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Bristow S76 down in Lagos discussion (Not condolences)

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Bristow S76 down in Lagos discussion (Not condolences)

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Old 1st Mar 2018, 00:44
  #161 (permalink)  
 
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Originally Posted by Copterline 103 View Post

..You told me that you can't see anything wrong or anything unusual in the erecting plama flake in the picture. Do you still concur?
I never said that. I said, I don't care about the photo. What I care about is that routine maintenance didn't detect the internal leak in the faulty servo, and it should have. Also of concern is mandatory operational system checks by the pilots weren't done by the book and that might have been another missed opportunity to detect the faulty servo.

@212man is correct. Servo had nothing to do with either Nigeria accident (the crash, and the hero pilot ditching), or the Indonesia accident.
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Old 1st Mar 2018, 07:37
  #162 (permalink)  
 
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gulliBell

It's a shame to spoil your day, but FDR data reveals that Stick Jump test was completed during the start up in the morning on August 10, 2005. There was no other engine start-ups before accident.

The crew flew in the morning on 10th of August, 2005 eleven 18 minutes flight sequences with one start.This will kill your theory completely.

Instead, now focus on Servo Actuator's design and how it meets the Type Certification conditions as well as what TC Holder has known since the late 70's? Why all the relevant data has been concealed? Is it the affect to the airworthiness of a helicopter type?

You have good information about Nigeria, but so I have first-hand information, for example contamination of hydraulic fluids etc. All the parties (stakeholders, family members, relatives etc.) related Nigeria S-76 accidents I'm ready to share my knowledge and all related documents to these "whom don't know" that the cause of the Nigerian accidents were not servo actuator or improper overhaul related.
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Old 1st Mar 2018, 09:26
  #163 (permalink)  
 
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Originally Posted by Copterline 103 View Post
It's a shame to spoil your day, but FDR data reveals that Stick Jump test was completed during the start up in the morning on August 10, 2005...
That's great, but what about the 11 times it wasn't done in the previous 13 starts? Your photos do nothing to dim my comments on this. I'd like to see the FDR data that was captured on those hydraulic checks...half the crews I've seen in the sim don't do the check properly. If that is typical across the wider S76 pilot cadre then there is an issue with training, and with CRM. One pilot can't be watching the other do the check incorrectly and say nothing. Or not do a mandatory check at all and the other says nothing. They might as well not be there. Might as well not do the check either if you're not going to do it properly, because doing incorrectly does not reveal the malfunction your checking for.
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Old 1st Mar 2018, 10:26
  #164 (permalink)  
 
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Originally Posted by gulliBell View Post
That's great, but what about the 11 times it wasn't done in the previous 13 starts?
Let's go back to the right tree! The case is the possible lack of airworthiness of the S-76 helicopter type. The case is that there might be still hundreds of Servo Actuator Piston's which has been reworked with improper overhaul procedures. In addition the identification of the maintenance history of the reworked piston has been lost. This will make most like impossible to track defected and unairworthy pistons because nobody doesn't know which pistons have been installed to the specific Servo Actuator. The tracking capability has been lost during the improper overhaul process where the original piston's serial number has been over sprayed by new plasma coating. Due to this is unknown which S-76 helicopters have these improperly overhauled pistons and whichone not.

The type certification of S-76 (transport class helicopter) don't allow any kind of risks "low likelihood" in the critical flight components or critical systems.

This is the a tree that should bark.
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Old 1st Mar 2018, 12:05
  #165 (permalink)  
 
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Originally Posted by gulliBell View Post
That's great, but what about the 11 times it wasn't done in the previous 13 starts? Your photos do nothing to dim my comments on this. I'd like to see the FDR data that was captured on those hydraulic checks...half the crews I've seen in the sim don't do the check properly. If that is typical across the wider S76 pilot cadre then there is an issue with training, and with CRM. One pilot can't be watching the other do the check incorrectly and say nothing. Or not do a mandatory check at all and the other says nothing. They might as well not be there. Might as well not do the check either if you're not going to do it properly, because doing incorrectly does not reveal the malfunction your checking for.



It could of course be argued that if so many crews do the check so badly, there is either a problem with the description of the check, or the check is too difficult for the average crew to do satisfactorily, meaning the design is not airworthy. Of course a manufacturer will always want to blame the crews and the training when things go wrong, but sometimes the manufacturer needs to look closer to home.
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Old 1st Mar 2018, 23:46
  #166 (permalink)  
 
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Originally Posted by HeliComparator View Post
meaning the design is not airworthy.
This is the right question; is the Servo Actuator design airworthy?

I hope that the attached attachments will also be useful for finding the possible root causes of the Bristow's Nigerian accidents.

Please note that the very sophisticated MSC.Software EASY5/Adams "NTSB Sikorsky S-76 Investigation, S-76 Flight Controls study and modelling has been made using the FDR Data from Copterline 103 accident despite as descript on the page 95, the first row "Loads were always set to the reduced Sikorsky-provided condition for 80 % VNE (124 kts.). Copterline 103 accident speed was 93,5 % VNE (145 kts.).

It is very easy to understand the aerodynamical and load differences between the actual Copterline 103 speed and this Sikorsky-provided speed assumption for the NTSB simulation results?

The other NTSB EASY5/Adams test report with the 93,5 % VNE will extend the collective max up position about one second and the Sikorsky-provided 80 % VNE will extend the collective max up position within 3,5 second.

The FDR Data between Copterline 103 and Bristow 12th August, 2015 its well matching. Maybe the real root cause of the Copterline 103 accident was a separated Control tube from the Rod End?
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Old 2nd Mar 2018, 00:22
  #167 (permalink)  
 
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Originally Posted by 212man View Post
I assure you!
Could you explain how you can assure me and the others? Why the accident reports are still pending? Do you know what were the root causes of Bristow's accidents 12th August, 2015 and 4th February, 2016? You should know it if you can deny all Servo Actuator defects away?

Also you may have information about Indonesia? What was the story there?
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Old 2nd Mar 2018, 06:32
  #168 (permalink)  
 
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Originally Posted by Copterline 103 View Post
Could you explain how you can assure me and the others? Why the accident reports are still pending? Do you know what were the root causes of Bristow's accidents 12th August, 2015 and 4th February, 2016? You should know it if you can deny all Servo Actuator defects away?

Also you may have information about Indonesia? What was the story there?
I am not going to give any details but can say with certainty that the two BHNL accidents are unrelated (other than concerns about what happened on the 12th August may have impaired decisions/analysis on the 4th Feb), whereas the first BHNL accident and the Indonesia one are almost certainly similar, and none of them are related to servo actuators.

Maybe the real root cause of the Copterline 103 accident was a separated Control tube from the Rod End?
No idea, but continue that thought.....
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Old 5th Mar 2018, 08:28
  #169 (permalink)  
 
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The root cause and the consequence must be kept separete from each other

Since the final accident report of Bristow 12th August 2015 crash is heavily overdue, one can both wonder the reason for such a delay and also make some assumptions based on the data released in the preliminary accident report.

a) The accident was violent and totally surprised the crew; no MAYDAY call was made.
b) At accident onset, aircraft pitched up and entered left roll.
c) Pushrod separation from rod end was a pre-impact condition, not pre-onset

For helicopter to pitch up, forward servo actuator must have been operated either with or without pilot control. If, for argument's sake, we assume that forward servo was operated without pilot input due to similar servo piston flaking as in COPTERLINE 103 case, following chain of events can occur.

1) Forward servo extends to the max.
2) Cyclic travels to full aft position
3) Collective raises to full up position (due to mechanical connection to the Servo Actuator scissor coupling)
4) Left pedal is floored by mixing unit (mechanical compensation link)
5) Controls are stuck.
6) Perplexed pilots are tossed around in the cockpit in heavy g-loads from violent rotation.
7) Fueled by sheer adrenaline, pilots begin fighting back to regain the control of the aircraft.
8) Both pilots exert in excess of 600kg of combined force on both left pedal and cyclic.
9) Since the cyclic control travel is normally on the order of 30cm and resulting control rod movement 3.5cm, the links, mixing unit and everything between pilots and servo actuator control valve act as a reduction gear of 10:1.
10) Pilots fighting for their and passengers' life are stressing the control rod by 6000 kg of force.
11) Aluminum threads give way. Control pushrod is detached from control rod end.
12) All means to control the aircraft have been lost.

In normal case, when system works as planned, the friction load in links and mixing unit is roughly 5 lbf (2-3 kg). In the normal operation the Control Tubes, Rods, Rod Ends, links or the Mixing Unit never face more stress or force that the systems itself mechanically creates through friction. The Flight Controls (Collective, Cyclic Stick, Pedals) have mechanical limiters which are stopping the travel of the Flight Controls. Since the Flight Control system has never been designed for a situation, where both pilots are pulling the pushrod with thousands of kilos, the system components will most likely fail. It must be remembered, that pushing the cyclic forward in a fully extended forward servo actuator situation will initiate a positive tension (pull) in each of the control line member, including the reported and failed pushrod. That, in turn, can create a situation where aluminum threads, which are designed for 2-3 kg loads, fail at stress of thousands of kilos.

When contemplating other routes of reported failure, one must take into account:
1) none of the control line member are able to rotate, so threads must have given way by de-threading and sliding
2) Pushrod is "secured" by witness wire only, ie. manufacturer knows, that threaded joint is not prone to fail. Witness wire serves as a means to verify "a correct lenght installation".
3) The mass of pushrod is about 100 g. Vibration induced damage in a system, where both ends of the connected pushrod and rod end are fixed to the same vibrating frame, is unlikely.

If pushrod would have been detached from the rod end pre-onset, controls would have been free and pilots would have been able to affect the spiral through mixing unit (not necessarily recover though). Nothing of a sort was heard from survivors. Therefore, an assumption of stuck controls is plausible.

This and everything else speculative related to this "mysterious" crash would be unnecessary if the final report was released. Interestingly, identical behavior was reported in Indonesia and the final accident report is overdue there as well.

Factually, the Indonesia 21st March, 2015 accident and the Nigeria 12th August, 2015 accident have been initiated by a sudden nose pitch-up within a second from the zero-time line. Similarly, it is also an undeniable fact that the nose-up needs to have FWD Servo Actuator extension commanded by a pilot input (cyclic) or uncommand Servo Actuator run away. If this FWD Servo Actuator extension doesn’t take place, the helicopter will maintain the level flight. If the case has been that the helicopter nose has dive down the pilots or electrical line actuator commands has been push “the Control Tube forward” to steer FWD Servo Actuator down or lower position. This action should has push the FWD Servo Actuator Input Control Pushrod and Rod end apart from each other, SEPARATING the Rod End from Input Control Pushrod. But this was not the case, the helicopter pitched up!

The recovered FDR DATA will reveal all of this. It will be easy to see the cyclic position at the time when the helicopter nose pitched up and later how the pilots tried to stabilized the helicopter which had suddenly and without any cautions or warnings become unflyable.

If it turns out that these accidents happened as depicted above, my worries are increasing how this S-76 helicopter could hold it Type Certificate. Also, if the manufacturer does not know or does not want to reveal why the S-76 helicopters are losing the controllability from time to time resulting in fatal accidents, the airplane is not safe and the fleet needs to be grounded for further analysis, until the helicopter type is safe and airworthy to operate.

The root cause and the consequence must be kept separate from each other.
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Old 5th Mar 2018, 12:10
  #170 (permalink)  
 
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Interestingly, the detailed preliminary report appears to have gone now!

Pushrod separation from rod end was a pre-impact condition, not pre-onset
You have added the last bit yourself based on what? I know the EAD says "pre-impact" but that is simply stating a fact evident from its condition and does not attempt to act as the actual investigation conclusion about whether it was pre-onset or occurred after the upset onset.

You omit to note that the Indonesia one was survived by the crew, so their testimony on how the controls were behaving and what forces they experienced would have been passed on.
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Old 5th Mar 2018, 19:17
  #171 (permalink)  
 
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Originally Posted by 212man View Post
I know the EAD says "pre-impact" but that is simply stating a fact evident from its condition and does not attempt to act as the actual investigation conclusion about whether it was pre-onset or occurred after the upset onset.
As many have already commented earlier, the weight of the pushrod would have commanded FWD servo DOWN, not UP if decoupling would have been pre-onset. The only way of producing described aerodynamical behavior (nose up, left roll) is to extend FWD servo.

Additionally, de-threading by pushing the rod end into pushrod is not possible due to jamnut. Therefore, if threaded joint has been destroyed by pilot action, it has been subjected to positive tension of the Pushrod - Rod End (pulling the rod, not push). In that scenario pilots are trying to pull extended FWD servo down by pushing the Cyclic stick forward by brute force.

FDR data will stop all speculations and the truth will be revealed.
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Old 8th Mar 2018, 13:38
  #172 (permalink)  
 
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Transportation category helicopter?

This picture tells more than a thousand words. Everyone is able to imagine what power is needed to break this collective head and what circumstances can it happen?

I hope that gulliBell and 212man will make comments about the facts what I have revealed. My benefit has been the fact that I was able to see behind the curtain and to know what is the ultimate truth of the matter. Sometimes the truth can hurt somebody.
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Old 7th Aug 2018, 17:39
  #173 (permalink)  
 
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I couldn't find the Heavylift accident thread but it does not matter because it has direct relevance to this one - as has been mentioned earlier. The final report oft the Heavylift accident is out: http://knkt.dephub.go.id/knkt/ntsc_a...L%20Report.pdf

It confirms, what several of us already knew through other sources, that the circumstances are identical to this accident and neither are related to the Copterline 103 accident and there is specific discussion about and the resulting Sikorsky actions.
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Old 8th Aug 2018, 02:16
  #174 (permalink)  
 
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Everyone is able to imagine what power is needed to break this collective head and what circumstances can it happen
Force would be substantial and far more than anyone could apply with their thumb. Have no idea what you're implying.
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Old 8th Aug 2018, 02:29
  #175 (permalink)  
 
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That bit of broken plastic on the collective head certainly has nothing to do with anything a hydraulic servo might have done. If that was the implication. The HL crash had nothing to do with the hydraulic system, which we said right from the outset. Neither did the Bristow Lagos crash. But the Copterline accident did.
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