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

Bristow S76 Ditched in Nigeria today Feb 3 2016

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

Bristow S76 Ditched in Nigeria today Feb 3 2016

Old 28th Mar 2016, 22:36
  #581 (permalink)  
 
Join Date: Aug 2015
Location: Finland
Posts: 82
Likes: 0
Received 0 Likes on 0 Posts
@keke napep
keke, this all looks good and it just like it should be (the flight crew training).

I'm disapointed that I couldn't give my knowledge early enough to Jay and his copilot. It would be a different story if they could make the recovery in the situation where they suddenly vent. It was cavok, 1000 ft. and 120 KTS.

I'm sure that Jay and his copilot tried to make everything to understand what is going on. I have been told that Jay was very capable on his duties.
Copterline 103 is offline  
Old 3rd Apr 2016, 20:37
  #582 (permalink)  
 
Join Date: Aug 2015
Location: Finland
Posts: 82
Likes: 0
Received 0 Likes on 0 Posts
@megan
Yes they can, because I've had it. Trouble is, I can't recall the root cause (we're talking 20 or more years ago), but the regulator was wondering if the aircraft should be certified IFR capable with such a single point failure. Nothing eventuated. Contact with Australian ATSB or the CASA Moorabbin office should elicit a copy of the incident report.
I did that already 2008. I got the incident report and other related material from Australian ATSB.
Megan, Is this the case you mentioned? You are right, there is a single point failure which could lead to the loss of controllability of helicopter. This Australia case was a lucky one due to stuck controls in the ground.

As you have seen the incident report which proves that there was none caution or warnings during this blockage. This single point defect or failure is well known and for sure still makes headaches to the factory and the authorities.....has this ever been acceptable.....?

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations), PART 39-105
Civil Aviation Safety Authority
Scheduled of Airworthiness Directives
Sikorsky S76 Series Helicopters
AD/S-76/22 Main Rotor Control Servo Actuators-Inspection 6/82 for Balance Tube Passage
Applicability: All models.
Document: Sikorsky Alert SB 76-67-14A. NOTE: Helicopter previously inspected to SB ASB 76-67-4 are to be re-inspected
Compliance: Within 30 hours time in service after 28 April 1982
Background: Restricted flight control motion was found to be due to the omission of a passage in the servo oil return system.
Copterline 103 is offline  
Old 3rd Apr 2016, 22:04
  #583 (permalink)  
cpt
 
Join Date: Dec 2002
Location: 1500' AMSL
Age: 67
Posts: 412
Received 1 Like on 1 Post
Hi Copterline,

But in this Australian case, it was more likely a case of a mistake in the manufacturing process or a poorly overhauled servo....I suppose this fault has been revealed at the flight control check after a servo change ? it would rather highlight a quality control flaw, more than a design misconception.
cpt is offline  
Old 4th Apr 2016, 07:53
  #584 (permalink)  
 
Join Date: Aug 2015
Location: Finland
Posts: 82
Likes: 0
Received 0 Likes on 0 Posts
@cpt
Hi Copterline,
But in this Australian case, it was more likely a case of a mistake in the manufacturing process or a poorly overhauled servo....I suppose this fault has been revealed at the flight control check after a servo change ? it would rather highlight a quality control flaw, more than a design misconception.
cpt: The Australian case was an operator reported restriccted flight control motion on the ground. Troubleshooting determined the cause to restrected movement in the retract mode of one main rotor servo actuator stage. The cause of malfunction has been confirmed to be the omission of a passage connecting a chamber to system return. The servo had been reported to have been previously checked per the basic Alert Service Bulletin No. 76-67-14 (Sikorsky Message CST-SPT-81-0587, dated August 26,1981).

After this Australian AD an revised ASB 76-67-14B was issued by the manufacture.

In the Baltic Sea accident the findings were:
a) the plasma material was wrong
b) during Servo Actuator's overhaul process a non FAA approved maintenance instructions and procedure were used
c) the maximum certified thickness of the plasma coating was 4 microns but the actual plasma coating was 1,2 mm (1200 microns) which was 300 time more than the certified and accepted maximum

Despite the fact what is the reason why the C3 port or ports are blocked it not the biggest problem. The main problem is that a single defect in Servo Actuator could lead in loss of the helicopter controllability.
This is a helicopter type certification issue.
Copterline 103 is offline  
Old 4th Apr 2016, 09:49
  #585 (permalink)  
 
Join Date: Dec 2005
Location: England
Posts: 1,426
Received 12 Likes on 8 Posts
The type certification issue applies to just about every helicopter as far as I can see. The problem to me is that you seem to hang this problem solely on the S76 whereas surely it applies to just about everything flying including far more modern sircraft than the S76. You come over as being selective in your criticism. I see little difference between the S76 servos and any other.
ericferret is offline  
Old 4th Apr 2016, 12:10
  #586 (permalink)  
 
Join Date: Jun 2006
Location: In the air with luck
Posts: 1,017
Received 1 Like on 1 Post
Perhaps this is what 103 is suggesting Eric, Selective maybe (loss of friends colleagues) but the oil filter problems that killed people were known as well
500e is offline  
Old 4th Apr 2016, 15:20
  #587 (permalink)  
 
Join Date: Dec 2005
Location: England
Posts: 1,426
Received 12 Likes on 8 Posts
Hi 500e

I take it that you are referrring to the S92 MGB oil filter. I take your point. However if the problem is addressed which it appears to be what more can we expect. I note that the Allison 250 engine also suffered from oil filter stud failures in the late 70's early 80's and this was designed out. As for the S76 servo failures as far as I can see they have not been the result of design error but of manufacture or repair failings. The idea that a single failure should not lead to the loss of an aircraft just doesn't seem to hold up against any design out there. As long as we have mechanical linkages we will have a problem,
fly by wire may resolve a lot of these issues but if you lose a blade what then?

I feel that the idea of a helicopter with total redundancy of systems is a long way off.
ericferret is offline  
Old 4th Apr 2016, 21:17
  #588 (permalink)  
 
Join Date: Aug 2015
Location: Finland
Posts: 82
Likes: 0
Received 0 Likes on 0 Posts
@ericferret
As for the S76 servo failures as far as I can see they have not been the result of design error but of manufacture or repair failings.
The type certification design requirement is very straightforward. The manufacturer and all the authorities have had a very good knowledge of this issue for a long time. The issue is the money versus accepted loss rate. The industry has a good knowledge how to design the true fail safe Servo Actuator, ensuring the continued safe flight in any kind of single defect or a single failure.

The certification requirements are:

29.695 Power boost and power-operated control system.

(a) If a power boost or power-operated control system is used, an alternate system must be immediately available that allows continued safe flight and landing in the event of:
(1) Any single failure in the power portion of the system; or
(2) The failure of all engines.
(b) Each alternate system may be a duplicate power portion or a manually operated mechanical system. The power portion includes the power source (such as hydraulic pumps), and such items as valves, lines, and actuators.
(c) The failure of mechanical parts (such as piston rods and links), and the jamming of power cylinders, must be considered unless they are extremely improbable.
Copterline 103 is offline  
Old 5th Apr 2016, 23:23
  #589 (permalink)  
THG
 
Join Date: Aug 2015
Location: Brazil
Age: 42
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Preliminary Report

http://www.aib.gov.ng/files/pre-report-bristow-5N-BQJ.pdf
THG is offline  
Old 6th Apr 2016, 11:46
  #590 (permalink)  
 
Join Date: Sep 2006
Location: Inside the Industry
Posts: 876
Received 0 Likes on 0 Posts
THG

Welcome but......read the thread. The link to the report was posted about 1 month ago.
industry insider is offline  
Old 7th Apr 2016, 00:38
  #591 (permalink)  
THG
 
Join Date: Aug 2015
Location: Brazil
Age: 42
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by industry insider
THG

Welcome but......read the thread. The link to the report was posted about 1 month ago.
Sorry about that.
THG is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.