today one of saudi MOI s-92 had INPUT CHIP caution the cew experienced Unusual vibrations and noise after take off at 3000ft (1000 ft) AGL then thy descend for landing and at about 300 ft AGL the caution illuminated the aircraft and the crew landed Safely
Exactly, so my point is if your machine is set up properly then, in my experience ,the vibration in the S92 is no worse than any other aircraft, infact I find it a more pleasant experience than the 225.
NST, my experience of the vibration level of the S-92a is that there is significantly more vibration present in comparison to the Puma family, S-61, S-76, and the old Tiger model that Bond used to fly from Aberdeen back in the early 90s. None of these helos had anti-nodal servos to my knowledge. I've never flew in a 225 so cannot comment on that model's vibration levels versus the S-92a.
I recall earlier posts on this thread commenting on the S-92a vibration issues, mostly blamed on helo weight and 4-rotor design. There have been other good points raised recently such as the use of the aux fuel tanks, payload, flying at max. altitude to improve fuel efficiency etc. over here in NL.
Are we pushing this helo past its design without even realizing it?
Is there any conclusions from HUMS data wrt. variance potential in S-92a vibration levels with AVS on/off, full payload, aux tanks in/out?
When will the TSB release a preliminary report on the stud failure mode?
I suppose being a technical guy I'm looking for a technical explanation and solution. Everything is fixable given the right tools/resources.
Yes the new checklist will tell you to get on the ground/water, and that is bloody important when it comes to surviving. It is what should have happened in the Cougar accident
The RFM hasn't changed, and always said that. Individual operators may be placing more emphasis on what land immediately actually means, perhaps?
From the passenger's point of view there is not much to choose between them - you can either have the slightly larger-cabined but vibratory 92 or the slightly smaller but smoother 225. But I know that the Norwegian offshore wokers unions have repeatedly complained about vibration levels on the 92 - I suspect they would prefer the 225 if they tried it.
Now that I am officially out of the rotorcraft industry, I can finally post on the “vibration issues” with the S-92. In my former position I had the opportunity to go around the world to help customers put the S-92 in service. During that time, I have had the opportunity to ride on customer 92s in the Gulf, the North Sea and Newfoundland. Barring some maintenance issues, all of the 92s I have flown on have been within limits. And there in lies the problem. While the limits on the 92 are acceptable on a military aircraft they are not acceptable in the civil market. It is my experience that some of the operators do just enough track and balance work to get the ship within limits. If you want to feel what a well tuned 92 feels like you need to take a trip to Newfoundland. Their 92 is the smoothest customer aircraft that I have flown in. A well tuned 92 is every bit as good as a Super Puma (which I have also had the opportunity to fly in.)
Road Warrior
Ref post #612
Road warrior, hope you're still reading these posts, I have a question that hopefully you can answer. I stopped at your post as my eyes were glazing over trying to go back through all the history, plus you made a very important comparison to numerous S-92s that you'd flown in globally. For those interested, see posts 207, 221, 473 and trawl through after 612 for more applicable posts.
Does the S-92a AVS automatically compensate for variable payload, weight distribution in the passenger cabin, or does it have to be manually tuned? Could this explain the differing feedback on vibration levels noticed? I'm thinking along the lines of maximum payload + uneven weight distribution in the cabin = quiescent imbalance on airframe. Correct me if I'm way off base (no pun intended) and the ratio of PAX and fuel/cargo combined payload is insignificant in comparison to total aircraft weight.
I'm curious now as thinking back over the last 4 years of S-92 flying I can recall days when the vibes were worse, just wondering why the difference when all the a/c are assumed to be well tuned and knowing that Cougar would have been doing the highest maintenance standard, making it seem more odd that a variable vibration issue should be present. Or is it all down to how hard the rotors are working and all the variables in play there?
Ah well, back to trawling through the posts whilst waiting for some hopefully beneficial insight...
Max,
the system does not automatically compensate for anything, once tuned. The force generators are units containing dual eccentrically rotating masses, which by altering the phase will generate a force in a particular axis and frequency.
The perceived vibration will vary as a function of payload and the relative mass of fuel and load is significant - together they represent a 1/3 of the total max weight, so 50% of the empty weight. Generally, heavily loaded aircraft have greater fuselage damping, so will feel smoother.
I don't believe this argument is relevant to anything relating to the MRGB.
212man, I hear you and would like to be convinced that the way the S-92s have been operated over here has not contributed to the stud failures. Would a detailed examination of various sources of S-92 HUMS data not give us a feel for common/abnormal inherent vibration issues at the MGB? Just wondering when we're going to find out the root cause failure mode for the titanium studs so that we can move forward with confidence that the replacement steel studs cannot suffer from the same fate. I'm assuming that there is now increased maintenance/inspection frequency on these studs, perhaps even change out of the studs every time the filter housing is removed. Can Horror box or someone else in the maintenance crews confirm this?
max,
Your religious belief in HUMS as omniscient and all-knowing is comforting, but totally misplaced. So too is your belief that "the way it is operated" somehow makes studs break or not.
Please, I would bet you are very good at something (I earnestly believe everyone is good at something). Please tell us what that is, and stick to that.
It is almost pathetic to see you appeal to anonymous posters on a rumor web site for assurances. I understand how you feel, but cannot for the life of me understand how you are attempting to put your fears aside using the (sometimes) inane posts of strangers who (like me) do not even believe themselves enough to post with their real names.....
Ramen - the way a helicopter is operated (MAUM, High IAS, High DA, lots of manoeuvering etc) has everything to do with the fatigue spectrum.
The only question really is whether the vibration caused by the rotor in the S-92 has contributed to failure of the filter studs - if so then the way the aircraft is operated may be very pertinent indeed.
crab, you are certainly right in the very general case, but that is such a broad statement in this case it is worthless in this specific case. An oil operator carrying passengers to a rig cannot operate so poorly that it could affect the basic fatigue life, especially in a modern aircraft. The S92 has only 7 parts that have any fatigue life.
It is a disservice to put in the minds of the unwashed, like max, who is seeking answers, the notion that the way a operator flies could make bolts break. They are not mustering cattle in the bush with a one pilot operation! There are other pilots, HUMS. passengers and such to help monitor.
An oil operator carrying passengers to a rig cannot operate so poorly that it could affect the basic fatigue life, especially in a modern aircraft. The S92 has only 7 parts that have any fatigue life.
You are a very self confident person aren't you? In this case you don't know what you are talking about. The company I worked for operated the 92 at a slower cruise IAS than our competitor, and they had a lot more cracks in the airframe structure than we had and have. The reasonfor the higher IAS (Sikorsky figures) was that their contract with the oil company dictated a shorter sector time than we wanted to offer (shorter flight time, lower costs), so they won the contract. How is that for safety concerns in the business??
Anyway - don't put people down when they have legitimate concerns of the machine they are forced to sit in.
I have been in the offshore business for more than 30 years and I understand Max very well.
I have also been a test-pilot for almost the same number of years too, working closely with Part M people so don’t tell me vibration is not a factor in airframe (and possible other components) fatigue life, regardless what the OEM's say.
I am not suggesting that the oil filter studs broke because of vibration, but let people express their concerns without hitting them on their head.
I have nothing to hide, have you? My work name is Max, speak to anyone over here and they'll tell you all about me. I am a metering/measurement consultant, who specializes in state of the art database and instrumentation that measure various fluid and gas production/flows to a high level of confidence and accuracy. If you read though my earlier posts you'll get to know me a whole lot better...
I am also originally from the nuclear power industry and have extensive electrical and electronic engineering qualifications/experience. I am also a time-served craftsman (instruments).
I am not a pilot/avionics engineer, but have been in the offshore industry since '91 and have many flying hours experience as a PAX. So does that classify me as unwashed in the experiences of helo flying? Please clarify your definition of unwashed...
Wrt. HUMS I do not worship the system, but see it as a diagnostic tool that requires extensive experience to fully comprehend. Hopefully one day a neural network system will simplify and improve its analytical and condition-based monitoring potential.
I do not believe that you fully understand how I feel as I'm assuming that you're qualified and work in a different branch of this industry from me. The only commonality we may have is using helos as a mode of transport.
I'm not attempting to allay fears, I'm just trying to understand the collective view of this helo from multiple opinions. I'll make my own judgement on what to believe from this forum, thank you very much.
Anyway, back to the constructive posts. L2driver, glad to hear you understand us PAX along with other posters such as carholme, 212man, to name just a few recent contributors to this post.
Still waiting to hear from Horror Box what has been changed, is maximum IAS one of the modified parameters in the RFM? If you like please PM me.
Rest assured, I've got a list of questions that I'll personally be putting forward to the oil company HSEQ advisors, and if I don't get acceptable answers I'll go straight to Cougar. I'm still hoping that the pending TSB report will provide clarification to some of my questions, but may be a long way away.
This may officially be a rumour network, but in reality contains a wealth of knowledge and experience that IMO is invaluable.
Pages 3-31 to 3-33 of the RFM revised. A red caption "Warning" for low MGB pressure now advises "A total loss of MGB oil pressure may result in a MGB failure in less than 10 minutes. If MGB OIL PRES is less than 5 psi, Land Immediately". Warning repeated at least once.
Some language to explain to white-shirt pilots that never poke under a cowling that the oil-bypass system won't save you if the reason for the oil leaking out of the MGB is in the gearbox housing itself. All S92 pilots should be gurus on this subject by now.
Seems very odd wording, not really a confidence builder like something that states "should be able to make 10 minutes" or something giving a positive time to take response. As worded it indicates a failure after oil loss could be anywhere from 10 minutes down to instantaneous (which history has shown is not likely).
Sultan,
That is most likely them covering their asses. If they do put a definite number to the time and one goes in less than that they will be in for some very expensive please explaining.
widgeon and max,
You are right, I was snarpy. Sorry, truly. I am also impressed with your background, and believe you are probably an expert on FMEA's and such, the exact topic of this thread.
But my point was that you mustn't look on this site as a font of wisdom, but rather a collage of thoughts, from cheap rumors without substance to great words of wisdom. IMHO, the posts from folks like 212man have the ring of wisdom, and many of the others have the thud of uninformed tripe.
Yes, I am a pilot, and yes, I treat my pax with respect. And yes, I'd say the same thing to my pax if they began to quote PPRuNe posters to me as sage advice.
And maxwelg2, regarding posting anonymously, if you please post a pic of your driver's liscense, if it says "maxwelg2" as your name, I will send you a paypal for 100 euros!
I beg to differ with you about different operators having different methods that directly affect the operation and stress on aircraft in the same role offshore.
Take yourself back to the Helicopter Services experience in the S-61 Spindle Shucking contest on the North Sea....they won 2-0 over Bristow as I recall.
All laid down to an RPM issue during particular maneuvers.....I am sure some old North Sea hands can add the details for you.
Stratford-based Sikorsky Aircraft today announced that India's Tata Group will build cabins for Sikorsky's civilian workhorse S-92 helicopter in the East Asian nation.
Financial terms were not disclosed.
The first cabin is scheduled for delivery in late 2010 from a facility that Tata Advanced Systems Ltd. will construct Andhra Pradesh.
Sikorsky President Jeffrey P. Pino said the subsidiary of United Technologies Corp. is tapping into India's work force in India's growing aerospace market.
Although Sikorsky is the first UTC unit to set up manufacturing in India, UTC employs about 4,000 workers there.
Ratan N. Tata, chairman of parent company Tata Sons, said the manufacture of the S-92 cabin in India is a "significant first step in the growth of India as a global hub for aerospace manufacturing."
Nearly 100 S-92 helicopters have been built for search and rescue, and transporting heads of state and oil workers to offshore platforms.
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