caution on most flights - though a Caution, it (mostly) does not have huge implications and is normally easily reset. There are some others of an almost equally benign nature, benign because of the high level of redundancy.
To the last: the factual information contained in a few earlier posts, are just that; the best information at present. The relevant components will be stripped and tested. An open and honest finding will be released by a very competent team of investigators/engineers.
Cheers,
Doc
Nick,
I actual do know about helicopters. My premise was based on:
Quote from an AHS paper from 2003 authored by an AMCOM PHD:
"The H-60 main transmission employs a 5-planet epicyclic gear train. Recent inspections of two Army UH-60A Blackhawk main transmissions, initiated by indications of low or fluctuating oil pressure, revealed a crack in the planetary carriers."
Now if this can occur one can theorize that it is possible that debris from an undetected planetary failure could cascasde to take out accessories and light off all of the chip detectors. This would make for a very nasty day.
It will be interesting to see what the HUMS data shows in the days/hours leading up to the event, especially that I believe the CAA relies on the HUMS as a mitigation to offset S-92 transmission design concerns.
The Sultan
I actual do know about helicopters. My premise was based on:
Quote from an AHS paper from 2003 authored by an AMCOM PHD:
"The H-60 main transmission employs a 5-planet epicyclic gear train. Recent inspections of two Army UH-60A Blackhawk main transmissions, initiated by indications of low or fluctuating oil pressure, revealed a crack in the planetary carriers."
Now if this can occur one can theorize that it is possible that debris from an undetected planetary failure could cascasde to take out accessories and light off all of the chip detectors. This would make for a very nasty day.
It will be interesting to see what the HUMS data shows in the days/hours leading up to the event, especially that I believe the CAA relies on the HUMS as a mitigation to offset S-92 transmission design concerns.
The Sultan
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The Sultan might know something about helicopters, but he knows nothing about the S92, and even less about this incident.
The pilot of the incident has told him so, and now I have, twice.
The stupid slurs that he "believes" are not true, and even less knowledge based.
The pilot of the incident has told him so, and now I have, twice.
The stupid slurs that he "believes" are not true, and even less knowledge based.
It will be interesting to see what the HUMS data shows in the days/hours leading up to the event, especially that I believe the CAA relies on the HUMS as a mitigation to offset S-92 transmission design concerns.
Oh, sorry, that was wrong: in fact there were no indications on HUMS either prior, during or post the incident. Actually, there were no chips either, until the last few moments. The bulk of the chip cautions were as a result of the dual CHIP/TEMP switch function of the chip detectors, showing hot (V. Hot!) oil, although we didn't know that at the time (Dave couldn't be arsed to consult the System Status pages!
)It will all come out in the wash soon, hopefully by the time of HAI.
"Well, obviously, there was a trend of increasing vibrations and other general indications of gear failure, but we took no heed of them as we knew they were spurious. Now they will prove invaluable in the investigation."
212man - You break me up - FUNNY!
Sultan:
I think I see where you are coming from but think it is a huge leap of logic from a 2003 paper by an AMCOM PHD concerning the AH-60 to a S-92 problem in 2008.
Just curious but are the UH-60s still having the same planetary failures or were they isolated incidents?
Still this is a "Rumours" network so everybody is entitled to an opinion or theory.
Now if we can just all play nice all will be well.
ANYBODY - Any other comments on the airstair door redesign?
212man - You break me up - FUNNY!
Sultan:
I think I see where you are coming from but think it is a huge leap of logic from a 2003 paper by an AMCOM PHD concerning the AH-60 to a S-92 problem in 2008.
Just curious but are the UH-60s still having the same planetary failures or were they isolated incidents?
Still this is a "Rumours" network so everybody is entitled to an opinion or theory.
Now if we can just all play nice all will be well.
ANYBODY - Any other comments on the airstair door redesign?
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albatross,
While I agree that "rumors" have a place, slurs do not, and frankly, The Sultan might take the cake on this one.
I know the history of the Black hawk intimately, and there is no history of planetary failures (the few cracks on Black Hawk planetary carriers were benign ones), yet Sultan actually got you to ask, "Just curious but are the UH-60s still having the same planetary failures or were they isolated incidents?"
That is the way it works, if you are as good as Sultan at it. He got you to ask, "When did the S92 stop beating its wife?" He talks without any real knowledge, describes a mythical failure mode , assigns it to a helicopter he doesn't like, and then gets to public to describe it back to him for erudite comment. Good public relations trick.
As 212man has said, the problem with the S92 that he flew was in input module that got hot, really hot. The input module is about 4 feet from the planetary section, and totally unrelated. So not only have their been no planetary failures , but the precautionary landing that now consumes this thread (rightly so) is not a planetary failure, anyway!
Regarding the airstair door, I have no direct knowledge, but will check. Heli Expo is right around the corner, lots of Sikorsky folks to talk to.
While I agree that "rumors" have a place, slurs do not, and frankly, The Sultan might take the cake on this one.
I know the history of the Black hawk intimately, and there is no history of planetary failures (the few cracks on Black Hawk planetary carriers were benign ones), yet Sultan actually got you to ask, "Just curious but are the UH-60s still having the same planetary failures or were they isolated incidents?"
That is the way it works, if you are as good as Sultan at it. He got you to ask, "When did the S92 stop beating its wife?" He talks without any real knowledge, describes a mythical failure mode , assigns it to a helicopter he doesn't like, and then gets to public to describe it back to him for erudite comment. Good public relations trick.
As 212man has said, the problem with the S92 that he flew was in input module that got hot, really hot. The input module is about 4 feet from the planetary section, and totally unrelated. So not only have their been no planetary failures , but the precautionary landing that now consumes this thread (rightly so) is not a planetary failure, anyway!
Regarding the airstair door, I have no direct knowledge, but will check. Heli Expo is right around the corner, lots of Sikorsky folks to talk to.
Last edited by NickLappos; 10th Feb 2008 at 04:17.
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Nick,
I will be the first to admit I know very little about the S-92 and this incident, so please don’t berate me for this. I do however know a little bit about the UH-60 carrier fault and what the Sultan speaks is true (unless you classify a planetary carrier crack as a mythical failure). If you doubt him please read the 2003 AHS paper presented in the 59th Annual Forum in Phoenix titled “Vibration Monitoring of UH-60A Main Transmission Planetary Carrier Fault”
vibguy
I will be the first to admit I know very little about the S-92 and this incident, so please don’t berate me for this. I do however know a little bit about the UH-60 carrier fault and what the Sultan speaks is true (unless you classify a planetary carrier crack as a mythical failure). If you doubt him please read the 2003 AHS paper presented in the 59th Annual Forum in Phoenix titled “Vibration Monitoring of UH-60A Main Transmission Planetary Carrier Fault”
vibguy
Thanks Nick
"Regarding the airstair door, I have no direct knowledge, but will check. Heli Expo is right around the corner, lots of Sikorsky folks to talk to."
Thanks Nick.
Have fun at Heli Expo - 30+ years and have never made it yet - some kind of conspiracy against me no doubt.
Next year for sure!
Cheers
Albatross
Thanks Nick.
Have fun at Heli Expo - 30+ years and have never made it yet - some kind of conspiracy against me no doubt.
Next year for sure!
Cheers
Albatross
Albatross,
Do not know if the planetary problem was isolated to the two examples and not seen again. I know it caused some significant concern on the Army's part as the scenario is pretty ugly:
1. A major drive component developing a crack and generating a lot of material.
2. No chip indications.
3. No oil filter bypass indication.
4. First indication was problems with oil pressure being noted by the flight crew.
A lot of bench testing was conducted with damaged planetaries to develop methods for HUMS to detect the fault. The last stuff I saw was that there was no reliable method to detect the fault in operational service using vibration analysis.
Nick,
The only slurs I have seen on this thread are from you (the "airmanship" post is making the rounds). I am ambivalent to the S-92 as it is just another helicopter. However, it is fact that the CAA in the early 2000's set the bar so high for drive system reliability that it was almost impossible to prove by analysis alone. One method of relief was to add a HUMS and at a CAA meeting it was stated that the S-92 and 235 took this approach. Now North Sea operators are mandated to comply with CAP 693/753 and have comprehensive HUMS. These have to have all sorts of gearbox analyses to be compliant. It will be interesting to see the final report and whether or not HUMS should have detected the fault before it resulted in a ship in the dirt, and how this will impact HUMS mandates.
212Man:
Liked your HUMS response. My experience with HUMS is it can be damn good detecting the second occurance of a problem. On the first undetected occurance the excuses generally are the "analysis was not tuned properly", the accelerometer was in the wrong place, the operator did not buy the proper support package, etc.... Once an incident does occur, all of the data can be reviewed and a proper analysis done to detect the next exact same event. Note: While I question the usefulness of HUMS gearbox diagnostics in the real world (chip detectors work very well), it is damn good at shafts, grease packed bearings and tail rotors all of which in the pre-HUMS days had faults go undetected for hours/days/weeks before they finally failed and caused loss of the aircraft.
The Sultan
Do not know if the planetary problem was isolated to the two examples and not seen again. I know it caused some significant concern on the Army's part as the scenario is pretty ugly:
1. A major drive component developing a crack and generating a lot of material.
2. No chip indications.
3. No oil filter bypass indication.
4. First indication was problems with oil pressure being noted by the flight crew.
A lot of bench testing was conducted with damaged planetaries to develop methods for HUMS to detect the fault. The last stuff I saw was that there was no reliable method to detect the fault in operational service using vibration analysis.
Nick,
The only slurs I have seen on this thread are from you (the "airmanship" post is making the rounds). I am ambivalent to the S-92 as it is just another helicopter. However, it is fact that the CAA in the early 2000's set the bar so high for drive system reliability that it was almost impossible to prove by analysis alone. One method of relief was to add a HUMS and at a CAA meeting it was stated that the S-92 and 235 took this approach. Now North Sea operators are mandated to comply with CAP 693/753 and have comprehensive HUMS. These have to have all sorts of gearbox analyses to be compliant. It will be interesting to see the final report and whether or not HUMS should have detected the fault before it resulted in a ship in the dirt, and how this will impact HUMS mandates.
212Man:
Liked your HUMS response. My experience with HUMS is it can be damn good detecting the second occurance of a problem. On the first undetected occurance the excuses generally are the "analysis was not tuned properly", the accelerometer was in the wrong place, the operator did not buy the proper support package, etc.... Once an incident does occur, all of the data can be reviewed and a proper analysis done to detect the next exact same event. Note: While I question the usefulness of HUMS gearbox diagnostics in the real world (chip detectors work very well), it is damn good at shafts, grease packed bearings and tail rotors all of which in the pre-HUMS days had faults go undetected for hours/days/weeks before they finally failed and caused loss of the aircraft.
The Sultan
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ANYBODY - Any other comments on the airstair door redesign?
"When did the S92 stop beating its wife?"
Is there any "wife beating" involved? Can HUMS detect the cracking hinge on the airstair door?
Both silly questions I understand.
I feel someone on this thread has a complex or fixation on wife beating? I have now read this many times! My esteemed mother in law has a very naughty dog which needs some lessons on 'who is boss' (I know, but this dog is really stupid). Please Mr Lappos take the dog, I need no cash exchange, just accept my offer and put your anger I read against Mr Sultan and HC behind you. It is the start of the next year, highly auspicious year of the rat! Please be gentle!
The airstair door also has some problems as I read before, is this a vibration problem or is 'beefing up' good enough?
With HUMS I think I understand what Sultan means, that many defect can be caught before aircraft even flies, so I do not understand why with such an input module failure no indication was found before? If it is a sudden failure with no lead in indications is this not more serious? Or is there some area not covered?
Finally to Doc, thank you for straight forward answers. So many people on this thread try to be funny and avoid questions. Some are not funny and answer only certain questions. So a salute to you Doc for your time!
An apology for asking more questions,
"When did the S92 stop beating its wife?"
Is there any "wife beating" involved? Can HUMS detect the cracking hinge on the airstair door?
Both silly questions I understand.
I feel someone on this thread has a complex or fixation on wife beating? I have now read this many times! My esteemed mother in law has a very naughty dog which needs some lessons on 'who is boss' (I know, but this dog is really stupid). Please Mr Lappos take the dog, I need no cash exchange, just accept my offer and put your anger I read against Mr Sultan and HC behind you. It is the start of the next year, highly auspicious year of the rat! Please be gentle!
The airstair door also has some problems as I read before, is this a vibration problem or is 'beefing up' good enough?
With HUMS I think I understand what Sultan means, that many defect can be caught before aircraft even flies, so I do not understand why with such an input module failure no indication was found before? If it is a sudden failure with no lead in indications is this not more serious? Or is there some area not covered?
Finally to Doc, thank you for straight forward answers. So many people on this thread try to be funny and avoid questions. Some are not funny and answer only certain questions. So a salute to you Doc for your time!
An apology for asking more questions,
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fat&furious,
Thanks for the upbraiding, every now and then I need it. I was an attack helo pilot, and I think rolling in with guns blazing is a lot more fun that clean intellectual discourse, especially when dealing with bigoted blowhards.
The point I try to make is that the silly speculation by Sultan is both wrong, and wrong-headed. But it does cost little to just ignore. "Wife beating" is my way of commenting on how a person can start a rumor, and then help fan it until it becomes a truth, all with no facts at all!
That being said, lets see if the questions you ask have answers:
1) airstair - I will check, but I think the issue is a ground opening clunk when the stair drops to full extend, as well as the point loading of the single support strut while the airstair has its max load on it. I seriously doubt that flight vibration has anything to do with it. Generally, all designers design doors as "extras" that have no structural loads in flight (the hole is just that while in flight, a hole). I would bet dollars to donuts the redesign is not major, but just providing an extra load path that drops the point loads now experienced, probably an extra strut and a doubled mounting plate on the frame to bring home the loads. I really don't know if they will also reposition the existing strut to keep it from contacting the pax, as albatross has reported (this is a surprise to me, but I do not doubt it, it is the kind of thing that we all learn the hard way, in real life. The airstair is relatively easy to fix, as well, at least from 1,000 miles away sitting at a keyboard, as I am.
2) There is a school of thought that HUMS sees the future, and this is almost foolish in its very concept. HUMS is a very important tool, but only by connecting it to the rad alt and the fuel gage can it become more prescient, since most accidents are caused by us, unfortunately.
3) The speculation about this forced landing is interesting, it brings out the best/worst in all of pprune, and provides a convenient stage for all to prance about clothed in their predispositions. I have tracked fairy tails about massive oil leaks as they were described by those who were not there, as well as transmission cracks by those who have no real knowledge, and now we have planetary carrier cracks diagnosed by ignoramuses!
4) The S92 transmission is bigger, taller, beefier and heavier that the Black Hawk transmission by almost precisely the amount of extra power that it transmits. To say "the S-92 is just a UH-60 with the rubber bands wound a lot tighter" is like saying "The Sultan is like a pilot, but without a brain."
5) I am not inside the Sikorsky loop anymore, as I volunteer to not stretch the integrity of friends by asking for inside scoop, a stretch that I cannot in good conscience make. My educated guess is that the input module overheated as a result of oil not circulating properly for some reason, while there was enough oil in the input module to provide lubrication but not allow the oil to get to the cooler for cooling.
6) the S92 transmission is a true modular trannie, designed with structural partitions and independence of lube so that a section can be shot away (yes, shot away) and not compromise the ability of safe operation of the remaining sections. The input module is no exception. I speculate that had the module jumped off the aircraft, the net effect would be as if the engine had failed, and safe flight for many minutes would have been possible, but I await real info before I believe this speculation. This is however confounded by the info the cockpit gives the pilots, which does not support flying on. That is some of the concept behind my post about "airmanship" vs "reading checklists" which I certainly hope is circulating about, even if Sultan does not understand it! IMHO, 212man and co showed very very nice "airmanship"
7) The S92 trannie design is the precise opposite of the early 1960's designs where the entire box is a single entity, and much closer to the CH-53 type design were the nose gearboxes are free-standing. Such isolation has some weight penalty, but graet flight safety improvements.
8) It is possible that the diagnostics are already known, and the 92 team awaits test confirmation of the probable cause. As the former guy who sat in the PM seat, I would generally ask that the theory be matched with test data that proved the theory. These tests often take weeks to set up and run, just due to the need to scramble together the parts, screw them up to match the theory, and then carefully run the test to prove the theory without blowing up the lab and the parts. Makes Test Engineering one of the fun professions, IMHO.
Again, thanks for the upbraiding!
Thanks for the upbraiding, every now and then I need it. I was an attack helo pilot, and I think rolling in with guns blazing is a lot more fun that clean intellectual discourse, especially when dealing with bigoted blowhards.
The point I try to make is that the silly speculation by Sultan is both wrong, and wrong-headed. But it does cost little to just ignore. "Wife beating" is my way of commenting on how a person can start a rumor, and then help fan it until it becomes a truth, all with no facts at all!
That being said, lets see if the questions you ask have answers:
1) airstair - I will check, but I think the issue is a ground opening clunk when the stair drops to full extend, as well as the point loading of the single support strut while the airstair has its max load on it. I seriously doubt that flight vibration has anything to do with it. Generally, all designers design doors as "extras" that have no structural loads in flight (the hole is just that while in flight, a hole). I would bet dollars to donuts the redesign is not major, but just providing an extra load path that drops the point loads now experienced, probably an extra strut and a doubled mounting plate on the frame to bring home the loads. I really don't know if they will also reposition the existing strut to keep it from contacting the pax, as albatross has reported (this is a surprise to me, but I do not doubt it, it is the kind of thing that we all learn the hard way, in real life. The airstair is relatively easy to fix, as well, at least from 1,000 miles away sitting at a keyboard, as I am.
2) There is a school of thought that HUMS sees the future, and this is almost foolish in its very concept. HUMS is a very important tool, but only by connecting it to the rad alt and the fuel gage can it become more prescient, since most accidents are caused by us, unfortunately.
3) The speculation about this forced landing is interesting, it brings out the best/worst in all of pprune, and provides a convenient stage for all to prance about clothed in their predispositions. I have tracked fairy tails about massive oil leaks as they were described by those who were not there, as well as transmission cracks by those who have no real knowledge, and now we have planetary carrier cracks diagnosed by ignoramuses!
4) The S92 transmission is bigger, taller, beefier and heavier that the Black Hawk transmission by almost precisely the amount of extra power that it transmits. To say "the S-92 is just a UH-60 with the rubber bands wound a lot tighter" is like saying "The Sultan is like a pilot, but without a brain."
5) I am not inside the Sikorsky loop anymore, as I volunteer to not stretch the integrity of friends by asking for inside scoop, a stretch that I cannot in good conscience make. My educated guess is that the input module overheated as a result of oil not circulating properly for some reason, while there was enough oil in the input module to provide lubrication but not allow the oil to get to the cooler for cooling.
6) the S92 transmission is a true modular trannie, designed with structural partitions and independence of lube so that a section can be shot away (yes, shot away) and not compromise the ability of safe operation of the remaining sections. The input module is no exception. I speculate that had the module jumped off the aircraft, the net effect would be as if the engine had failed, and safe flight for many minutes would have been possible, but I await real info before I believe this speculation. This is however confounded by the info the cockpit gives the pilots, which does not support flying on. That is some of the concept behind my post about "airmanship" vs "reading checklists" which I certainly hope is circulating about, even if Sultan does not understand it! IMHO, 212man and co showed very very nice "airmanship"
7) The S92 trannie design is the precise opposite of the early 1960's designs where the entire box is a single entity, and much closer to the CH-53 type design were the nose gearboxes are free-standing. Such isolation has some weight penalty, but graet flight safety improvements.
8) It is possible that the diagnostics are already known, and the 92 team awaits test confirmation of the probable cause. As the former guy who sat in the PM seat, I would generally ask that the theory be matched with test data that proved the theory. These tests often take weeks to set up and run, just due to the need to scramble together the parts, screw them up to match the theory, and then carefully run the test to prove the theory without blowing up the lab and the parts. Makes Test Engineering one of the fun professions, IMHO.
Again, thanks for the upbraiding!
UH-60 and S-92 Main Box History
There has been some information put up that is partially correct and also a bit mixed up. I didn't recall all of the details as exactly as needed to post a note here, so I called a friend who is in a position to know. All of this is subject to the recollective quality of our collective memories.
The multiple main gear box issues with the original UH-60 2800 SHP boxes which one writer referred to were traced to a ring gear failure of ring gears from a particular manufacturer. SA got rid of those gears.
There were two planetary gear carrier fatigue crack induced failures that I learned about. Neither involved a complete failure of the planetary gear, and see immediately below for the story.
The one planetary carrier failure of a 3400 SHP gear box was caused by a fatigue crack and subsequent investigation disclosed that this customer ( non US Army ) was flying a GAG ( Ground-Air-Ground ) cycle powerwise that was way beyond the power ( should have said torque ) usage that formed the basis for the main box TBO . That failure did in fact result in deformation of the carrier plate, allowing it to contact an aluminum shim, generating lots of aluminum chips and clogging the filter, eventually shutting off oil flow. A precautionary landing was made without incident. No chip detection reported. The TBO for this operator was reduced in keeping with the power/time-at-power spectrum that he was in fact flying.
I did not get the history behind the single planetary carrier failure of a UH-60 2800 SHP main box, but based on the investigation of the 3400 SHP box event, assume it was a fatigue crack initiated thru usage far beyond the power/torque/time-at-power spectrum for which that TBO was formulated.
All of this history is a different technical question than the S-92 issue under discussion here, which has been noted as being an overheat in the No.1 side input module. One can be certain that this investigation is receiving very high priority attention.
I was just thinking that the planetary carrier plate issue is a perfect point to launch a discussion about on-wing real time fatigue measurement/real time TBO calculation being an integral part of each ship's HUMS ( an idea that to my knowledge was first espoused and advocated by Nick Lappos ), but I'm not sure this is the place.
Thanks,
John Dixson
The multiple main gear box issues with the original UH-60 2800 SHP boxes which one writer referred to were traced to a ring gear failure of ring gears from a particular manufacturer. SA got rid of those gears.
There were two planetary gear carrier fatigue crack induced failures that I learned about. Neither involved a complete failure of the planetary gear, and see immediately below for the story.
The one planetary carrier failure of a 3400 SHP gear box was caused by a fatigue crack and subsequent investigation disclosed that this customer ( non US Army ) was flying a GAG ( Ground-Air-Ground ) cycle powerwise that was way beyond the power ( should have said torque ) usage that formed the basis for the main box TBO . That failure did in fact result in deformation of the carrier plate, allowing it to contact an aluminum shim, generating lots of aluminum chips and clogging the filter, eventually shutting off oil flow. A precautionary landing was made without incident. No chip detection reported. The TBO for this operator was reduced in keeping with the power/time-at-power spectrum that he was in fact flying.
I did not get the history behind the single planetary carrier failure of a UH-60 2800 SHP main box, but based on the investigation of the 3400 SHP box event, assume it was a fatigue crack initiated thru usage far beyond the power/torque/time-at-power spectrum for which that TBO was formulated.
All of this history is a different technical question than the S-92 issue under discussion here, which has been noted as being an overheat in the No.1 side input module. One can be certain that this investigation is receiving very high priority attention.
I was just thinking that the planetary carrier plate issue is a perfect point to launch a discussion about on-wing real time fatigue measurement/real time TBO calculation being an integral part of each ship's HUMS ( an idea that to my knowledge was first espoused and advocated by Nick Lappos ), but I'm not sure this is the place.
Thanks,
John Dixson
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JD: perfect point to launch a discussion about on-wing real time fatigue measurement/real time TBO calculation being an integral part of each ship's HUMS
NL: There is a school of thought that HUMS sees the future, and this is almost foolish in its very concept.
Case closed?
Meanwhile is this the definately only such case of an overheated input drive box anywhere in the world?
NL: There is a school of thought that HUMS sees the future, and this is almost foolish in its very concept.
Case closed?
Meanwhile is this the definately only such case of an overheated input drive box anywhere in the world?
2) There is a school of thought that HUMS sees the future, and this is almost foolish in its very concept. HUMS is a very important tool, but only by connecting it to the rad alt and the fuel gage can it become more prescient, since most accidents are caused by us, unfortunately.
HC
Apparently the airstair project has taken some pretty high priority, from the sound of things.
HC: harsh and not true! The SAC HUMS is the first truly integrated HUMS system on any modern type (even more so than ARMS or M'ARMS), and is so integrated that perhaps SAC have failed to realise the importance of appropriate information/guidance to aircrew on the information it yields.
Certainly, I can say that there is no indication that HUMS would have predicted this particular event (it could easily have been caused by 'floating' debris blocking a pipe) and equally I can confidently say it could readily predict many other failures before they became significant.
HUMS does support HFDM: not sure where that statement comes from. Workarounds are always necessary, as well you know from your HOMP experience and EAG/RACAL discussions.
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Just because a HUMS is integrated doesn't automatically mean that it is good. I think a HUMS should have the capability to make quality measurements which can be used to indicate impending faults like the one this thread is discussing.
vibguy
vibguy
Last edited by vibguy; 12th Feb 2008 at 04:13. Reason: make it nice