Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

S92 "unexpected control responses"

Rotorheads A haven for helicopter professionals to discuss the things that affect them

S92 "unexpected control responses"

Old 12th Jan 2017, 16:01
  #121 (permalink)  
 
Join Date: Aug 2009
Location: Texas
Age: 64
Posts: 7,131
Received 320 Likes on 204 Posts
Originally Posted by jimf671
No room left under the rug with this one since the same thing happened with the pilots and the aircraft behaviour. They were presented with what we now know was evidence of impending failure but in the circumstances they were able to assure themselves that the effect was typical of local air conditions.
Jim: all points taken and accepted. Our hindsight is 20-20, but your point on the human factors piece of the pilots diagnosing the yaw/controllability excursion as something else (since there were not other cockpit indications?) fits my general idea.


Regarding that thing ...


"huh, what's with the controls here, what just happened"


I am having a flashback to a 1982 SH-2F accident. A control position/controllability issue arose and the pilots landed. They tried to figure out what was wrong and reset the boost/flight control system, thinking it to be an electronic anomaly. (Occasional hiccups in the flight control system, electronic sub systems, wasn't that uncommon). They decided to take it back to the hangar to get it looked at.


As it happened, when they lifted up to air taxi there, the helicopter came apart. (A guy in my squadron saw it happen; he was at the other end of the airfield awaiting clearance to take off and happened to be facing so he had a front row seat).

It was later discovered that the azimuth (for an H-2 that's basically the swashplate) had come untorqued and when the load to pick up hit it, it separated. A novel failure, to say the least, but a nasty one. As you can imagine, parts went everywhere. One fatality, the crewman, trapped in the burning wreckage because the radar came off the rack and pinned him.

Some changes to various flight control malfunction/emergency procedures was made, and the Navy/OEM got together to make some improvements to the azimuth/swashplate to prevent that happening again. From memory, I don't recall that particular issue ever came up again.
Lonewolf_50 is offline  
Old 12th Jan 2017, 16:21
  #122 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 10,293
Received 611 Likes on 267 Posts
Any indications of how many (if any) of the bearings that have been checked are in the 'distressed' condition shown in the picture (even the early stages of 'distress')?

Was this a design issue (probably not since we haven't had a spate of similar failures), a manufacturing failure (similar comment unless there has been a bad batch) or a maintenance issue (poor installation, poor technique, wrong tools etc)?
crab@SAAvn.co.uk is offline  
Old 12th Jan 2017, 19:13
  #123 (permalink)  
 
Join Date: Nov 2009
Location: Inverness-shire, Ross-shire
Posts: 1,452
Received 20 Likes on 14 Posts
It's late, it's January and it's dark, cold, windy or snowing, and in some locations all of those, around the North Sea, and the Barent, but there are plenty S-92 out there right now making up for lost time.

Safe flying to all.
jimf671 is offline  
Old 12th Jan 2017, 20:57
  #124 (permalink)  
 
Join Date: May 2002
Location: Downeast
Age: 75
Posts: 18,267
Received 467 Likes on 191 Posts
Lone,

Unless the Human Interface in the system does as it is supposed to do by Procedure, Policy, Practice, and Experience....no system devised will be effective.

Case in Point is the Cougar Tragedy....had the Captain followed the Checklist Procedure (which the Co-Pilot advocated to do...) then there would have been a much different outcome to that sad affair.

To validate your point about False Indications....you probably recall the Blade BIM system on the Sikorsky Iron....which had both a Blade Indicator and an In-Cockpit Warning Light. The Blade Indicator was prone to give false indications occasionally....but the Cockpit Warning was notoriously prone to lie. My outfit removed the Cockpit system and went with a visual inspection of the Blade BIM's every time we shut down and set a Time Limit between Blade Checks.

There will always be False Fault Indications I would guess...but a False Positive is an inconvenience or nuisance whereas a False Negative (No Warning) could be quite deadly.

As to your SH-2 Crew....being on the ground at their maintenance base....shutting down and calling for a Tech or even a Tug would have prevented that Fatality.

Did not the USMC not lose a HueyCobra at Twenty Nine Palms not so long ago from a similar decision to continue flight following some kind of fault warning rather than land out and call for technical assistance?
SASless is online now  
Old 12th Jan 2017, 21:11
  #125 (permalink)  
 
Join Date: Sep 2004
Location: Canada
Posts: 1,724
Received 138 Likes on 67 Posts
Oh the number of test flights I have done on the XXX ( not the 92 ) helicopter because of false vibration excedences..Drag it into the hangar, tighten all the accelerometers ..off on a nice 30-40 minute test flight ..return.
albatross is offline  
Old 12th Jan 2017, 21:11
  #126 (permalink)  
 
Join Date: Aug 2009
Location: Texas
Age: 64
Posts: 7,131
Received 320 Likes on 204 Posts
Originally Posted by SASless
As to your SH-2 Crew....being on the ground at their maintenance base....shutting down and calling for a Tech or even a Tug would have prevented that Fatality.
SAS, that's the problem with symptoms looking like one thing and being something else. Having a landing area being separated by a body of water from the hangar area. To be sure, our wing commander raised the same question you did: why not shut down and get a tow back? The answer was,
"we trouble shot the malfunction we thought we had"
From boost off up, add boost/lateral coupler/ASE/AFCS -- each sub system had its little quirks that occasionally made one have to set her down and reset the system. The whole community (both coasts) were quite surprised at that particular failure.

As to the BIM, yeah, familiar.
Lonewolf_50 is offline  
Old 13th Jan 2017, 02:35
  #127 (permalink)  
 
Join Date: May 2016
Location: Home
Posts: 72
Likes: 0
Received 0 Likes on 0 Posts
From the report:
A routine download of the HUMS was performed on the evening of 27 December 2016 and the helicopter was released to service. A detailed analysis of the data, conducted after the accident, showed that the Tail Gearbox Bearing Energy Analysis limit had been exceeded on 27 December 2016.
CHC and it engineers are taking quite a grilling but I'm not sure that the report is clear enough to justify that. It does not state that they missed obvious limit exceedances or knowingly returned an unserviceable aircraft to service. It does however states that a "detailed" (not routine) analysis was conducted after the fact and it showed the aircraft exceeded the limit. This detailed anaylsis was probably conducted by a team of engineering/programming personal at Sikorsky. Also probably using different software/hardware then what was available to the engineer or operator at the time. It's a shame that these initial reports leave so much interperation. They seem to create more questions then provide answers. Kinda reminds you of the last major accident where the blame was quickly put on the maintenance staff .... Everything from rumoured test flights to washers/pins sitting in a guys tool box.

The imd_ground station, from what I understand, is what most are still using. The Sikorsky created Tool for monitoring this item is a pretty straight forward go-no go tool. Open the toolbar, look at the trend, insure it's not on the rise and that it's below the limit. Beyond that, there is a big green box with the letters "OK" in it if all is good. You don't really have to dig hard to find the info. There are several items that are closely monitored with their own deicated tools and I find it hard to believe that any operator are ignoring these items. Now, if the info inside the tool is not correct or as accurate as it could be, that's a manufacture issue.

Last edited by Satcomm; 13th Jan 2017 at 03:06.
Satcomm is offline  
Old 13th Jan 2017, 06:00
  #128 (permalink)  
 
Join Date: Aug 2001
Location: Cornwall
Age: 75
Posts: 1,307
Likes: 0
Received 0 Likes on 0 Posts
A good ECL will contain, in addition to the basic drill/procedure, supplementary information:

1. Immediate actions - There always will be situations that demand an immediate response from the handling pilot, autorotation following double engine failure for one. The problem is the regulators seem not to understand this need consequently IMMEDIATE ACTIONS may be missing from the RFM.
2. Subsequent Actions - Every malfunction has a context and therefore warrant some guidance based on the extensive experience gained on this or other similar types. Over optimistic assertions in the RFM may be technically correct but if you think I am going to 'CONTINUE FLIGHT' with both batteries indicating 'HOT' then you can think again. 'Subsequent Actions' are an opportunity to recognise that simple cockpit warnings may not be telling the whole story. Wisdom can be passed on via comments and suggestions made under this heading.
3. Considerations - The RFM based QRH is essentially 'generic' and may not cover some specific role equipment fitted to your aircraft. Any and all other relevant advice can be included under 'considerations'.

Unless and until the regulators insist on something other than a brand new, factory-fresh helicopter situated downwind in the traffic pattern at the flight test facility being used for the production of emergency procedures we are unlikely to see the smaller organisations (who cannot afford to produce their own ECL) benefit from the collective wisdom of the helicopter community.

G.
Sim Trainer ? Sim Trainer
Geoffersincornwall is offline  
Old 13th Jan 2017, 06:36
  #129 (permalink)  

Avoid imitations
 
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 14,561
Received 402 Likes on 210 Posts
UK NOTAM in place regarding worldwide grounding of S-92. Any update?
ShyTorque is offline  
Old 13th Jan 2017, 09:21
  #130 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 10,293
Received 611 Likes on 267 Posts
Geoffers - as an example of what you describe, the 365 RFM doesn't differentiate between a TR control failure and a TR drive failure (loss of thrust) - it is wrapped up into one drill which advises a running landing with a left sideslip on approach and if possible a wind from the right. There is no mention that you will have right sideslip with a drive/thrust failure and no consideration of an EOL for some control/thrust failures at all.

Back to the 92 and the question is how did that vital bearing get to that 'distressed' state without someone noticing something (apart from the crew when they lifted to the hover and convinced themselves the wind was responsible for the undemanded yaw).
crab@SAAvn.co.uk is offline  
Old 13th Jan 2017, 10:20
  #131 (permalink)  
 
Join Date: Oct 2012
Location: SE England
Posts: 111
Likes: 0
Received 0 Likes on 0 Posts
Satcomm - I think you're making quite a large jump there. I'd say the footnote on page 4 more or less clarifies the ananlyis tool was available to view, just missed by whoever was inspecting it.

"The IMD-HUMS includes the use of additional stand-alone mechanical diagnostic software tools for the HUMS
Ground Station (GS) that help assess the condition of a number of specific components, one of which is the Tail
Gearbox Bearing Energy Analysis software tool; however, these require the user to visually inspect the data and
search for exceedances. The helicopter manufacturer now offers an alternative GS analysis system which offers
a number of enhancements to IMD-HUMS, including more advanced algorithms and the automatic alerting of all exceedances on receipt of new HUMS data."
FC80 is offline  
Old 13th Jan 2017, 12:13
  #132 (permalink)  
 
Join Date: Jan 2017
Location: Northeast US
Posts: 9
Likes: 0
Received 0 Likes on 0 Posts
11 bearings have been removed however none showing any distress like incident bearing.
LAXX5 is offline  
Old 13th Jan 2017, 12:58
  #133 (permalink)  
 
Join Date: Aug 2007
Location: mobile
Posts: 241
Likes: 0
Received 0 Likes on 0 Posts
Couldnt agree more SASLESS Back in the day Bristow were developing an IHUMS system whereby the aircraft perameters were monitored at all time by an engineer on the ground who could notify the aircraft comander of any impending excedences or failures and discuss options with him. This seems to have disappeared with the Airlog takeover.
mtoroshanga is offline  
Old 13th Jan 2017, 13:18
  #134 (permalink)  
 
Join Date: May 2002
Location: Downeast
Age: 75
Posts: 18,267
Received 467 Likes on 191 Posts
Lone,

"we trouble shot the malfunction we thought we had"
The follow up questions I have re your description of the incident and background of that particular aircraft type/model/configuration:

If there are multiple systems that can trigger the symptoms that are presented to the crew.....is there a method to work down through some sort of Trouble Shooting Tree to correctly identify the culprit causing the problem?

Your narrative makes me question the crew action to determine the fault as it would seem (without access to the Accident Report with its information) they may have decided to delay that analysis until they had hovered over to the Maintenance Area and give the aircraft to the Maintainers or have their assistance available in checking out the problem. There are several logical and relatively minor causes for some binding in flight controls that are not threats to the safety of the aircraft and crew.

Would you happen to have a way of calling up that Accident Report as it would make for interesting reading.

I am not finding fault with the Crew by any means....just trying to see how all the Cheese Holes lined up that day.
SASless is online now  
Old 13th Jan 2017, 13:28
  #135 (permalink)  
 
Join Date: Feb 2006
Location: On the big blue planet
Posts: 1,027
Received 24 Likes on 12 Posts
just trying to see how all the Cheese Holes lined up that day.
Not all cheese holes, at least one was not ...

skadi
skadi is offline  
Old 13th Jan 2017, 14:02
  #136 (permalink)  
 
Join Date: Aug 2009
Location: Texas
Age: 64
Posts: 7,131
Received 320 Likes on 204 Posts
Originally Posted by SASless
If there are multiple systems that can trigger the symptoms that are presented to the crew.....is there a method to work down through some sort of Trouble Shooting Tree to correctly identify the culprit causing the problem? {snip the rest}
@SAS The points you raise (good ones) were the topics of a hell of a lot of discussion in our Wing. What was found out was that the NATOPS manual / training wasn't crystal clear on some important details. (The final tech fix to prevent the mechanical failure ended up being some bolts in the azimuth and new preflight check procedures). The NATOPS manual changed, and the control system malfunction procedures were revised to address the distinct differences in symptoms: control position errors versus other system errors. The former became "shut it down" in nature once that accident was thoroughly understood.


NATOPS was written/rewritten in blood ... again .. thanks to a one of a kind failure. Sorry that we are drifting form the S-92 topic, but flight control degradation malfunctions and emergencies are the ones that give me the chills. The initial report from the AIIB gets the hair up on the back of my neck.
Lonewolf_50 is offline  
Old 13th Jan 2017, 19:58
  #137 (permalink)  
 
Join Date: May 2016
Location: Home
Posts: 72
Likes: 0
Received 0 Likes on 0 Posts
FC80 - Don't believe it's that big of a jump. You are right and as I stated the toolbar for the TRPCS is there and has been for a long time. All I believe is that it is possible that the engineers at the time, may not have had the same blinding evidence that something is about to happen as Sikorskys team of engineers had in hine sight with their more advanced software. Rumor has it, a new, more advanced Toolbar is hitting the streets. Imagine that!

Mitcha - Dont know what to say. For an operator to put in additional procedures and safety precautions in the wake of a catastrophic event is to be expected IMO, not incriminating. I'm willing to bet every single operator of a S92 has reviewed their HUMS procedures and possibly made changes in the last few days.
Satcomm is offline  
Old 13th Jan 2017, 20:49
  #138 (permalink)  
 
Join Date: Dec 2000
Location: Arlington, Tx. US
Posts: 696
Likes: 0
Received 11 Likes on 7 Posts
The post mortum of most, if not all, detectable drive system faults that led to an accident were "missed" not by operator error, but by:

1. System diagnostic programming errors which showed false/erroneous readings which could not detect any faults.

2. Incorrect limits which were set too high and missed the event.

3. (Related to 2) Trying to use sensors located in non-optimum locations to monitor the target component. In the case of the 92, how close is the accel used to the faulty bearing?

4. Routine false alarms which destroys trust in the system, so if something real happens it is lost in the noise (G-REDL). I attended a CAA meeting where operators reported a 100 to 1 false alarm rate with North Sea HUMS.

HUMS is pretty good at detecting the second occurence of what causes an accident after fixing the system short comings highlighted in the accident review. In case of the 92 it appears it requires 3 or more examples.

The Sultan

Last edited by The Sultan; 13th Jan 2017 at 20:57. Reason: Dropped word
The Sultan is offline  
Old 13th Jan 2017, 23:05
  #139 (permalink)  
 
Join Date: Dec 2000
Location: Arlington, Tx. US
Posts: 696
Likes: 0
Received 11 Likes on 7 Posts
Mitch

I well know HUMS detects faults. I was specifically talking about accidents (North Sea) where people point fingers at operators while believing HUMS is infallible. In accidents where the fault theoretically should have been detected, but wasn't. The majority are due to HUMS shortcomings, not operator negligence.

The Sultan
The Sultan is offline  
Old 14th Jan 2017, 00:57
  #140 (permalink)  
 
Join Date: Nov 2009
Location: Inverness-shire, Ross-shire
Posts: 1,452
Received 20 Likes on 14 Posts
Nye helikopterproblemer i Nordsjøen - Nordsjøen - Børs og Finans - E24

Bing Translator
"No one has come to or from the platform since Monday because the helicopter blocks landing place, the BA.

The Sikorsky helicopter from CHC Helikopter Service has been fixed at Kvitebjørn due to an oil leak in gear box. The error should be rectified, but the tests that should be done, have not been implemented because of the bad weather.

-It is of course reassuring that helicopter the company takes all precautions and make the necessary testing, but it is also regrettable for the crew that has been given an involuntary stay on installation, says Morten Eek in Statoil to the newspaper Friday.

On Tuesday reported the CHC that all Norwegian helicopters of the type Sikorsky S-92 carrying oil workers to the platforms in the North Sea, is set on the ground. The reason is that a helicopter of this type spun around and cut a hole in the deck during a landing on the platform West Franklin on the Scottish continental shelf before new year. Now, all the helicopters inspected before the next flight.

The helicopter that crashed last year at Turøy outside Bergen, also belonged to CHC"
jimf671 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.