Bristow S76 Ditched in Nigeria today Feb 3 2016
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@keke napep
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.
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@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.
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.
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.
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.
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.
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@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.
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.
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.
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.
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.
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.
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@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.
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 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.
