Omni H160 Down - Brazil

[The Sultan]

Originally Posted by 212man

Actually, my mistake. The customer webinar had a slide on it, and reference to a safety information notice (SIN 3786-S-62) that describes actions in the event of T&B adjustment problems, but it is dated 15th April 2022. I know I am not alone in having interpreted the webinar comments as being related to this specific aircraft.

Thanks for the clarification. I considered the info in the safety notice to be a shotgun CYA best practices until they determine the root cause. If it had a track and balance issue I would be considering the damaged damper as more causal than as an effect.

[The Sultan]

Originally Posted by That lights normal!

The reported current PCL service life of 160hrs seems alarming. Something like resonance, or unexpected forces through the PCL resulting in the extremely short service life.
Hopefully not a knee jerk reaction to a problem not yet understood.

I ran into a problem where a component developed cracks well before its expected service life. Turned out the component bowed under load which was not accommodated for. I wonder if the long thin pitch links on the 160 are similarly bowing under compressive load which would increase the loads due to localized bending in the threaded section of the rod ends. Since this is the area of the threads, strain gages are not applied during testing for direct load measurements. Instead the loads are extrapolated from gages in more convenient (smooth) locations. If this is the case here expect to see larger diameter pitch links in the near future.

[212man]

Big sighs of relief at Airbus, I think!

https://dedalo.sti.fab.mil.br/file/P...ion_Rev_02.pdf

Basically looks like an operator maintenance screw up!

[Chu Chu]

That’s the clearest report I’ve ever read.

[MLHeliwrench]

What a fantastic, extremely useful, and intriguing report. Everyone should read it and maintenance managers should be using it as safety presentation topic on maintenance shortcuts and having enough resources (aka:staff). Removing one instead of both cowls, and hanging the pitch links off the top to free up the swashplate for the required check instead of removing or properly stowing them out of the way could be seen as a smart way to save time - but there are risks. And above all - if you cock something up (which everyone is capable of doing) report it and investigate the outcome to ensure safety.

[casper64]

Originally Posted by MLHeliwrench

What a fantastic, extremely useful, and intriguing report. Everyone should read it and maintenance managers should be using it as safety presentation topic on maintenance shortcuts and having enough resources (aka:staff). Removing one instead of both cowls, and hanging the pitch links off the top to free up the swashplate for the required check instead of removing or properly stowing them out of the way could be seen as a smart way to save time - but there are risks. And above all - if you cock something up (which everyone is capable of doing) report it and investigate the outcome to ensure safety.

Totally agree. If you think maintenance/safety is expensive… try an accident 😉 Luckily everyone survived and the cameras were there to tell the story! 👍👍👍

[MLHeliwrench]

Originally Posted by casper64

Totally agree. If you think maintenance/safety is expensive… try an accident 😉 Luckily everyone survived and the cameras were there to tell the story! 👍👍👍

I do say, those pitch links are pretty long and spindly compared to the rest of the beefy looking rotor head. I'm no aerospace design engineer, but if human power and manual leverage from the aircraft itself can catastrophically damage such a critical part - maybe there needs to be more Safety fudge factor built in?

[admikar]

There is. Don't do what that maintenance guy did.

[Blackhawk9]

This reinforces what many of us think about the standard of maintenance in some countries/regions, this is always an elephant in the room skirting this problem no one wants to confront, no one is perfect but some just shouldn't be working on Helo's. I have seen engineers fail type courses but are pushed thru because of the cultural nuances of where they are from, and the subject is discussed with managers in private before you go to one of these countries to try and help them, but a lot of the time you come away feeling you are headbutting a brick wall and eventually they will loose a machine again. You see safety notices come out and one of the first things said is which country did this happen, if it is one of the usual suspects everyone just shakes their head and says yep you can expect that, when it's from what is considered a first line country/operator then the discussions actually start to look into what caused the incident.

[Jabberwocky82]

Quite impressive that the aircraft still flew considering the free flapping blade.

[Blackhawk9]

Originally Posted by Jabberwocky82

Quite impressive that the aircraft still flew considering the free flapping blade.

Yes modern elastomeric's at least hold the blade in a generally neutral position, an old bearing'd head the blade would have turned 90o and it would be all over.

[212man]

Originally Posted by Blackhawk9

Yes modern elastomeric's at least hold the blade in a generally neutral position, an old bearing'd head the blade would have turned 90o and it would be all over.

Yes, I know of a B212 incident with a rotating swashplate drive link failure, that went real bad real quickly. Also maintenance related.

[helispotter]

Originally Posted by Jabberwocky82

Quite impressive that the aircraft still flew considering the free flapping blade.

The Bell 222 that crashed fairly recently at Huntington Beach seemingly had a failed tail rotor pitch link a while before it finally lost control. What happens to a blade in such an event presumably depends on the aerodynamic pitch moment created about the axis of rotation of the blade. I would like to think bladed are designed to drive to a fine pitch if any link fails?

[212man]

Originally Posted by helispotter

The Bell 222 that crashed fairly recently at Huntington Beach seemingly had a failed tail rotor pitch link a while before it finally lost control. What happens to a blade in such an event presumably depends on the aerodynamic pitch moment created about the axis of rotation of the blade. I would like to think bladed are designed to drive to a fine pitch if any link fails?

Im sure they’re not, I don’t know how you’d achieve it and, more importantly, it wouldn’t solve anything if they did! The whole point of cyclic control of the swashplate is to change the pitch of the blades, cyclically, throughout each rotation. A fixed pitch blade would cause as many problems as one adjusting its pitch autonomously through aerodynamic forces - I would suggest.

[The Sultan]

There was an incident at PHI on a 222UT where the one of the drive/pitch link attachments failed in flight causing loss of pitch control on one blade. The pilot (Frenchy, don’t remember full name) very quickly found a collective angle (as he lowered it in response) where the vibration was “tolerable” and flew the aircraft back to shore and did a successful run on landing. Basically he was setting the pitch on the blade he could control to “match” the angle of the “free” blade.

[212man]

Originally Posted by The Sultan

There was an incident at PHI on a 222UT where the one of the drive/pitch link attachments failed in flight causing loss of pitch control on one blade. The pilot (Frenchy, don’t remember full name) very quickly found a collective angle (as he lowered it in response) where the vibration was “tolerable” and flew the aircraft back to shore and did a successful run on landing. Basically he was setting the pitch on the blade he could control to “match” the angle of the “free” blade.

It’s impressive, but I don’t really understand the physics. The uncontrolled blade will change pitch according to the forces acting through the centre of pressure, if I’m not mistaken.

[The Sultan]

As stated above the free blade angle is controlled by the angle and spring rate of the elastomers.

I was of the school that a pitch link failure in flight was an unsurvivable event. This one, and one on an AH-1S flown by Vance Barton, proved that assumption wrong, though I would recommend it.

[wrench1]

Originally Posted by The Sultan

There was an incident at PHI on a 222UT where the one of the drive/pitch link attachments failed in flight causing loss of pitch control on one blade. The pilot (Frenchy, don’t remember full name) very quickly found a collective angle (as he lowered it in response) where the vibration was “tolerable” and flew the aircraft back to shore and did a successful run on landing. Basically he was setting the pitch on the blade he could control to “match” the angle of the “free” blade.

I believe that was the incident where one swashplate drivelink became disconnected due to lack of a cotter pin on the nut. Since the other drive link and the walking beam were still connected he was able to keep things in check till he got it down. But the vertical was strong enough to throw his headset off, blur the instruments and start cracking the tailboom mounting. However, it was a 222 and the pilot wasn't Pierre if that is who you were thinking of. However, there was an earlier 222 incident in TX where the walking beam failed and that guy got down as well, but not PHI. Regardless, I think the greatest 222 save was that guy in Minnesota who had the servo web assy come loose off the transmission in cruise.

[That lights normal!]

Imagine the investigation without the maintenance security footage.
Wow

[Agile]

Originally Posted by That lights normal!

Imagine the investigation without the maintenance security footage.

Yes I was thinking about that, many maintenance shop who trully care about safety will have to install high grade 4K security camera.
it could come a time not so far in the future, when AI can scan through the video and flag something not right, before the flight.
The camera on the tail of the H160 spoting and recording the tail rotor shaft failure timing is also another simplification in the investigation.