Helicopter crash off the coast of Newfoundland - 18 aboard, March 2009
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The crew had a right to expect (even if they didn't understand FAR29) a gearbox that could run for 30 minutes after any credible type of oil loss because that is the requirement in the latest FARs which Sikorsky were happy to trumpet they complied with.
Bucket Speed, Min Power call it what you like, with GB problems wouldn't (shouldn't) you fly using the lowest amount of power possible?
P
(Treetoupow)
I can almost guarantee Ti studs were originally used for weight issues. During a period of time during work on the CH148 production modification SAC was willing to pay the engineering teams multiple thousands of dollars worth of engineering hours per pound saved...especially from the dynamic system. The 92 was seemingly perpetually overweight.
And its laughable to consider the gearboxes/oil filter arrangement of the 92 versus UH60 as being one-in-the-same. For one thing, the filter on the 60 is mounted vertically, not cantilevered off the side of the MGB casting shaking on giant moment arm with the 1P.
The relationship between 92 and S70/UH60 was only ever as close as whoever the potential customer wanted it to be.
US or foreign military? Its the same proven helicopter!
Commercial or VVIP? Its an thorough evolution into a new state of the art machine, not some old 1970s technology! (Its got AVC!)
And its laughable to consider the gearboxes/oil filter arrangement of the 92 versus UH60 as being one-in-the-same. For one thing, the filter on the 60 is mounted vertically, not cantilevered off the side of the MGB casting shaking on giant moment arm with the 1P.
The relationship between 92 and S70/UH60 was only ever as close as whoever the potential customer wanted it to be.
US or foreign military? Its the same proven helicopter!
Commercial or VVIP? Its an thorough evolution into a new state of the art machine, not some old 1970s technology! (Its got AVC!)
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To Nick and all the expert out there, can the Aux Tank can be the cause of the titanium failure. Let me explain, the only 2 aircrafts which had studs failure where equipped with the same aux tank. Is it possible the aux tank which is located under the transmission, induce a vibrations that can be the source of the studs break down?
FH
FH
brian
I think I posted that sheet "tech info 7" some pages ago but had the same response, not in the RFM, but people had that thought in their minds, & when it is put it in the sea, or fly it I don't know what I would do, I know what pilots were told to do but!! (FAR29 said?) & it is a big but, how many will die of hypothermia? (remember the suits also came in for criticism)
Read report there appear to be faults all round, FAA, should have been more proactive, Sikorsky should have fronted up & said in plain speak it wont run for 30 min as stated in TI 7, & pilot CRM lacking.
A really sad outcome for all, especially the families
I think I posted that sheet "tech info 7" some pages ago but had the same response, not in the RFM, but people had that thought in their minds, & when it is put it in the sea, or fly it I don't know what I would do, I know what pilots were told to do but!! (FAR29 said?) & it is a big but, how many will die of hypothermia? (remember the suits also came in for criticism)
Read report there appear to be faults all round, FAA, should have been more proactive, Sikorsky should have fronted up & said in plain speak it wont run for 30 min as stated in TI 7, & pilot CRM lacking.
A really sad outcome for all, especially the families
To Nick and all the expert out there, can the Aux Tank can be the cause of the titanium failure. Let me explain, the only 2 aircrafts which had studs failure where equipped with the same aux tank. Is it possible the aux tank which is located under the transmission, induce a vibrations that can be the source of the studs break down?
Transport Canada require that supplemental underwater breathing apparatus be mandatory for all occupants of helicopters involved in overwater flights who are required to wear a Passenger Transportation Suit System.
Leads to question: do all Pax on such flights have to show a "I am HEEDS bottle trained" card or be denied passage?
Did HEEDS training in USN a while back ... over a decade ago ... I don't think it's a trivial training cost, depending on if you have to do a full pool exposure or not to meet a training spec.
EDIT to ADD:
In the discussion of MGB malfunctions for the SH-60 family, a SAC product which I flew, there is this WARNING (NATOPS Manual a couple of revs out of date, but probably still there, as it is the same as when I first learned it in the late 80's)
WARNING
• Catastrophic transmission failure will result in loss of helicopter control. Consideration should be given to transiting at minimum power airspeed and a low altitude flight profile (approximately 80 feet and 80 KIAS) to permit a quick flare followed by an immediate landing/ditching.
• Operation of the main gearbox with no oil pressure may result in failure of the tail rotor drive takeoff pinion gear and subsequent loss of tail rotor drive.Note
• A loss of all main transmission lubricating oil may result in unreliable temperature indications from the main transmission temperature gauge and temperature sensor (caution light).
Question: do most helicopters have similar language to the above? (EDIT: reloading the page just gave me the second half of the report, so I see analysis of "similar language" on that score.)
I would expect SAC helicopters to have similar language, unless that is some Navese imported from another helicopter type into the SH-60 manual.
EDIT: I just noticed that the training manual does not appear to have made a point in re the NATOPS Note above:
. 
EDIT: I just noticed that the training manual does not appear to have made a point in re the NATOPS Note above:
The PTM does not include information regarding how the temperature gauge senses temperature (i.e., that it is a wet bulb requiring immersion in oil) or that it would be unreliable in the event of a total loss of oil, as it would, in such a case, measure ambient temperature inside the MGB case
And ...
.
The RFM makes no mention of how MGB oil temperature will react to a complete loss of lubricating oil (i.e., that it will be unreliable because it measures ambient temperature inside the MGB case)
I noted in the narrative of the mishap 
that for one reason or another, the investigators infer that the crew either did not expect imminent failure ... or as SASless so poignantly put it, they were faced with not just "between Devil and Deep Blue Sea" but also "sea state that may kill us before we get out, and freeze us if we do" as choices available.
that for one reason or another, the investigators infer that the crew either did not expect imminent failure ... or as SASless so poignantly put it, they were faced with not just "between Devil and Deep Blue Sea" but also "sea state that may kill us before we get out, and freeze us if we do" as choices available. Vaya con Dios, amigos.
LAST EDIT: From the report
LAST EDIT: From the report
1.18.6 Social Media
Starting in March 2000, before the S-92A went into commercial use, website visitors engaged in discussions about the introduction of the S-92A. Many of the individuals who posted on this website chose to remain anonymous. However, others such as one of Sikorsky's senior managers for the S-92A program, who was a regular contributor to the online discussion, chose to identify themselves. Over the course of several years, the subject of the S-92A's compliance with Part 29 was discussed at length among members of this internet forum. From these online discussions, it was evident that those involved understood that the S-92A did not have a run dry capability.
It was determined during the TSB investigation that at least one senior manager, and several other pilots at Cougar Helicopters periodically reviewed the material posted on the above mentioned internet forum.
It was determined during the TSB investigation that at least one senior manager, and several other pilots at Cougar Helicopters periodically reviewed the material posted on the above mentioned internet forum.
Last edited by Lonewolf_50; 15th Feb 2011 at 19:58.
From these online discussions, it was evident that those involved understood that the S-92A did not have a run dry capability.
SAC has been consistently economical with its marketing hyperbole - the 'heritage' claimed from the 60 implied similar components with proven track records but it now seems that any compatibility is only backwards such that the S-92 transmission could be retro-fitted to the 60 if it needed to be upgraded.
SAC traded heavily on the safety credentials of its new baby - ironically those credentials appear to have been acquired by obfuscation and manipulation of weak legislation.
Not before the Cougar crash it wasn't.
Not before the Cougar crash it wasn't.
Crab's reputation takes another dive
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Finally came back to look at this thread as it intrigued the heck out of me. I also made an OB way back about whether the oil temp gauge worked off a wet bulb or not. If it did, then the temp guage will quite quickly reduce in temp as the oil disappears, (the same as a motor car water radiator wet bulb after one clobbers a Kangaroo or some other road loiterer and buggers the radiator) leading to a false conclusion that all may not be quite so bad. This looks like a conclusion reached by the crew in the lead up paras of the report when they levelled off at 800 feet.
Nowadays we all seem to have to adhere to these blessed SMS courses and manuals.
This report overlooks any safety aspect in the company SMS material (according to the report) that may emanate from lack of oil or how the wet bulb will not then work, and what to do about it.
Fat lot of good all that money spent on SMS in this case. Loaded the crew up with a whole heap of gaff, except the really important stuff!
I wonder if the recurrency training is now doing anything about this, not only this type but all types that use a wet bulb sensor.
In the extract below one can see clearly why the pilot made the mistake of flying on. I.E. no knowledge, or simply overlooked, how to interpret a cooling wet bulb temp after it had first run hot. together of course with no oil pressure.
It is so sad that something so simple can be overlooked and lead to catastrophe. A revolting systemic abomination.
1.17.3.2 S-92A Classroom Training
For the S-92A, Cougar Helicopters sends many of its pilots to the Flight Safety International (FSI) facility in West Palm Beach, Florida, for the initial course and subsequent recurrent training. Although less frequently, Cougar Helicopters also sends pilots to the FSI facility at Farnborough, United Kingdom. The captain had completed his most recent recurrent training from 05 to 09 January 2009 at the FSI facility at Farnborough UK. Having completed his initial S-92A training in May 2008, the first officer was due for recurrent training in June 2009.
FSI has been the Sikorsky factory-authorized training source for pilots and maintenance technicians since 1983. The FSI web site advises that it is dedicated to keeping its instruction accurate and up to date. Similarly, the Sikorsky web site indicates that Sikorsky's alliance with FSI provides its S-92 commercial customers with the highest quality training available, with factory-approved curriculum for the helicopter at its Learning Center in West Palm Beach, Florida. Although Sikorsky does not actually approve the content of the S-92 Pilot Training Manual (PTM), Sikorsky pilots who take the S-92 ground school and simulator programs monitor the content, and provide recommendations for improvement to FSI. There is frequent contact between FSI and the Sikorsky customer service representative to address questions about training.
The recurrent ground training, including helicopter systems training, is taught referencing the FSI S-92A PTM and the S-92A RFM and consists of 22 hours of classroom instruction. An assessment of the course content was completed based on investigation interviews, a review of the FSI training module and a review of Chapter 10 of the PTM, which covers the S-92A powertrain.
The PTM powertrain chapter explains that lubrication of the MGB is through a dual lubrication pump system. The PTM includes a lubrication system schematic for the powertrain that depicts the dual lubrication pumps and a picture of the two external oil pumps mounted on the front of the powertrain. It also notes that if one pump should fail, the lubrication system can still supply sufficient lubrication; however, the pressure will drop to the lower green range (i.e., approximately 45 PSI). The PTM states that if both pumps should fail (loss of all lubrication), safe operation is still possible for a short period of time. There is no mention as to how long the gearbox would be able to continue operating, nor is there an identified recommended maximum time of continued safe operation, following a loss of lubricant in either the PTM or RFM.
The PTM is consistent with the RFM, part 2, section 1 with the exception of its explanation of the oil pressure sensing system. The PTM mentions that if the MGB oil pressure drops below 24 psi (sensed by the switch at the left accessory module) or 35 psi (measured by the pressure transducer in the input manifold), the red MGB OIL PRES warning message appears and a "gearbox pressure…gearbox pressure" audio sounds. However, the manufacturer has since clarified to the TSB that the information in the RFM is correct and that each sensor must independently record low oil pressure conditions; the transducer oil pressure must drop to 35 psi and the oil pressure at the left accessory module must decrease to 24 psi in order for the aural warning and the master warning to activate.
Other MGB components identified in the PTM include the chip detector, the oil temperature sensor, the MGB oil pressure switch, and the oil pressure sensor. The PTM does not include information regarding how the temperature gauge senses temperature (i.e., that it is a wet bulb requiring immersion in oil) or that it would be unreliable in the event of a total loss of oil, as it would, in such a case, measure ambient temperature inside the MGB case.
Nowadays we all seem to have to adhere to these blessed SMS courses and manuals.
This report overlooks any safety aspect in the company SMS material (according to the report) that may emanate from lack of oil or how the wet bulb will not then work, and what to do about it.
Fat lot of good all that money spent on SMS in this case. Loaded the crew up with a whole heap of gaff, except the really important stuff!
I wonder if the recurrency training is now doing anything about this, not only this type but all types that use a wet bulb sensor.
In the extract below one can see clearly why the pilot made the mistake of flying on. I.E. no knowledge, or simply overlooked, how to interpret a cooling wet bulb temp after it had first run hot. together of course with no oil pressure.
It is so sad that something so simple can be overlooked and lead to catastrophe. A revolting systemic abomination.
1.17.3.2 S-92A Classroom Training
For the S-92A, Cougar Helicopters sends many of its pilots to the Flight Safety International (FSI) facility in West Palm Beach, Florida, for the initial course and subsequent recurrent training. Although less frequently, Cougar Helicopters also sends pilots to the FSI facility at Farnborough, United Kingdom. The captain had completed his most recent recurrent training from 05 to 09 January 2009 at the FSI facility at Farnborough UK. Having completed his initial S-92A training in May 2008, the first officer was due for recurrent training in June 2009.
FSI has been the Sikorsky factory-authorized training source for pilots and maintenance technicians since 1983. The FSI web site advises that it is dedicated to keeping its instruction accurate and up to date. Similarly, the Sikorsky web site indicates that Sikorsky's alliance with FSI provides its S-92 commercial customers with the highest quality training available, with factory-approved curriculum for the helicopter at its Learning Center in West Palm Beach, Florida. Although Sikorsky does not actually approve the content of the S-92 Pilot Training Manual (PTM), Sikorsky pilots who take the S-92 ground school and simulator programs monitor the content, and provide recommendations for improvement to FSI. There is frequent contact between FSI and the Sikorsky customer service representative to address questions about training.
The recurrent ground training, including helicopter systems training, is taught referencing the FSI S-92A PTM and the S-92A RFM and consists of 22 hours of classroom instruction. An assessment of the course content was completed based on investigation interviews, a review of the FSI training module and a review of Chapter 10 of the PTM, which covers the S-92A powertrain.
The PTM powertrain chapter explains that lubrication of the MGB is through a dual lubrication pump system. The PTM includes a lubrication system schematic for the powertrain that depicts the dual lubrication pumps and a picture of the two external oil pumps mounted on the front of the powertrain. It also notes that if one pump should fail, the lubrication system can still supply sufficient lubrication; however, the pressure will drop to the lower green range (i.e., approximately 45 PSI). The PTM states that if both pumps should fail (loss of all lubrication), safe operation is still possible for a short period of time. There is no mention as to how long the gearbox would be able to continue operating, nor is there an identified recommended maximum time of continued safe operation, following a loss of lubricant in either the PTM or RFM.
The PTM is consistent with the RFM, part 2, section 1 with the exception of its explanation of the oil pressure sensing system. The PTM mentions that if the MGB oil pressure drops below 24 psi (sensed by the switch at the left accessory module) or 35 psi (measured by the pressure transducer in the input manifold), the red MGB OIL PRES warning message appears and a "gearbox pressure…gearbox pressure" audio sounds. However, the manufacturer has since clarified to the TSB that the information in the RFM is correct and that each sensor must independently record low oil pressure conditions; the transducer oil pressure must drop to 35 psi and the oil pressure at the left accessory module must decrease to 24 psi in order for the aural warning and the master warning to activate.
Other MGB components identified in the PTM include the chip detector, the oil temperature sensor, the MGB oil pressure switch, and the oil pressure sensor. The PTM does not include information regarding how the temperature gauge senses temperature (i.e., that it is a wet bulb requiring immersion in oil) or that it would be unreliable in the event of a total loss of oil, as it would, in such a case, measure ambient temperature inside the MGB case.
Interesting thought re the stud failures on the oil filter housing!
its laughable to consider the gearboxes/oil filter arrangement of the 92 versus UH60 as being one-in-the-same. For one thing, the filter on the 60 is mounted vertically, not cantilevered off the side of the MGB casting shaking on giant moment arm with the 1P.
My understanding - which could be wrong - is that the baseline impurity levels for oil in the can is for larger particulates than the filter. Hence the nuisance bypass pop out indications and hence the reason 'some' (no names, no pack drill) operators use pre-filtering. As mentioned in the report.
It would be nice to know why more attention wasn't given to the electrical power loss. Was it a sudden Nr drop or AC GEN overheat - caused by loss of cooling oil? I think it's also a bit simplistic to say the AC Generators are engine driven, too. They are essentially MGB driven, and most certainly MGB oil cooled.
It would be nice to know why more attention wasn't given to the electrical power loss. Was it a sudden Nr drop or AC GEN overheat - caused by loss of cooling oil? I think it's also a bit simplistic to say the AC Generators are engine driven, too. They are essentially MGB driven, and most certainly MGB oil cooled.
Interesting thought re the stud failures on the oil filter housing!
Here is everything you ever wanted to know about the UH60 drive system in a nice concise document with lots of pictures (note the explicit entry of "With a loss of all oil, the main XMSN will continue to operate in flight for another 30 minutes"):
http://aasf3-ny.org/4-Standards/Docu...r%20System.pdf
Look on the lower right
http://www.army.mil/-images/2009/04/...-16-150409.jpg
My understanding - which could be wrong - is that the baseline impurity levels for oil in the can is for larger particulates than the filter. Hence the nuisance bypass pop out indications and hence the reason 'some' (no names, no pack drill) operators use pre-filtering. As mentioned in the report.
212, if the S-92 is similar to the Hawk series (S-70 derivatives) IIRC the main generators dropoff when Nr droops in the Nr = low 90's high 80's. (The number in my memory is 92% but that might not be right).
EDIT: Heh,
memory is not all bad ... from the FCF checklist a few iterations ago ...
b. Underfrequency protection — Test.
I think that in the Cougar mishap, the backup generator (powered by the APU) was up and running. That said, in the Hawk series, the switch over from #1 / #2 gen to Backup Gen powering the various AC and DC busses isn't what I'd call seamless. (TYpically SAS and AFCS kick off, though I don't think Boost would kick). I'll guess it isn't in the S-92. (I think this has been addressed both in this thread, and in the TSBoC report).
SansAn ... thanks for the training manual, it restores a bit that was lost in memory.
EDIT: Heh,
memory is not all bad ... from the FCF checklist a few iterations ago ... b. Underfrequency protection — Test.
(1) No. 1 and No. 2 PCLs — Retard slowly.
(2) #1 GEN and #2 GEN cautions — Appear between 92 and 97 percent N
r. Allow a 3-second time delay. Note Nr.
(3) No. 1 and No. 2 PCLs — FLY. Note #1 GEN and #2 GEN cautions disappear.
(3) No. 1 and No. 2 PCLs — FLY. Note #1 GEN and #2 GEN cautions disappear.
I think that in the Cougar mishap, the backup generator (powered by the APU) was up and running. That said, in the Hawk series, the switch over from #1 / #2 gen to Backup Gen powering the various AC and DC busses isn't what I'd call seamless. (TYpically SAS and AFCS kick off, though I don't think Boost would kick). I'll guess it isn't in the S-92. (I think this has been addressed both in this thread, and in the TSBoC report).
EDIT: More data that my memory isn't completely shot.
Power transfer from the APU generator or EXT PWR to the No. 1 generator may cause disengagement of SAS 1, SAS 2, TRIM, AUTO PLT, and stabilator.
SansAn ... thanks for the training manual, it restores a bit that was lost in memory.
Last edited by Lonewolf_50; 16th Feb 2011 at 17:42.
For SansAnhedral.
I am not so sure. Ti also has superior corrosion resistance, and if the S-92 was expected to be sold to maritime environment operators, that consideration (as well as dissimilar metal interface issues where the studs seat in the mag housing) may also have been a factor. At that order of magnitude, the weight of three Ti studs or Steel Studs looks negligible ... however, if as you say it was financially incentivized, perhaps the material selection was, for that reason, more heavily weighted than would otherwise have been the case. (Sorry for that poor pun 
). A lot of little fractions of a pound saved here and there add up to pounds saved from the transmission deck ... and thus not passed into the airframe via the xmission mount ... and so on.
Every helicopter does the weight battle for that ten pounds here and the fifty pounds there during design, does it not? It's a never ending battle and series of compromises.
FWIW, I don't see the oil filter bowl as part of the dynamic system ... I see from the swashplate to the ends of the rotor blades as the dynamic system, but perhaps I misunderstand what you are referring to there. Are you referring to "the dynamic system" as being that load of stuff mounted to the transmission deck, and thus vibrating as soon as the rotors start to turn?
I think the term you seek is "one and the same" but I caught your drift. 
"Giant?" (do you mean that in reference to the cross section of the bolt?)
and why the 1P rather than the 4P?
I agree with your point on the stress analysis having to consider vibration and loads differently than with the sump mounted filter in the Hawk series ...
I can almost guarantee Ti studs were originally used for weight issues.
). A lot of little fractions of a pound saved here and there add up to pounds saved from the transmission deck ... and thus not passed into the airframe via the xmission mount ... and so on.
During a period of time during work on the CH148 production modification SAC was willing to pay the engineering teams multiple thousands of dollars worth of engineering hours per pound saved...especially from the dynamic system. The 92 was seemingly perpetually overweight.
FWIW, I don't see the oil filter bowl as part of the dynamic system ... I see from the swashplate to the ends of the rotor blades as the dynamic system, but perhaps I misunderstand what you are referring to there. Are you referring to "the dynamic system" as being that load of stuff mounted to the transmission deck, and thus vibrating as soon as the rotors start to turn?
And its laughable to consider the gearboxes/oil filter arrangement of the 92 versus UH60 as being one-in-the-same.
For one thing, the filter on the 60 is mounted vertically, not cantilevered off the side of the MGB casting shaking on giant moment arm with the 1P.
For one thing, the filter on the 60 is mounted vertically, not cantilevered off the side of the MGB casting shaking on giant moment arm with the 1P.
shaking on giant moment arm with the 1P
and why the 1P rather than the 4P?
I agree with your point on the stress analysis having to consider vibration and loads differently than with the sump mounted filter in the Hawk series ...
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Aux tanks: I personally can't see either the tanks or the sector length having an effect on the filter studs.
Filter removals: This seems a bigger potential factor. Sadly it is not possible from the information presented to determine if the CHC and Cougar filter removals (particularly on the two aircraft that had oil oss in flight) was significantly worse than other operators.
Oil filtering: 212man, yes perhaps some operators choose to pre-filter their oil. However if that was essential it shuld have been in the Maintnance Manual!
Titanium: No matter what reason, gaulling makes titanium a poor material choice and this should have been considered in the FMEA.
Part 29.927(c)(1) Design Assessment FMEAs: As Sikosky failed to even consider the oil loss from the filter housing (see below) it is no surprise thatneither was the material choice challenged or recoconsidered when service experience showed high filter removal rates (and so high gaulling potential)/
Studs are critical: Two events of oil loss now show that the studs are what FAR29 defines as 'Critical Parts', irrespective of what material they are. AFAIK they are still not subject to the enhanced critical parts control regieme required by FAR29 for such parts.
Social media: My reading of the TSB report is that they are implying that they believe that contributors to a certain forum did understand the situation but TSB aren't necessarily claiming that contributors actually wrote what they understood.
Blackhawks: Great info guys! A contact in Australian Army tells me that their aircraft have steel bolts (not studs) - highlighting another difference. If the US Army documents are correct in saying the its MGB can operate for 30 minutes without oil then the S-92 is a massive retrograde step and by no means the wonder that some made it oput to be.
Filter removals: This seems a bigger potential factor. Sadly it is not possible from the information presented to determine if the CHC and Cougar filter removals (particularly on the two aircraft that had oil oss in flight) was significantly worse than other operators.
Oil filtering: 212man, yes perhaps some operators choose to pre-filter their oil. However if that was essential it shuld have been in the Maintnance Manual!
Titanium: No matter what reason, gaulling makes titanium a poor material choice and this should have been considered in the FMEA.
Part 29.927(c)(1) Design Assessment FMEAs: As Sikosky failed to even consider the oil loss from the filter housing (see below) it is no surprise thatneither was the material choice challenged or recoconsidered when service experience showed high filter removal rates (and so high gaulling potential)/
Neither the FAA nor Sikorsky specifically considered a failure in the MGB oil filter bowl assembly, or its attaching fasteners, in the context of Part 29.927(c)(1).
Social media: My reading of the TSB report is that they are implying that they believe that contributors to a certain forum did understand the situation but TSB aren't necessarily claiming that contributors actually wrote what they understood.
Blackhawks: Great info guys! A contact in Australian Army tells me that their aircraft have steel bolts (not studs) - highlighting another difference. If the US Army documents are correct in saying the its MGB can operate for 30 minutes without oil then the S-92 is a massive retrograde step and by no means the wonder that some made it oput to be.
Sans, thanks, "dynamic systems" being all them things moving ... like gears and shafts. 
Aux tanks: I personally can't see either the tanks or the sector length having an effect on the filter studs.
Oil filtering: 212man, yes perhaps some operators choose to pre-filter their oil. However if that was essential it shuld have been in the Maintnance Manual!
The Manufacturer might not be the best at assessing this for a given operator. Given the variability of oil suppliers, any operator may have
a) best supplier, and no need to filter
b) variable suppliers, and maybe a standing need to filter
Titanium: No matter what reason, gaulling makes titanium a poor material choice and this should have been considered in the FMEA.
Don't know.
Studs are critical: Two events of oil loss now show that the studs are what FAR29 defines as 'Critical Parts', irrespective of what material they are. AFAIK they are still not subject to the enhanced critical parts control regieme required by FAR29 for such parts.
Blackhawks: Great info guys! A contact in Australian Army tells me that their aircraft have steel bolts (not studs) - highlighting another difference. If the US Army documents are correct in saying the its MGB can operate for 30 minutes without oil then the S-92 is a massive retrograde step and by no means the wonder that some made it oput to be.
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L_50, in fact HEEDS is now in use for passenegers flying out of St Johns. It took 6+ years to introduce and had been stalled up until after the accident.
HC, yes Rick Burt left for Australia in the middle of lasy year. I don't know why, but the travelling from home in BC to NL and the Inquiry appreances after the accident must have been a strain.
HC, yes Rick Burt left for Australia in the middle of lasy year. I don't know why, but the travelling from home in BC to NL and the Inquiry appreances after the accident must have been a strain.