Sikorsky S-92: From Design to Operations

[Horror box]

I agree with Riff Raff here. This does not have so much to do with the S92 and more to do with the general defense procurement procedures. Every military suffers this when they introduce a new type. Just Google the UK Typhoon project (originally EF2000!) for a incredible example, then look at the Future Lynx, EH101 Merlin, the Australian Tiger introduction and their NH90 programme. It is not just limited to the aviation world either. The army and Navy get equally bad service. In a process that is often drawn out over many years, national interests and budgets change, requirements are added and removed from the list, training has to be implemented, new wars pop up, and the project inevitably stalls somewhat while the two parties try and solve the new problems. It is generally a fairly dynamic process from start to finish. If the Canadians manage to replace their fleet within 2-3 years of the original date, I would say they have done bloody well.

[pasptoo]

The delay with CH148 isn't all bad though, the CDN$ is almost parity with the US$ so making the project cheaper than first seen.

The Chretien government messed around with the Sea King replacement so much that the contract is actually THIRTY YEARS LATE, so another 2-3 years late is nothing.

The CF will, I'm sure, get an airframe that is very 21st Century and ideal for every theatre. It is so very unfortunate that the civil airframe got some very bad press so close to home. All eyes are now on the replacement of the bad mouthed Sea King (she is almost 50) so it has a lot to live up to.

Chinooks? Well there is another Chretien own goal! He replaced all the CF Chinooks with Griffins back in the 90s - I think, of course the Griffin are ideal for carrying lots of troop and lifting big loads, (if you have lots of them). Hope they don't loose the Griffin as a result of the Chinook purchase.

[maxwelg2]

It is so very unfortunate that the civil airframe got some very bad press so close to home.

So losing 17 lives is "unfortunate" is it, rather poor choice of words sir. Are you for one second even suggesting the lack of 30-minute dry-run time is just "bad press"?

Assuming that the CH-148 will have this capability, I'm also assuming that some of the overspend of nearly twice the original budget of this variant can be directly attributed to its development.

Hopefully we will soon see this feature in the S-92b, as well as no more mounting feet cracks.

Safe flying

Max

[Variable Load]

Max...patience is a virtue. The CH-148 has nothing to do with civil S-92 "run dry" capability. The aircraft you are flying in is intrinsically safe, even though you emotions won't let you realise that.

[Lt.Fubar]

I'm reading this and few other discussions and it amaze me to see the lack of "30 minutes run dry capability" being perceived as the biggest issue here. Because:

A. I can't think about a design in a 12ton MTOW airframe that would be trully capable of that. And actively cooling components doesn't count, as that's more of a "semi-dry" and not truly dry system, and when that system fails, the MGB will seize in minutes if not seconds.

B. What if such system would be made and put into the S-92, and another crash took place... would we write then, that's because there is no 45 minutes run dry capability ?

That one gearbox withstood more than was needed to safely ditch that helicopter. There are other things that are wrong with that airframe, as noise, vibrations and poor "hot&high" performance, yet barely anyone mention it, and every third post I read is about that mythical 30 minutes dry run thing.

[dangermouse]

Fubar, ....you are wrong

I am not privvy to all the details but from what has been posted here

A 30 minute dry run requirement was not applicable to the S92 as the safety case concluded that the likelihood of lubrication failure was 'extremely remote' and was therefore correctly certified (as was allowed, no one did anything illegal, although with hindsight were the safety case conclusions wrong?), however this allowance was (probably) misunderstood and may have influenced the actions of the crew that day.

If the crew had followed the FRC actions (if I recall 'land immediately') a tragedy may have been avoided.

regarding a 'mythical' 30 minute dry run capability:

EH101 MTOW 14600 kg, 30 minute DRY RUN MGB qualified and in service.

30 minutes (not 45) is the FAA/JAA requirement and aircraft procedures are written around that.

Cocievably if a longer capability was demonstrated to the authorities satisfaction you could allow use of that greater capability

DM

[maxwelg2]

That one gearbox withstood more than was needed to safely ditch that helicopter.

Lt. Fubar, good point, and one I'm sure will be pressed hard during the next month or so as the TSB report is issued.

Your second valid point relates to "what do we consider an acceptable run dry capability". My personal opinion is "consider none exists", it should be a safety contingency to allow the PIC to consider options such as landing on the nearest helideck/landing area. Where that is not possible then our PPE and helicopter safety evacuation training should be our safety system that we rely on. This then raises the issue of flying a civilian helo in adverse weather conditions and the current sea state/flying limits.

Variable Load, it is not emotions but the cold facts that form my current opinion of the S-92. It is only via extensive additional control measures and inspections that our operator still agrees to fly this helo i.e. MGB feet visual inspection prior to each flight. This may have changed as I have not flown in 6 months but I haven't heard of the uprated MGB mounting feet being implemented. Is this the case now?

Was the S92a not meant to take the advanced technology previously developed for the Blackhawk/Seahawk to make it the safest helicopter available? If that was the case then why was there no 30-minute run-dry time capability as would be expected to be a requirement for the MIL versions? It certainly is with the CH-148 and only now is it being pushed forward.

Why was the filter housing bowl stud failure not foreseen as a possible failure mode for the S-92a instead of only the intercooler system? Vespel spline failure was another one that wasn't accounted for in failure mode analysis or it wouldn't have to have been resolved post-production.

Why did the Broome stud failures and subsequent independant failure analysis report not prompt an immediate SB with immediate effect, especially in light of the FAR29 extremely remote classification that the MGB/lube oil system had?

These questions and many more have been already posted on this forum, I guess as a mere PAX I'm just curious as to where the definitive answers will come from.

Safe flying

Max

[Brian Abraham]

I'm reading this and few other discussions and it amaze me to see the lack of "30 minutes run dry capability" being perceived as the biggest issue here

The 30 minute dry run to me is possibly the greatest issue, because the question is, to what extent was the crews decision making influenced by the widely promoted claim that the aircraft did have the 30minute capability. Not only in the professional aviation press, but also Sikorskys own promotional material - see below. Unfortunately we will never know.

[pasptoo]

Max,

I sense you have an attachment to the Cougar accident, and I sympathise with you. I lost a friend in that accident and will not be forgotten.

I have many more friends flying or soon to be flying the S92/CH148 so I too would like to see the upgraded gearbox et al.

As you will see from my post I was highlighting the misgivings of previous Canadian Governments to allow the military to find itself in the situation it does. The government can not have its' cake and eat it.

Hopefully you can be less emotional in your posts and I am sure that the aircrew flying the machines will be just as curious as to where the answers are coming from. After all they are flying them everyday.

Pas.

[FH1100 Pilot]

Brian, in court when that document is produced (as it most assuredly will be), the SAC lawyers/engineers/whomever will shuffle their feet, clear their throats and go, "Well...aahhhh...uhhhhhh...geez. You see, we really believed that the lines to the oil cooler were the ONLY possible point-of-failure in the transmission lubrication system."

Then, if the plaintiff's attorney is smart, he'll ask: "Are there NO other places that oil might leak out of the transmission? For instance, does the transmission have input seals for the engine driveshafts?"

SAC: "Yes, of course."

ATTY: "I see. And is there an oil seal up where the mast comes out of the transmission?"

SAC: "Yes, of course."

ATTY: "Is there an oil seal where the tail rotor drive shaft comes out of the transmission?"

SAC: "Yes, of course."

ATTY: "So that's four oil seals so far...which are used when you want to keep oil *inside* something, is that correct?"

SAC: "Yes, of course."

ATTY: "And there's no way on God's green earth that oil under pressure could even possibly leak out from those locations?"

SAC: "No. No way. Those seals would never fail. Seals don't fail."

ATTY: "Oh, they don't, huh? Well, humour me for a moment, please. IF a seal did fail, could all of the transmission oil be pumped overboard and lost?"

SAC: "Well...yes...theoretically...if you want to split hairs."

ATTY: "Well that is what we attorneys do best, sir! But thank you. But we'll come back to your seals-that-never-fail in a bit. Meantime, does the S-92 have an externally-mounted oil filter"

SAC: "Yes, yes of course."

ATTY: "And tell the court, please, how is that filter attached to the main structure of the gearbox?"

SAC: "Well, we use studs to secure the filter housing to the transmission."

ATTY: "Ah yes, the infamous studs. And is there an oil seal of some sort there as well?"

SAC: "Yes, of course."

And the jury will see that there are PLENTY of places where oil might possibly leak out of an S-92 transmission, not just the oil cooler lines as Sikorsky claimed. The jury will likely conclude that the manufacturer was either negligent in their thinking, OR the FAA was "in bed" with them on this issue. How or why the FAA allowed Sikorsky to get away with that wacky (and insufficient IMHO) isolate-the-lines-to-the-cooler system is something they're probably worried about right now. I can imagine the FAA Administrator at his desk, cradling his head in his hands and going, "Holy Geez, did we REALLY approve that cockamamie setup? Why...WHY?!"

Either way, with their goofy "emergency bypass system," SAC circumvented the letter *and* spirit of the regulations under which the aircraft was certified. That's pretty clear. Then they tried to mislead the customers into thinking that the aircraft could run for a half-hour without transmission juice. That's pretty clear, too.

In fact, the S-92 does not have a "30-minute run-dry" capability. Sikorsky knew that it would last only ten minutes if it *really* ran dry. Which is just about what Cougar got. On the other hand, I'd be surprised if *any* gearbox could run for more than a couple of minutes with no oil whatsoever.

And so it will be interesting to see how a jury feels about two dead pilots...how sympathetic they'll be to their plight: Over the inhospitable, icy, rough North Atlantic Ocean, faced with two different emergency procedures based on whether the transmission oil pressure gauge read 5 psi or 0 psi - and unless it's a digital gauge the difference will be hard to detect...

Tell you what, even *I* wouldn't want to be sitting on that jury.

[maxwelg2]

FH1100, excellent post, I reckon you'll be pretty close to the mark when the actual transcripts are released.

Safe flying

Max

[500e]

Think I posted that page back some, It clearly states 30 Min run dry, I also appreciate the RFM might say different BUT & a big But there I am Gbox oil pressure Going or gone X passengers 2 crew Sea state 2\3 Mtrs Temp -3\4 or lower.
I now have to make a decision, do if I put it down now, or use the mythical 30 minutes! after-all I did see it in a Sikorsky tech sheet, if I land now, there is a fair chance a No.of people will die in the water.
I do not know if this was the thought process but it seems logical, get down low in case it feels as if it is tightening up then we put it in the sea.
If the pilot had followed the FRC & there had been deaths, the pilot would be in the clear,but then who would have held up the tech Info sheet & said he should have flown it back
I went in water in relative warmth of English channel & 400 mm sea state was fished out in under quarter hour with mild hypothermia, admittedly not in survival suit but 2 layers of good quality ocean racing water proofs.
Whatever the outcome these people are gone there may be faults on all sides but the folk left have lost near & dear I don't think I would be to calm either,

[dangermouse]

official document use

playing devils advocate the ONLY documentation a crew should use is the officially certified documentation supplied with the aircraft i.e the RFM, not sales brochures, press briefings or hearsay. Aircrew are not in possession of all the facts regarding how an aircraft is certified and on what basis the RFM actions are generated, so it MUST be the aircrews bible.

The assumptions on which that RFM was written may in the future be shown to be invalid but at the time of the accident it was certified independently.

fh youu are right the FAA and SAC both need to review their safety assumptions and the basis under which the S92 is declared compliant with FAR, because as far as I can see it can't be. The big question in my mind is why is the aircraft STILL flying under a Category A clearance when it is clear that 'extremely remote' isn't.

Again, the EH101 and I believe the Aw139 and the EC225 family do actually HAVE a 30 minute dry run capability, designed, proven and certified. That means you fill the box, drain it out and run at flight powers for 30 minutes, with authority wintesses.

DM

[Horror box]

500e - I think you hit the nail nicely on the head. Pretty much my thoughts exactly.

[industry insider]

FH1100

Only thing is that the court case for the relatives and pilots never happened as settlement was reached before it all went to court. The only outstanding court case is a semi procedural one to compensate Cougar for the hull loss and loss of revenue.

Nice emotive script though.....

[Brian Abraham]

playing devils advocate the ONLY documentation a crew should use is the officially certified documentation supplied with the aircraft i.e the RFM, not sales brochures, press briefings or hearsay

Spoken like a true lawyer dangermouse Unfortunately there are times when following the RFM will kill you, you make the best call you can on the day knowing that you will have to defend your actions if you survive. I'm reminded here of the early 76 Allison overspeed boxes. The FAA/manufacturer came out with an edict that if the engine was installed in a single it was to be disabled (mandatory) but in a twin it was to be serviceable and in use (mandatory). Bearing in mind that a false overspeed trip (of which there were more than a few) could result in an accident (rig take off) guess where most pilots put the circuit breakers (illegal).

I'd be surprised if *any* gearbox could run for more than a couple of minutes with no oil whatsoever

Have had two incidents whereby the MGB emptied itself, fortunately one was on downwind at home base on return from an offshore flight, and the other entailed a 15 minute flight to get somewhere "safe". The latter was done based on prior information from the manufacturers tech rep, not what was in the RFM. Do I recommend not following the RFM? Of course not, but it needs to be remembered it's your butt in the sling. Which ever way it turns out the Monday morning quarterbackers will get you in any event.

[albatross]

Just out of curiousity what is the "date of issue" of that sales brochure?
Very early in the program I would suspect.

[FH1100 Pilot]

Industry Insider:

Only thing is that the court case for the relatives and pilots never happened as settlement was reached before it all went to court. The only outstanding court case is a semi procedural one to compensate Cougar for the hull loss and loss of revenue.

Funny, but as I was writing that bit (and getting a mighty big chuckle out of it I have to admit), I wasn't specifically thinking of the Cougar trial. Sikorsky and the FAA will eventually have to answer for this goofy "Emergency Bypass System" workaround. Maybe not with Cougar, but with some other instance. I wouldn't rule out a civil case in which SAC is challenged as to how their wonderful, safest-aircraft-ever-built aircraft actually meets the requirements of FAR Part 29.

Or not.

[riff_raff]

Again, the EH101 and I believe the Aw139 and the EC225 family do actually HAVE a 30 minute dry run capability, designed, proven and certified. That means you fill the box, drain it out and run at flight powers for 30 minutes, with authority wintesses.

dangermouse,

I agree that all rotorcraft drivetrains should have a demonstrated run dry capability. I also support the US AATD's push for 60 minutes instead of the current 30 minute standard. But having said that, engineering an MRGB with even a 30 minute run dry capability is pretty difficult to do. It can also add quite a bit of expense and complexity, since it usually involves things like multiple, redundant lube system components and exotic high-temp tolerant gear and bearing steels.

In a typical multi-engine MRGB, the lube system is by far the most complex element. Since the lube oil is the primary method of cooling the gears and bearings, once oil flow is interrupted the gears and bearings will quickly build up heat, lose temper strength, and structurally fail.

The problem is made worse when there are multiple, high power engines. The achilles heel of a gearbox like the S-92's is the input bevel gear set. Here you have 100% of engine power passing through a single spiral bevel gear mesh. The high transmitted power combined with the relatively lower efficiency of the spiral bevel gear mesh means this is the most likely point of failure with loss of lube.

As for analyzing and certifying a lube system catastrophic failure event as being "extremely remote", that would have been the result of a statistical reliability analysis and FMEA. The statistical failure rates for each component used in the reliability analysis should have been the same used throughout the industry. The first thing a good attorney would do is get a copy of that reliability analysis and nitpick every failure rate value used. With so many components in the lube system, even a very small change in each component reliability rate would be compounded into a very large change in the overall system reliability rate.

riff_raff

[sox6]

So in summary:

Run-dry is really expensive to do, Sikorsky wanted to do it but failed so they then used an argument that they didn't need it to get certified?

The Lappos rehetoric rings a bit hollow now.
That failure assesment will be very interesting in court as will the testimony of the FAA man who witnessed the first gearbox fail on test.

If the Canadian Cyclone is higher power dosen't that mean its gearbox will fail even faster without oil?