Sikorsky S-92: From Design to Operations
Wow, never seen a Vespel do that before. Kinda scary. Are they lubricated type, or dry type? All the ones I've inspected over the years look near new even when years and years old. I hope it's an easy fix for Sikorsky.
Noooby
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Old ageing 61 not a problem, MGB, one pump, never have known of one to fail, okay had to change one several years ago for borderlne pressure, but normally not a problem.
S61 Hyd pumps, okay as long as both the internal and external splines were lubed.
Where they screwed up on the S76 Hyd pumps was when they went to the non-metallic splines, problem was that they forgot to tell the operators that the internal splines on the pump were still steel splines, smaller diameter as well so didn't last too long without grease.
Would like to know the reason why they go with the steel/ plastic type, as to plastic/ plastic obviously not for ease of maintenance, its a bit more difficult to lube the inner splines, is it a case of the Pump manufacturers going with steel ????
S61 Hyd pumps, okay as long as both the internal and external splines were lubed.
Where they screwed up on the S76 Hyd pumps was when they went to the non-metallic splines, problem was that they forgot to tell the operators that the internal splines on the pump were still steel splines, smaller diameter as well so didn't last too long without grease.
Would like to know the reason why they go with the steel/ plastic type, as to plastic/ plastic obviously not for ease of maintenance, its a bit more difficult to lube the inner splines, is it a case of the Pump manufacturers going with steel ????
Mars
Its my understanding that the S92 does not have true 30 min dry running capability. In order to meet the certification requirements it relies on retaining some oil in the sump by shutting off the external pipework. This fudge clearly only works if
a) the leak is from something other than the main gearbox and
b) the pump(s) are still running.
If there are no pumps working, dry running time is unknown but less than 30 minutes.
In this case it seems that the pumps had not stopped working altogether, as apparently there was still about one tenth of normal pressure showing on the gauge, and with the destination platform being so close they got away with it. With the drive to both pumps presumably slipping, I doubt it would have been long before the wear caused the pumps to stop altogether.
I must say I didn't realise that the pump drive splines were plastic - I suppose this explains how they can wear out on an aircraft with only about 200 hrs since new. Its a bit worrying though!
It will be interesting to see whether the perceived certification fudge that allowed the S92 to enter service without true 30 minute dry running time will come back to haunt SKy sooner than we thought!
RJSquirrel
I believe you are not correct, both pumps lost drive and both spline couplings show severe signs of wear/slippage according to my rumour source. So it could have been a disaster (well at least a ditching) but fortunately circumstances were on their side.
HC
Its my understanding that the S92 does not have true 30 min dry running capability. In order to meet the certification requirements it relies on retaining some oil in the sump by shutting off the external pipework. This fudge clearly only works if
a) the leak is from something other than the main gearbox and
b) the pump(s) are still running.
If there are no pumps working, dry running time is unknown but less than 30 minutes.
In this case it seems that the pumps had not stopped working altogether, as apparently there was still about one tenth of normal pressure showing on the gauge, and with the destination platform being so close they got away with it. With the drive to both pumps presumably slipping, I doubt it would have been long before the wear caused the pumps to stop altogether.
I must say I didn't realise that the pump drive splines were plastic - I suppose this explains how they can wear out on an aircraft with only about 200 hrs since new. Its a bit worrying though!
It will be interesting to see whether the perceived certification fudge that allowed the S92 to enter service without true 30 minute dry running time will come back to haunt SKy sooner than we thought!
RJSquirrel
I believe you are not correct, both pumps lost drive and both spline couplings show severe signs of wear/slippage according to my rumour source. So it could have been a disaster (well at least a ditching) but fortunately circumstances were on their side.
HC
Last edited by HeliComparator; 7th Apr 2005 at 22:13.
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What kind of input bearings does the S92 have??? most gearboxes will survive without oil pressure as long as there is oil in the box so it can be splash lubed, but the inputs are critical.
Tynecastle,
You're right about inputs being critical. I had a peek at the AB139 MGB used for the 30min certification. It doesn't look too bad, except for the burnt brown paint on the inputs!! I must say though, the input gears were in remarkably good condition considering what they had been through, and considering that the inputs rotate at 21000RPM.
It would be surprising if the Vespels were the main problem here. They have been in use for decades with no problems, as long as they are maintained properly. for the 412, that meant inspect and lube every 300 hours if I remember correctly. But of all the 412 Vespels I've inspected, I've never seen a bad one, just lube it up and put it back. Talking to another engineer, he is of the same opinion, unlikey that the Vespel is the main problem, expecially with only a small number of hours on it (what is the total time on this particular machine??).
Noooby
You're right about inputs being critical. I had a peek at the AB139 MGB used for the 30min certification. It doesn't look too bad, except for the burnt brown paint on the inputs!! I must say though, the input gears were in remarkably good condition considering what they had been through, and considering that the inputs rotate at 21000RPM.
It would be surprising if the Vespels were the main problem here. They have been in use for decades with no problems, as long as they are maintained properly. for the 412, that meant inspect and lube every 300 hours if I remember correctly. But of all the 412 Vespels I've inspected, I've never seen a bad one, just lube it up and put it back. Talking to another engineer, he is of the same opinion, unlikey that the Vespel is the main problem, expecially with only a small number of hours on it (what is the total time on this particular machine??).
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Sorry AirJockey I can't let this go without comment.
You said: "Sounds like the pilots did a heck of a job and followed procedures. A good save for crew, pax and "Sikorsky"."
According to the company "...a warning of low oil pressure on main gear box was received 3 minutes before landing.
The pilots sent out a “mayday call” as a matter of routine, and a normal landing was made on the rig’s helicopter deck."
Let's face it this is hardly the stuff from which Hollywood movies are made. If the Norsk company website is to be believed the crew did their job, plain and simple. Nothing more and nothing less than their passengers, their colleagues at Norsk Helikopters, their families and the industry watchers at Rotorheads have a right to expect of them.
To over dramatize the matter does not, IMHO, do our industry any favours.
You said: "Sounds like the pilots did a heck of a job and followed procedures. A good save for crew, pax and "Sikorsky"."
According to the company "...a warning of low oil pressure on main gear box was received 3 minutes before landing.
The pilots sent out a “mayday call” as a matter of routine, and a normal landing was made on the rig’s helicopter deck."
Let's face it this is hardly the stuff from which Hollywood movies are made. If the Norsk company website is to be believed the crew did their job, plain and simple. Nothing more and nothing less than their passengers, their colleagues at Norsk Helikopters, their families and the industry watchers at Rotorheads have a right to expect of them.
To over dramatize the matter does not, IMHO, do our industry any favours.
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helicomparitor says:
"its a bit worrying though!"
That's because he is a Eurocopter salesman, and should certainly be worried about 225 sales!
I note the comments he made are quite inaccurate, but are to be expected, of course.
The S-92 transmission has a dual pump system, one shaft lost drive because it wore prematurely. The box had pressure on landing. The crew did as they should.
The spline system used on the 92 is similar to that used on many pumps and generator drives, the plastic prevents spline damage from contaminating the box. There is an excellent team working to identify the cause of the premature wear, of course.
The inputs are not the most critical part of most gearboxes, but they certainly are on the S-61, which has sleeve bearings at very high speed. For the record, only the S-92 and the AB-139 have met the latest FAR/JAR safety requirements in every way, with the certification as proof. Helicomparitor has a difficult time with this fact, n'est-pas?
"its a bit worrying though!"
That's because he is a Eurocopter salesman, and should certainly be worried about 225 sales!
I note the comments he made are quite inaccurate, but are to be expected, of course.
The S-92 transmission has a dual pump system, one shaft lost drive because it wore prematurely. The box had pressure on landing. The crew did as they should.
The spline system used on the 92 is similar to that used on many pumps and generator drives, the plastic prevents spline damage from contaminating the box. There is an excellent team working to identify the cause of the premature wear, of course.
The inputs are not the most critical part of most gearboxes, but they certainly are on the S-61, which has sleeve bearings at very high speed. For the record, only the S-92 and the AB-139 have met the latest FAR/JAR safety requirements in every way, with the certification as proof. Helicomparitor has a difficult time with this fact, n'est-pas?
Hi Nick
Glad to see you're still here and your feverish defence of the 92 hasn't waned since you left the company. Life might get boring otherwise!
Despite your bluster, I think you will find that in fact both pumps drives failed, although as I mentioned they must have been rotating slowly as pressure didn't quite fall to zero. Let me put it another way, (in the form of a technical question to you) - if you are in an S92 with only one pump working, what sort of MGB pressure would you expect to see? If the answer is "5 psi" then you are right, one pump was working. But it would seem strange that 2 pumps gives you about 55 psi and 1 pump only gives you 5 psi. Its true that the relationship between flow rate and pressure is somewhat non linear, but surely not to that extent?
History will soon show which of us is correct. I'll say "sorry" if I'm wrong - will you?
Can I ask another question? If one pump fails, do you get some sort of warning light? - it was interesting to note that PHI had a worn shaft on inspection but I was not clear whether the drive had actually failed and/or showed signs of slippage
By the way, do I really have to tell you again that I don't work for EC? Can't you just accept that not everybody thinks that the S92 (good aircraft though it is in many ways) should be worshipped unreservedly and any mention of its flaws considered blasphemy?
Hope you are enjoying Gulfsteam...
HC
Glad to see you're still here and your feverish defence of the 92 hasn't waned since you left the company. Life might get boring otherwise!
Despite your bluster, I think you will find that in fact both pumps drives failed, although as I mentioned they must have been rotating slowly as pressure didn't quite fall to zero. Let me put it another way, (in the form of a technical question to you) - if you are in an S92 with only one pump working, what sort of MGB pressure would you expect to see? If the answer is "5 psi" then you are right, one pump was working. But it would seem strange that 2 pumps gives you about 55 psi and 1 pump only gives you 5 psi. Its true that the relationship between flow rate and pressure is somewhat non linear, but surely not to that extent?
History will soon show which of us is correct. I'll say "sorry" if I'm wrong - will you?
Can I ask another question? If one pump fails, do you get some sort of warning light? - it was interesting to note that PHI had a worn shaft on inspection but I was not clear whether the drive had actually failed and/or showed signs of slippage
By the way, do I really have to tell you again that I don't work for EC? Can't you just accept that not everybody thinks that the S92 (good aircraft though it is in many ways) should be worshipped unreservedly and any mention of its flaws considered blasphemy?
Hope you are enjoying Gulfsteam...
HC
Nick
Good answer - short, to the point, avoids answering any of my points, and once again wrong!
If I say "the L2 / EC225 MGB left hand accessory module sucks" and "the EC225 cabin and cockpit are too small" and " the EC225 boot (trunk to you) is too small" and "Eurocopter's attempts at windscreen wipers are utterly hopeless" and " EC's fire detection systems for engine and transmission are criminally crap" and some other things I can't think of right now, then do you still think I work for EC? Does that make you feel any better?
S92Mech
Thanks for the clarification. Out of interest, what sort of hours does your machine now have on it? Do you still just have the one machine in service?
HC
Good answer - short, to the point, avoids answering any of my points, and once again wrong!
If I say "the L2 / EC225 MGB left hand accessory module sucks" and "the EC225 cabin and cockpit are too small" and " the EC225 boot (trunk to you) is too small" and "Eurocopter's attempts at windscreen wipers are utterly hopeless" and " EC's fire detection systems for engine and transmission are criminally crap" and some other things I can't think of right now, then do you still think I work for EC? Does that make you feel any better?
S92Mech
Thanks for the clarification. Out of interest, what sort of hours does your machine now have on it? Do you still just have the one machine in service?
HC
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S92 Mech / Nick
Okay Guys, but I'm just curious to know what kind of bearings are used in the S92 Box for the inputs? also what is the RPM, I take it that it is reduced before it gets to the transmission.
Cheers.
TC
Okay Guys, but I'm just curious to know what kind of bearings are used in the S92 Box for the inputs? also what is the RPM, I take it that it is reduced before it gets to the transmission.
Cheers.
TC
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The S92 gear box uses big roller bearing sets for the inputs. Very hardy and virtually identical to (but larger than) the Black Hawk.
These are not like the older technology sleeve kind like the S-61, which need lots of oil to keep whole, and if not supplied, can fail in a few minutes, thus the aux lube system needs of the S-61.
These are not like the older technology sleeve kind like the S-61, which need lots of oil to keep whole, and if not supplied, can fail in a few minutes, thus the aux lube system needs of the S-61.
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That situation would not occur on an EC225 since the two oil pumps, main and stand by, are working permanently but independently, each one having its own warning in case of malfunctioning... In case of both failing, an emergency lubrication cooling still gives 30 ‘ to land ! And it’s backed by the millions hours experience of the Super Puma family, it’s simple and it works safely.
One can be amazed at the certification of the S92 pretending to be “the only” helicopter certified according to FAR 29 amendment 45 (refer to a former long post on that matter which made our friend Nick to go ballistic once or twice). It’s presumed to be the latest of the latest standard, but apparently some vital aspects remain far beyond today’s standards.
One can be amazed at the certification of the S92 pretending to be “the only” helicopter certified according to FAR 29 amendment 45 (refer to a former long post on that matter which made our friend Nick to go ballistic once or twice). It’s presumed to be the latest of the latest standard, but apparently some vital aspects remain far beyond today’s standards.
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Hi Nick,
All this power play has missed my crib(cot in the UK)
but could you explain what you mean when you mention the " Sleeve bearing", are you referring to the sort of bearing that would be in the form of sintered brass or Phospher Bronze that is an interferance fit to the main body whilst the shaft spins in/ or though the bearing thus the need for constant lube, or is it the sort of split sleeved ball bearing type used in the feathering device of props,
many regards
PeterR-B Vfr
All this power play has missed my crib(cot in the UK)
but could you explain what you mean when you mention the " Sleeve bearing", are you referring to the sort of bearing that would be in the form of sintered brass or Phospher Bronze that is an interferance fit to the main body whilst the shaft spins in/ or though the bearing thus the need for constant lube, or is it the sort of split sleeved ball bearing type used in the feathering device of props,
many regards
PeterR-B Vfr
Helicomp....
I have yet to see a windshield/windscreen wiper on any helicopter that was worth a pinch of owl butter.
Windows on all helicopters are too small...except for those that are after market mods.
Baggage storage....and in cabin storage is always too small...goes with the fact that engines and transmissions take up so much room and weight....along with the need to trade off fuel for pax/baggage.
Saying it does not make it true but when true...accept it.
As to where you work dear boy...Nick has it on you...he is out in the open and takes his spears like a man. Not so you....since you deny his statements regarding your employer.....maybe it is time you revealed yourself as Nick has done.
For me...until you do...in this argument between you and Nick...I will at least side with the guy in the open....until proven wrong. Nick at least is willing to publically take a stand and risk his reputation upon what he submits to public scrutiny. Not so you.
Give'em Hell Nick!
I have yet to see a windshield/windscreen wiper on any helicopter that was worth a pinch of owl butter.
Windows on all helicopters are too small...except for those that are after market mods.
Baggage storage....and in cabin storage is always too small...goes with the fact that engines and transmissions take up so much room and weight....along with the need to trade off fuel for pax/baggage.
Saying it does not make it true but when true...accept it.
As to where you work dear boy...Nick has it on you...he is out in the open and takes his spears like a man. Not so you....since you deny his statements regarding your employer.....maybe it is time you revealed yourself as Nick has done.
For me...until you do...in this argument between you and Nick...I will at least side with the guy in the open....until proven wrong. Nick at least is willing to publically take a stand and risk his reputation upon what he submits to public scrutiny. Not so you.
Give'em Hell Nick!
Hi Mr Sasless
I don't think we have sparred before so here goes...
I was under the misunderstanding that this was an anonymous forum, hence my pseudonym. I didn't realise that Sasless was your real name - is it Mr Sasless, or are you one of those important people like "Prince" who only has one name?
Anyway, flippancy aside, does it actually make any difference who I work for? I have already told Nick that I am a North Sea helicopter pilot, I have told him that I have flown the S92. I think it would be a little careless of SKy to allow the opposition's salesmen to fly their aircraft.
He chooses to ignore that because discrediting me personally is his easiest option. You will notice that he hardly ever actually refutes what I say - could that be because he knows I am mostly right?
Anyway, I would PM you with my real identity but I know that Sikorsky are very quick to reach for their lawyers. If my identity got back to them I would not be surprised to find a law suit on my doorstep for defamation of their products - that's probably called "heresy" if its an American product. Under those circumstances it doesn't matter who is right - its who has the most expensive lawyers that wins. I am not joking here.
Having read many of your previous posts, you seem to be intelligent, articulate and a truth-seeker. However if in this case your patriotism is more important than the truth, then I find that a little sad. I wonder whether all Americans refuse to believe that there could be anything wrong with their home-grown aircraft - perhaps that's why they crash so much in the GOM!
HC
I don't think we have sparred before so here goes...
I was under the misunderstanding that this was an anonymous forum, hence my pseudonym. I didn't realise that Sasless was your real name - is it Mr Sasless, or are you one of those important people like "Prince" who only has one name?
Anyway, flippancy aside, does it actually make any difference who I work for? I have already told Nick that I am a North Sea helicopter pilot, I have told him that I have flown the S92. I think it would be a little careless of SKy to allow the opposition's salesmen to fly their aircraft.
He chooses to ignore that because discrediting me personally is his easiest option. You will notice that he hardly ever actually refutes what I say - could that be because he knows I am mostly right?
Anyway, I would PM you with my real identity but I know that Sikorsky are very quick to reach for their lawyers. If my identity got back to them I would not be surprised to find a law suit on my doorstep for defamation of their products - that's probably called "heresy" if its an American product. Under those circumstances it doesn't matter who is right - its who has the most expensive lawyers that wins. I am not joking here.
Having read many of your previous posts, you seem to be intelligent, articulate and a truth-seeker. However if in this case your patriotism is more important than the truth, then I find that a little sad. I wonder whether all Americans refuse to believe that there could be anything wrong with their home-grown aircraft - perhaps that's why they crash so much in the GOM!
HC
Last edited by HeliComparator; 8th Apr 2005 at 22:06.
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I think we are missing the point here. The S92, like any other ac just beyond prototype status is experiencing growing pains. Given that there are so few in service with so few operational hours, why the shock? Give it a few years and a few thousand hours and I'm sure the guys at Sikorsky will sort it out. I'm sure the S92 will be a great success. Just needs some time to get established, like all of the really good helos around today.