Sikorsky S-92: From Design to Operations
Does any other aircraft out there have a MGB oil pump fail warning system?
YES, the venerable 61.
If the oil pressure drops below 8 psi, whether due to a pump failure or loss of oil, the ELS automatically kicks in and you get a XMSN PRESS caution light as well as a green light on the ELS.
Sometime the old ways are better.
YES, the venerable 61.
If the oil pressure drops below 8 psi, whether due to a pump failure or loss of oil, the ELS automatically kicks in and you get a XMSN PRESS caution light as well as a green light on the ELS.
Sometime the old ways are better.
Currently a single pump failure will result in a pressure of around 5-7 psi. That is enough to allow gearbox operation virtually indefinitely, albeit with a temperature rise.
VL - yes the S61 ELS is responding to low oil pressure and the beauty of the system is that failure of one pump isn't enough to trigger ELS so lower than normal oil pressure is indicative of a pump failure. The design of the gearbox means that one pump is more than capable of providing lubrication and, if the other pump fails as well, the ELS takes on the job to get you home.
How is it that a 21st century helicopter, with the latest certification, can't manage the same? The weak link of any driven component is its driveshaft, vespel splined or otherwise, so how did the the engineers ignore that failure mode and persuade the FAA to do likewise? - there is little practical difference between not having any oil to pump round the MRGB and not being able to pump it because the pumps are inadequate.
How is it that a 21st century helicopter, with the latest certification, can't manage the same? The weak link of any driven component is its driveshaft, vespel splined or otherwise, so how did the the engineers ignore that failure mode and persuade the FAA to do likewise? - there is little practical difference between not having any oil to pump round the MRGB and not being able to pump it because the pumps are inadequate.
212man, is this not only true for a failure similar to the vespel spline problem where the pump windmills. If the pump seizes I thought the pressure drop was much less?? This I was told was the only failure mode Sikorsky had considered at the design stage and hence no check valves
Only if the failed pump is allowed to windmill of course, if it is jammed for some reason then expect around 17 psi (as per the -103 set up)
Last edited by 212man; 17th Mar 2009 at 11:14. Reason: Added proviso about jamming
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stones and glass-gearboxes
Sea King drivers with wet nappies should take a few lessons from those that flew the spanky new creations from Yeovil in 1970 and NOT crow about how good their machines are TODAY! It took nearly 40 years of broken oil feeds and similar disasters that terrified the pants of us brave fellows that ventured into the Arctic Sea day and night and waited for the next chip light before those 'safety features' were even thought of.
Some clever fellow advised me to never, no never, fly the 'A' model of anything. (I think it was SAS) and I think he had a point. Trouble is, until the 'B' model appears you're stuck with the learning curve and a pair of crampons to get up it.
(and YES the same tale can be told of the dear old lady (S61) to whom my career - and my bank account - owe a debt of gratitude. She never let me down but frightened me witless a couple of times).
G
PS - can you tell I'm on night-shift
Some clever fellow advised me to never, no never, fly the 'A' model of anything. (I think it was SAS) and I think he had a point. Trouble is, until the 'B' model appears you're stuck with the learning curve and a pair of crampons to get up it.
(and YES the same tale can be told of the dear old lady (S61) to whom my career - and my bank account - owe a debt of gratitude. She never let me down but frightened me witless a couple of times).
G
PS - can you tell I'm on night-shift
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Should we be worried
Hi GentsPlease forgive my intrusion into you domain, but offshore we have been watching this thread with interest.Two weeks ago leaving Scatsta for offshore we made a very rapid landing just after take off, caused by the gear box oil pressure falling to 5 psi. This fault does seem a lot more common than it should be, resulting in a lot of worried passengers.Are we over reacting or is this justified?
Could you confirm it was 2 weeks ago and how you know what the pressure was?
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Emergency Lub systems I think generally had a certain design ethos. The the Super Puma L1 had two pumps the normal pump with a shorter intake and higher pressure than the emergency pump; each pump had its own pressure gauge. Failure of the main pump or oil loss below the pump inlet produced a MGB COOL warning and pressure drop. The emergency pump set at a lower pressure then took over. The MGB P red warning was held off as long as the emergency pump pressure at the pressure switch remained above 1 bar. The only down side was that the ELP pressure was below the filter bypass valve setting. Good pressure on the ELP indicator, COOL light ON normal pressure gauge zero but RED MGB P out, system working as advertised.
The 61 ELS, oil supply to the Emergency pump at the bottom of the gearbox, main pump inlet a distance from the bottom of the sump. Oil leak exposed the pump inlet, RED MGB P warning light ON nil or extremely low pressure on the gauge, this switched the ELP on and delivered oil to the high speed inlet bearings (white metal) through a separate delivery system. Confirmation of operation GREEN run light ON, gauge pressure and RED MGBP. Or the pilot could select the ELS ON from a control switch. Duff Torque indications when on ELS. Least that’s how I remember it worked.
Outhouse.
The 61 ELS, oil supply to the Emergency pump at the bottom of the gearbox, main pump inlet a distance from the bottom of the sump. Oil leak exposed the pump inlet, RED MGB P warning light ON nil or extremely low pressure on the gauge, this switched the ELP on and delivered oil to the high speed inlet bearings (white metal) through a separate delivery system. Confirmation of operation GREEN run light ON, gauge pressure and RED MGBP. Or the pilot could select the ELS ON from a control switch. Duff Torque indications when on ELS. Least that’s how I remember it worked.
Outhouse.
Geoffers - I am well aware of all the problems of the early Sea King - that is why I made the point that a helicopter built in the last 10 years should NOT have to go through the same process to make it airworthy and fit for purpose.
Who was it who said 'those that do not learn the lessons of history are doomed to repeat them'?
Found it - "Those who cannot remember the past are condemned to repeat it." George Santayana 1863-1952
BTW your maths don't add up - 1970 + 40 years = 2010
Who was it who said 'those that do not learn the lessons of history are doomed to repeat them'?
Found it - "Those who cannot remember the past are condemned to repeat it." George Santayana 1863-1952
BTW your maths don't add up - 1970 + 40 years = 2010
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Hi,I know it was 2 weeks ago because I was on the flight (Thursday 5th March)It is standard practice with our company to get the Captain to brief you after any incident. This he did soon after when he told us that the oil pressure dropped to 5 psi soon after lift off.
Yes, I have been known to say "Never fly the "A" model of anything!"
Yes, I have flown a lot of "A" models....with the resulting laundry problems they can produce.
At least I am much luckier than some of my business associates who were around for the more catastrophic events that happened.
They learned about tail booms falling off, tail rotor gear boxes complete with tail rotors and vertical fins disappearing into the forest, main blades rotating in the cuff, main rotor blades departing for parts unknown, control rod ends pulling loose from the rods, swash plates failing, synch shafts failing, short shafts being installed in reverse, plastic liners separating inside engines, power turbines exploding and severing high pressure fuel lines, mast bumping, mast failures, and a few other minor occurrences.
That is why I am suspect of "A" models!
That and I care not to be an unpaid Test Pilot.
Yes, I have flown a lot of "A" models....with the resulting laundry problems they can produce.
At least I am much luckier than some of my business associates who were around for the more catastrophic events that happened.
They learned about tail booms falling off, tail rotor gear boxes complete with tail rotors and vertical fins disappearing into the forest, main blades rotating in the cuff, main rotor blades departing for parts unknown, control rod ends pulling loose from the rods, swash plates failing, synch shafts failing, short shafts being installed in reverse, plastic liners separating inside engines, power turbines exploding and severing high pressure fuel lines, mast bumping, mast failures, and a few other minor occurrences.
That is why I am suspect of "A" models!
That and I care not to be an unpaid Test Pilot.
Ah but soggy, I believe the ELS was introduced in the 90s (not sure 'cos I was a Wessex pilot then) so he is still temporally confused.
I expect he means nearly 40 years after it first flew in 1959
I expect he means nearly 40 years after it first flew in 1959
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History lessons
CRAB Please accept my apologies for any errors of history after all it was in the previous century and I did say I was on night shift.
By the way, I believe it was the German philosopher Hegel who basically agreed with Mr George Santayana by delivering to the world this fine observation of human nature.... quote
The one thing we learn from history is that we never learn from history
I think that Hegel was a little more accurate in his expectations.
G
By the way, I believe it was the German philosopher Hegel who basically agreed with Mr George Santayana by delivering to the world this fine observation of human nature.... quote
The one thing we learn from history is that we never learn from history
I think that Hegel was a little more accurate in his expectations.
G
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EASA caution to S-92A operators
Anyone out there familiar with this SSA Sikorsky supposedly sent out in September? Looks like EASA is very upset that the company is suggestions RFM changes that have not been approved. Sikorsky tells me they have no idea what EASA is getting at here....
or E-mail: [email protected].
EASA Safety Information Bulletin
SIB No.: 2009-05
Issued: 17 March 2009
Subject: Sikorsky S-92A Main Gearbox (MGB) Malfunctions.
Ref. Publications:
Issued: 17 March 2009
Subject: Sikorsky S-92A Main Gearbox (MGB) Malfunctions.
Ref. Publications:
Sikorsky Safety Advisory SSA-S92-08-006 dated 26 September
2008; and Sikorsky CCS-92-AOL-09-0008 dated 14 March 2009.
2008; and Sikorsky CCS-92-AOL-09-0008 dated 14 March 2009.
Description:
The Sikorsky Aircraft Corporation published SSA-S92-08-006 to
inform owners and operators of impending Rotorcraft Flight Manual
(RFM) changes, prompted by service difficulties with the S-92A
MGB lubrication system. More recently, CCS-92-AOL-09-0008 was
published to inform owners and operators about a recent accident
with an S-92A helicopter. The latest advisory document contains
reminders of existing Sikorsky service publications that
recommend specific action(s) that may or may not be related to the
root cause(s) of the latest accident. CCS-92-AOL-09-0008 also
specifies that ‘compliance’ with Sikorsky Safety Advisories is
‘essential’.
After reviewing the information and pending the investigation,
EASA supports the recommendations contained in CCS-92-AOL-
09-0008, with the exception of SSA-S92-08-006. This advisory
document refers to RFM changes that have not yet been approved
by the FAA. In fact, the SSA specifies the ‘corrective action’ as
“Ensure all flight crews become familiar with the RFM changes
when received”. This SIB is published to ensure that all owners
and operators of affected rotorcraft, registered in European Union
Member States or associated countries, are aware that the
procedures specified in SSA-S92-08-006 have not been approved
by FAA or EASA. The relevant emergency procedures in the
approved RFM must be observed.
inform owners and operators of impending Rotorcraft Flight Manual
(RFM) changes, prompted by service difficulties with the S-92A
MGB lubrication system. More recently, CCS-92-AOL-09-0008 was
published to inform owners and operators about a recent accident
with an S-92A helicopter. The latest advisory document contains
reminders of existing Sikorsky service publications that
recommend specific action(s) that may or may not be related to the
root cause(s) of the latest accident. CCS-92-AOL-09-0008 also
specifies that ‘compliance’ with Sikorsky Safety Advisories is
‘essential’.
After reviewing the information and pending the investigation,
EASA supports the recommendations contained in CCS-92-AOL-
09-0008, with the exception of SSA-S92-08-006. This advisory
document refers to RFM changes that have not yet been approved
by the FAA. In fact, the SSA specifies the ‘corrective action’ as
“Ensure all flight crews become familiar with the RFM changes
when received”. This SIB is published to ensure that all owners
and operators of affected rotorcraft, registered in European Union
Member States or associated countries, are aware that the
procedures specified in SSA-S92-08-006 have not been approved
by FAA or EASA. The relevant emergency procedures in the
approved RFM must be observed.
Applicability:
Sikorsky S-92A helicopters, all serial numbers.
Contact:
For further information contact the Airworthiness Directives, Safety
Management & Research Section, Certification Directorate, EASA.
E-mail: [email protected].
Copies of the referenced advisory documents and any other
related Sikorsky service publications may be obtained upon
request from Sikorsky Commercial Product Support, or call the
Customer Service Engineering Desk, telephone: +1 203-416-4299,
Management & Research Section, Certification Directorate, EASA.
E-mail: [email protected].
Copies of the referenced advisory documents and any other
related Sikorsky service publications may be obtained upon
request from Sikorsky Commercial Product Support, or call the
Customer Service Engineering Desk, telephone: +1 203-416-4299,
or E-mail: [email protected].
Brian Abraham
The S92 DOES NOT HAVE 30 mins DRY RUN TIME
Firstly the document you refer to is sales literature. Its never a good idea to believe what you read in sales literature. Secondly it says "30-minute drive system after oil leak" - that is an OIL LEAK not a complete loss of oil. After an oil leak you have to press a button to (hopefully) cut off the oil leak, then you can continue with less oil and no cooler, but not with no oil.
This has been flogged to death on this forum and even Nick Lappos never said that the S92 had 30mins dry running time.
HC
The S92 DOES NOT HAVE 30 mins DRY RUN TIME
Firstly the document you refer to is sales literature. Its never a good idea to believe what you read in sales literature. Secondly it says "30-minute drive system after oil leak" - that is an OIL LEAK not a complete loss of oil. After an oil leak you have to press a button to (hopefully) cut off the oil leak, then you can continue with less oil and no cooler, but not with no oil.
This has been flogged to death on this forum and even Nick Lappos never said that the S92 had 30mins dry running time.
HC
Last edited by HeliComparator; 18th Mar 2009 at 10:06. Reason: removing personal comments
HC,
When did Brian trump all that fancy training and flight checks, and education on the 92 professional pilots get?
I know Brian is a dinosaur from the dark ages and has shackle marks on his ankles and all....but laying that kind of guilt on him seems to be stacking up the charges just a wee bit dont you think?
Tell me anyone that has not looked down at the North Sea when it is living up to its reputation for being a very, very, very bad place to park a helicopter....and not thought about that last line in the Checklist that says..."Ditch Immediately"?
I will bet almost everyone of us at one point in time thought...."Not as long as this old girl is still flying!" We may have made a mental sub note saying something like..."get low and slow and let the whole World know...get SAR coming....and get prepared to ditch if anything whatsoever happens to show this is for real!"
When did Brian trump all that fancy training and flight checks, and education on the 92 professional pilots get?
I know Brian is a dinosaur from the dark ages and has shackle marks on his ankles and all....but laying that kind of guilt on him seems to be stacking up the charges just a wee bit dont you think?
Tell me anyone that has not looked down at the North Sea when it is living up to its reputation for being a very, very, very bad place to park a helicopter....and not thought about that last line in the Checklist that says..."Ditch Immediately"?
I will bet almost everyone of us at one point in time thought...."Not as long as this old girl is still flying!" We may have made a mental sub note saying something like..."get low and slow and let the whole World know...get SAR coming....and get prepared to ditch if anything whatsoever happens to show this is for real!"
Brian,
that statement you quote is by Peter Grey the article's author - not Bob Spaulding. Where Peter got that information is anyone's guess. Clearly, in that article he is 'selling' the aircraft (as he tends to do in most of his 'flight tests'.)
I agree that HC's comments are somewhat emotive, and do not wish to become embroiled in a transtlantic and north/south hemisphere spat. However, I can say that HC is absolutely correct in his assertion that the MGB does not have a run dry capability. I'm not going to mention sources, but rest assured those sources are as 'horse's mouth' as it is possible to be.
Let's get away from debating if it's true or not.
that statement you quote is by Peter Grey the article's author - not Bob Spaulding. Where Peter got that information is anyone's guess. Clearly, in that article he is 'selling' the aircraft (as he tends to do in most of his 'flight tests'.)
I agree that HC's comments are somewhat emotive, and do not wish to become embroiled in a transtlantic and north/south hemisphere spat. However, I can say that HC is absolutely correct in his assertion that the MGB does not have a run dry capability. I'm not going to mention sources, but rest assured those sources are as 'horse's mouth' as it is possible to be.
Let's get away from debating if it's true or not.
As someone who has been quite close to the machine for the last 5 years I can say that HC and 212man are correct. There are two facts in play that can confuse:
Fact 1. The aircraft is certified to JAR29 amdt 47. The TCDS confirms this.
As such Sikorsky had to satisfy the FAA that it complied with FAR 29.927. They did this by persuading the regulators that the only possible cause of loss of lubrication was an oil leak somewhere in the oil cooler line and hardware, hence the inclusion of the shutoff valve.
Fact 2. The aircraft has NO 30 minute MGB run dry capability. The salesmen can get clever and imply it by virtue of Fact 1!!!
When the MGB was first tested against FAR 29.927 Sikorsky were confident that the gearbox would pass the run dry test, why not be - the S70 gearbox is OK. However it did not run for 30 minutes (I could quote a figure as to how long it did run but to do so might be dangerous in light of the Cougar accident?), hence the "bolt on" oil cooler shut off valve - and it does look like a bolt on! This is also why, I believe, selection of the valve is not yet automated. The valve was so last minute that there was no time available to get clever with it!
So Brian, the aircraft is "compliant" with the "run dry" certification clause, but only because of a pretty big fudge factor that the regulators bought. Bottom line is that MGB does not have a certified 30 minutes operating capability without any MGB oil circulating.
HTH?
Fact 1. The aircraft is certified to JAR29 amdt 47. The TCDS confirms this.
As such Sikorsky had to satisfy the FAA that it complied with FAR 29.927. They did this by persuading the regulators that the only possible cause of loss of lubrication was an oil leak somewhere in the oil cooler line and hardware, hence the inclusion of the shutoff valve.
Fact 2. The aircraft has NO 30 minute MGB run dry capability. The salesmen can get clever and imply it by virtue of Fact 1!!!
When the MGB was first tested against FAR 29.927 Sikorsky were confident that the gearbox would pass the run dry test, why not be - the S70 gearbox is OK. However it did not run for 30 minutes (I could quote a figure as to how long it did run but to do so might be dangerous in light of the Cougar accident?), hence the "bolt on" oil cooler shut off valve - and it does look like a bolt on! This is also why, I believe, selection of the valve is not yet automated. The valve was so last minute that there was no time available to get clever with it!
So Brian, the aircraft is "compliant" with the "run dry" certification clause, but only because of a pretty big fudge factor that the regulators bought. Bottom line is that MGB does not have a certified 30 minutes operating capability without any MGB oil circulating.
HTH?
SAS
No SAS, that would be a really bad idea, assuming you have multiple indications of no oil circulating (gauges + seperate lights etc) however you could be right in that, in desperation, a crew might cling to that idea especially if they had read on Pprune that lots of Old and Bold pilots were "recommending" it.
If that were the correct thing to do, it would say so in the RFM. Low and Slow = high power and low cooling air. In general, a gearbox doesn't give out gracefully, there is too much energy involved. Most likely it will seize rapidly with minimal warning and rip itself out of the airframe, in the mean time imparting a lot of angular acceleration to the passengers (ie breaking a few neck, banging a few heads) before departing from the fuselage and allowing it to drop like a brick. Do you know what it feels like to be in a helicopter that is dropped from even 50' whilst spinning rapidly? (neither do I but I'm sure its not nice). Don't think the water is soft - its like concrete under those circumstances. Then you have unconscious passengers + broken fuselage + water = not survivable.
Bottom line is a controlled ditching is always the best option, even if you don't like the look of the sea state - unless you are seconds away from somewhere solid to land on.
If the sea state means that the RFM instruction "Land Immediately" translates into "prepare to meet your maker", then perhaps you shouldn't be flying there in the first place.
HC
..."get low and slow and let the whole World know...get SAR coming....and get prepared to ditch if anything whatsoever happens to show this is for real!"
If that were the correct thing to do, it would say so in the RFM. Low and Slow = high power and low cooling air. In general, a gearbox doesn't give out gracefully, there is too much energy involved. Most likely it will seize rapidly with minimal warning and rip itself out of the airframe, in the mean time imparting a lot of angular acceleration to the passengers (ie breaking a few neck, banging a few heads) before departing from the fuselage and allowing it to drop like a brick. Do you know what it feels like to be in a helicopter that is dropped from even 50' whilst spinning rapidly? (neither do I but I'm sure its not nice). Don't think the water is soft - its like concrete under those circumstances. Then you have unconscious passengers + broken fuselage + water = not survivable.
Bottom line is a controlled ditching is always the best option, even if you don't like the look of the sea state - unless you are seconds away from somewhere solid to land on.
If the sea state means that the RFM instruction "Land Immediately" translates into "prepare to meet your maker", then perhaps you shouldn't be flying there in the first place.
HC
Last edited by HeliComparator; 18th Mar 2009 at 11:00. Reason: removing personal comments
Brian
Your point about the Wessex is a slightly different one. With "something funny going on" I agree that low and slow might be a good idea, but when there are clear multiple indications of no oil circulating, its a bad idea and you have to land/ditch asap.
HC
Your point about the Wessex is a slightly different one. With "something funny going on" I agree that low and slow might be a good idea, but when there are clear multiple indications of no oil circulating, its a bad idea and you have to land/ditch asap.
HC
Last edited by HeliComparator; 18th Mar 2009 at 10:26.