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The assumption is that this AD is related -
FAA AD 2015-19-51 DATE: September 14, 2015 AD #: 2015-19-51 AIRWORTHINESS DIRECTIVE Aircraft Safety Alerts www.gpoaccess.gov/fr/advanced.html This emergency airworthiness directive (EAD) 2015-19-51 is being sent to owners and operators of Sikorsky Aircraft Corporation Model S-76A, S-76B, S-76C, and S-76D helicopters. Background This EAD was prompted by an accident of a Sikorsky Aircraft Corporation Model S-76C helicopter. During preliminary investigation, a failed servo input control pushrod (pushrod) assembly was identified. Separation of the pushrod tube and the control rod end with bearing was found. This EAD requires inspecting the main rotor (M/R) forward, aft, and lateral pushrod assemblies, the tail rotor (T/R) pushrod assembly, and the jamnuts, and applying slippage marks across the pushrod tubes and jamnuts. These EAD actions are intended to prevent loss of M/R or T/R flight control and subsequent loss of control of the helicopter. FAA’s Determination We are issuing this EAD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of these same type designs. Related Service Information Sikorsky issued Alert Service Bulletin No. 76-67-57, Basic Issue, dated September 10, 2015 (ASB), which specifies a one-time inspection of the M/R forward, aft, and lateral pushrod assemblies, the T/R pushrod assembly, and the jamnuts for proper installation, condition, and security. If a pushrod or jamnut does not meet criteria specified in the inspection, the ASB specifies replacing the assembly. The ASB also specifies applying two slippage marks across each M/R and T/R pushrod tube and jamnut. Further, the ASB references the applicable maintenance manual for a new recurring inspection of the slippage marks. EAD Requirements This EAD requires, within five hours time-in-service, inspecting each M/R and T/R pushrod assembly by inspecting the position of the control rod end in the pushrod tube. If the lockwire passes through the inspection hole, this EAD requires replacing the pushrod assembly. If the lockwire does not pass through the inspection hole, this EAD requires inspecting the jamnut to determine seating position against the pushrod and whether the jamnut can be turned with finger pressure. If the jamnut is not seated against the pushrod or is loose, this EAD requires replacing the pushrod assembly. This EAD also requires, both for those pushrod assemblies that are replaced and for those that pass the inspections, applying two slippage marks across each M/R and T/R pushrod tube and jamnut. |
Emergency airworthiness directive (EAD) 2015-19-51
This was not a surprise that the Servo Actuator is once again part of the accident cause.
The next step should be that investigators will find out which is the real reason why Rod End breaks down. It’s pretty obvious that there is another reason is behind this fail of Rod End. Most likely the failed Rod End is a consequence not a cause of the accident. |
In following the requirements of the ASB the main focus is on the jam nut that secures the rod end, inspection is to make sure is tight and if found loose. The push rod assembly is removed and replaced with a new part that is assembled correctly.
The ASB also requires the jam nuts to be marked so that on future inspection can see if the nut has slipped ( moved ) . |
EAD
The preliminary inspection and in turn this Emergency Airworthiness Directive points straight to the cause of the accident and in turn to maintenance. This may sound harsh but be your own judge on this one.
The procedure to be carried out, as prescribed in the EAD is a very basic one and every aircraft mechanic is supposed to do it while checking and or making adjustments on the rod end / push rod. :ugh: The two parts separated, so some one did not do the job. Very sad story. |
It is not proven or a correct assumption some one did not do their job unless you know something you should'nt?
Conjecture is not the correct way to come to the reasons for an accident. |
Ainippe
This is from the EAD; During preliminary investigation, a failed servo input control pushrod (pushrod) assembly was identified. Separation of the pushrod tube and the control rod end with bearing was found. This EAD requires, within five hours time-in-service, inspecting each M/R and T/R pushrod assembly by inspecting the position of the control rod end in the pushrod tube. If the lockwire passes through the inspection hole, this EAD requires replacing the pushrod assembly. If the lockwire does not pass through the inspection hole, this EAD requires inspecting the jamnut to determine seating position against the pushrod and whether the jamnut can be turned with finger pressure. Talk to any certified engineer and he will explain to you what happened or why the separation did occur. This is not a faulty part, otherwise the parts would have to be replaced and not like in this case, inspected for correct assembly. |
Separation of the pushrod tube and the control rod end with bearing was found. A possibility for the lost bolt could be this hydraulic system kickback affect which has cut the bolt which is connecting the pushrod tube and the control rod end? Any picture available? |
Copterline,
Go back and read the text - it has NOTHING to do with the bolt in the rod end. Show us where a bolt is mentioned. The rod end has separated from the control rod. |
Dear Helinaut,
be careful what you say - I have been a licensed S76 engineer since 1994 and a practising LAE since 1980, I do not need lessons from you on how to read an incident report. Has the item you are referring to actually been identified and confirmed as causing the accident? |
This is a emergency AD. It is early days and as it says it is interim action as the investigation is ongoing. So no defined reason for the incident and this is a holding action to ensure safety.
Possible causes could be a manufacturing issue or miss-assembly. I would wait for the final report. |
Can someone post a picture of the rod /rod end in question.
https://c2.staticflickr.com/4/3068/3...dcd291490d.jpg |
CAUTION: GENERIC EXAMPLE Generic Installation Adjustment. (a)Adjust rod end bearing on rod. (1) Hold rod end bearing in position. (2) Hold fixed nut. (3) Tighten nut against key washer. (4) Ensure that rod end position has not been disturbed. b. Check for proper thread engagement by attempting to insert wire in witness hole. (1) If wire can be inserted in witness hole, thread engagement is not correct. Use wire. (2) Check for correct parts and adjust push-pullrod during rigging procedure. (3) If wire cannot be inserted in witness hole, thread engagement is correct. (4) Lockwire nut to keywasher (5). Use wire. c. Inspect (QA). d. Perform rig check on collective, directional,lateral, or longitudinal flight control system,as required. |
One inch out
If this happened in flight it is amazing there are survivors. My speculation is that when they rigged the input they misread the tape measure and made this an inch longer than it should be and then compensated by adjusting the pitch links to bring it in rig. The problem is that too much maintenance gets done to helicopters by engineers that don't have enough experience on type.
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Eric, I agree with you completely.
Just some information, I read the EAD to refer to the servo input rods, both main rotor and tail servo inputs. Having looked at the S76A i.p.c. 67-15-00, it seems to me that for the adjustable rod end to disconnect from the tube one of the bolts would have to be removed, as the other rod end is rivetted to the tube. If both rod ends were threaded (l.h. and r.h. threads) and both of the lock nuts were loose and not locked then the rod could have could have lost a rod end, on the servo rods only one end is adjustable. There is, of course, a chance that the rod end itself has failed on the threaded part. I await comment from a current S76 L.A.E. |
S76 Wizard,
I believe that if these rods were that far out of adjustment they could not have been fitted. The servo input rods are not very long at all, The tail rod is about 5 inches long and the mains about 7 or 8 inches, if my memory serves ! Perhaps someone current can confirm that. |
Bluesafari,
The Baltic Sea S76C+ accident factual findings were: Due to blockage of C3 return port (by plasma flakes) the Servo Actuator came fully extended. The Control Stick came full aft and collective vent full (max) up position, right pedal vent full down. The flight crew were able to recognize that it was an emergency situation, but could not identify what the emergency was and why the helicopter was responding the way it was. The helicopter come unflyable but the crew tried to fight against stuck flight controls. During this 37 seconds the helicopter made 13 spirals to the right... Finding 1. A plastic cover for the engine power control switch had separated from pilot’s collective control handle. Finding 2. The rod (tube) under the cockpit floor that connected the pilot’s and the co-pilot’s cyclic controls was broken Finding 3. The cyclic control stick on the right side (pilot) was bent slightly forward near the floor. I have heard more than 30 times together with the accident investigator the CVR recording of COPTERLINE 103.The crew was fighting 37 seconds against stuck flight controls. Our crew was able to bent the cyclic control stick forward, broke the Rod Tube which is connecting pilot and co-pilot controls and the captain broke the plastic cover for pilot’s collective control handle when he was fighting against fully up standing collective. It is possible and more likely that the Crew of Lagos S76C+ has broke this Control Rod end by the power what they had on hands and legs. The Rod tube and the Rod end should be fail safe but not designed for dying men's (the crew) adrenaline boosted fighting power. Do not blame technicians or pilots! |
Blue safari
You might be right about not being able to fit it. I had an old style input in my tool box and the difference from the way this one came out of the aircraft and from where the rod end can come out is 1 inch. I know in the mm it says to adjust the input to a nominal length when doing a rig. |
Copterline 103, can you provide more details? Why haven't the interim report finished yet?
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It will fit
Blue safari
You can fit it. But it would take a lot of work to make it not right.if that makes sense. So I don't think this was the case. I guess we will find out soon. |
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